Fishery independent stock assessment of Virginia's hard clam population of the Chesapeake Bay Final report, for the period September 1, 1994

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

Task 26 FINAL PRODUCT VM-RC@
FY 1993 Hard Clam Stock Assessment

FINAL REPORT
FOR THE PERIOD SEPTEMBER 1, 1994 - MARCH 31,1995
SUBMITTED TO:

THE VIRGINIA COASTAL RESOURCES MANAGEMENT PROGRAM

ATTENTION: LAURA MCKAY, COASTAL PROJECTS COORDINATOR

DEPARTMENT OF ENVIRONMENTAL QUALITY
P. 0. BOX 10009
RICHMOND, VIRGINIA 23240

SUBMITTED BY:
JAMES A. WESSON
CONSERVATION AND REPLENISHMENT DIVISION
VIRGINIA MARINE RESOURCES COMMISSION
P. 0. BOX 756
NEWPORT NEWS, VIRGINIA 23607

FOR THE PROJECT ENTITLED:
[FISHERY INDEPENDENT STOCK ASSESSMENT OF VIRGINIA'S
HARD CLAM POPULATION OF THE CHESAPEAKE BAY
o PTMOsp@,
DATE REPORT SUBMITTED JUNE 7, 1995

This Clam Stock Assessment Project was funded,
0
nom in part, by the Department of Environmental
Quality's Coastal Resources Management Program
through Grant #NA370ZO360-01 of the National
0 >
-4 Oceanic and Atmospheric Administration, Office of
0 Ocean and Coastal Resource Management, under
7Z the Coastal Zone Management Act of 1972,
as amended. The views expressed herein are
those of the authors and do not necessarily
reflect the views of NOAA or any of
Its subaqencles."
00
@A4ENT Of

ABSTRACT

The hard clam (Mercen aria mercenaria) is one of the most importnt commercial species

harvested in Virginia!s Bay waters. As the oyster and other commercially harvested species have

declined, a portion of the displaced workforce has joined the clamming fleet. Declining catches

have raised concern for both watermen and fishery managers; however, little current information

was available for either hard clam standing stock levels or age structure. The current project used

a fishery independent stock assessment method using a hydraulic patent tong sampling device to

survey hard clams in the James River-Hampton Roads area. When compared with results from

previous stock assessment estimates in this area, the current clam densities and standing stocks

were not obviously different. Age and size structure has changed since earlier studies, with less

larger and older clams in the current population. Declines in the commercial clarnmer's catch per

day may be explained by a decrease in the number of high density clam areas over the many years

of fishing. Today's clam populations may be more uniformly distributed, resulting in the

individual clarnmer catching less clams per day because in each patent tong grab there are less

clams and the physical limit on the number of tong grabs that can be handled on any one day.

A(XNOWLEDGEMENTS

We thank John Register and Calvin Wilson for boat operation and patent tong sampling; Gerry
Showalter, William Kuster, and Benny Stagg for map preparation; David Bower for sampling
assistance; and Kathy Leonard for report preparation, all from Virginia Marine Resources
Commission. We also thank numerous Virginia Institute of Marine Science students, Linda
Crewe, Tommy Leggett, and Lee Ferguson for their assistance with field sampling, under often
unpleasant weather conditions.

WrRODUCTION

The hard clam ercenaria mercenaria) is one of the most important commercial species

harvested in Virginia!s Bay waters. Annually since 1987, dockside values have varied from four

to six million dollars, with over a n-dilion pounds of meats landed each year. As the oyster and

commercial finfish resources have declined, the clam industry has absorbed some of that displaced

fishing effort (Figure 1, Table 1). There has been a doubling of the clamming workforce during

the: past 10 years and this added harvesting pressure on the clam resource has caused concern for

fishery managers at the Virginia Marine Resources Commission (VMRC). Catch figures indicate

an initial increase in harvest levels following the increase in the workforce; however, since 1990

there has been a decline in harvest and a decrease in the total catch per licensee. Anecdotal

information from watermen has also suggested that the fishermen are working longer hours with

more sophisticated equipment to catch the same or declining quantities of clams.

