Aquaculture and its potential environmental impact on Guam's waters

[From the U.S. Government Printing Office, www.gpo.gov]

AQUACULTURE AND ITS POTENTIAL ENVIRONMENTAL

IMPACT ON GUAM'S COASTAL WATERS

COA S TA L Z 01VE
"'TOP, lqA -rjojVXpNr

-IV

BUREAU OF PLANNING
GOVERNMENT OF GUAM
AGANA,GUAM

TD
194.56
-G8
A88
1980
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AQUACULTURE AND ITS POTENTIAL ENVIRONMENTAL

IMPACT ON GUAM'S COASTAL WATERS

William J. FitzGerald, Jr.

This-study was funded by a grant from the
Office of Coastal Zone Management, U.S.
Department of Commerce

TABLE OF CONTENTS

PAGE

LIST OF TABLES .................................................... ii

LIST OF FIGURES .................................................... ill

INTRODUCTION ...................................................... I

LAND RESOURCES ................................................. 3

14ATER RESOURCES ................................................... 6

SPECIES APPLICABLE FOR CULTURE ON GUAM ............................ 11
Freshwater Organisms ............. :,**''***'*'*'**"**''.* ... - 12
Brackishwater and Saltwater Organisms ........................ 20

FACILITIES FOR AQUACULTURE ........................................ 25

ENVIRONMENTAL IMPACT DUE TO AQUACULTURE PRACTICES AND POLLUTION
ABATEMENT MEANS ................................................... 32
Pollution Parameters ......................................... 33
Pollution Abatement ...................... 41
Public Health ................................................ 46
Exotic Species ............................................... 46

ROLE OF AQUATIC AND WILDLIFE RESOURCES ............................. 48

CONCLUSION ........................................................

ACKNOWLEDGMEMTS ................................................... 52

LITERATURE CITED .................................................. 53

LIST OF TABLES

TABLE PAGE

1. Land area suited for aquaculture ........................... 5

2. Minimum water flow record ................................. 8

3. Discharge measurement at low water flow (partial record
stations) ................................................. 9

4. Nitrate and phosphate values .............................. 40

LIST OF FIGURES

FIGURE PAGE

1. Map of Guam showing areas having suitable terrain
and soil type for aquaculture ........................... 58

INTRODUCTION

Aquaculture has the potential of suppling a substantial portion of

Guam's consumption of fishery products, which is almost exclusively im-

ported to the island at present. Some of the worlds'. countries obtain

20 to 40 percent of their aquatic food products through aquaculture, in-

cludina Indonesia, India, and China; while in the United States an esti-

mated 2 percent of -fishery products consumed (mainly oysters, catfish, and

trout) are Produced by a0Uaculture (Corbin, 1976). In addition to the on-

island market, aquaculture is an industry that can produce an export Dro-

duct. Together, these features give aquaculture an important potential

role in Guam's economy.

A properly managed, vertically integrated aquaculture system covers

the whole spectrum of the production of aquatic species from energy input

to the marketing of the product (i.e., hatchery operation, grow-out Dhase,

manufacture of feeds, processing, and marketing of the product). The ex-

pansion of aquaculture into a large capital generating enterprise encom-

passes [email protected],managerial-problems that must'be overcome to be success-

ful. The major areas of concern are species for culture, [email protected]

nology, engineering technology, site location, feed, manpower, marketing,

as well as legal, institutional, and financial considerations. Such systems

are being developed in the United States, especially in the Culture of the

channel catfish.

The development of aquaculture facilities, both marine and freshwater,

requires a well thought out islandwide plan, that will take into considera-

tion its positive as well as negative aspects in regards to the economy and

environment. Guidelines must be placed on the development not to hinder,

but to restrict abusive use of the island's natural resources. These

guidelines will have to be part of a comprehensive plan and enforced by

the involved governmental agencies.

LAND RESOURCES

Aquaculture development should be limited to -the centrai and southern

area of Guam, since the use of water from the lens system which is the main

source of potable.water for Guam would possibly put an excess demand on this

finite water supply. In addition, the major part of the northern area consists

of limestone which would be unsuitable for pondag es due to its.permeability.

Plastic-lined or concrete tanks would be required. Full explotation of

southern sites should be the priority.

Criteria for land to be used for aquaculture ponds are as follows: The

soil should be of character to retain water, preferably having a minimum of

25% clay. Fertile soil is prefered, but marginal soil can be used through the

addition of fertilizers and lime. The area should be free of flooding or cor-

rective means can be made without excessive investment.- The soil should be free

of pollution that might endanger cultured species. Prior knowledge of the land

use would be informative to the type of pesticides or chemicals used. The con-

tour distance should be greater than or equal to 100 ft. (30.9 M) for every

10 ft. (3.1 m) horizontal rise (slope maximum 10%). The size of the ponds be-

comes smaller as the contour interval approaches 100 ft.; beyond this, pond con-

struction of small ponds becomes too costly. The land to be useable must be

accessible by vehicle year round. This is a requirement for proper management.

The area must have suitable topography so as to allow the complete drainage of,

ponds.

An estimated total land area suitable and available (no permanent structures)

for aquaculture on Guam is 3652 ha. This estimation is based on the soil type

and terrain. Figure 1 shows the delineated areas and Table 1 shows the quantity

of area within each site. The preferable soils are Pago and Inarajan clays. Of.

the two clays under the soil type number 6, the Agat clay is not suitable for

ponds, mainly due to its excessive slope. The Atate clay (#6) is marginally

acceptable. It depends on the depth at which the C horizon is located. There

are ponds constructed on this soil type. The total estimated suitable land area

does not indicate the potential developable land,since each site must be consider-
ed seperately with referral to the type and quantity of wker supply available.

This will then determine how much of a given site can be developed. Naturally,
conflicts with other uses of the land (e.g., agriculture, housing develo'pment).will

further limit the development.

All aquaculture practices within the marine environment are considered to be

in navigable waters and thus require/s a permit from the Army Corps of Engineers.

Aquaculture sites for the culture of marine organisms are limited to areas that

afford a reasonable degree of protection from surf, and storm damage. The major

sites that afford such protection are Apra Harbor between the drydocks and Polaris'

Point (Sasa Bay) and Cocos Lagoon primarly in the area around Achang Bay (possible-

siganid culture in sea grass beds). The Inner Habor of Apra Harbor and the salt

water pond adjacent to San Luis Point have suitable sites, but are restricted due

to Naval operations. In addition, the Piti Channel area has suitable physical

features; however, the possibility of toxic effluents from the nearby power plants

have to be concidered. Small protected bays along the southeast coast of Guam

(e.g., Pauliluc Bay, Agfayan Bay) can be utilized for small scale culture oper-

ations. The use of large areas of reef flats around Guam would be ill-advised
due to the environmental impact such operations would have and the very limited

degree of managebility of such sites without major construction and alteration

of the reef flat areas. However, the impoundments on the reef flat created by

the construction of the sewage disposal plant in Agana could be technically

utilized for aquaculture.

Table I Land Area Suitable for Aquaculture.

Man Section Soil_Types
#2 #3 #6 #9 #10 #11
T
Toto Clay Chacha-Saipan Clay Atate-Agat Clay Pago Clay Inarajan Clay Mucks
Hectares Hectares Hectares Hectares Hectares Hectares
Total Available Total Available Total Available Total Available Total Available Total Available

East Guam
1. 8 8 793 233

West Guam
1 45 45 16 0 162 130 40 16 25 12 163 147
2. 7 0 11 10 12 0 90 45 25 22
3. 79 35 4 4 60 0 10 10 32 0
4. 2 0 3 2 129 97 16 4 0
5. 20 0 20 10 89 45 125 100 4 4
61. 30 0 119 30 26 13 13 13 29 7
7. 10 0 34 0 56 56 54 0 8 2
8. 36 0 63 0 21 21 15 0
9. 11 0 145 36 29 29 2 2
10. 4 4 90 90 7 7
4 4 78 39
12. 152 152 21 21
13. 26 26 40 40
14. 3 3
15. 136 68
16. 172 172
17. 2 2
18. 27 27
19. 19 19

South Guani
86 69 4 4 32 0 3 3
2. 25 25 3 3 4 4
20 20 26 13 15 15
4. 32 16 3 3 3 3
r, 6 6 24 0 145 102
6. 7 7 17 17 9 9
7. 35 6 6 2 2
S. 43 43 24 24 23 23
9. 15 15 52 52 64 51
10. 5 5 285 235 4 4
11. 579 579 5 5 2 2
12. 36 36 3 3 59 59
13. 161 129 10 10 8 8
14. 39 39 5 5
15. 31 31
16. 5 5

Total 53 53 1,004 273 2 , 2 3 1 1 759 1 '019 797 866 585 268 185

WATER RESOURCE'S

Aquaculture is dependent on an adequate quantity and quality of water.

The latter can be influenced by the use of pesticides or other chemical

agents, sewage and other pollutants from the adjacent land. In the case

of marine aquaculture it is also susceptable to oil spills. Possible del-

eterious effects of toxins or pollutants on cultured organisms are mortality,

injury, interference with growth or other vital functions, concentration

in the organisms to such an extent as to render them unflit for human con-

sumption or making them unpalatable. Organisms under intensive aquaculture

practices are often under physiological stress due to artificial diets

being incomplete in nutritional needs, and unnatural crowded living condi-

tions that possibly cause hormonal or other biochemical imbalance. There-

fore, they are rather susceptable and vulnerable to further deterioration

of water quality, often more so than organisms in the wild.

