Development of fed and starved striped bass (Morone saxatilis) larvae from the Roanoke River, North Carolina

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

/10

DEVELOPMENT OF FED AND STARVED STRIPED BASS (Morone saxatilis)
LARVAE FROM THE ROANOKE RIVER, NORTH CAROLINA

Completion Report for ECU Grant/Contract No. 5-21431

For

North Carolina Department of Natural Resources
and Community Development
Division of Marine, Fisheries
Morehead City, NC 28557

Roger A. Rulifson, John E. Cooper, and Giuseppe Colombo
Institute for Coastal and Marine Resources
East Carolina University
Greenville, NC 27858

(ICMR TECHNICAL REPORT 86-03)

Submitted July 1986

This project was funded by the North Carolina Legislature, House Bill 129
(Chapter 15, 1985 Session Laws).

SH167
S68D48
1986

This report should be cited as follows:

Rulifson, R.A., J.E. Cooper, and G. Colombo.
1986. Development of Fed and Starved Striped Bass (Morone saxatilis)
Ta-
larvae from the Roanoke River, North Carolina. N. =.ept. o7 t.
Res. and Community Develop., Div. Mar. Fish., Completion Rep. for ECU
Contract No. 5-21431.

of Wow

US Department of ComzPAPq9-..i
NOAA coastal Services Center Librazy
2234 South Hobson Av*nUO,---
Charleston, SC 29405-2413

ABSTRACT

Fed and unfed striped bass larvae were reared in a laboratory using
ambient Roanoke River- water to determine differences in growth and
devel opment. These differences were used to histologically determine the
nutritional state of Roanoke River striped bass larvae collected from the
Roanoke River delta and western Albemarle Sound from 1984 through 1986. An
additional experiment examined the effects of high concentrations of
aluminum in acidified waters on larval striped bass skin. Larvae that were
given Artemia as a food source were successful at feeding by 6.5 days post-
hatch. Decline in nutritional state of unfed larvae was apparent as. soon
as 5.5 days post-hatch. The organs and tissues showing signs of poor
nutritional state were the eyes, liver, digestive tract, kidney, and trunk
muscul ature. The pancreas may also be an indic ator organ but results were
not conclusive. Changes in these tissues occurred within 11.5 days post-
hatch. Unfed larvae showed abnormal eye development by 7.5 days post-
hatch. The livers of fed larvae showed moderate multifocal glycogen
accumulation, while unfed larvae showed reduction in liver glycogen by 6.5
days post-hatch. Fed and unfed larvae possessed yolk 4.5 days after
hatching; the rate of yolk absorption was highly variable in both groups.
Fed larvae had distended, thick-walled digestive tracts; the guts of unfed
larvae were collapsed and empty as soon as 4.5 days post-hatch. The
hemopoietic tissue in the pronephric kidneys was reduced in unfed larvae
5.5 days post-hatch and older. Fed larvae had thickened, well-developed
muscle fibers, while muscles.of unfed larvae appeared thinner and separated
as soon as 6 days post-hatch. Wild Roanoke River larvae examined
histologically showed normal tissue development, indicating that they were
not in a starving condition. It is quite likely, however, that larvae
dying from or weakened by starvation are easily preyed upon or are not
suscepti-ble to net capture. Results of the pH-aluminum experiment
indicated that the microridge structure of the larval epidermis was
severely altered in the presence of low pH (5.5) and high aluminum (680 ug
Al 3+/l). Our results suggest that Roanoke striped bass larvae may suffer
high mortality one to two days post-hatch from skin stress, followed by a
second mortality from starvation.

TABLE OF CONTENTS

Page

ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . iv

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Starvation Experiments . . . . . . . . . . . . . . . . . . . . 3
Histological Preparation . . . . . . . . . . . . . . . . . . . 5
RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Larval Growth . . . . . . . . . . . . . . . . . . . . . . . . 6
Histological Variation of Hatchery Larvae . . . . . . . 11
Histological Examination of Wild Larvae . . . . . . . . . . . 25
Aluminum-pH Effects on Skin . . . . . . . . . . . . . . . . . 27
DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
SUMMARY . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . 37
ACKNOWLEGEMENTS . . . . . . . . . . . . . . . . . . . . . . 38

LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . . 39

LIST OF TABLES
Page

Table 1. Results of rearing experiment 1 showing the age-
length relationship (+ SD) of striped bass larvae
held in ambient Roanoke River water . . . . . . . . . . . . . 7

Table 2. Results of rearing experiment 2 showing the age-
length relationship (+SD) of striped bass larvae
held in ambient Roanoke River water . . . . . . . . . . . . . 8

Table 3. Water quality at the striped bass hatchery at
Weldon, North Carolina, and the Roanoke River at
Keeter's Dock (adjacent to hatchery) during the 1985
study . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Table 4. Results of rearing experiment 3 showing the feeding
schedul e, age at sampl i ng, and mean 1 ength (mm TO
at sampling of fed and unfed striped bass larvae
held in ambient Roanoke River water . . . . . . . . . . . . . 12

Table 5. Summary of the nutritional state of fed and unfed
striped bass larvae held in ambient Roanoke River
water in 1985. 14

Table 6. Capture date and location of histological ly-examined
striped bass larvae collected from the lower Roanoke
River and western Albemarle Sound in 1984-1986 . . . . . . . 26

LIST OF FIGURES
Figure 1. Map of the Roanoke River and western Albemarle Page
Sound, North Carolina, showing Weldon (rearing
experiments) and sampling locations for wild
striped bass larvae in 1984, 1985, and 1986 . . . . . . . 2

Figure 2. Sagittal section of a wild Roanoke striped bass
larva (20x) approximately eight days post-hatch
(6.5 mm TL) showing relative position of organs
and tissues 15

Figure 3. Eyes of striped bass larvae (50x) showing: (A)
normal development of retinal pigment (RP) in fed
specimens (7.5 days post-hatch); (B) reduced
retinal pigment in unfed specimens (7.5 days post-
hatch); and (C) eye degeneration in unfed specimens
(11.5 days post-hatch). . . . . . . . . . . 16

Figure 4. Branchial arches of a fed striped bass larva
showing: (A) arch configuration (20x); and (B) gill
filament development (1004 at 11.5 days post-
hatch . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 5. Liver of striped bass larvae showing: (A) glycogen
(clear spaces) within the cytoplasm (50x) of a fed
larva 12 days post-hatch; and (B) small compact
cel ls with no glycogen (100x) of an unfed larva
10.5 days post-hatch .. . . . . . 0 . 0 0 .. . . . 0 . 0 . 20

Figure 6. Digestive tract (50x) of: (A) a fed larva 7.5 days
post-hatch; and (B) an unfed larva 4.5 days post-
hatch... . . . . . . . . . 22

Figure 7. Pancreas (P) of a fed larva (100x) 6.5 days post-
hatch with islet of Langerhans (IL) visible . . . . . . . 23

Figure 8. Pronephric kidney (K) of a fed striped bass larva
(50x) 12 days post-hatch . . . . . .. .. . . . . . . . . . . 24

Figure 9. Scanning electron microscope (SEM) micrographs
(1350x) of the epidermis in the head region of
striped bass-larvae held for 20 hours: (A) in tap
water at pH 7.5; and (B) in water containing 608 ug
A13+/l (22.5 uM) at pH 5.5 . . . . . .. . . . . . . . . . . 28

Figure 10. Scanning electron microscope (SEM) micrographs
(1350x) of the epidermis in the bell region of
striped bass larvae held for 20 hours: (A) in tap
water at pH 7.5; and (B) in water containing 608 ug
A13+/l (22.5 u14) at pH 5.5. 29