A clam management committee at VMRC is currently meeting regularly to discuss and

evaluate the regulatory changes necessary to protect the fishery participants and to stabilize the

claim resource. Options being considered include limited entry, minimum and maximum size limits

on clams, daily time and catch limits, and sanctuary areas. They have been unable to offer

significant suggestions for further regulation due partly to the lack of real data on clam stocks. It

is extremely difficult to propose and defend new regulatory efforts based only on catch figures

without having current information on standing stocks and age structure of hard clam populations.

This project was proposed to begin quantitatively assessing the current status of hard clam

resources in Virginia. We have been using a random sampling methodology, employing a

hydraulic patent tong to give a fishery independent stock assessment of oysters and we have

adapted this procedure to collect similar data for hard clams. Rather than proposing an

exhaustive survey to sample from all areas within the Bay, we have initially sought to provide

adequate comparative and baseline data for areas where management decisions are urgently

needed. Specifically, this project had three goals:

i) Assess the relevant clam survey literature from past projects in the Chesapeake

Bay and determine where direct comparisons could be made with current data on

clam population numbers.

ii) Map, produce sampling grids with randomly selected samples, and sample the

current clam populations on the areas that were identified in the literature search as

well as those identified by VMRC as important harvesting areas.

iii) Estimate the current stock densities, age, and size distributions of clam populations

for comparison to previous projects, and establish a baseline for evaluating the

effects of current or future management decisions.

WITHODS

A search of reports on Virginia!s clam resources uncovered several hundred locations that

had previously been sampled for clam densities (Haven, et al, 1973, Haven and Kendall, 1974;

Haven and Kendall, 1975; Haven, et al, 198 1; and Kvaternik, 1982). The stock assessment

methods varied in these reports, but all could be converted to an estimate for clams per acre or

total standing stock. Additionally, some of the reports had information on the size distribution of

clams at that time. Using these reports, our efforts began in the lower James River-Hampton

Roads area where past data was most complete and an important clam fishery exists today. The

entire Hampton Roads and lower James River area was mapped, and gridded with Loran

coordinates by the Surveying-Engineering Division of VMRC. Sample locations were randomly

selected and marked on a map at a rate of one sample for each 10 acres of submerged bottom.

Approximately 25,000 acres were plotted and 2500 samples selected for the area between the

Hampton Roads (1-64) Bridge Tunnel and the James River Bridge (Route 17), including most of

the Elizabeth and Lafayette Rivers. All potential clam producing areas were included, except for

areas that were leased by private individuals. Swnples were collected with a hydraulically

operated patent tong operated from the 42 foot fiberglass workboat, I B. Baylor. This type of

patent tong separates the closing action of the tong from the retrieval action. In our studies, this

has proven to be the most accurate method for consistent bottom penetration for sampling. The

open dimensions of the tong were such that it sampled I square meter.

On each sampling day, a crew of 6 or 7 people conducted the sampling operation. The

boat operator located the sampling location with a Northstar Loran which has been corrected to a

known location on each sampling day. At the sampling location, the tong operator lowered the

open tong to the bottom, closed the tong, and raised the sampling grab on to a sorting table on

the boat with the assistance of a second individual. The entire sample grab, including mud, shells,

and clams was processed by hand and running water by the other 3 individuals on the boat.

Water depth, bottom consistency, and the length, width, and height of all five clams and clam

boxes (emply clam shells with the hinge attached) was recorded. We had originally planned this

prcject for the summer months. Funding was only available in the winter and the sampling

process was somewhat more difficult than anticipated. We had estimated that we could sample

anti process up to 200 patent tong samples per day. The work on the boat was more difficult in

the cold and windy conditions of winter and with the cold water, the bottom sediments were

harder to sort than originally envisioned resulting in only 100 samples being processed per day. In

the 20-day sampling period, approximately 2000 samples were processed and more than 20,000

acres were surveyed. When it became apparent that we could only process 100 samples per day,

we concentrated on the most important areas of the Lower James and Hampton Roads and did

not attempt to go further in the Bay.