The average daily quanti.ty of water that needs to be added to a pond

to maintain the water level is 1.3% of the total volume. This is the water

lost due to evaporation and seepage. Some water is gained through rainfall,

but there is an average net lost of 34,000 gal/day/ha of pondage. Thus,

this requires a minimum continuous water flow of 23.6 gal/min/ha. This

figure is based on the actual operation of the Division of Aquatic and

Wildlife Resb,urces; ponds at Talofofo during 1974 to 1.975. During this

period, precipitation averaged 0.275 in/day and evaporation averaged

0.200 in/day. During periods of drought a larger volume flow will be

required. Likewise, during periods of excessive rainfall, less volume

will be required.

A large-scale development of pondage @,%rould necessitate the construction

of a dam to assure an adequate flow of water during the dry season and to

allow the full potential of the area to be developed. For the construction

of a dam, a permit from the Army Corps of Engineers is required for rivers

having an average annual flow of 5 cu. ft/sec or qreater. A permit is also

required from the Guam Environmental Protection Agency for the construction.

of any obstruction of a waterwa The construction of government-funded
y

dams (e.g., proposed Ugum River Dam) should be encouraged so as to allow

the fuller utilization of the island:'s water resources. Aquaculture would

be greatly benefited by such conservation measures of the island's water

supply. If no dam is to be constructed at the pondage site the maximum

area that can be developed should be based on the minimum flow months of

the year (Table U3. Following this procedure would greatly reduce the

area that could be supported by the water supply. Drainage and filling of

ponds should be coordinated to best utilize the water supply. Tables 2 & 3

gives the maximum area that can be developed using the average flow over

a number of years for a given river system that has been monitored by the

U.S. Geological Survey personnel. The criteria for this area of develop-

ment is the damming of the river with the option of 25, 50, o r 75% of the

average flow being utilized for pondages. In areas with the river systems

flow rate not being monitored, an estimated average discharge for one square

mile of drainage area on Guam is 2 million gallons per day (personal com-

munication, Chuck Huxel).

The use of wells and springs can serve as a main or supplemental water

supply in the southern areas. Thorough aeration is generally required of

well water before use in the ponds. This type of water supply has the

Table 2 M i n i mum Flow Recorded Permanent Monitor Stations. 1) 34,000 gal/day/ha. 2) 1.3% Evaporation seep age
water/day. 3) 1 cu ft/sec =@646317 x 106 gal/day.

Ti,naga River
Station Finile River Umatac River Geus River Inarajan River (Pauliluc River)

Number of Years Monitored 15 23 22 23 23

CU ft/sec/month 3.25 6.30 0 32.89 7.43

Gal/day 70,018 135,727 0 708,579 160,071

Pond Area Supported Hectares
(100% Utilization) 2.1 4.0 0 20.8 4.7

Long Term Average Flows

Cu ft/sec/month 42.0 251.7 90.6 513.0 166.8

Gal/day 904,845 5,422,600 1,951,877 11,052,020 3,593,523

Pond Area Supported Hectares
(25% Utilization) 6.7 39.9 14.4 81.3 26.4

Pond Area Supported Hectares
(50% Utilization 13.3 79.7 28.7 162.5 52.8

Pond Area Supported Hectares
(75% Utilization) 19.9 119.6 43.1 243.8 79..3

1111ong River Almogosa Spring Almogosa River Maulap River Ylig River Pago River Total

14 19 4 4 23 24

18.39 0.28 10.07 12.43 4.72 2.53

396,192 6,032 216,947 267,791 101,687 54,506

-11 .7 0.2 6.4 7.9 3.0 1.6 62.4

Long Term Average Flows

297.6 108.0 169.8 129.3 846.0 720.0

6,411,465 2,326,741 3,658,154 2,785,626 18,9"26,139 15,511,608

47.1 17.1 26.9 20.5 134.0 114.1 528.4

94.3 34.2 53.8 40.9 273.0 228.0 1066.2

141.4 51.3 80.7 61.5 402.0 342.2 1584.6

Table 3. Discharge Measurement at Low Flow-Partial Record Station.

Average Area Supported
Number of Minimum Flow (100% Utilization)
Years Measured Cu Ft/Sec/Month Gal/Day Hectares

Fonte River 15 6.27 135,080 4.0
Masso River 11 5.52 118,922 3.5
Faata Springs 13 5.61 120,861 3.6
Taleyfac River 17 @21.15 455,653 13.4
Cetti River 8 9.72 209,407 6.2
Lagafua River 23 19.14 412,350 12.1
Piga Springs 21 4.56 98,240 2.9
Astaban River 16 4.35 93,716 2.8
Laelae River 16 17.67 380,681 11.2
Toguan River 25 5.07 109,228 3.2
Siligin Spring 19 1.83 39,425 1.2
Ajayan River 14 8.61 185,492 5.6
Ag-I'ayan River 14 20.07 432,386 12.7
Aasamano River 16 28.68 617,879 18.2
Yledigao River 16 28.59 615,940 18.1
Fintasa River -16 23.22 500,249 14.7
Fensol River 16 5.10 109,873 3.2
Asalonso River 25 12.54 270,160 7.9
Agum River 16 82.38 1,774,786 52.2
(Above Bubulao)
Bubulao River 16 113.01 2,434,676 71.6
Ugum River 16 213.90 4,608,240 135.5
Manengon River 16 19.11 411,704 12.1
Tolaeyuus River 6 150.78 3,248,389 95.5
Lonfit River 3 43.83 944,269 27.8
Sigua River 3 48.63 1,047,680 30.8
Atantano River 5 28.92 623,050 18.3
Madag River 16 7.47 160,933 4.7

advantages of a*.relatively stable quality, free of pollutants, and free

of unwanted aquatic species.

SPECIES APPLICABLE FOR CULTURE ON GUAM

Guam affords an ideal climate for the culture of warm water species.

Year round warm temperatures allow growth to be at its maximum rate with

subsequent high yields. For species to be of value to culture on Guam,

there would have to be an existing demand or a potential demand located on

Guam or within an economical shipping radius (which would have to be defined

for each species). The majority of cultured species will be exotic (intro-

duced species) to Guam. It is highly preferable to use species of i,,,hich

the complete life cycle can be controlled. Species of subtropical and trop-

ical orgin are most suited for Guam's climate. Temperate species will often

be at their upper limit of temperature tolerance and unsuitable for econ-

omic culture due to raised metabolism, thus reducing-the food conversion

ratio.

In determining which species are s uitable for aquaculture, both fresh

and marine, the basic criteria is economic feasibility. All other factors,

biological, technological, environmental, management, and market demand con-

tribute to determining the economic success of a species.

Aquaculture on Guam inevitably will be limited to a few species that

are proven to be most profitable to culture. The limited resources avail-

able (land and water)on Guam deters diversification of cultured species due

to the economics involved in large scale culture, namely labor costs, opti-

mum-design for containment of a Species (including a hatchery), processing

costs, and market establishment.

Aquaculture can be divided into the raising of aquatic organisms caught,

fish farming, and a second catagory,
from the wild, which would be called

fish culture, which would be the raising of aquatic organisms through their

entire life cycle in captivity. Aquaculture practises invol ving low stock-

ing (from wild stock), low capital investment, no or minimal control of the

aquatic environment, no supplemental feeding, little or no fertilization,

low prodUCtion/area, and being labor-intensive are considered extensive aqua-

culture practices. This type of aquaculture is common in underdeveloped

countries throughoust southeast Asia. At the other end of the manaqerial

spectrum in aquaculture is intensive aquaculture, which involves supple-

mental feeding, control over the complete life cycle, maximum control of

the aquatic environment, high stocking density, high production/area, and

-is capital intensive. This paper deals mainly with the latter.

Aquaculture is similar to agriculture in that a selected species or

group of species are confined to a given area from which a maximum production

is obtained by the application of fertilizers, feeding, disease control,

environment quality management, and control of predation. Biological and

technological factors favoring intensive culture of a species have a low

Lrophic level, (efficient food conversion), disease resistance, Gregarious

nature, rapid.growth rate, control of the complete life cycle, high fecundity

and survival, and hardy nature. A reliable source of juveniles is a necessity

to a successful aquaculture business. This , in most cases, would necess-

itate knowledge of propagation and rearing of larval stages in a hatchery,

since total reliance on wild stocks will result in unpredictable production.

Freshwater organisms

Macrobrachium rosenbergii
The giant MIalaysian prawn (Macrobrachium rosenbergii) is endemic t o

the southeast Asia and Indo-Pacific area, with its furthest northeastward

extent beinq to the Pdlau Islands. Preliminary work on culture of M.

rosenbergii was done by Ling (1967) with subsequent investigation into the

mass cultivation of the larvae by Fujimura (1970). Culture of this species

i s practi ced i n S. E. Asi a, Uni ted States, Mlexi co, South Ameri ca,. Phi I i ppi nes ,

Micronesia, South Pacific, Taiwan, and Japan.

This is one of the most thorough scientifically investigated species

with the intent of optimizing knowledge of its culture. The majority of

the research has been carried out in the U.S. This extensive [email protected],-:con-

tributes to the desirability of this species for cultivation, along with

characteristics of complete control of the life cycle, relatively free of

disease, suitable for polyculture, luxury product demanding.premium prices,

omnivorous feeding habits and applicable to intensive or extensive culture.

The production capability of this species on Guam is 4637 kg/ha/year

(FitzGerald, 1975). This is based on the harvest of two crops per year.

This production was carried out in a stagnant pond (no water discharge,

only maintenance of water level). Supplemental feeding of a commercially

prepared food, turkey starter (28% protein), was used. The u se of a poly-

culture system is recommended, with Chinese carp being the secondary species.