Page

Figure 11. Scanning electron microscope (SEM) micrographs
(2600x) of the caudal fin epidermis of striped bass
larvae held for 20 hours: (A) in tap water at pH
7.5;'and (B) in water containing 608 ug A13+/l
(22.5 uM) . . . . . . . . 0 0 0 a 1 0 0 0 0 0 . 0 0 . 0 . 0 30

Figure 12. Simplified drawing depicting the springtime
densities of Stage 1 (with yolk) striped bass,
Stage 2 (no yolk) larvae, and zooplankton in the
Roanoke River, North Carolina, in a year of high
ri ver f 1 ow (1984) and I ow ri ver f 1 ow (1985) . . . . . . .36

INTRODUCTION

Stri ped ba s s (M orone saxati I i s) i n hab i ti ng A 1 b emar 1 e So und and i ts
tributaries support important commercial and recreational fisheries in
coastal North Carolina. The major spawning area for Albemarle Sound
striped bass is located in the Roanoke River, which discharges into the
extreme western end of Albemarle Sound approximately seven river miles (RM)
downstream from Plymouth, North Carolina (Figure 1). The primary spawning
ground is upstream between the towns of Halifax (RM 120) and Weldon (RM
130), North Carolina. The historical spawning grounds further upstream
were blocked by construction in 1955 of the Roanoke Rapids Dam at RM 137
(McCoy 1959). Spawning occurs from late April through early June (Hassler
et al. 1981); peak spawning activity is associated with water temperatures
near 2OoC (McCoy 1959). Eggs develop to the hatching stage as they are
transported downstream by currents. After hatching, the larvae continue to
be swept downstream through the Roanoke River delta to the historical
nursery grounds in western Albemarle Sound (Street 1975).
In recent years,-the striped bass fishery in this area has suffered
from reduced numbers of harvestable adults. The population decline may be
due to a variety of factors such as reduced egg viability (Guier et al.
1980, Hassler et al. 1981), poor survival of larvae during downstream drift
from spawning grounds to nursery areas (Rulifson 1984, Rulifson and Stanley
1985; Rulifson et al. 1986), and poor survival of juveniles on the nursery
grounds (Hassler et al. 1981). Estimates of the number of eggs spawned
each year in the Roanoke River indicate that adequate numbers of eggs and
larvae are produced to maintain population levels (Kornegay 1981, Kornegay
and Mullis 1984). However, surveys of larvae and early juveniles in
nursery areas of the western Sound indicate low recruitment of these life
stages (Rulifson 1984; Rulifson, Stanley and Cooper, unpublished data).
Thus, extensive mortality may be occurring in the lower Roanoke River.
Starvation of larvae has been hypothesized as one of the principal
causes of mortality (Rulifson 1984; Rulifson and Stanley 1985; Rulifson et
al. 1986). Striped bass larvae appear to be food limited in the Roanoke
River system in years of high flow and extremely low flow (Rulifson et al.

KERR
DAM
VIRGINIA
F;@E- @ZiIDS NORTH CAROLINA
GASTON DAM
DAM C
WELDON rmillo

HALIFAX
rrn 120

svi"o

WILLIAMST15N PLYMOUTH
rm 375 3 fin 6

__j

230

N 220

Stock ALBEMARLE 25
walnut
point SOUND
0
26

V.-(cmeler
eATCHELOR
21"
stal.tt "'de 16 Is SAY 27* 1"2?
0 0 29
14 20
13 17
*Is 28'

Rice
Is

10 Hv 45
9s@ it

Thoroughfare
S

6 Roper

0PLYM UTH

Weyerhaeuser

Figure 1. Map of the Roanoke River and western Albemarle Sound,
North Carolina, showing Weldon (rearing experiments) and
sampling locations for wild striped bass larvae i n 1984,
1985, and 1986.

1986). High river flow, caused by freshwater discharge from Roanoke Rapids
Lake, sweeps striped bass eggs and yolk-sac larvae into areas of extremely
poor zooplankton productivity in western Albemarle Sound (Rulifson and
Stanley 1985). Low flow conditions allow greater zooplankton productivity
in the lower Roanoke River, but not in concentrations great enough for
larvae to feed successfully (Rulifson et al. 1986). Poor water quality or
the presence of pollutants, possibly causing aberrant feeding behavior of
the larvae and resulting in starvation, has been hypothesized also
(Rulifson 1984). Further changes in water quality and flow conditions
associated with the proposed Lake Gaston pipeline to Virginia Beach and new
pulp mills proposed for construction below the striped bass spawning
grounds may aggravate these problems to the point at which damage to the
striped bass population will be beyond its natural potential for recovery.
The goal of this study was to determine the nutritional state of
Roanoke striped bass larvae. The.work was designed in a manner comparable
to research condu cted in Maryland to examine starvation of Potomac River
striped bass larvae (Martin and Malloy 1981). Specific objectives of our
study were: (1) to create a histological grading.scale of nutritional state
in larvae; (2) to utilize this scale to estimate the nutritional state of
Roanoke River larvae; and (3) to relate the findings to ongoing larval
striped bass and food availability studies in the Roanoke River and western
Albemarle Sound.

METHODS

Starvation Experiments

Rearing and starvation experiments of striped bass larvae were
conducted from 23 April to 8 May 1985 at the State hatchery in Weldon,
North Carolina. Parental stock was captured by electroshocking from the
Dan River, Virginia (part of the Roanoke River watershed above the John H.
Kerr Reservoir),, and transported by tank truck to the Weldon hatchery.
Striped bass were spawned according to procedures described by Bonn et al.
(1976).

Experiment 1. Eggs of two female striped bass were fertilized with a
mixture of milt taken from several males and placed in MacDonald hatching
jars. The water source was unfiltered ambient water pumped from the
Roanoke River into the hatchery using a once-through system. Hatching
larvae were allowed to swim into aquaria. After two days they were
transferred to experimental tanks at an estimated density of 1500 larvae
per tank (87 larvae/1). Each rearing tank was constructed of a five-gallon
plastic pickle bucket with a 14-mm I.D. PVC standpipe to control water
level. The standpipe was covered by a 52-mm IJ PVC pipe fitted with a
series of holes and screened with 250-um nitexmesh to allowthe maxim um
amount of water to drain from the tank throughout the water column with a
minimal velocity at any given point. Water flow into each tank was
maintained at approximately 53 ml/second (t1O.6, n=36) for the duration of
the experiment. Complete water exchange occurred about every 5.4 minutes.
Freshly hatched brine shrimp (Artemia) nauplii were fed to the larvae at
un iform intervals throughout the day, and approximately one hour prior to
procuring daily subsamples of the larvae for examination. Larvae were
sampled every 24 hours, placed on ice for 10 minutes to minimize
regurgitation and body flexure, and preserved in 10% buffered formalin.
Only live larvae were preserved so that starvation effects would not be
confused with postmortem lysing. Each larva was measured to the nearest
0.1 mm total length (TL) using an ocular micrometer.
Experiment 2. The egg s of one femal e stri ped bass were ferti I i zed
wi th a mi xture of mi 1 t f rom severa 1 ma 1 es and al 1 owed to hatc h i n the
manner described above. Two-day old larvae were transferred to the rearing
tanks at an estimated density of 1000 larvae per tank (58 larvae/1). Water
flow into each tank was maintained at about 52 ml/second (t8.7, n=67).
Larval feeding, sampling, and preservation methods were identic.al to
Experiment 1.
Experiment 3. Striped bass eggs were spawned in a circular tank from
one female in the pr esence of four males. At age 4.5 days post-hatch,
larvae were transferred at a density of 19/1 to 85-1 glass aquariums
equipped with the standpipe design described above. Larval feeding,
sampling, and preservation methods were identical to the previous

experiments.
Experiment 4. In 1986 a special study was conducted on two-day old
larvae to determine the effects of pH and aluminum on the skin. Groups of
65 striped bass larvae from the Weldon hatchery were kept in 2-1 aquariums
filled with filtered tap water. The experimental design consisted of a
four by four matrix of pH (7.5, 6.5, 6.0, and 5.5) and concentrations of
aluminum (0, 202, 405, and 608 ug A13+/,) as AlC13, High larval mortality
was observed after 20 hours. The test was stopped and samples of the
surviving larvae were fixed in a solution of 1.25% gluteraldehyde and 2%
paraformaldehyde in a phosphate buffer (0.75 M) at pH 7.2. After
dehydration in graded ethanol solutions, larvae were prepared for light
microscopy or for scanning electron microscopy (SEM).