Clam numbers and sizes, as well as the bottom type and depths were archived in a custom

database program at VMRC. Clam densities were determined for the entire area and a map of

densities was generated. A subsample of clams in each density area was analyzed for the size

distributions.

RESULTS AND DISCUSSION

Mean densities of clams are presented in Figure 2. The highest densities of clams were in

the center, deeper areas of the lower James River between Newport News Point and the Hampton

Roads Bridge Tunnel. Areas were separated for presentation using a combination of depth,

density, bottom sediments and similar divisions in previous studies. A general description of

each individual area follows:

A. Northern nearshore area between Newport News Point and Hampton Roads

Bridge Tunnel, mostly shallow (<8 feet) with sandy bottom and a moderate density

of clams (area approximately 2,180 acres; 7,001 clams/acre).

B. Mddle area on the north shore between Newport News Point and Hampton Roads

Bridge Tunnel at intermediate depths (8 - 18 feet) with sandy or sandy-mud

bottom, and moderately high density of clams (2,770 acres; 10,450 clams/acre).

C. North channel edge and channel between Newport News Point and Hampton

Roads Bridge Tunnel, sandy or sandy-mud bottom, > 18 feet deep, with the second

highest density of clams (1,950 acres; 13,193 clams/acre).

D. South side of the channel and part of middle ground area, >18 feet deep, generally

sand or sandy-mud, with the highest density of clams (1,040 acres; 15,055

clams/acre).

E. Mddle ground area, soft mud to sand, 16 - 25 feet deep, moderately high clam

density (1,520 acres; 6,100 clams/acre).

F. Craney Island area - north, east and west of Craney Island with hard sand to soft

mud of varying depths. No clams were caught in any of more than 150 sample

locations (4,000 acres).

G. Elizabeth River - varying bottom types with low density of clams (3,415 acres; 298

clarns/acre).

H. Lafayette River - mostly sand or sandy-mud bottom with a moderate density of

clams (580 acres; 5,058 clams/acre).

1. Nearshore area on north side of James River between 1-664 and the James River

Bridge, mud, mud-sand, and sandy bottom mostly in the channel area adjacent to

Newport News Shipyard, moderate clam density (2,150 acres; 6,799 clams/acre).

J. South side of Newport News Channel from 1-664 to the James River Bridge, mud

to sandy-mud, 10-30 feet deep, low clam density (1,375 acres; 1,781 clams/acre).

K. Middle of James River between 1-664 and Cruisers oyster bar, moderate depth,

with muddy bottom and low density of clams (1,225 acres; 93 clams/acre).

L. Cruiser's Oyster Bar, old oyster bar with significant shell deposits and low clam

density (425 acres; 1,721 clams/acre).

M. Middle of the James River above Cruiser's Rock, moderate depth with mud

bottom, zero clams were found in more than 100 samples. (1,400 acres)

N. Nfiddle of the James River next to the James River Bridge, moderate depths with

some oyster shell and mud or sandy-mud bottom with low clam density (1,500

acres; 171 clams/acre).

Areas A, B, C, D, E, and I are the main areas for the summer relay clam season in the

James River, where in many years more than 50% of the annual harvest of clams in the entire

state has originated. This area is closed to harvest except during the summer because of high

bacterial levels. Fishing is permitted during the summer in a relay program, whereby, polluted

claims are harvested and moved under state supervision to other clean water areas where the clams

must remain for 15 days prior to direct marketing. The focus for much of the discussion on clam

management has centered on this important area. Accurate figures for harvests for the past 14

years are included in Figure 3. Harvest figures increased from 1986 - 1988, which is mostly

attributable to the increase in the patent tong clam fleet presented in Figure I and Table 1.