As wi th other crustaceans the occurrence of mol ti ng i n :the pond makes the

prawns vulnerable to cannibalism; however, this can be minimized by providing

numerous shelters.

At present -the entrepreneurs engaged in the culture of this species

on Guam receive post-larvae for stocking from the Hawaii Fish and Game

Department through Guam's Division of Aquatic and Wildlife Resources at no

cost, except for air freight charges. Hawaii has set a limit in the past

of one million post-larvae (sufficient for stocking 5 hectares) as the

maximum it can supply Guam. As Hawai i's prawn industry has grown its abi 1 i ty

to Supply Guam with post-larv ae will terminate. A hatchery will have to

be developed on Guam and a temporary alternate source of post-larvae found
(e.g., Palau) to sustain existing farms and to meet the demands of the

growing industry. Sixth the addition of a hatchery for prawns on Guam, the

management and production capabilities will increase. Year round production

of post-larvae will allow the use of a staggered stocking method which

can increase production and allow a continuous supply of harvestable prawns

to be available. Guam imports an estimated 500,000 pounds of shrimp per

year. Production of N. rosenberqii could fill a large portion of this local

market demand. Japan presents an enourmous foreigh market for prawn and

fishery products with premium prices paid for 16-20 prawns/pound size.

Anguilla japonica

The freshwater eel Anguilla Japonica is a catadromous species with the

migration of mature eels to the sea for spawning and the return of the

elvers to rivers. It is at this point that the elvers are captured and

held before stocking in grow out ponds. All pond culture of this species

is dependent on this capture of wild stock. Progress has been made on the

artificial propagation of A. japonica, but it is still only on an experimen-

tal bases. The source of juveniles for stocking are Mainland China, Korea,

Taiwan, and Japan, with the later two countries usually not being able to

meet their own demand. There is the possibility of substituting a similar

Australian - New [Zealand species, Anguilla australis, since the supply

of wild elvers is not always available in adequate quantity from the prev-

iously mentioned coutries. Other species suitable for culture are the Euro-

pean A. anguilla and the American A. rostrata.

Culture of this species is intensive and usually as a monoculture.

The eels are carnivores by nature, but are fed on a commercially pre.paired

balanced diet. Production varies with the method used.fromless than I kg/
m in earthen ponds up to 60 kg/m 2 in concrete environmentally controlled

tanks. Guam's Aquatic and Wildlife Resources' experimental eel culture was

on a polyculture basis in a earthen pond. Growth was shown to be very rapid

under the warm water conditions, with harvestable size obtained as early

as after 4 months of culture. A key factor in good production results of

this species is the ability to have close management control. This is

mainly needed for the required sorting of size classes during the grow out

phase, in addition to disease prevention, and observance of the general

condition of the eels which is usually evident in feeding behaviour.

Guam has one entrepreneur engaged in eel culture. This i s with the

use of concrete walled ponds with an area of 2 hectares which will be expand-

ed with future demands. The expected production from these ponds will be

100 mtons/year. The major market for the eels is Japan. There is a small

local market, but future expansion of eel culture will be solely for an

export market.

Pangasius sutchi

The S.E. Asian catfish Pangasius sutchi is generally grown as a mono-,

culture, but polyculture can be used with suitable species (e.g., carp).

They live in rivers, and lakes, and can be raised in ponds or cages. They

will not reproduce in ponds since they require moving water for reproduction

to occur. This fish has great potential for Guam due to its capability of

high production per unit area.(e.a., 75,000-95,000 kg/ha/year) (persona 1

communication, Nukit). The species is omni'vorous. and is usually fed on a

mixture of vegetable matter and fish. The main draw back to their produc-

tion on Guam is the requirement of 20'Z or greater protein in their diet

Lo obtain the desired growth rate. They also require a high feeding rate

of 10-12% body weight/day. This necessitates an abundant supply of an in-

expensive food source to fulfill dietary requirements. Possible areas of

a cheap food source would occur with the development of a proposed vegetable

cannery, livestock slaughter house, tuna cannery, or utilization of acti-

vated sludge from the waste'treatment plants. The initial cultivation on

Guam by the Division of Aquatic and Wildlife Resources met with unfavorable

results which were mainly attributed to improper diet and the competition

for food with Tilapia. There is a breeding stock being held at Aquatic

and 14ildlife Resources for future artificial propagation.

Clarias (Clariidae)
Clarias (C. batrachus, C.-macrocephalus, and C. fucus) are other
Southeast Asian catfish that offer high production per unit area (80,000-

90,000 kg/year/ha). They are easily bred in captivity, of hardy nature,

and feed on a wide variety of vegetable and animal matter. C. batrachus

is favored for culture through southeast Asia due to its more rapid growth

rate. C. batrachus occurs on Guam and is usually found in swampy areas

that are subject to drying up during periods of low rainfall. It has the

characteristic of having an accessory air breathing organ that enables it

toexist in oxygen poor waters and to leave pondages in search of food.

The advantages of the ability to withstand low oxygen waters is obvious;

however, its ability to leave a body of water and move across land requires

precautions. It has the ability of burrowing into the mud to survive

extensive dry periods. Due totiis ability, a pond used for this species

should not be altered with the culture of species that might become prey

of the catf i sh (e. g. , prawns) , s i nce compl ete erad i cati on f rom a pond woul d

be difficult as the result of their ability to burrow in-to mud. A possible

solution to this would be a concrete tank culture.system. The culture

of these catfish would require a fencing enclosure around the pond to

prevent escape. Clarias is presently imported to Guam's fish markets.

The Division of Aquatic and Wildlife Resources is examining the feasibility

of the commercial Culture of C. batrachus,on Guam.

Chinese Carp

These fish are mainly recommended on' Guam as a secondary species to

increase overall production by more fully utilizing the three dimensional

space of the pond, and help maintain a balanced pond environment. Grass

carp (Ctenopharyp res that helD control grasses
g2_don idellus) are herbivo

growing along the pond banks. Silver carp (Hypoph-thalmichthys molitrix)

are microphagos herbivores, feeding on the,phytoPlankton. Big head carp

(Aristichthys nobilis) are microphagos carnivores, feeding on zooplankton.
Common carp (@@rir@us carpio) are detritus feeders. At present, stock is

obtained from Taiwan, but they can be artifically propagated on Guam once

a breeding stock is established.

Tilapia sp.

This genus of fish has a variety of feeding habits, but in general is

an aggressive opportunistic feeder. They breed naturally at a high rate

in ponds, thus overpopulating, causing a general reduced growth rate, and

a crop of an unsuitable size mixture for marketing. Monosex Culture would

be the only suitable means of culture on Guam. This is done by the crossing

of species to produce a hybrid progeny of all males, or by hormone in the

feed of sexually indetermined fry to produce an all male population. In

general, Tilapia are an invader species (often interfering with the culture

of highly valued species) and are hard to eradicate from ponds where they

are not desired. Their aggressive feeding takes food away from the desired

cultured species. Tilapia would be suitable for use in stabilization ponds

where they would feed on the natural productivity of the pond. It's low on-

island market value would eliminate the desire to be cultured on a large

commercial scale on Guam, unless market changes are made through product

promotion. The catering to the Japanese tourist resturants with a live

product to satisfy culinary tastes would support a limited production.

Soft Shell Turtle

The soft shell turtle (Trionyx sinensis) is a high-priced item that

is considered a delicacy in Taiwan and Japan. Its culture is carried out

in ponds with concrete or stone walls with an overhang to prevent escape.

T. sinensis are mainly fed on trash fish and animal products. Growth of

the turtle normally takes approximately two years before it reaches a

harvestable size (600 g); however, this growth period could be reduced to

about one year on Guam due to its favorable climatic conditions. Stocking

varies according to the size of-the turtle, and size segregation must be

practised to prevent cannibalism. Reproduction occurs in special rearing
ponds in which mature turtles (3 years or older) are placed. Egg laying

occurs in a small brick enclosure with a sand floor. Hatching takes approx-

imately 50 days.

Soft shell turtle culture on Guam was initiated on a small scale by

a private entrepreneur. The initial venture proved unsuccessful due to an

inadequate enclosure to prevent esca.pe. A second entrepreneur has construct-

ed three small ponds (7 m x 17 m) for the Culture of turtles and carp. The

marketing will be mainly in Taiwan. This is a rather limited culture for

a special market.

Bait Fish

A key factor in the.development of skipjack tuna fisheries in this area

of the Pacific would be a suitable supply of bait fish. A number of species

have been considered and used as bait fish including Tilapia mossambica,

Dorosoma petenense, Poecilia vittata, Poecilia mexicana, Sardinella melan-

ura, Engraulus japonicus, Chanos chanos, Kuhlia sandviciensis, mullets, and

cyprinids (Gopalakrishnan, 1976). Live bait Dole and line method of cat-

ching skipjack tuna is the most productive means at present for harvesting

skipjack. Large purseseini'ng boats have not proved to be viable in this

area of the Pacific to present.

Important factors influencing the selection of a suitable bait fish

are: to be prolific, continuous breeding, gregarious, of good-growth

rate, hardy (both in culture and during holding in bait wells), show suit-

able behavior, size, color, and shape to attract tuna, and must be accepted

by fishermen for use. A promising genus that is presently being worked

on in Hawaii and American Samoa is Poecilia (Baldwin, 1974; Swerdloff, 1973).

This genus is suited to mass culture (Baldwin, 1972).