Histological Preparation

Striped bass larvae from Experiment 3 were prepared for histological
examination in accordance with standard laboratory methods for paraffin
processing. Fish larvae were placed on lens paper, which was folded to
form an env.el ope, and placed in a plastic cassette. The cassette was
either placed directly into a Fish Histomatic tissue processor in 10%
buffered-neutral formalin, or stored in preservative for later processing.
Larvae in the tissue processor were su bjected to a 12-hour normal cycle
paraffin infiltration process consisting of six separate baths of isopropyl
alcohol ranging in concentration from 70%-100%, three xylene baths, and two
paraffin infiltration baths. The infiltrated specimens were removed from
the lens paper, oriented on agar blocks, and then placed into a cassette
pan. Liquid paraffin was poured over the specimen to form a paraffin
block.
Specimens were sectioned serially at 6-um intervals and floated in a
water bath containing granular gelatin and an Aerosol solution to reduce
surf ace tensi on. The resu 1 tant secti on ri bbon s were f 1 oated onto g 1 as s
sl ides, which were then dried in an oven for 30 minutes at 600C and al lowed
to cool to room temperature. The slides were stained with hematoxylin and
eosin.

Wild striped bass larvae collected from the lower Roanoke River in
1984, 1985, and 1986 were also prepared for histological examination, but
using a plastic embedding technique to minimize separation of tissues
during sectioning. Larvae were removed from the formalin preservative and
subjected to two 70% ethanol baths for one hour each, then two 100% ethanol
baths for one hour each. No cassette was used in this procedure. Larvae
were infiltrated with L.R. White plastic resin over a 24-hour period.
Infiltrated larvae were then oriented in J.B.-4 molds; resin was added and
polymerized in an oven at 600C for 16-20 hours. Blocks were trimmed and
mounted on a "00" size block for sectioning using a L.K.B. Cambridge Huxley
microtome. Sections were floated in a 60% acetone-40% water bath onto
slides and dried on a slide warmer. Specimens were stained with Toluidine
Blue (1%) in a 1% sodium borate solution for 15 seconds at 60oC.
Specimens from the pH-aluminum experiment were post-fixed in a
phosp hate- buffered 1% OsO4 solution, dehydrated in graded ethanol,
critical-point dried, and coated with gold-palladium for examination under
a ISO.40 Scanning Electron Microscope.

RESULTS

Larval Growth

Extensive mortality of the larvae was observed in experiments 1 and 2,
which caused both experiments to end prematurely. Larvae were
approximately 5 mm TL two days after hatch, and grew about 0.3 mm by day
three (Table 1, Table 2). Growth averaged 0.2 mm from day three to day
four. None of the larvae appeared to be in feeding condition. In both
experiments, high mortality was probably caused by excessive turbidity
during water release episodes from Roanoke Rapids Lake. Water quality
remained fairly stable for both experiments (Table 3). Water temperatures
ranged between 200C and 240C during the eight-day period.
Significant differences (p = 0.05) in rate of growth were observed
between fed and unfed larvae in experiment 3. Fed larvae grew from 5.04 mm
TL two days after hatching to 6.40 mm TL 11.5 days after hatching (Table

Table 1. Results of rearing experiment 1 showing age-length (+SD) relationship of striped bass larvae raised in
ambient Roanoke River water. h.a.h. = hours after Fatching; d.a.h. = days after hatching.

Mean length (mm TO
Experimental Sample Age at sampling Temp. Fed Starved
Date Day Time (h.a.h) (d.a.hJ OC) 1* 3 5 8 2 4 6 7

4/23/85 1 1530 51.5 2 21.5 5.10 5.00 5.02 5.10 5.00 5.03 5.05
+0.5 +0.18 +0.00 +0.06 +0.19 +0.29 +0.08 +0.08
(2) _(12) _(9) _(10) _(8) _(7) 7(12) _(10)

4/24/85 2 1200 72.0 3 20.0 5.44 5.44 5.45 5.43 5.48 5.36 5.30
+1.0 +0.18 +0.30 +0.27 +0.30 +0.32 +0.32 +0.19
_(2) _(8) _(9) _(11) _(9) _(11) _(11) _(8)

4/25/85 3 1230 96.5 4 21.4 5.57 5.40 5.58 5.78 5.77 5.73 5.56
+1.1 +0.30 +0.42 +0.38 +0.23 +0.29 +0.24 +0.38
(3) _(8) _(5) _(6) _(9) _(13) _(11) (5)

4126185 4 1200 120.0 5 23.1 5.80 5.50 6.1 5.5
+1.1
T-3

*Refers to the number of the holding tank.

Table . 2. Results of rearing experiment 2 showing age-length (+SD) relationship of striped bass larvae
raised in ambient Roanoke River water. h.a.h. = hd'u'rs after hatching; d.a.h. = days after
hatching.

Mean 1 ength (mm TL)
Experimental Sample Age at sampling Temp. Fed Starved
Date Day Time K. a. h. (d. a. h. M) 1* 3 5 8 6 7

4/26/85 1 1700. 48.0 2 23.1 5.00 5.00 5.00 5.00 5.25 4.82 5.10 4.90
�1. 1 �0 . 00 �0 . 00 �0.00 �0.00 �0.5 �0.24 �0.22 �0.14
(3) (4) (4) (4) (5) (4) (4) (5) (4)

4/27/85 2 1750 73.0 3 21.2 5.36 5.34 5.34 5.18 5.26 5.28 5.35 5.43
+0.6 +0.20 +0.24 �0.21 �0.29 �0.25 �0.20 �0.23 �0.14
CO (3) (8) (9) (7) (9) (9) (9) (8) (9)

4/28/85 3 1330 97.5 4 23.2 - 5.83 - 5.70 5.50 5.50 - 5.56
+1.0 +0.58 +0.24 (1) �O-00 �0.43
(3) (3) (6) (2) (5)

4/29/85 4 1825 121.5 5 20.9 - 5.87 - - -
+1.0 +0.19
(3) (7)

4/30/85 5 1630 143.5 6 20.8 6.00
+1.5
(3)

*Refers to the number of the holding tank.

Table 3. Water quality information for the striped bass hatchery at Weldon, North Carolina, and the
Roanoke River at Keeter's Dock (adjacent to hatchery) during the 1985 study. Dissolved oxygen
(mg/1) and pH determined by Hach kit; nitrogen and phosphorus measurements (mg/1) by EPA methods.
Total Al (ug/1) for unfiltered water samples. Unless noted, concentrations of Cr, Cu. Hg, Ni, Pb'
and Zn (ug/1) below detectable limits*.