Harvests have declined since 1988 and the commercial clarnmers have indicated that their

catch/boat has also declined. Prior to the study, we would have predicted a substantial decrease

in the standing stock of clams in these areas from those reported in previous studies. Published

results from Haven, et a] (1973) and Haven and Kendall (1975) in Figures 4 and 5 show mostly

similar distributions and densities of clams to the current project, although there appear to be

more high density areas in the earlier studies than in thepresent study. Methodologies were quite

different between studies, with less sites and more replication within sites in the previous studies

than the current project. In a later report, Haven, et al (1981) combined data from all their

previous reports and produced an estimate of the clam standing stocks in the entire area. This

estimate was 565,712 bushels or 141,428,000 clams in the James River-Hampton Roads area.

Kvaternik (1982) also estimated the standing stock of clams for this area using the harvest figures

and catch per unit effort information with the Leslie method. This method could be quite

accurate in this area because of the excellent harvest figures that have been maintained each year

with the relay program. For the period from 1978 through 198 1, standing stocks varied from

70,290,535 clams to 139,815,328 clams with an average of 99,582,920 clams for the four-year

period. If calculations are made with data in the current project, the standing stock would be

estimated at approximately 112,000,000 clams. All of these estimates of standing stocks are

reasonably similar and do not obviously indicate any major decline in clam populations associated

with harvesting activity. Anecdotal information from the commercial fishermen suggests very

strongly that their catch per day has indeed declined, especially during the last 5 to 6 years. At

first inspection, these results seem to be contradictory; however, inspection of the sampling results

in Figures 4 and 5 shows some very densely populated clam areas within the overall area. The

patchy nature of high density areas of clams in the past may explain the higher catch rates in

previous years. The efficiency of the clam harvester has improved with the use of better depth

sounding equipment along with the Loran equipment that allows the watermen to both locate and

return to these "patch" high density areas. It is very likely that with the increase in harvester

numbers and the increase in efficiency, that the high density spots have mostly been caught and

what now remains are relatively uniform concentrations of clams. The density per acre and

standing stock for this entire area has remained constant; however, the success of the harvester

has declined, because there are less "hot spots" or high density areas and the catch in each patent

tong grab has declined and the clarnmer can only make a certain number of grabs in any one day.

The clam populations appear to be healthy and able to maintain a relatively stable population with

the observed 15% to 20% annual harvest rate (approximately 15,000,000 - 20,000,000 of a total

of 1.00,000,000 clams).

One change in the harvested clam population that does appear to be occurring is in age

structure. Table 2 presents results of the mean size and size frequency of a subsample of clams

from several of the sampled areas in the current project. In Table 3, a comparison between 1974

and 1995 data for mean size and size frequency is presented. It would appear that the average

size of clams has declined during the past 20 years. Additionally, there are fewer clams in the

chowder or larger clam category in the current project. Both of these observations may be cause

for concern and should be monitored in later studies. It would appear that very few clams escape

harvest and reach the larger size category. Clams are long lived and grow slowly, and may take

12 to 20 years to reach chowder size (Haven, et al, 1975); and therefore, even though the harvest

of chowder clams is limited, clams are subject to harvest at smaller sizes for many years. Very

small quantities of clam boxes were observed in any of the sample areas which would indicate

very little natural mortality besides harvesting. If larger animals are better spawners, over time

there may be a reduction in spawning success in future years.

Much of the Elizabeth and Lafayette Rivers were sampled in the current project because

there has been some interest in opening this area to harvest and the relay process. Currently these

rivers are closed entirely to the harvest of shellfish because of pollution. Stock assessment results

provide little evidence of significant clam stocks in the Elizabeth River (Figure 2). A moderate

density of clams was present in the Lafayette River; however, the total acreage was small and

would not support a very large fishery. The excellent reputation of Virginia!s clam products could

be jeopardized by the opening of this insignificant clamming area.