Brackish Water and Saltwater

Chanos chanos

The milkfish or sometimes called bangus (Chanos chanos) is a eury-

haline fish with a tolerance of 0-35 It has been cultured on Guam

on a small scale in freshwater by Aquatic and Wildlife Resources (FitzGerald,
1975), and in salt water by a group of Filipino workers. There is no means

of ar tificial propagation at present. All stock must be caught from the

wild. The closest possible supply of milkfish fry at present is Palau or

Yap; however, their runs are too unpredictable in quantity and time to be

a dependable source. Runs of fry have been reported on Guam but are too

few and unpredictable,'also. The major area of abundant milkfish fry runs

is in the Philippines; however, they have enforced a moritorium on tile

export of milkfish fry. Until artificial propagation can be practised

with this species or a stable supply of wild stock is established, further

pursuit of the culture of this species on Guam would be futile.

Grey Mullet (Mugilidae)

The mullet is a marine species of fish, which enters estuaries and

the lower extents of rivers. The salinity tolerance is similar to the

milkfish in that they can adapt to freshwater or sal twater. Their dis-

tribution is wide spread with MLt@ cephalLIS (the preferred species for

culture) being a circumtropical species. Some of the favorable character-

istics of this species are euryhaline 0-38 %., eurythermal 3-35 C, low

trophic level (herbivore), and high quality flesh. M. cephalus.naturally

reproduces in salt water, but artificial propagation has recently become

successful on a practical scale (Shehadeh and Norris, 1972).

Cultivation of mullets is usually in brackish water ponds, where they

feed on plankton (both zoo and Phytoplankton), benthic algae, and detritus.

They also accept artificial feed. Growth varies with density of stocking

and feeding from 200-500 g in one year. They can be raised as a monocultUre,

but more commonly are raised in a polyculture situation. On Guam, their

culture would be mainly as a secondary species, filling a niche that the

primary species does not occupy. Mullets are stocked at low densities.

Their low production per unit area i,,iill eliminate their desireability for

large scale culture on Guam.

Scylla serrata
The mangrove crab (Scylla serrata) is an extremely territorial and

aggressive species which makes its economic culture very difficult., It

is a high valued product, but the low production capability per unit area,

under present culture methods, makes its cultivation unlikely for Guam.

It does occur naturally on Guam. An unsuccessful small scale culture was

attempted by Aquatic and Wildlife Resources in conjun ction with one of the

commercial pond operators, and a basic growth and natural history study,

was done at the Universtiy of Guam Marine Laboratory (Dickinson,1977).

The ability to culture S. serrata through its larval stages is known

(Ong Kah Sin, 1964). A culture of this crab on a capital intensive rather

than labor intensive scale is presently not practical. Developments along

this methodology, which would be similar to that of the American lobster

(Homaru americanus), is possible in the future. Its culture in Asian

countries is on an extensive basis, and is usually only held for a short

fattening period after its capture from wild stock before being marketed.

Its commercial pond culture prospects being of significant importance is
unlikely (Ong Kah Sin, personal communication).

Crassostrea gigas (Oysters)

An experimental culture of C. gigas was conducted at various locations

around Guam by Aquatic and Wildlife Resources (FitzGerald, 1975). The gen-

eral lack of biologically rich marine waters around Guam makes the culture

of filter feeding organisms less productive than areas Of Droductivel
I y

rich waters. The Apra Harbor area appears to be the only feasible site a-

round Guam for oysters or other filter feeding bivalves on a large commer-.

cial scale. Some of the sheltered small bays may afford a suitable area

for a family consumption type of culture.

Mytilus (Mussels)

This bivalve mollusk is one of the most efficient feeding animals..

It has a rapid growth rate with a high nutritional value, and excellent

palatability. Mytilus culture would be limited to the same areas as

oyster culture, namely the Apra Harbor area. The major means of culture

would be raft culture.

Penaeid Shrimp

A number of penaeid species are suitable for culture; however, PenaeUS

monodon (the Philippine sugpo) along with P. Japonica Would probably be the

most desired. Penaeid culture is usually carried out in tidal ponds. The

filling and emptying of the ponds are correlated to the spring and neap

tides. The maximum difference of a tidal cycle on Guam is 3.5 ft. This

would be a limiting factor in the ability of this.culture method. Util-

ization of pumps for water, exchange would be necessary. Gravid females are

usually caught from the wild, with the subsequent raising through the

larval stages to post-larvae in captivity. Development of bringing about

maturation and ovulation in captivity by eye stalk ablation is being refined

so the whole life cycle can be completed in captivity.

Siganids

Rabbitfish (Siganu spinu , and $_ argL@eu_s) are very popular reef

fish on Guam and throughout Micronesia. There is a wild stock available on

Guam. In addition, artificial propagation is known (Bryan,et. al., 19175).

Jnus and S. argenteus are the two species that usually have large juve-

nile runs on Guam (Kami, 1976). Preferably 5- ar-gent-aus, due to its

better growth rate, would be stocked into ponds or enclosed areas of the

reef or floating cages (Tsuda, et. al., 1976). The major drawback to the

culture of this species is obtaining an economical food source that will

produce an acceptable growth rate. Conditions for the culture of the

prefered alga food for this species is known (FitzGerald, 1976), but supple-

mental protein has to be added to the diet to obtain rapid growth.

Grouper, Sea Bass, and Snapper

These species (Lut.ianu.s argenjtifli&culatus, Lates calcirife and

Epinephelus tauvina) are suited for cage culture. They are high valued

species. They are carnivores and require an inexpensive supply of scrap

fish. This is the main deterent to culture of these species on Guam. If

a tuna cannery or fishing industry develops on Guam, a possible cheap source

,of protein would be available. The complete life cycles of these species

have been acheived in captivity (Wongsomnuk and Brohmanonda, personal

coi-,imuni cat -ion)

Algae

Commercial culture of algae would be very limited due to the res-

triction on available areas that would be feasible for its culture on

Guam. The only areas that would afford adequate protection from storm

damage to crops wouldbe Apra Harbor and Cocos Lagoon. There is no developed

local market so all of the production would have to be processed for export.

Genera that could be used for culture on Guam would include Eucheuma,

Gracilaria, Gelidiella, Caulerpa, Porphyra, and Enteromorpha. Eucheuma,

Gracilaria and Gelidiella could be used in marine colloid production.

Enteromorpha, Gracilaria, Porphyra, and Caulerpa could be used as human

food. The use of alga as an animal feed (e.g., Enteromorpha in'Siganid

culture) could be feasible, but would be most economically based on the

utilization of a waste nutrient source (e.g., effluent from pond culture).

Various other genera have been used as cattle fodder (Jensen, 1972).

Present methods of algal culture are mainly labor-intensive.- This

will discourage its development on Guam until an efficient economically

capital-intensive means of culture becomes viable. As for example an

annual net income from a family-operated 0.5 hectare labor-intensive

Eucheuma farm in the Philippines is $1360 (Deveau and Castle, 1976).

4
Guam would be incapable of competing on a world-wide marine colloid

market with such competition from labor-intensive countries. Capital-

intensive methods of growing Eucheuma are being examined in Florida, but
have not yet proven economically viable (Deveau and Castle, 1976)..

FACILITIES FOR AQUACULTURE

Ponds

Earthen pond culture is the oldest and most widespread means ol@ con-

taining cultured species. Ponds vary greatly in size from less than 0.1

ha to over 40 ha. This depends greatly on the species being cultured, the

intensity of -the culture, and the terrain. The present general trend is

towards smaller ponds (e.g., 0.1-1.0 ha ponds) since they afford closer

management practices. Earthen ponds are constructed by the excavation

of the soil from the pond area to form dikes. Heavy equipment (bulldozers

and backhoes) should be equiped with LGP tracks (low ground pressure)

since most ponds are constructed in areas consisting of soft soils. Con-

ventionally equipped machinery would frequently become stuck or inoperative.

As the soil is excavated and placed along the dikes it is firmly packed

so that the bank does not allow leakage or possible breakage due to insuf-

ficent compaction. The soil should be free of vegetation, roots, and large

rocks. It is preferable to minimize alteration as much as possible of the

bottom and banks that are formed naturally by the terrain, since this soil

is already compacted and less likely to allow seepage or breakage.

The actual lay-out of the ponds depends on the terrain., In.V-shaped

slightly obliquely truncated valle s, small diversion ponds can be con-
y

structed. In rounded off V-shaped valleys, barrage ponds or a series of

linked diversion ponds are constructed. In V-shaped valleys that are

slightly horizontally truncated, strongly truncated or totally truncated

the use of linked or parallel diversion ponds is recommended (HUet, 7970).

The type of soil the pond is constructed of is crucial. Thesoil must

have the characteristic of water retention. This usually requires a mini-

mum clay content of 25%. Fertile soils are naturally preferred, but mar-

ginal soils that are unsuitable foragriculturial use can be utilized by the

addition of fertilizers and lime (acidic soils). Mineral content of tile

soil should be examined. A high salt content can be deleterious to the

culture of some species. Previous use of the land should be known. If

pesticides were used the area may be unsuitable or require considerable

leaching to remove the pesticide residue.

The width of the dikes depends on their use other than retaining the

water. If vehicle access is required the width should be at least 6 m at

the base and 3 m at the berm. Dikes separating ponds running parallel to

each other can be of a reduced width if they are not intended for vehicle

passage.

The slope of the banks varies according to the size of the pond. For

ponds of the 0.1-1.0 ha size, an inside slope of 1:2 and an outside slope

of 1:1 is recommended*@ Larger ponds require a 1:3-1:4 slope. The main

purpose of sloping the banks is to reduce erosion of the banks by water

movement. The dike height should be at least" 30 cm above the surface of

the pond water. Water level inside the pond should be 0.7 to 1.2 m deep.