T N02-N+ Total Total
Date Station Time pH D.O. (0c) NH3-N TKN 1403-N P04-P P Al Other

4/23/85 Hatchery 1911 21.0 0.04 0.4 0.12 0.04 0.07 200
River 1930 - - 0.06- 0.2 0.17 0.04 0.07 200

4/24/85 Hatchery 1730 7.5 10.0 21.0 0.02 0.4 0.11 0.04 0.06 200
River 1750 7.5 9.0 21.0 0.03 0.3 0.12 0.05 0.08 800

4/25/85 Hatchery 1320 - 8.5 21.5 0.02 0.2 0.13 0.03 0.10 300
Hatchery 1845 7.5 9.3 22.5 0.03 0.5 0.13 0.04 0.07 300 Zn(30)
River 1905 7.5 9.7 22.0 0.04 0.4 0.11 0.03 0.10 2400

4/26/85 Hatchery 1700 7.5 9.2 24.0 0.05 0.3 0.09 0.05 0.08 200
River 1721 7.5 7.9 23.5 0.05 0.4 0.09 0.04 0.08 500

4/27/85 Hatchery 1310 7.0 8.4 21.5 0.05 0.3 0.12 0.04 0.07 200
River 1820 7.0 8.1 21.0 0.08 0.4 0.13 0.04 0.07 400

4/28/85 River 2030 - - - 0.09 0.4 0.16 0.04 0.10 800

4/29/85 Hatchery 1300 7.5 8.5 21.5 0.11 0.4 0.20 0.06 0.09 200
River - 7.0 9.4 21.5 0.13 0.4 0.22 0.07 0.10 300

4/30/85 Hatchery 1658 7.8 9.0 22.5 0.06 0.3 0.20 0.05 0.09 200
River 1709 7.5 9.5 22.0 - - - - - 200

5/1/85 Hatchery 1736 7.5 8.4 22.5 0.05 0.3 0.20 0.05 0.08 200
River 1746 7.5 9.3 22.5 0.04 0.3 0.20 0.05 0.09 600

Table (Continued)

T N02-N+ Total Total
Date Station Time PH D.O. (OC) 40-N TKN N03-ti P04-P P Al Other

5/2/86 Hatchery 1609 7.0 7.8 22.5 0.05 0.3 0.17 0.03 0.08 400
River 1603 7.0 8.2 22.5 0.05 0.3 0.16 0.02 0.12 1600 Pb(zoo)

5/3/85 Hatchery 1715 7.0 8.4 20.0 0.22 0.4 0.13 0.03 0.10 800
River 1730 7.0 8.1 20.0 0.21 0.3 0.14 0.04 0.11 1100

V4/85 Hatchery 1700 7.5 7.2 22.5 0.05 0.3 0.16 0.03 0.08 300
River 1730 8.0 9.4 22.0 0.06 0.3 0.18 0.04 0.08 700 Zn(20)

5/5/85 Hatchery - 7.5 9.3 23.0 0.06 0.5 0.19 0.04 0.07 300 Zn(40)
CD River - 8.5 9.6 22.0 0.07 0.3 0.20 0.06 0.08 Soo

5/6/85 Hatchery 1705 7.5 8.4 24.8 0.05 0.4 0.15 0.03 0.06 700
River 1715 7.5 8.8 23.2 0.06 0.3 0.14 0.03 0.11 1600

*Minimum detectable limits (ug/1): AI=100; CR=50; Cu=20; Hg=O.2; Ni=100; Pb=100; Zn=20.

4), for an increase of 1.36 mm. Larvae were observed feeding actively on
Artemia from 5 days post-hatch until the experiment terminated. Unfed
larvae exhibited very little growth, averaging 4.93 mm TL on the fifth day
after hatching and 4.98 mm TL by day 10, a change of I ess than 0.1 mm
(Table 4). Significant difference in total length between the two groups
was evident at 7.5 days post-hatch (F=2.73; df=19, 14; P<0.05). Water
temperatures were between 200C and 230C during the 11-day period. Ammonia
(NH3. -N) and total al uminum 'were the only water qual i ty parameters th at
changed during experiment 3 (Table 3).

Histological Variation of Hatchery Larvae

The organs and tissues examined using lightmiscroscopy were: eyes,
brain, gills, heart, liver, digestive tract, pancreas, kidney, trunk
musculature, skin, and cartilage. A summary of the information is
presented in Table 5. Comments on the degree of development are noted in
the text where appropriate. Relative position of the organs and tissues of
a Roanoke striped bass larva approximately eight days post-hatch are shown
in Figure 2.

Eyes

Eye lens development was apparent in the youngest larvae examined (108
hours after hatching) and eye development appeared normal in both fed and
starved larvae 6.5 days after hatching. By 7.5 post-hatch, abnormal
development of the eyes was evident in several starved specimens. This
abnormality appeared as reduced pigmentation in the retina (Figure 3).
Sparce, retinal pigment was also evident in unfed specimens 10.5 days and
11.5 days post-hatch.

Brain

Development of the brain appeared normal in all specimens.

Table 4. Results of rearing experiment 3 showing the feeding schedule, age at sampling, and mean length
at sampling (mm TO of fed and starved striped bass larvae raised in ambient Roanoke River water
h.a.h. = hours after hatchtng ; d.a.h. = days after hatching.

D.
Mean length (TO at sampling T(OC) (mg/1)
Experimental Feeding Age at Sampling Fed Starved + SD + so
Date Day (h.a.h.) th.a.h.) (d.a.ff-.7 n mm n M (n) (n)

4/29/85 4 104 Stocked @ 19.5 larvae/liter 20.9 8.7
106 +0.98 +0.66
111.5 108 4.5 T3) (-3)

4/30/85 5 128.0 20.8 8.6
131.5 +1.53 +0.45
134.5 135 5.5 19 5.04 19 4.93 -(3) -(3)

5/1/85 6 152.5 22.0 8.3
158.5 159 6.5 19 5.23 19 4.98 +1.32 �0.40
(3) (3)

iI5/2/85 7 176.5 22.1 8.1
180.0 +0.69 +0.52
181.25 183 7.5 20 5.22 14 4.98 (3) (3)

5/3/85 8 200.5 20.0 8.0
203.0 +0.00 �0.35
206.0 207 8.5 15 5.63 20 4.94 C3 (3)

5/4/85 9 224.25 21.5 8.9
228.0 +1.32 f0.46
229.0 231 9.5 20 5.72 15 4.90 (-3) (3)

Table 4. (Continued)

077
Mean length (17L) at sampling T(00 (mg/1)
Experimental Feeding Age at Sampling Fed Starved + so + so
Date Day (h.a.h.) (h.a.h.) (d.a.h.) n mm n mm (n) -(n)

5/5/85 10 248.0 21.2 8.9
251.5 +2.02 +0.53
254.0 255 10.5 21 5.68 15 4.98 (3) (3)

5/6/85 11 272.5 22.9 8.3
274.5 +1.90 +0.17
277.0 280 11.5 18 6.40 1* 2.60 (3) (3)

*Remainder of larvae were contorted and could not be measured.

Table 5. Summary of the nutritional state of fed and unfed striped bass
larvae raised in ambient Roanoke River water in 1985.