CONCLUSION

In conclusion, results in this project indicate that the standing stock of clams in the lower

James River-Hampton Roads area appears similar to previously reported levels from studies as

long as 25 years ago. A decrease in the success of the clammers as reflected by a decline in the

overall harvest and the catch per unit effort may be explained by a change in the distribution of

claims on the bottom. Years of harvest may have reduced the "patches" of high density clam

areas and resulted in mostly uniform distribution of clams. This seems to indicate that a relatively

stable clam population level may be maintained at the same time that the health of an industry is

declining.

Secondly, there appear to be changes in size and age structure during this 20-year period

resulting in less larger, older clams in the current clam population. These changes have not

resulted in a decline in clam populations, but this area should be resurveyed at a later date.

Additionally, further sampling of other clam areas should be completed for comparison. If gear

and season regulations remain the same, it is unlikely that catch per unit effort will increase

substantially over those observed currently. If harvesting pressure is decreased by limiting the

panicipants in the fishery, it would appear likely that densities of clams could increase and allow

the catch per day to improve.

Results of this study will be presented to the VMRC Clam Management Committee and to

the full Marine Resources Commission.

LUERATURE CMD

Haven, D. S., J. G. Loesch, and J. P. Whitecomb. 1973. An investigation into commercial
aspects of the hard clam fishery and development of commercial gear for the harvest of
molluscs. Contract No. 3-124R. Virginia Institute of Marine Science, Gloucester Pt., VA.
58 p.

Haven, D. and P. Kendall. 1974. A final report to Virginia Department of Highways on hard
clam, Mercenaria mercenanj populations in the vicinity of Hampton Roads Bridge Tunnel
(1-64). Virginia Institute of Marine Science, Gloucester Point, VA. 36 p.

Haven, D. and P. Kendall. 1975. Studies for a proposed Nansemond River Sewage Treatment
Plant. Volume 4. A survey of commercial shellfish in the vicinity of Newport News Point
and Pig Point in the lower James River. Virginia Institute of Marine Science, Gloucester
Pt., VA. 30 p.

Haven, D. S., R. Morales - Alamo, and W. I. Priest. 198 1. Oyster and hard clam distribution and
abundance in Hampton Roads and the lower James River. pp 38-43. In A Study of
Dredging Effects in Hampton Roads, Virginia. W. L Priest, ed. Special Report in Applied
Marine Science and Ocean Engineering No. 247, Virginia Institute of Marine Science,
Gloucester Point, VA. 266 p.

Kvaternik, A. C. 1982. Analysis of population and price aspects of the Virginia hard clam
(Mercenaria mercenaria) fishery. M. A. Thesis. College of William and Mary,
Williamsburg, VA. 103 p.

FIGURE 1. HARD CLAM LANDINGS (POUNDS)
NUMBER OF PATENT TONG LICENSES

1.8- 400
i .......... ............. .... .... ..... ..............L
p 1.6 . ..... ..... ... .. .......... . .... .. . ... . . ..... ........ ... ........... ............ ... ... . ..... ................... ..... . . . .... ..... ....... ---i
0 . . ................... . ... . .@\ ................ . ... .. . .........I. . ....... ................ . ...... . .-.. . . . . . .. ...................... . .. .................. .. . ................ .c
u 1.4 . . . .... . ........... . .. . ........ . ....... . . . ... ....... . ............... ...................... 300 e
n n
1.2 . .. . .............. . . ..... ............. . ...... . ... ...... ..... . ........
d -, li;@ , s
19W 619,712
s . .. . ...... ..... ... . .. ..... . ........ . . 1541 1.11 e
1 A - - - ----- --------------- -Im s
M -Im 200
i 0.8 . .. . ..... . 39"- Ing.191 - - ------ . . . . ............ . ....... . ..H
INS 461=4
M M177 u
1 0.6 -1"7 n
d
100
o 0.4 . . .... ........ . . ..... .......................... . .. . ... . ..... ...... . ...... . ..... ..... . . . . ...... . ..... . ................ ..... ... . . .... . ......r
n 101 L-0-06 e
s 0.2 . .. ...... .............. ................... . ........... . ..... ... .......... ... . ............ . .......... . . . ............. . ................. . ..... ......... ........... ...... . ..... ........ . ............... .. . ................ .... . ........ . ...... ...........d
--rim
s
0- 0
80 81 82 83 84 85 86 87 88 89 90 91 92 93
Years