Historic review of maximum flood water height should be made, with the sub-

sequent construction of the dike height to prevent entrance of flood waters

into the pond. The addition of a grass with good soil retaining capabilities

is also recommended as a cover and soil binder to extend the life of the

banks. The planting of vegetation with large woody root systems is dis-

couraged since this weakens the dikes and facilitates leakage.

The pond bottom should have a slope of 0.2 to 0.5% towards the drain.

It should be uniform in construction with no pot holes or roots remaining,

It should also be compacted if possible while being bulldozed. A collec-

tion basin may be constructed at the drainage site. This basin should not

exceed 10% of the pond area. The pond should be capable of complete drain-.

age to facilitate eradication of undesired sDecies, control of disease

problems, and. mineralization of the bottom soil.

Water addition to the pond is done at the end opposite to the drain.

Dispersion of water is in a manner to prevent erosion of the bank and bot-

tom. Aeration is accomplished by splashing or spraying the water as it

enters the pond. The water.-source should be screened sufficiently to prevent

introduction of unwanted species. It should be free of pollution, also.

Drains (e.g., sluice gate, monk, stand pipe) also vary in design and

construction. However, the basic functions are to control water level

(overflow), prevent escape of cultured fish (also introduction of undesired

species from drainage canals), and to allow complete drainage of the pond.

The preferred flow of water out of the pond is in such a manner that the

bottom water is drained. Each pond should have its own drainage system

that empties into a drainage canal. It is ill-advised to link ponds through

the drainage, s ince this decreases management efficiency, and also increases

the possibility of spreading of disease through all the ponds.

Culture of species in impoundments where a stagnant water flow method

is used would impose the least direct burden on the environment due to its

limited discharge (except during complete harvest). In addition it requires

the least amount of water resources to maintain the system.

Flow-through systems for species requiring a very high water quality

or so intensely stocked that a continual flow is necessary to maintain basic water

quality requirements would be a means of culture that adds a continual and

often substainal quantity of waste water.

Raceway Culture

Raceways are designed to allow a continuous large flow of water through

the enclosure to facilitate flushing of wastes, maintenance of high oxygen

leVels, and in the case of circular designed raceways, the movement with

the current of species of fish that tend to continually swim. Raceways

are commonly used in trout and channel catfish (Ictalurus punctatus) culture.

Due to the high water quality maintained in raceways, the stocking density

is greater than that used in ponds, thus givinq a higher production per

unit area.

The application of a raceway to the culture of aquatic.organisms

can be diverse. Culture of filter feeding organisms (e.g., oysters) is

feasible with the introduction of a water source containing a high density

of planktonic food organisms. The system can be of an open or closed

circulation type with flow rates suited to optimize delivery of food organ-

isms, removal of waste products, and maintenance of desired oxygen level.

The Dractice of polyculture is feasible within a raceway system as demon-

strated by Ryther (1975) in the production of fish (Pseudopleuronectes

atrer-icanus , shellfi"Sh (Crassostrea.virginica, Miercenaria mercenaria),

lobster (Homarus amp@ricanu
L' _ js , and macro-algae (Gracilaria foliifera,

Agardhiella tenera) within a raceway system.

Raceway culture is a sophisticated capital intensive means of aqua

culture. Its use on Guam could be applied to both fresh and marine-cultured

species. However, the requirements of large water volume flo w through a

raceway would limit its use, especially for freshwater, unless the

water is filtered and recycled.

Floating Cage Culture

This method of culture originated in Cambodia,and has spread through-

out the'Mekong River system. Modified versions are used in the culture of

numerous species both in fresh and marine waters throughout the world.

Cage,culture allows the utilization of an existing body of water
(lake, river, ocean) for the culture of species that will tolerate intense.

stocking in a confined space. This method of culture has the advantage over

pond culture of usually requiring less initial capital investment. Oper-

ational expense can also be less (e.g.,, no water pumping expense); however,

the life expectancy is less than that of a pond. Frequent cleaning of algae.
growth from the cage is necessar y to prevent obstruction of water circu-.

latibnn.which is necessary to flush wastes and renew oxygen levels.

Greater stocking densities are usually practiced in cages than ponds.

Thus a species to be suitable to this type of culture must tolerate crowding.

Examples of species that are used in cage culture are @anq@ ius sutchi,

carp, sea bass,grouper, and red snapper.

The sizes of cages vary from a cubic meter to 625 cubic meters, which

are essentially floating cages upon which the entrepreneur lives in a hut.
A practical size range for use on Guam would be 10 m 3 to 200 m3. A cage can

be constructed of a number of materials, but the type that would be suit-

able to Guam would basically consists of a framework forming the structural

shape of the cage, around which a netting material is attached to form the

enclosure. This structure is attached to floating devices, or fastened to

poles secured into the substratum where a tidal fluctuation does not occur.

The net must extend beyound the water surface sufficiently to prevent the

escape of the fish or introduction of,undesired species. In cases with

species that tend to jump (e.g., Pangasius sutchi) netting must be extened

over the top.

On Guam, the utilization of cage culture can contribute very substan-

tially to the total aquaculture production. For example, obtaining the

use of a portion of Fena Lake for the purpose of fish cage Culture would

be*a productive means of utilizing an existing asset. Possibly,-.a cooper-.

ative venture could be arranged with the Navy, who ,.-controls the lake. In

addition, it could be used to augment production within dammed areas ad-

jacent to large fish culture operations. This culture method would be

very applicable to marine species also. In most cases this being the pre-

ferred means, since it does afford a higher degree of management as compared

to penning in an area of a reef flat. However, the use of cages in the

marine waters would require that they do not obstruct passage of vessels.

Areas where this might be practiced would be Apra Harbor and Cocos Lagoon.

Raft and Stick Culture

Raft and stick culture methods are used for oysters and mussels.

Stick culture being limited to shallow water. Oyster spat that have

settled on collector shells are attached to a stick which is anchored

into the substratum. This method of shellfish culture is susceptable to

predation by benthic organisms and aerial exposure due to tidal fluctua-

tion.

The raft culture method is more productive per area and a more man-

ageable means of culture. This consists of a raft constructed of cross-
members (u.sually wood) which are floated (e.g., attachment of 55 gallon

oil cans). From the crossmembers are hung the culture lines. The materials

used for construction and design vary.

ENVIRONMENTAL IMPACT DUE TO AQUACULTURE PRACTICES

AND

POLLUTION ABATEMENT MEANS

Intensive culture of aquatic species within ponds or other enclosures

with the addition of fertilizers and supplemental feeds results in the pro-

duction of large quantities of wasteproducts both directly from the cultured

species and from biological activity associated with this eutrophic envir-.

onment. The discharge of this effluent into receiving waters can be a con-

siderable pollution source, if not properly managed. Since the pond can

be considered as a point source of eutrophication, pollution abatement

measures must be designed into the system. The costs of these abatement

measures can become the limiting factor in the viability of an operation

and'deserves careful examination by the entrepreneur. Three broadly grouped

categories of polluting factors from the effluents of fish culture activ-

ities are recognized (Hinshaw, 1973). The first category includes the@

passing of pathogens and parasites into natural waters from hatcheries o'r'

ponds. The close proximity of species during culturing facilitates the

transmission of disease. A second category is the prophylactic or thera-

peutic use of chemicals and drugs to control diseases and parasites. These

can be introduced directly into the impoundment or through the feed. The

third group are factors that affect the chemical or physical water quality

of the recieving waters. Metabolic wastes from the fish, unused food,

algae, and detritus from ponds can have adverse affects on the receiving

waters. Increased biochemical oxygen demand, carbon dioxide, ammonia,

nitrate, and nitrite levels would be associated with this ef fluent. The

31j

dissolved and suspended solid level would also contribute to the pollution

factor of the effluents.

Water pollutants may alter natural conditions by reducing the dissolved

oxygen, by changing the temperature, or by direct toxic action that can

be lethal or more subtly, can affect the behavior, reproduction, and physi-

ology of the organisms. Although a substance may not directly affect a spe-

cies, it may endanger its continued existence by eliminating essential

sources o,f food and metabolics. FurIll-hermore, conditions permitting the sur-

vival of a given organism at one stage of its life may be intolerl-ble at

another stage.

Physical alteration of the environment during construction and the

resulting physical structure of aquaculture ponds can cause a lasti-ng effect

on the biological community by altering water flows and circulation, es-

pecially in estuary areas where blockage of large sections can prevent

flushing (Odum, 1970; Copeland, 196-0). Effective planning to allow for

natural circulation is needed or -the addition of an artificial circulation.

Alteration or destruction of estuary areas, that may serve as a nursery

for numerous species, may secondarily affect sport or commercial fisheries

by reducing the natural stock. As with any construction envolving the

grading or moving of earth the potential for sedimentation is increased.

Pollution Parameters

Water pollution is'defined by Warren (1971). as any impairment of the

C 4
suitability of water for any of its benefi lal uses, actual or potential,

by man-caused changes in the quality of the water. A more workable defini-
tion, limiting effluent.discharge, is used by the Guam Environmental Pro-

-11-ection Agency as the water quality below the discharge point must be equal

to or better than that above the discharge.

Parameters and their effects contributing to water pollution of the

receiving waters of fish pond effluent are as follows:

Nitrates

Nitrates are the most highly oxidized phase in the nitrogen cycle.

They can reach high concentrations during biological oxidation. High

concentrations are indicative of organic pollution. Nitrate concentration

in natural waters usually rtanges from 0.5-5.0 PPM (Hutchinson, 1957).