Tissue Fed Unfed

Nervous System

Eye Normal Reduced retinal
pigment in older
larvae
Brain no differences noted

Notochord no differences noted

Respiratory System

Gills no differences noted

Cardiovascular System

Heart no differences noted

Gastrointestinal System

Liver large, well developed; small, atrophied;
glycogen accumulation nuclei closely
spaced; no glycogen

Digestive Tract partially or fully collapsed; empty
distended; food visible

Pancreas islet of Langerhans islet smaller;
well-developed; possible degenera-
surrounded by exocrine tion noted in one
pancreatic tissue older specimen

Urinary System

Kidney hemopoetic tissue hemopoetic tissue
present in the reduced in the
cephalic kidney cephalic.kidney

Musculoskeletal System

Musculature robust, thickened; thin and fragmentary
well developed in older larvae

Cartilage no differences noted

Integumentary System

Skin no differences noted

,*s7"
5

ME A=

WOW'",

S B
K

GA
Y/O
E
H

L
I

Figure 2. Sagittal section of a wild Roanoke striped bass larva (20x)
approximately eight days post-hatch (6.5 mm TO showing relative
position of organs and tissues. G = gut; N notochord; P
pancreas; L = I i ver; SB swim b I adder; K kidney; Y/O
yolksac and oil globule; H heart; GA gill arch; B brain; E
eye.

%
Ap,
L
tj@

Y 4y
Ch

!RjtA

R P

Figure 3. Eyes of striped bass larvae (50x) showing: (A) normal development of retinal pigment (RP) in fed
specimens (7.5 days post-hatch); (B) reduced retinal pigment in unfed specimens (7.5 days post-hatch);
and (C) eye degeneration in unfed specimens (11.5 days post-hatch).

Figure 3. (Continued)

Notochord

Development of the notochord appeared similar for both fed and unfed
larvae. No shrinkage was evident.

Gills

Branchial arches were developing at 4.5 days post-hatch. Gil 1
filaments were not developed, indicating that the gills were not functional
at this stage of 1 arv al devel opment. By 11.5 days after hatching, fed
larvae possessed gill capillaries on the branchial arches (Figure 4). Gill
development of unfed specimens appeared to be similar to fed specimens of
the same age.

Heart

Both fed and unfed larvae had hearts that appeared as simple tubes 4.5
days after hatching. Development of the heart appeared -normal in all
specimens.

Liver

Livers of both fed and unfed larvae had mild to moderate multifocal
glycogen accumulation, a condition normal for larvae still possessing yolk.
Fed and unfed I arvae possessed yol k 4.5 days after hatching; the rate of
yolk absorption was highly variable in both treatment groups. By day 6.5,
the livers of fed larvae possessed large amounts of glycogen. Unfed larvae
had livers with compact cells, indicating, reduction in glycogen content
(Figure 5). Only fed larvae retained liver glycogen through day 12. Blood
vessels containing red blood cells were visible in livers of fed larvae
10.5 days post-hatch.

At.
0

V
$W
Ilk

eb
w,

Figure 4. Branchial arches of a fed striped bass larva showing: (A) arch configuration (20x); and (B) gill
filament development (100x) at 11.5 days post-hatch.

dp -Ab
@Tz @-O
Z 0

4
A"A

:r
r4 Lt@.@
IL

kv.

i. iV
CV

IMM
- VT.,

Figure 5. Liver of striped bass I arvae showing: (A) glycogen (clear spaces) within the cytoplasm (50x) of a
fed I arva 12 days post-hatch; and (B) smal I compact cel Is with no glycogen (100x) of an unfed
larva 10.5 days post-hatch.

Digestive Tract

The esophagus, midgut and hindgut of 4.5 day old larvae were well
di f f eren ti ated. No further differentiation was noted during the
experimental period. Larvae that were fed Artemia exhibited partially
distended guts after 6.5 days, indicating that feeding efforts were
successful. All fed larvae possessed distended digestive tracts through
day 11 (Figure 6). The guts of unfed I arvae were collapsed and empty from
4.5 days post-hatch (Figure 6) through termination of the experiment;
however, no degeneration of intestinal mucosa was observed.

Pancreas

At 4.5 days after hatching the pancreas was developed and appeared
normal. By day 6.5, the islet (Isle of Langerhans) was visible surrounded
by exocrine pancreas (Figure 7). The islet appeared to be slightly smaller
in an unfed specimen 5.5 days old; the i slet was not vi sibl e on
histological sections of older larvae so effects of starvation could not be
determined. No other differences in pancreatic development were observed

between fed and unfed larvae.

Kidney

Pronephric kidneys appeared in larvae 4.5 days post-hatch, with few
tubules extending cephalically to the liver region. By 12 days post-hatch,
the kidney duct was visible extending caudally behind the rectum and
hemopoietic (red blood cell forming) tissue was present cephalically and
around the pronephric tubules (Figure 8). Hemopoietic tissue was reduced
in unfed larvae 5.5 days post-hatch and older.

Muscle

Fed larvae possessed thickened, well-developed muscle fibers
throughout the experiment (Figure 6). Muscl-e fibers appeared thinner and

oy"
A

Of
o7, A,,*,

-it

igure 6. Digestive tract (50x) of: (A) a fed larva 7.5
days post-hatch; and (8) an unfed I arva 4.5 days
post-hatch.

zt@

U-

. . . . . . . . . .

Figure 7. Pancreas (P) of a fed larva (100x) 6.5
days post-hatch with islet of Langerhans
(IL) visible.

o
hill-
hm,

Figure 8. Pronephric kidney (K) of a fed striped bass larva (50x)
12 days post-hatch.

separated in unfed larvae as early as 6 days post-hatch. Older unfed
larvae were difficult to section and came apart during processing, probably
due to their frail condition. Fragmentation of muscle fibers was evident
in unfed larvae 12 days after hatching, the same condition was noted by
O'Connell (1976) for severely starved anchovy (Engraulis mordax) larvae.

Cartilage

No differences in cartilage development were noted between fed and
unfed larvae. In the older larvae, cartilage was well developed.
Cartilage cells of larval striped bass were in a wide extracellular
cartilage matrix and similar in appearance to those of jack mackerel
Trachurus symmetricus larvae (Theilacker 1978) and starved northern anchovy
larvae (O'Connell 1976).

Skin

Cross-sections of the epidermal layers showed no visible differences
between fed and starved larvae. By 10.5 days post- hatch, - scal e-produci ng
cells were visible in the epidermis. Tooth development was visible in the
oral cavity of fed larvae 11.5 days after hatching.

Histological Examination of Wild Larvae

Histological examination showed normal tissue development in 60
striped bass larvae collected from the lower Roanoke River in 1984, 1985
and 1986 (Table 6). Food items were present in the digestive tracts of
several specimens, indicating successful feeding. The empty digestive
tracts of the other wild larvae were deeply invaginated and had thicker
walls than unfed larvae from experiment 3, indicating that the larvae were
not in a starved condition. All specimens had large cells in the
esophagus, and livers ranged from mostly dense and compact to moderate
glycogen accumulation. Several larvae had abnormal body proportions (i.e.,
stunted in appearance), but appeared normal histologically. The stunted

Table 6. Capture date and location of histological ly-examined wild
striped bass larvae collected from the lower Roanoke River and
western Albemarle Sound in 1984-1986. Station numbers as in
Figure 1.

Number
Date Station examined Remarks

5/22/84 1 4 Normal
11 1

5/23/84 3 3
10 3

5/29/84 9 3
13 1
is 2 Stunted appearance; histologically
no difference compared to lab-fed
larvae

6/2/84 13 1 Normal

6/8/84 13 7

4/28/85 a 3
13 3

5/16/85 4 2

5/22/85 6 3
11 5

5/24/85 6 2

5/26/85 8 2 Cross-sections of cladocerans in
gut

6/2/85 6 3 Normal

6/6/85 9 3

5/22/86 11 4

5/31/36 6 5 it

larvae still possessed yolk and not all organs were. fully developed.
Therefore, the. stunted appearance was probably not due to lack of food.

