MARINE F I S H PROPAGATION WITH ATLANTIC CROAKER

C. Robert Cooke, Jr. and Richard G. Mooney Texas Parks and W i l d l i f e Department

Olmito S t a t e F i s h Hatchery I n l a n d F i s h e r i e s Funct ion Brownsvi l le , Texas 78520

ABSTRACT

A t l a n t i c c r o a k e r (Micropogon u n d u l a t u s ) were c o l l e c t e d by hook and l i n e i n t h e Lower Laguna Madre a t P o r t I s a b e l , Texas. The f i s h were t r a n s p o r t e d t o t h e Olmito S t a t e F ish Hatchery a t Brownsvi l le , Texas i n a 3,780 l i t e r t r a n s p o r t t a n k .

A t t h e h a t c h e r y each f i s h was weighed, c a t h e t e r e d f o r egg sample, and p laced i n a 3,780 l i t e r p l a s t i c swimming pool . Female c r o a k e r were i n j e c t e d w i t h 300 I . U . o f c h o r i o n i c gonado- t r o p h i n per 454 g of body weight . The hormone caused t h e c roaker t o g a i n 50 g of w a t e r weight , and eggs matured i n 33 hours a f t e r i n j e c t i o n a t 2 2 t o 25 C . A t t h i s t i m e , eggs were s t r i p p e d i n t o a s m a l l bowl, and m i l t was added and spread w i t h a f e a t h e r . S a l t w a t e r was added t o a c t i v a t e sperm and diatomaceous e a r t h was used t o c o a t eggs t o prevent clumping.

F e r t i l i z e d eggs were p laced i n v a r i o u s i n c u b a t i n g systems t o de te rmine t h e b e s t system f o r c r o a k e r and r e l a t e d s p e c i e s . Hatching began a t 20 hours a f t e r t h e eggs were p laced i n incu- b a t o r s when t h e tempera ture was he ld a t 20 t o 25 C . A t h a t c h i n g t h e l a r v a e were approximately 1.5 mm i n l e n g t h , t r a n s p a r e n t , eyes unpigmented, and d i g e s t i v e s y s t e m and mouth l a c k i n g .

INTRODUCTION

Numerous marine s p e c i e s have been a r t i f i c i a l l y propagated and a l s o have been t r a n s p l a n t e d t o f r e s h w a t e r r e s e r v o i r s i n West Texas wi th moderate s u c c e s s (Henderson, 1972) . T h i s , w i t h

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t h e s u c c e s s o f s t o c k i n g s t r i p e d bass (Roccus s a x a t i l i s ) , i n t o r e s e r v o i r s has prompted r e i n v e s t i g a t i o n o f marine f i s h i n t r o d u c - t i o n i n t o f r e s h w a t e r . However, any major i n t r o d u c t i o n of mar ine f i s h s p e c i e s t o a l a k e depends on p r o d u c t i o n of a p r e d i c t a b l e number of j u v e n i l e s . Encouraged by i n i t i a l o b s e r v a t i o n s , t h e Texas Parks and W i l d l i f e Commission approved a s t u d y f o r a r t i f i c i a l p r o p a g a t i o n of s e v e r a l mar ine f i s h s p e c i e s from t h e Gulf of Mexico. The s p e c i e s s e l e c t e d f o r t h i s s t u d y were: r e d drum, (Sciaenops o c e l l a t a ) ; s o u t h e r n f l o u n d e r ( P a r a l i c h t h y s l e t h o s t i g m a ) ; s p o t t e d s e a t r o u t ( g n o s c i o n n e b u l o s u s ) ; common snook (Centropomus u n d e c i m a l i s ) ; and sheepshead (Archosargus p r o b a t o c e p h a l u s ) . Most o f t h e s e a r e w e l l known s a l t w a t e r game f i s h e s i n Texas. It i s hoped t h a t i n t r o d u c t i o n of t h e s e s p e c i e s can l e a d t o b e t t e r f i s h - i n g i n r e s e r v o i r s and more p r e d a t i o n on t h e abundant rough f i s h p o p u l a t i o n s o f most l a k e s .

The A t l a n t i c c r o a k e r (Micropogon u n d u l a t u s ) was s e l e c t e d as an a l t e r n a t e s p e c i e s i n t h e e v e n t t h a t s u f f i c i e n t numbers of brood r e d drum were n o t ob ta ined d u r i n g t h e f a l l spawning season . S i n c e t h e c r o a k e r i s c l o s e l y r e l a t e d t o t h e r e d drum and t h e spawning season and h a b i t s a r e s i m i l a r , i t was f e l t t h a t any a r t i f i c i a l p r o p a g a t i o n t e c h n i q u e s developed would be a p p l i c a b l e t o both s p e c i e s .