Nitrates are the most usable form of nitrogen for plant growth. Generally

an increase in nitrates is followed by an increase in algal production

and an increased productivity of the whole ecosystem. However, an increase

of nitrate level beyond 20 PPM has detrimental effects for fish culture

(Spotte, 1970).

Nitrite

Nitrite is an intermediate of the nitrification process (ammonia-nitrite-

nitrate). It can accumulate during the development of nitrifying activity,

due to elevated ammonia levels, or when the normal nitrification path is

interrupt ed, for example, by addition of chemotheraputics to the water.

Nitrite can be toxic to fish by means of reducing oxygen transport efficiency

of the blood resulting in hypoxia in extreme cases. The nitrite oxidizes

hemoglobin to methemoglobin which is incapable of releasing oxygen on

demand (Smith and Russo, 1975). Lethal levels for nitrite range from
0.14-0.55 mg NO 2- N/1 (Forster et.al., 1977). Concentrations as low.as

0.096 mg/l NO showed a small, but significant increase of methemoglobin
2
in trout which were exposed for 8 days (Smith, 1975). A LC 50 of 0.23 mg
NO 2-' N/1 was found for trout (Brown and McLeay, 1975).

Ammo n i a

Ammonia originates from mineralization of organic substances by bacteria

and from excretion by fish. Unionized ammonia is very toxic to fish and

should not exceed 0.1 PPM. Toxicity varies by the concentration of undisso-

ciated ammonium hydroxide in the water, which in turn is a function of the

pH and temperature. Spotte (1970) notes that even at sublethal levels

ammonia will have four adverse effects to fish populations: (1) increased

susceptibility of fish to other unfavorable conditions such as low oxygen,

(2) inhibited normal growth, (3) decreased fecundity, and (4) decreased

resistance to disease. High levels affect the gill tissues and reduce the

ability of hemoglobin to combine with oxygen. High, but nonlethal, ammonia

concentrations will cause extensive proliferation of eithelium .@.,hich preve nts

normal respiration (Smith, 1972). Spotte (1970) sites chronic ammonia

levels as the most serious problem that the fish culturist must deal with.

Settleable and Suspended Solids

Settleable solids and suspended solids can be organic or inorganic in

origin. They have a greater effect on fish populations in a natural en-

vironment than in fish ponds where artificial feeding occurs. Light pene-

tration would be limited, thus reducing algal growth which is the basis for

the food chain. In aquaculture, the suspended solids may cause a buildup

of sludge on the bottom, consisting mainly of the remains of plankton

which decompose and@increase the BOD in the pond. High loads of suspended

solids may cause gill tissues to be affected and should remain below 80 PPM

for optimum health in fish culture (Wedemeyer and Wood, 1974). The com-

position of suspended particles in surface waters are important because

of their effects on light pene-tration,.temperature, soluble products, and

aquatic life. The mechanical or abrasive action of particulate material

is of importance to the higher aquatic-organisms, such as mussels and

fish. Gills may be clogged and their proper functions of respiration and

excretion impaired. Blanketing of plants and sessile animals with sediment

as well as the blanketing of important habitats, such as spawning sites,

can cause drastic changes in aquatic ecosystems. If sedimentation, even of

inert particles, covers substantial amounts of organic material, anaerobic

conditions can occur and produce noxious gase s and other objectionable char-

acteristics, such as low dissolved oXygen.and a decrease in pH. Odui-9 (1974)

sites the increase of sedimentation under rafts, mainly due to feces and

pseudofeces, in the case of oyster culture.

Biochemical Oxygen Demand

Biochemical oxygen demand is the quantity of oxygen required for the

biochemical oxidation in a given time at a given temperature of organic mat-

ter. The introduction of effluent with a high BOD into a stream puts an

excess burden upon it. This type of pollution can be very destructive

when relatively large amounts of putrescible organic materials, which require

oxygen for their decompostion, are introduced into the waters. The oxidation

is dependent upon the availability of dissolved oxygen in the waters and

the ability of the body of water to maintain this oxygen level'above the

BOD through exchange with the atmosphere and the photosynthesis of algae.

If the dissolved oxygen falls below that required by the BOD loading, an-

erobic conditions arise.

Toxins

Since we are dealing with the culture of organisms, the use and occurr-

ence of toxins are avoided. Usually the only time a toxin is introduced

into a pond is after drainage. However, a class specific toxin may be

used during culture to rid the pond of pest species (e.g., fish from prawn

culture ponds). A fish toxin may be introduced to eliminate undesira.ble

species that may remain in small bodies of water or the mud/water interface.

This should be held in the pond for the prescribed period of time for

deactivation of the toxin before refilling or further discharge. The

addition of chemical oxidants can speed,up this process. Careless use of

the toxins with its entry into the receiving waters can cause large fish

kills. Trained personnel should be available for"supervision during the

administration of toxins. Toxins from tank culture systems can include

algacides, and chemicals used in cleaning the tanks.

Coliform

The quantity of coliform bacteria is a standard means of indicating

pollution levels. Coliform bacteria (Escherica coli'and similar gram

negative bacteria) are normal inhabitants of fecal discharges from warm
blooded animals. Total coliform counts can be mi'sleading since certain

coliform bacteria occur naturally associated with various vegetation. The

Guam Water Quality Standards specifies fecal coliform counts as a standard

testing of Guam's waters for pollution. The presence of fecal coliform is

used to indicate a degree of pollution (possible presence of human Datho-

genic organisms) in waters; however, since fecal coliform is restricted

to warm blooded animals this is nQtrelevant as a pollution indicator from

fish ponds. As previously mentioned, the use of a total coliform count also

is not a reliable indicator of pollution.since certain species of coliform

bacteria occur, naturally in the environment. Certain coliform bacteria are

part of the natural nitrification process, and.most likely due -to the increase

in ammonia (metabolic waste) within fish ponds, the presence of this coliform

bacteria will increase.

If it were possible to monitor a common intestinal bacteria restricted

to fish, this would be more suited as a pollution indicator from fish

ponds than fecal or total coliform counts. The monitoring of Other para-

meters (e.g., ammonia, nitrate, phosphate) will-be a more useful guide to

the degree of pollution a fish pond contributes to the receiving waters.

Study of Hatchery and Pond Effluent

A study conducted at six hatcheries in the United States showed a

degradation due to hatchery effluent of the receiving waters (Hinshaw, 1973).

Of the parameters tested, ammonia (major nutrient contributing to the efflu-

ent), BOD, MPN coliform, and suspended solids were the factors contributing

significantly to a change in the receiving waters. A correlation was

found with the water quality above the discharge point ItO that below. A

high quality water showed degradation less than in water of lower ini tial

quality. Waters with a high degree of enrichment prior to use resulted in

hatchery effluents that were considered a possible public health problem.

Contrary to this, waters of high quality, prior to hatchery use did not

significantly degrade receiving waters below the discharge point. In

general, hatchery effluents showed a significant increase in MPN coliform

counts, which could pose a potential public health hazard (Hinshaw, 1973).

BOD levels were increased significantly, which were mainly attributed to

the use of animal offal or wet feeds that were not consumed. The enrich-

ment of the receiving waters by hatchery activities has increased the

growth and propagation of many fish food organisms and supplementally in-

creased the fish population supported by the waters. This could be con-

sidered a desirable affect depending if the species of fish were of use

to a sport or commercial fisheries. However, the number of pollution in-

tolerant benthic species tended to decrease. In contrast, the organic

enrichment, from a water quality and public health stand point may not be

desirable.

Data recorded by Aquatic and Wildlife Resources (FitzGerald, 1975) for

the parameters of nitrate and phosphate sampled from their demonstration

.ponds and the water Supply Source (Talofofo River) indicate a significant

(p = 0.05) increase in phosphate in the pond waters over the river water

supply source (Table4). However, nitrate levels showed no significant in-

crease, and actually a slight decrease (not significant) in pond 2 as

compared to the river. This lowered nitrate level reflects its uptake

by the phytoplankton and macroalgae populations within the ponds. Pond 2

illustrates to a certain extent the efficiency of the use of a stabiliaz-

tion pond in pollution abatement. The operational proceedure of Aquatic and

Wildlife Resources personnel was to supply pond 2 with sufficient water

to maintain the water level by siphoning water from pond 1. Occassionally,

when additional water was needed or adverse conditions arose within pond 2

Table 4 Nitrate and Phosphate Values from Aquatic and Wildlife Resources
Experimental Ponds and Talofofo River (FitzGerald, 1975).

Pond I Pond 2 River
mg/ I mg/1 mg/l mg/l mg/l mg/l
Date Nitrate Phosphate Nitrate Phosphate Nitrate Phosphate

10/1/74 0.200 0.300 0.140 0.240 0.430 0.192

10/8/74 0.360 1.200 0.260 0.330 1.230 0.470

10117174 0.150 0.730 0.120 0.310 0.170 0.320

10/21/74 0.140 0.290 0.060 0.240 0.210 0.190

10/30/74 0.330 0.800 0.070 0.340 0.330 0.640

11/4/74 0.940 1.390 0.210 0.410 0.820 0.530

11/20/74 0.222 0.258 0.249 0.444 0.167 0.228

12/3/74 0.610 1.529 0.249 0.944 0.167 0.159

12/20/74 0.360 0.241 0.167 0.797 0.222 0.228

1/3/75 0.332 2.133 0.277 1.034 0.250 0.334

3/10/75 0.332 1.588 0.222 0.419 0.111 0.119

4/4/75 0.279 0.719 0.580 0.211 0.049

5/4/75 1.387 2.280 1.218 0.419 0.775 0.089

n 13 13 13 13 13 13

x 434 1.035 .294 .476 .384 .273

water was pumped directly from the river. The data illustrates a reduction

of nutrients (nitrate and phosphate) in pond 2 as compared to pond 1.