Aluminum-pH Effects on Skin

Light microscopy observations of larval striped bass skin exposed to
low pH in the presence of aluminum showed no clear morphological
differences among the experimental groups. However, observations using
scanning electron microscopy showed clear differences in the surface
pattern of epidermal cel I s between control 1 arvae and 1 arvae exposed to the
various concentrations of pH and al uminum. Larvae exposed to high al uminum
concentrations showed a clear reduction of epidermal microridges on the
head and caudal fin (Figures 9-11).

DISCUSSION

Histological comparisons *indicate that fed and unfed striped bass
larvae show physiological differences: starvation is apparent as either
development retardation or tissue degeneration as early as 5.5 days post-
hatch. The results of our study are similar to those reported by O'Connell
(1976) for early post yolk sac larvae of northern anchovy (Engraulis
mordax). In our study, the organs and tissues showing signs of poor
nutritional state included the eye, liver, digestive tract, kidney, and
muscul ature. The pancreas may al so be an indicator organ. These changes
occurred within 11 days post-hatch. Theilacker (1978) found that larval
jack mackeral (Trachurus symmetricus) show the first signs of poor
nutritional state in the digestive tract and associated gl ands and the
extent of cellular deterioration increased with length of starvation.
Martin and Malloy (1981), using slightly larger (and presumably older)
striped bass larvae than we used, found that starvation effects could be
detected in four tissues: abdominal body wall, epaxial musculature, gut
epithelium, and liver. Their study suggested that retinal tissue may be
the most sensitive to poor nutritional state, but indicated that additional
studies were needed. Research conducted at the University of Rhode Island

Ilk

A2,

x
00

v
V 'AL\

ALI-I 1350 AL-4-4

Figure 9. Scanning Electron Microscope (SEM) micrographs (1350x) of the epidermis in the
bass I arvae held for 20 hours: (A) in tap water at pH 7.5; and (B) in water cor
(22.5 uM) at pH 5.5.

It AR

flip.

P t! VISA,*-

AL WER.,

Figure 10. Scanning Electron Microscope (SEM) micrographs (1350x) of the epidermis in the b
bass larvae held for 20 hours: (A) in tap water at pH 7.5; and (B) in water coni
(22.5 uM) at pH 5.5.

A., t

Figure 11. Scanning Electron Microscope (SEM) micrographs (2600x) of the caudal fin epi
larvae held for 20 hours: (A) in tap water at pH 7.5; and (B) in water containi
uM) at pH 5..5.

on the eye and optic nerve of striped bass larvae indicate degeneration of
the retinal tissue and optic nerve within several days after last feeding
(Joel Bodammer, URI, 1985, personal communication). None of these studies
examined effects of starvation on skin.
Changes in the morphological characteristics or external appearance of
fish larvae have been used as diagnostic tools to identify starvation, but
thi s technique may not be applicable for striped bass several days post-
hatch. Shelbourne (1957) assessed the nutritional state of Pleuronectes
platessa larvae based on their external appearance. Morphological changes
used as diagnostic characters include decreased thickness in body of the
larvae (Kostomarova 1962; Nakai etal. 1969; Arthur 1976; Ehrlich et al.
1976; Powell and Chester 1985; Grover and 011 a 1986), and changes in fin
angle and the ratio of head to eye height (Ehrlich et al. 1976).
Theilacker (1973) used a combination of five morphometric measurements
(standard length, head length, eyediameter, bodydepth a't pectoral, and
body depth at anus) to estimate the nutritional state of jack mackeral
larvae; similar results were obtained for spot (Leiostomus xanthurus) by
Powell and Chester (1985). Grover and Olla (1986) found significant
differences in seven of eight morphometric measurements of "starved" and
.,normal" sablefish (Anoplopoma fimbria); nutritional state was made
circumstanti al 1 y by anal ysi s of gut contents. Martin and Mal 1 oy (1981)
found that head depth, body depth at pectoral , and the ratio of body depth
at anus to head depth could be used to identify starving striped bass
larvae reared in the laboratory; however, they recommended further study to
relate these changes to wild larvae.
Stunted wild striped bass larvae were present in small numbers in
Roanoke River samples, especially in 1984, but stunting may not have been
caused by starvation. Koo and Johnston (1978) reported that eggs of
striped bass exposed to sudden temperature changes resulted in deformed
larvae.' Deformities appeared as shortened bodies, enlarge finfolds, and
curved or twisted spines. In our larboratory experiments, the only
noticeable morphometric differences of striped bass larvae were in the body
lengths of fed (longer) and unfed (shorter) larvae. O'Connell's (1976)
experiment used anchovy larvae similar in age and size to the larval

striped bass reared in our experiment 3. His growth studies showed
significant differences in larval body length as starvation progressed.
Decreased mean length with age was assumed to represent shrinkage, which is
known to occur in starved herring larvae after yolk absorption (Blaxter and
Hempel 1963). O'Connell (1976) concluded that none of his morphological
measurements including larval length could be used to diagnose the starving
condition of northern anchovy larvae for the first nine days of life, but
might be useful for older larvae. Since the stunted wild striped bass
collected from the Roanoke River were still in the yolk stage, we can
speculate that stunting was caused not by starvation but by environmental
factors such as sudden changes in temperature or pH.
Evidence of poor nutritional state was not observed in the 60 wild
larvae examined, but this information does not contradict the possibility
that a high incidence of starvation occurs in the Roanoke River. It is
quite likely that larvae in a starving condition are easily preyed upon or
are not susceptible to capture by our nets as they cannot maintain
equilibrium in the water column, thereby causing them to sink. Thi s
statement is supported by the fact that in 1984, during high flow
conditions, larvae that had died prior to collection comprised 10-50% of
all larvae in the samples (Rulifson et al. 1986). This phenomenon was not
observed in low flow years (1985 and 1986), suggesting that reduced river
turbulence minimizes net capture of dead or dying larvae.
Larval starvation is probably one of the principal causes of mortality
(Hunter 1976), and is hypothesized as one of the contributors to poor year
classes of Potomac striped bass between 1974 and 1977 (Martin and Malloy
1981). Resul ts of our study indicate that striped bass 1 arv ae, if
unsuccessful at feeding while absorbing the yolk, wil I undergo
physiological changes that may further reduce their chances of feeding
successfully after the yol k is absorbed. Thus, the chances of postyol k
larvae feeding successfully are reduced further as starvation progresses:
visual contact with prey organisms will be reduced due to changes or
reduction in retinal pigment; degenerative trunk musculature and poor
glycogen reserves reduce the chances of successful feeding strikes; blood-
forming tissues are reduced, resulting in reduced capacity of the blood to