- Clams Licenses

*Preliminary data

REV 5/30/95
TABLE 1. HARD CLAMS LANDINGS (POUNDS)
NUMBER OF PATENT TONG LICENSES
.............. ... .....
..... .......... ......
.............
.......... ............ .
.......... ............. pou..
...........
.......... :::: . . ..... . ........ .. ........
...... ...
.......... .. . ........
.......... ... ............... ... ....
'SE.
... ND*,*:*:"***#'
ES:
1980 619,712 133 4,659

1981 1,110,530 174 61382

1982 711,170 186 3,823

1983 1,207,165 188 6,421

1984 739,191 163 4,535

1985 613,254 332 1,847

1986 905,177 230 3,936

1987 1,004,580 266 3,777

1988 1,307,863 335 3,904

1989 1,517,488 366-- 4,146,

1990 1,559,108 382 4,081

1991 1,068,243 367 2,911

1992 1,094,391 375 2,918

*1993 1,313fi59 357 3,680
1 --
Preliminary data

FIGURE 2
B/

17
Y17 1.
c
NEWPORT
F1 7- @l --4
NEWS
POINT
L6

Fo-1

Ell

CRANEY H

ISLAND

'AA V,

02-9-61

DENSITY

NZ 501-5000
I0-sw
17MI'
RT

1, @E
y

5001-10000
71@
10001-15000

15001-20000

FIGURE 3. CLAMS RELAYED
FROM POLLUTED SHELLFISH AREAS, 1980-1994

30 . .............. ... . . ... ... . ............ .. . . . ... . . . ....... .... .. . . ........ . ........................... ... ........................

25------- .. .. .. ........... .. ...... . . . ...... .......... ..... ............. ...... .. ... ....... ........... .

M
20 . ........... .. .. . .. ... .... . .... ....................................................................... .........................

0 15 . . . . . . ... .................... .. . ..................................... ............ .............. .............. .............. ............. .... ......... ... ..........
n
s

10- . . ...... . .... ............ .. . . . ......... .. ... ..

5- .. .. ............ ..... ...........-. .............. .. .............. ............. .......... .. .........

0-
80 81 82 83 84 85 86 87 88 89 90 91 92 93 94

COUNT

5/23/95

@Mn-kT r%V Q@r A 'rTr% 11 SAMPLIr I T@nt_%lk 4'
'Dyy JLIT
FIGURE 4. T OCA L3 X Ilk 110 No r A 'IM-4 I I O.NGS FROXIL
I KIL
CHARTERED VESSEL. ABUNDANCE CODE: HlGH (716,500 CLAMS/ACRE), CLOSED
TRIANGLE; NdEDIUM (6,900 - 16,500 CLAMS/ACRE), HALF-CLOSED TRIANGLES; LOW
(<6,900 CLAMS/ACRE), OPEN TRIANGLES. (ORIGINAL DATAFROM HAVEN, ET AL.,
1973)