Pollution Abatement

Various means of minimizing the impact of aquaculture effluents on

the environment are by -trickle filters, sand filters, stabilization ponds,

irrigation and spraying of crops.

Advanced waste treatment may be physical, biological, chemical or a

combination of these processes. Wastes from aquaculture can be treated by

the same means as sewage waste water is handled. Biological secondary

treatment is the most economical and most satisfactory means of processing

waste water (Parker, 1975). Disposal sources of waste water include fresh

water, oceans, underground injection, land surface, and reuse.

Trickle Filters

Utilization of trickle filters would be restricted by economics to

sophisticated compact aquaculture systems such as hatcheries, raceways,

and systems where recycling is used. A trickling filter makes use of a

natural cleansing system in which nitrification occurs by biological means

(biological oxidation process). It consists of a bed of inert material

(oyster shells, gravel, plastic material) on which an aerobic growth of

organisms (algae, fungi, bacteria, protozoans, worms, and insect larvae)

grow. Waste effluent is trickled from above through the filter. Wastes

are removed by the biological community within the filter. This type of

filter does not mechanically strain the effluent since the space between

the filter media is relatively large (45% of total filter volume) to

-low gaseous exchange and rapid flow. Factors influencing the ability of

the organisms in the film to assimilatethe organic matter depends on

the flow rate, organic loading aerobic conditions, and temperature.

Sand Filters

Sand filters, especially slow sand 'filters, can be used in-improving

the water quality of pond effluent. A sand filter consists of a layer of

sand 2-5 ft deep of 0.25 to 0.35 ml in effective size, underlain,by gravel.

Drainage is usually be perforated pipes laid under the gravel bed. Flow

of the water through the filter is by gravity. Mechanical and biological

cleansing of the effluent occurs within the filter. Flow rate is approxi-

mately 2.5 million gallons per acre of filter area per day. Higher flow

rates can be obtained with pretreatment of the effluent such as sedimentation.

The upper layer of the filter after a period of operation (varying with the

effluent) must be scraped off to prevent excessive clogging and reduction

of the filter efficency. The filtered water can then be recycle@d to the

pond, which reduces its total requirement from the water Supply, or it

can be drained to the receiving waters if reuse is not desired.

Rapid sand filters require pretreatment of the pond effluent @.,Jth

coagulants (e.g., aluminum sulfate, ferric chloride, ferric sulfate,

ferrous sulfate, and sodium aluminate) and sedimentation. Flow rates

are 125 million gallons of water per acre of filter surface per day

(Ehlers and Steel, 1965). The filter media consists of a gradation in size

of sand (0.4-0.8 ml effective size) 20 to 30 inches (50 to 76 cm) thick

underlain by 16 to 24 inches (41 to 61 cm) of gravel (1/8 to 2 1/2 inch

diameter). The sand filter consists of a tank, the inlet, the underdrain

system (perforated collecting pipIes) filtering medium, rate of flow con-

trollers, and loss of head gauges.

Spray Irrigation

Spray irrigation systems are designed so they can take primary

treated waste water. The water can be taken directly from fish ponds or a

stabilization pond. This means of disposing of the effluent is most suit-

able where agriculture crops and aquaculture are done together. The nutri-

ent enriched waters from the fish ponds serve as fertilization to the

agriculture crops with no additional costs thus, best utilizing the resources.

This would be a highly preferred method of effluent control from fish ponds.

Canal irrigation can be used to augment the spray irrigation for crops

for which this method would be preferable.

Stabilization Ponds (Oxidation Ponds)

The employment of stabilization ponds to effluent from fish ponds,

prior to its discharge back to the receiving waters, can be an effective

means of reducing BOD, nutrient levels, and suspended matter to acceptable

EPA standards. The stabilization pond basically consists of an impoundment

of water (less than 5 ft deep) that is held for a period of time to allow

the breakdown of waste materials through biological processes and a final

uptake of nutrients by algae. The period of holding varies with the BOD

loading. A decreased holding period can be obtained by added aeration

(mechanical) to the waters. Tsai (1975) points out the efficiency of

using a final pond for effluents in general. In periods of water shortage

this water can then be recycled to the fish ponds.

The basic concept behind the stabilization pond is that it allovis

the suspended matter to settle; waste material is decomposed and fed upon

by bacteria and zooplankton; sludges produced are degraded by faculative

anaerobes, including bacteria, protozoa, insects, and worms; nitrification

of ammonia wastes products, uptake of nitrates, carbon dioxide and other

plant nutrients is done by algae. The further addition of suitable fish

species can convert the algae and benthic fauna into a final marketable

product (helping to defer construction costs).

In areas where a large quantity of flat unutilized terrain, adjacent

to the ponds, exists; it can serve as a simplified evapotranspiration system

along with a leaching field of the effluents. However, since land is usually

at a premium on Guam this would be an uneconomical use of the land.

Wastewater Addition To Fish Ponds

The use of fish ponds in the purification of sewage water has been

noted by numerous authors (Schuster et.al., 1954; Schroeder, 1975; Schroeder

and Hepher, 1976; Woynarovich, 1976). Light loads of either organic-rich
raw sewage or nutrient-rich biological treatment (secondary) effluent can

be channeled through aquaculture systems which would essentially be an

extension of the waste treatment process and simultaneously derive an

economic benefit. Limiting factors to the use of aquaculturein waste

treatment would be the presence of toxic chemicals, petroleum, metals,

and pathogenic organisms above an acceptable level. Properly treated

(filtered, settled, and diluted) sewage water that does not contain signif-

icant poisonous industrial pollutants is a suitable mediUM for fish

culture. Fish culture associated with duck, chicken, and Dig rearing as

the source of fertilization is common in Countries throughout the world,

and is an effective Solution to domestic animal waste management problems.

This is mainly an Asian fish culture practice, but is also a long practiced

method in Europe (Bardach et. al., 1970; Woynarovich, 1976) and Israel

(Schroeder and Hepher, 1976); and is used on experimental bases in the United

States (Buck et.al., 1976). Odum (1974) also sites a stud in Israel;
y

fish ponds serve as nutrient traps where most of the organic compounds

are either precipitated, lost to the atmosphere, bound by the sediments,

or tied up in fish flesh so that a minimum amount of nutrients leaves the

ponds. The amount of sewage that.can'.be put through a pond is determined

by maintaining the BOD level at a safe point to prevent oxygen depletion.

Daily rates of sewage addition can be inexcess of 1.5 tons/ha. These

sources of nutrients serve to enhance primary prodution along with a fauna

associated with eutrophic conditions. The mineralized portion of the

manure provides nutrients to the phytoplankton while the non-mineralized

portion serves as a food base for zooplankton. This food source is in turn

utilized by the stocked fish population (usually Tilap_La or carp). Util-
ization of carp in the treatment of nutrient'-enriched waste waters is prac-

ticed in Indonesia and Germany (Bardach et.al., 1970). The carp feed on

the natural productivity of the waters. Recent studies (Carpenter, 1974;

Coleman et.al., 1974; Goldschmidt, 1970; Schroeder, 1975) have indicated

that fish improve the waste treatment capacity of pond systems. Utilization

of fish ponds for this purpose on Guam is feasible. They also have been

used in effluent wastes from dairies, sugar mills, slaughterhouses, and

starch mills. Part of pond ecology and proper management is the use of

species to utilize excess food thus affecting reduction of pollution,

improvement of pond environment, and greater production. Yiel'ds bf.fish

grown in such ponds, with no supplemental feeding, have been as high as

4000 kg/ha/year (Schuster eICI.al., 1954; Schroeder and Hepher, 1976).

Public Health

Fish may serve as a passive carrier of infectious human diseases

such as Salmonella, Vibrio parahemolyticus, Shigella, or other enterobac@-

teria (Janssen, 1970; Guelin, 1962; Buttiaux, 1962). The occurence of

these diseases from fish caught in polluted waters was noted by Shewan (1962).

However, the pathogens are confined to infecting the gut of fish (Allen,

Busch, and Mlorton, 1976), so that with proper precaution in preparation of.

the fish this possible hazard could be eliminated. There is danger of

introducing Schistosomiasis as had happened in the Caribbean (Odum, 1974).

With rapid air transport of live aquatic species from tropical areas the

survival chances of waterborne stages of flukes and other pathogens has

increased (Courtney and Robins, 1975). The limited knowledge in this area

(Sonstegard, 1975)will require further research as aquaculture expands..

Exotic Species

The introduction of exotic species for the purpose of aquaculture is

often a necessity in establishing a viable aquaculture industry; however,

cardidate species for introduction should be carefully examined in regards

to their ecology, behavior, reproduction, andmarketability. Indescriminate

introduction can lead to the detriment of the endemic species and possibly

their elimination in addition to threats to established culture species

(Allen, 1949; Frankenberg, 1966; Lanchner et.al., 1970; Buckow, 1969;

Idyll, 1969).

Some detrimental effects that may result from the introduction of

exotic species are; reduced growth of introduced species due to less

favorable environmental conditions than those found in their indigenous

area, a population explosion of the introduced species leading to competion

with, and possible elimination of native species, introduction of ne@.'l

pests, diseases, and parasites harmful to resident species, and destruc-

tive activitities of the introduced species affecting other fields of

economic interest (e.g., common carp in the U.S.) (Rosenthal, 1976).