provide a nutrient supply to tissues; reduced growth limits the ability of
the larvae to select prey of a nutritionally valuable size; and larvae
weakened from starvation are more susceptible to predation and unfavorable
environmental conditions.
Larvae must encounter an abundant food source when feeding is
initiated to optimize feeding success and increase chances of survival
after the yolk is absorbed. The timing of this encounter is dependent upon
several factors: (1) location of egg deposition by striped bass adults; (2)
speed of larval transport downstream; (3) effect of water temperature on
larval growth; and (4) seasonal timing of striped bass spawning to coincide
with maximum zooplankton production. In most watersheds supporting
anadromous striped bass populations, such as those in Chesapeake Bay
tributaries, these four factors coincide for the most part without human
intervention. Such is not the case in the Roanoke River watershed, which
is dominated by reservoirs for recreation and hydropower generation. Water
flow is determined by planned water releases that may not reflect natural
seasonal changes in river flow. Zooplankton concentration during the low
flow years are highest in the Roanoke River delta (Rulifson et al. 1986),
primarily in the Middle (Station 9) and Cashie Rivers (Stations 8 and 11)
near the Highway 45 bridge (Figure 1). Few zoopl ankton are present in
western Albemarle Sound at the same time (Rulifson 1984; Rulifson, Stanley
and Cooper, unpublished data). Therefore, under spring conditions of low
flow(as in 1985), striped bass larvae must begin to feed in the Roanoke
River delta where zooplankton concentrations are highest in order to
optimize changes of feeding successfully.
High-flow conditions were predominant in 1984, resulting in the
appearanceof striped basseggsand yolksac larvae in western Albemarle
Sound. Zoopl an kton concentration in thi s area was very low compared to
that in the delta. The mean abundance of eggs and larvae were
significantly correlated with water discharge from Roanoke Rapids Lake
lagged by three days; these I i fe stages were swept downstream into the
delta from upstream areas in three days (Rulifson et al. 1986).
The effect of water releases in large quantities for hydropower
generation will affect striped bass larvae in several ways. First, the

temperature of released water is cooler than the water downstream. Thi s
acts to curtail spawning activity of the adults and slows the development
of the larvae. Second, the spawning location (distance upstream) is
selected by striped bass adults based upon the amount of water flowing
downstream which determines water depth in spawning areas. This strategy
ensures the necessary length of river and flow rate needed at a particular
water temperature to optimize the number of eggs hatching successfully, and
subsequent development of yol ksac larvae to the feeding stage. Sudden
changes (increases or decreases) in water flow after eggs are spawned
causes an imbalance of this delicate set of conditions, resulting in high
egg and larval mortality. Third, high flow conditions are not conducive
for zooplankton production: turbulence, turbidity, and high rate of
downstream transport do not allow the zooplankton community to reach the
concentration needed for successful feeding of striped bass larvae.
Predictions can be made concerning the length of time needed
(depending on river flow) from the spawning location of the eggs to t he
food supply for larvae in the Roanoke River. Information needed for these
predictions include: (1) estimated spawning location; (2) time required for
eggs to hatch; (3) time after hatch at which feeding begins; and (4) speed
of travel from spawning grounds (as an egg) to optimum foraging grounds (as
a larva). For purposes of argument, we assume that Halifax (river mile
120) is the primary spawning ground for adult striped bass. Rearing
experiments show that striped bass eggs held in ambient Roanoke River water
hatch in approximately 48 hours from spawning. Larval feeding begins 5.5
days after hatching, or about 7 days after they were spawned. Significant
differences (P<0.05) in growth of fed and unfed larvae are apparent 7.5
days after hatching (10.5 days after spawning); larvae feeding successfully
are about 5.5 mm TL at this time (Table 4). Therefore, larvae must begin
to feed between 7 and 9 days after they are spawned.
The last component of information needed to complete the scenario is
missing: no information is available on the relationship between flow rate
measured at Roanoke Rapids and time of travel downstream An additional
unknown quantity is whether this relationship remains linear over the
distance traveled.

However, we do have two years of information on the abundance of
larvae and zooplankton under conditions of high flow (1984) and low flow
(1985). In 1984, transport of eggs and larvae downstream took only three
days under a flow regime of a mean daily rate of 14,000-18,000 cfs. Larval
abundance showed no correlation with low flows (2,000-6,000 cfs) in 1985.
Therefore, the best flow regime for optimizing the nutritional state of
striped bass larvae is between 2,000 cfs and 14,000-18,000 cfs; it must
al so be the f 1 ow rate that transports 1 arvae to the del ta 7 to 9 days af ter
they are spawned at Halifax.
Results of the 1984 and 1985 Roanoke River field studies are depi-cted
in Figure 12. In these simplified drawings, the importance of being in the
right place at the right time becomes apparent. In 1984, Stage 1 larvae
(those still possessing yolk) exhibited peak abundance upstream of peak
zooplankton concentrations. Therefore, the chances for successful feeding
at this crucial stage of development were quite low. By the time the fish
absorbed the yolk (Stage 2 larvae), they were past the greatest zooplankton
concentrations (Figure 12) and chances of feeding successfully were poor.
Gut analyses of 1984 Stage 1 and 2 larvae indicated that the rate of
successful feeding was poor. This must have resulted in high larval
mortality, because the juvenile trawl index for 1984 was 0.0 fish/trawl
(N.C. Div. Mar. Fish.), the worst on record. In 1985, conditions were more
favorable for larval feeding. The abundance of Stage 1 and Stage 2 larvae
occurred downstream close to peak zooplankton abundance (Figure 12). The
number of both Stage 1 and Stage 2 larvae with food in their guts was much
higher than in 1984, and the juvenile trawl index of 0.32 young-of-
year/trawl (N.C. Div. Mar. Fish.) indicated better survival.
Trauma to the ski n may al so contri bute to mortal i ty of stri ped bass
larvae. Since the gills and other body organs are not completely developed
and functional at early larval stages, the skin functions as the major
system in ion exchange and osmoregulation. Disease organisms such as
fungi, bacteria, and parasites present in the water have easy access to
skin. One adaptation to these stresses is in the specialized surface.
structure known as microridges (Yamada 1968).
Examination of the skin using scanning electron microscopy indicated

7- RIVER DELTA -@-SOUND --70

1984

5- -50

3- -30
CtCkdOcerG(\S ME
0
E 0
-10 V-
Sta e 2 L
CL CL
0 V)

Ld
U
0 7- -70 0
n Ld
< sta e I

U
5- 1985 50

.3 -30

-10

40 30 20 10 0 lb
RIVER MILE

Figure 12. Simplified drawing depicting the springtime
densities of Stage 1 (with yolk) striped
bass larvae, Stage 2 (no yolk) larvae, and
zooplankton in the Roanoke River, North
Carolina, in a year of high river flow
(1984) and low river flow (1985).

changes in the microridge structure after striped bass larvae had been
exposed to low pH (5.5) and high concentrations of al uminum (608 ug
Al 3+/ 1 ). These condi tion s are 1 ethal to stri ped bass I arv ae in the
laboratory (Mehrle et al. 1984; Colombo, unpublished data) and are
suspected of contributing to mortality of larvae held under in situ
conditions in the Nanticoke River estuary (Hall et al. 1985). KI auda and
Palmer (1986) reported abnormalities in the integument of bl ueback herring
(Al osa aesti Val i s) yol k-sac 1 arv ae exposed to I ow pH and hi gh al uminum.
Total aluminum Val ues as high as 2400 ug/l were recorded in the Roanoke
River during our study (Table 3). The methodology used to determine pH did
not have the accuracy required for data comparisons with other studies.
However, our results suggest that striped bass larvae may exhibit high
mortality one to two days after hatching due to skin stress, followed by a
second mortality due to starvation.

SUMMARY

Striped bass larvae held in ambient Roanoke River water were feeding
successfully on Artemia by 6.5 days post-hatch. The growth of unfed larvae
was significantly less (P<0.05) than fed larvae at 7.5 days post-hatch.
Histological examination showed a decline in the nutritional state of unfed
larvae as soon as 5.5 days after hatching. By 11.5 days post-hatch, unfed
larvae showed abnormal eye development, reduction in liver glycogen,
collapsed and empty digestive tracts, reduced hemopoietic tissue in the
pronephric kidneys, and thin and separated muscle fibers. The 60 wild
Roanoke River larvae histologically examined showed no signs of starvation.
.We believe that larvae dying from or weakened by starvation are easily
preyed upon or are not susceptible to net capture. High concentrations of
aluminum (608 ug A13+/l) in low pH waters (5.5) alters the microri dge
structure of larval skin, which functions as the gill at this stage of
devel opment. Poor water quality may place undue stress on the skin,
resulting in high mortal ity one to two days post-hatch. Another peak in
mortality may occur from starvation effects 5-10 days post-hatch.