7.60IP8" 76012-44' 760120
b's
.6@b
306&- &302
30410'
6298 30 vo 84
28 5. 217 370
370 299 .......
8
276 278.....-
289 00
5-0-r ........
267
IN, %3A
�44 4-*@'.-'- 266 275A@
295 265
3
..300 297 .11
264
U.
V)
263
.311 2 A-952 262
NEWPORT.-.
"""'273 274
% 309,@k 319 N.E WS 251@ 2@6p ALV - -
272
...... 308 J58,42V9
307
A
53 willou
223
vO
:@2
220. 2
244 &245 &J4
239A
240A
AH8 @jL235
237
23 eA 230 V43
..t- Xf 231 POL232
.:" ':fm.
;"-.:-'.NORFO
360 :.4229 22e@& A227 :'360
A226
225A
Hampton
56. A2 56
Ro ds
313 19 2i.@
A 216
214 215&
315
09
11 fe.,
0
WA2026%4
2of D
203
A201
760 28'. 760 24'f- 76012d
v
)83
2 9 9
3 4AA@,
A

FIGURE 5

DENSITY OF CLMff-.S PER ACRE IN THE
HAMPTON ROADS AREA FROM A REPORT
EY HAVEN AND KENDALL, 1975

CLAMS
CRUISER SHOAL AREA PER ACRE
ROCK
WARWICK 1. 90
HOTEL 2. 18,90Q
3. 17,460
-7 4. 1,800
PUBLI 5. 23,400
GROUND NEWPORT.
NEWS 6. 9,600
FISHING PT 7. 330
PT
8. 3,630
08 9. 1,650
10. 0

iuoLE'
GROUND

CANDY
Pl

PRIVATE
LEASES
Ie 1Q,
NANSEMOND 1,
RIOGE

CRANEY
ISLAND

BARREL

P R I VAT E.
EAS

PIG
POINT \+ 360 5- N-
W

CEDA STREETER
PT PRIVATE CR. HOFFLER
LEASES CR.

WEST
CR. 0. 1000 2000 3000
YARDS

KNOTTS BOUNDARY OF SAMPLE AREAS
CR. DiVISON BETWEEN FORMER AND LATTER
SAMPLING
BOUNDARY OF PUBLIC OYSTER GROUNDS
T

TABLE 2. MEAN LENGTH AND SIZE FREQUENCY OF HARD CLAMS
IN THE HAMPTON ROADS AREA
.......... ............. .. .... ... ...
............. ..........
.............. .
..............
....... TR QU...
E
.......... -TH
. .......... .. .. ........ . . ........
....... .......... .. ..... ... ...
. ......... .............. ............ ......... .... ................
. ................
R. RY:'***
:::K E Ef.
.......... ...........
....................
.... ....... ..... ... .... . .
.......... .... .. .....
....... ... . . .......
-:81
...... ... "'MEAN 60hibi
SD .........
4 @ ......... -. ....
.. ....... ..... . .............. . .. ........... .........
.......... . ........

A HAMPTON, INSHORE 77 70.7 14.4 17 56 27

B HAMPTON FLATS 60 67.2 16.4 25 50 25

C HAMPTON > 18 feet depth 161 63.5 16.9 37 48 15

D MIDDLE GROUND 143 73.4 10.3 10 65 25

1 NEWPORTNEWSCHANNEL 91 52.7 14.3 68 30 2

H LAFAYETTERIVER 45 63.7 9.4 36 64 0

5/30/95

TABLE 3. A COMPARISON OF MEAN LENGTH AND SIZE FREQUENCY OF HARD CLAMS
FROM 1974 (HAVEN, LOESCH, WHITCOMB, 1974) AND 1995

Iyjij@i@ ..... .......
............
............
................. ...............
............ .. ........ . .........
............ ...... . ......
.......I...........
... ..............
..........0 .........
...................... ...... .......... .........
N K:::::CHER
........................
FAN
YEA ....................
..... ......
RE.A::::: ............. .. :.LIT...TLE:: EC

1995 Hampton, inshore 70.7 17 56 27

1974 Hampton Bar 79.5 10 36 54

1995 Hampton Flats 67.2 25 50 25

1974 Hampton Flats 75.2 12 47 41

1995 Hampton > 18 feet 63.5 37 48 15

1974 Hampton > 18 feet 69.4 23 51 25

5/31/95

/I
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