ROLE OF AQUATIC AND WILDLIFE RESOURCES

The Division of Aquatic and Wildlife Resources should continue to

play an instrumental part of the developme nt and support of an aquaculture

industry on Guam. Aquatic and Wildlife Resources initiated investigation

into the prospects of aquaculture on Guam in 1973. The initial phase of

the program dealt with the investigation into feasible species for culture

on Guam with experimental-demonstration ponds located on the Talofofo

River. The second phase consisted of assisting in the establishment of

commercial ponds with extension set-vice provided to the entrepreneur.

This is continued into the present program with the addition of the pursuit

in establishment of a hatchery on Guam, so that Guam can become self-

sufficient in production of the major Cultured species juveniles.

All importation of live fish (including crustaceans and turtles)

requires a permit which is issued by Aquatic and Wildlife Resources. Ship-

ment of species from foreign countries (outside U.S. and T.T) requires,

in addition to the Aquatic and Wildlife Resources permit, a permit issued

by the Federal Fish and Wildlife Service for some species. This system

is intended to screen out the introduction of undesireable species and

species originating from countries that have a high disease occurence or

the presence of a disease that does not occur on Guam that might be carried

by the introduced species. This also can restrict importation of species

that might be detrimental to established aquaculture species.

The introduction of a large number of exotic species to Guam would

be ill-advised; however, the major species.that will be most suitable for

aquaculture will be exotic to Guam. The utilization of species which have

proven -their success as a culturable species should have priority for

examination of their potential on Guam. This usually involves an extensive

degree of technical and practical knowledge available on a species culture

and careful selection weighing all the pro and con arguments both concern-

ing its economic and biological impact. This regulatory and research func-

tion will have to be mainly full filled by the Aquatic and Wildl i fle Resources

Division. However, an interagency screening committee consisting of the

Guam Environmental Protection Agency, Univer sity of Guam Marine Laboratory,

and Aquatic and Wildlife Resources, should be formed to review all new

introductions.

For the aid in inforcement of an affective environmental protection

program the Aquatic and Wildlife Resources should keep the Guam Environ-

mental Protection Agency aware of scheduled large discharges (e.g., during

harvest). This allows for the proper monitoring of effluents. In addition,

Aquatic and Wildlife Resources should oversee application of toxic sub-

stances to fish ponds.for the purpose of elimination of pest species.

Potential farmers should be advised of requirements and permits required

from other agencies. The construction of the aquaculture 'facilities should

be observed by Aquatic and Wildlife Resources along with other appropriate

governmental agencies to assure that excessive abuse of the environment

does not occur.

Aquatic and Wildlife Resources in conjunction with the Public Health

Department, should screen all im.ported aquatic species coming from areas

that infectious diseases can be carried by fish (fish or human pathogens).

This could consist of impounding in concrete tanks and treating with proper

prophylatic drugs. Specimens that are obviously diseased should be destroyed.

If local facilities were available for the propagation of these preferred

culture species then this would eliminate the need for importation and its

possible accotiipanying health problems.

CONCLUSION

Guam has the climatic and physical conditions for the development of

a diverse and productive aquacultUre industry. This potential, needs -to

be recognized by both governmental agencies and private entrepreneurs, so

that proper and well-planned development can proceed.

A state program should be drawn up to cover the development of aqua-

culture and its supportive facilities (laws, policies, and administrative

procedures) to encourage its development. In addition, the over-seeing
of environmental protection measures should be realisticall.y enforced to

prevent abusive use.of Guam's waters. Decisive effort is needed to Put

into operation a viable aquaculture program that is consolidated into a

workable industry that will.attract the businessman/farmer into this new

industry on Guam.

The governmental agencies involved in this formation of a state program

should be limited to those directly concerned with the functional oDeration

of an aquaculture industry, thus preventing an over diversification of

authority, which would hinder development.

AC KNOWLEDIGIEMENT S

I would like to acknowledge Ken Morphew of the Guam Environmenilal Pro-

tection Agency for his very helpful assistance. I also appreciate the assis-

tance and information provided by Chuck Huxel and Otto Vander Brug of the

U.S. Geological Survey and Water Resources office. Alex Chan's assistance

in mapping is great)y appreciated.

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Bardach, J.E., J.H. Ryther, and W.O. McLarney. 1972. Aquaculture. The
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Brown, D.A., and D.J. McLeay. 1975. Effect of nitrite on methemoglobin
and total hemoglobin of juvenile rainbow trout. Progressive Fish
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Bryan, P.G., B.B. Madraisau, and J.P. McVey. 1975. Hormone induced
and natural spawning of captive Siganus canaliculatus (Pisces: Sigan-
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Buck, D.H., R.J. Baur,,and C.R. Rose. 1976. Experiments in recycling
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Buckow, E. 1969. Exotic: New threat to U.S. waters. Field and Stream.
May: 16-28.

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Courtnay, W.R., and C.R. Robin. 1975. Exotic organisms: An unsolved com-
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Deveau, L.E., and J.R. Castle. 1976. The industrial developmen t of
farmed marine algae: the case history of Eucheuma in the Philippines
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Dickinson, R.E. 1977. The occurrence and natural habitat of the mangrove
crab Scylla serrata (Forskal), on Ponape and Guam. Master of Science
Thesis, University of Guam Marine Laboratory.

Ehlers,V.M., and E.W. Steel. 1965. Municipal and rural sanitations.
McGraw Hill Inc. New York 633p.

FitzGerald, Jr., W.J. 1975. Potential of aquaculture on Guam. Annual
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1976. Ecological parameters effecting the optimim growth of Enter-
omorpha clathrata. M.S. Thesis. Univ. of Guam.

Forster, J.R.M., J.P. Harman, 'and G.R. Smart. 1977. Water economy its
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Frankenberg, R. 1966. Fishes of the family Galaxiidae. Australian
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Fujimura, T. and H. Okamoto. 1970. Notes on progress made in developing
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FAO Indo-Pacific Fisheries Council, Bangkok.

Goldschmidt, Y. 1970. Water quality management of the Israeli national
water system. In Developments in water quali-Ly research, ed. H.I.
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the skipjack fishery in the Pacific region. FAO Technical Conference
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Guelin, A. 1962. Pollut ed waters and the contamination of fish. In
Fish as food, Vol 2. Nutrition, sanitation, and utilization. Ed.
G. Borgstrom. New York, Academic Press. 481-502.

Hinshaw, R.N. 1973. Pollution as a result of fish cultural astivitie.s.
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1974. Potential effects of aquaculture on inshore coastal waters.
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Personal Communication

Brohmanonda, P. Chief, Songkhla Marine Fisheries Station, Songlkhla, Thailand

Huxel, C. U.S. Geological Survey and Water Resources, Guam

Nukit, T. Department of Aquaculture, Fac. of Fisheries, Kasetsart University,
Bangkok, Thailand

Ong Kah Sin. Senior Fisheries Research Officer, Ministry of Agriculture,
Glugor, Penang, Malaysia

Wongsomnuk, S. Fisheries Technologist, Songkhla Marine Fisheries Station,
Songkhla, Thailand

Figure 1. Map of Guam showing areas having suitable terrain and soil type
for aquaculture. The uncircled number indicates the soil type, while
the circled number corresponds to the paticular site listed in Table 1.
Major marine sites suitable for mariculture are also indicated. Refer
to -text for further details.

Legend: Soil Types (Tracey et.a.., 1959)

2 Toto Clay: Brown to pale-yellow, firm plastic, slowly permeable,
acid clay with reddish stains (GrIumusol); ranges 5 to 30 feet in
depth and averages 10 to 20 feet; has very high shrinkage and eA--
pansion (large cracks in dry season; depressions ponded in wet
season); prevailing surface gradient I to 8 percent.

3 Chacha-Saipan Clays: Yellowish-brown, firm clay (Chacha), and red,
firm clay (Saipan); neutral to acid reaction; Latosolic intergrades.
These soils with concave survaces they are 10 to 60 feet deep; pre-
vailing surface gradient I to 8 percent.
6 Atate-Agat tlay: Remnant benches or small mesas of an old red, gran-
ular, porous, acid Latosol (Atate clay) with deep, reddish, mottled,
plastic to too hard clay C horizon, pale yellow, olive, or gray in
lower part; and its truncated counterpart (Agat clay) with similar
C horizon of saprolitic clay, ranging in depth from a few feet to
about 100 feet and averaging about 50 feet; prevailing surface
gradient of Atate clay is 1 to 8 percent, and of Agat clay 8 to
15 percent.

9 - Pago Clay: Brownish, granular to firm and plastic Alluvial clay,
with gray mottling to within 914 to 30 inches of the surface; gen-
erally alkaline to neutral; soil depth is generally more than 10
and less than 150 feet; moderately well drained; subject to occa-
sional flooding; prevailing surface gradient I to 3 percent.

10 - Inarajan Clay: Similar to Pago clay but lower, wetter, and shal-
lower (thins out on coastal sands and bedrock); water table at or
near, the surface (within 30 inches) most of the time; poor drain-
age mottlings (gray) within 6 to 12 inches of the surface; depth
to sand or bedrock ranges from 3 to 25 or more feet; reaction is
alkaline in water saturated zone; poorly drained; frequently flood-
ed; prevailing surface gradient 0 to 1 percent.

11 Muck: Black to brown, soft muck and peat, with some clay and silt;
depth to underlying material (chiefly limesand or shelly clay)
ranges from 3 to 20 feet, averages 5 to 10 feet; alkaline reaction
below the water table, which is generally at or near the surface;
prevailing surface gradient is level or very nearly level.

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