ACKNOWLEDGEMENTS

We take this opportunity to thank the following people for
contributing to the completion of our study: personnel of the North
Carolina Wildlife Resources Commission, hatchery assistance; Ruth Carson
and Nancy Morse, histological preparation of specimens; Drs. Paul
Strausbauch and Eric May, tissue diagnostics; Drs. Charles Bland and
Gerhard Kalmus, histology equipment; Tim Charles, scanning electron
microscope; David Bronson, Scott Wood, Michael Andrews, Pete Kornegay, Al
Simpson, and Tony Mullis, collection of wild larvae; and Sandy Tomlinson,
manuscript preparation.

LITERATURE CITED

Arthur, D.K.
1976. Food and feeding of larvae of three fishes occurring in the
California Current. Sardinops sagax, Engraulils mordax, and Trachurus
symmetricus. Fish. Bull., U.S. 7 ".17-530.

Blaxter, J.H.S. and G. Henepel.
-1963. The influence of egg size on herring larvae. Journal du
Conseil, Conseil Int. pour l'Exploration de la mer 28:211-240.

Bonn, E.W., W.M. Bailey, J.D. Bayless, K.E. Erickson, and R.E. Stevens.
1976. Guidelines for striped bass culture. American Fisheries
Society, Bethesda, MD.

Ehrlich, K.F., J.H.S. Blaxter and R. Pemberton.
1976. Morphological and histological changes during the growth and
starvation of herring and plaice larvae. Mar. Biol. (Berl.) 35:105-
118.

Grover, J.J. and B.L. Olla.
1986. Morphological evidence for staration and prey size selection of
sea-caught larval sablefish, Anoplopoma fimbria. Fish. Bull., U.S.
84:484-489.

Guier, C.R., A.W. Mullis, J.W. Kornegay, S.G. Keefe, H.B. Johnson, and M.W.
Street. 1980. Biological assessment of Albemarle Sound-Roanoke River
striped bass. Prepared jointly by N.C. Wildl. Resources Comm. and
N.C. Div. Mar. Fish., 13 p. + Append.

Hall, L.W., Jr., A.E. Pinkney, L.O. Horseman, and Susan E. Finger.
1985. Mortality of striped bass larvae in relation to contaminants
and water quality in a Chesapeake Bay tributary. Trans. Amer. Fish.
Soc. 114:861-868.

Hassler, W.W., N.L. Hill, and J.T. Brown.
1981. Status and abundance of striped bass, 11orone saxatil-is, in the
Roanoke River and Albemarle Sound, North Carolin , 1956-1980. N.C.
Dept. Nat. Res. Commun. Devel., Div. Mar. Fish., Spec. Sci. Rep. No.
38, 156 p.

Hunter, J.R. (ed.)
1976. Report of a colloquium on larval fish mortality studies and
their relation to fishery research, January 1975. U.S. Dep. Commer.,
NOAA Tech. Rep. NMFS Circ. 395, 5 p.

Klauda, R.J. and R.E. Palmer.
1986. Laboratory and field bioassay experiments on blueback herring
(Alosa aestivalis) from Maryland coastal plain streams. The Johns
H-5-571'ns Univers7ty, Applied Physics Laboratory, Laurel, MD, Final
Report for DNR Contract No. PR-85-066-02.

Koo, T.S.Y. and M.L. Johnston.
1978. Larva deformity in striped bass, Morone saxatf 1 is (Wal baum),
and bl ueback herring, Al-osa aestf val is MIT= I ), due F heat shock
treatment of developing -eggs. Environ7 Pollut. 16:137-149.

Kornegay, J.W.
1981. Investigations into the possible causes of the decline of
Albemarle Sound striped bass. Final Report. N.C. Wildl. Resources
Comm., Raleigh, N.C., 18 p.

Kornegay, J.W. and A.W. Mullis.
1984. Investigations into the decline in egg viability and juvenile
survival of Albemarle Sound striped bass (Morone saxatilis). Final
Report on Proi. F-22, Study VIII. N.C. -WW=. Resourc s Comm.,
Raleigh, NC., 13 p.

Kostomarova, A.A.
1962. Effect of starvation on the development of the larvae of bony
fishes. Tr. Inst. Morfol. Zhivotn. Akad. Nauk. SSSR 40:4-77.

Martin, F.D. and R. Malloy,
1981. Histological and morphometric criteria for assessing
nutritional state of larval. striped bass, Morone saxatilis. Maryland
Sea Grant Program, UM-SG-RS-81-01, 10 p.

McCoy, E.G.
1959. Quantitative sampling of striped bass, Roccus saxatilis
(Walbaum), eggs in the Roanoke River, North Carolina. 'es I s
N.C. State Univ., Raleigh, N.C., 136 p.

Mehrle, P.M., D. Buckler, S. Finger and L. Ludke.
1984. Impact of contaminants on striped bass. U.S. Fish Wildl.
Serv., Columbia National Fisheries Research Laboratory, Interium
Report, Columbia, MO.

Nakai, Z., M. Kosaka, M. Ogura, G. Hayashida, and H. Shimozono.
1969. Feeding habit, and depth of body and diameter of digestive
tract of shirasu, in relation with nutritious condition. J. Coll.
Mar. Sci. Technol., Tokai Univ. 3:23-34.

O'Connell, C.P
1976. Hi;tological criteria for diagnosing the starving condition in
early post yolk sac larvae of the northern anchovy, Engraulis mordax
Girard. J. Exp. Mar. Biol. Ecol. 25:285-312.

Powell, A.B. and A.J. Chester
1985. Morphometric indices of nutritional condition and sensitivity
to starvation of spot larvae. Trans. Amer. Fish. Soc. 114:338-347.

Rulifson, R.A.
1984. Food and feeding of young striped bass in western Albemarle
Sound, North Carolina. N.C. Dept. Nat. Res. Commun. Devel., Div. Mar.
Fish., Compl. Rep. for Contract C-1366, 47 p.

Rulifson, R.A. and D.W. Stanley.
1985. Food and feeding of young striped bass in Roanoke River and
western Albemarle Sound, North Carolina, 1984. N.C. Dept. of Nat.
Res. Commun. Devel., Div. of Mar. Fish., Ann. Progr. Rep. for Project
AFS-24, Segment 1, 252 p.

Rulifson, R.A., D.W. Stanley and J.E. Cooper.
1986. Food and feeding of young striped bass in Roanoke River and
western Albemarle Sound, North Carolina, 1934-1986. N.C. Dept. Nat.
Res. Commun. Devel., Div. Mar. Fish., Compl. Rep. for Project AFS-24.

Shelbourne, J.E.
1957. The feeding and condition of plaice larvae in good and bad
plankton catches. J. Mar. Biol. Assoc. U.K. 36:539-552.

Street, M.W.
1975. The status of striped bass in Albemarle Sound, North Carolina.
Memorandum to N.C. Mar. Fish. Comm. and N.C. Wildl. Res. Comm., 10
December 1975.

Theilacker, G.H.
1978. Effect of starvation on the histological and morphological
characteristics of jack mackerel , Trachurus symmetricus, larvae.
Fish. Bull., U.S. 76:403-414.

Yamada, J. 1968. A study on the structure of surface cel 1 layers in the
epidermis of some teleosts. Annot. Zool. Jap. 41:1-8.

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
1
J
3 6668 00003 7020
IM '@l III M@;