COLLECTION OF BROODFISH

October 10, 1 9 7 2 , g r a v i d A t l a n t i c c r o a k e r s were n e t t e d i n t h e lower Laguna Madre n e a r P o r t M a n s f i e l d , Texas, t r a n s p o r t e d t o Olmito S t a t e F i s h Hatchery , and p laced i n a 3,780 l i t e r swimming pool c o n t a i n i n g s a l t w a t e r a t 34 ppt s a l i n i t y . By October 11, t h e f i s h were showing s i g n s of a b a c t e r i a l and f u n g a l i n f e c t i o n i n a r e a s where t h e trammel n e t had i r r i t a t e d and d is lodged s c a l e s . The f i s h were t r e a t e d w i t h Amifur a n t i b i o t i c 1 , a t a c o n c e n t r a t i o n of 454 g p e r 3,780 l i t e rs o f w a t e r . Most showed some s i g n of recovery by October 13; however, a l l f i s h d i e d on t h i s d a t e because o f a pump f a i l u r e . Due t o t h e damage by n e t s , a l l o t h e r c r o a k e r s were c o l l e c t e d by hook and l i n e a t P o r t I s a b e l , Texas.

INJECTIONS AND EGG DEVELOPMENT

A t 4:45 p.m. October 11, e i g h t g r a v i d females were s e l e c t e d

(Note: F ish f o r i n j e c t i o n w i t h hormones. These f i s h were a n e s t h e t i z e d f o r 2 minutes i n 10 t o 20 ppm s o l u t i o n of q u i n a l d i n e 2 . should be l e f t i n t h i s c o n c e n t r a t i o n of q u i n a l d i n e only long enough t o a n e s t h e t i z e . Over-exposure r e s u l t s i n d e a t h ) . A t t h i s t i m e , a n egg sample was t a k e n by a c a t h e t e r (S tevens , 1966)

l N o w i c h A g r i c u l t u r a l P r o d u c t s , Norwich, New York (Use of t r a d e names i s merely t o f a c i l i t a t e d e s c r i p t i o n ; no endorsement i s impl ied .

*Eastman Kodak Company, Roches te r , New York

Marine F i s h Propagat ion 157

t o de te rmine egg development b e f o r e i n j e c t i o n . Microscopic examinat ion determined t h a t eggs were approximate ly 0.5 nnn i n d i a m e t e r , opaque, g r a n u l a t e d , and had a c l e a r a r e a around t h e o u t s i d e edge.

Pregnant mare serum (PMS)3 and human c h o r i o n i c gonadotrophin (HCG)4 were s e l e c t e d f o r use on A t l a n t i c c r o a k e r because o f t h e work done on Gulf c r o a k e r , ( B a i r d i e l l a i c i s t i a ) (Haydock, 1971). PMS and HCG were both i n j e c t e d i n t r a m u s c u l a r and i n t r a p e r i t o n e a l a t an average of 120 IU/lOO g of body weight . Four f i s h were g iven i n t r a m u s c u l a r i n j e c t i o n wi th a 25.4 mm 24 gauge needle i n t h e deep muscles o f t h e back below t h e d o r s a l f i n . The o t h e r f o u r f i s h were i n j e c t e d i n t r a p e r i t o n e a l w i t h a 25.4 nnn 24 gauge n e e d l e just behind t h e p e l v i c f i n . F ish were i n d i v i d u a l l y marked by f i n c l i p p i n g and r e l e a s e d i n t o a 3,024 l i t e r s a l t w a t e r ho ld ing tank .

A t 5 :OO p.m. October 1 2 , an egg sample was taken from each o f t h e i n j e c t e d f i s h . Examination of t h e samples showed t h a t a l l HCG i n j e c t e d f i s h showed marked egg development. The eggs had begun t o c l e a r and p o l a r i z e o i l g l o b u l e s clumped i n t o t h r e e o r more drops w i t h i n t h e egg. Those f i s h i n j e c t e d wi th PMS showed no d i s c e r n i b l e development o f eggs.

A t 9:00 p.m., 2 8 hours a f t e r i n j e c t i o n , one HCG f i s h had f r e e l y f lowing eggs. The eggs were hand s t r i p p e d i n t o a smal l p l a s t i c bowl and m i l t was added by hand s t r i p p i n g a male. This m i l t was spread over t h e eggs w i t h a f e a t h e r . S a l t w a t e r was added t o a c t i v a t e t h e sperm. One minute was allowed f o r f e r t i l i - z a t i o n , then c o r n s t a r c h was added and s t i r r e d t o c o a t t h e eggs t o prevent clumping. The eggs were t h e n w a t e r hardened f o r 1 hour and placed i n a McDonald i n c u b a t i n g j a r a t 10:30 p.m.

A t 1 1 : O O p.m., a n o t h e r HCG f i s h was s t r i p p e d and t h e eggs f e r t i l i z e d and p laced i n an i n c u b a t i n g j a r a t 12:30 a.m. O f t h e two remaining HCG f i s h , one overhydra ted , caus ing d e a t h , and t h e o t h e r developed eggs w i t h blood s t r e a k s i n t h e egg mass and vas- c u l a r i z e d o v a r i a n t i s s u e .

The r i p e eggs s t r i p p e d from t h e females , were approximately 0.75 mm i n d i a m e t e r , p e r f e c t l y s p h e r i c a l , t r a n s p a r e n t , and wi th a s i n g l e s l i g h t l y opaque o i l g l o b u l e . Two t o 4 hours a f t e r f e r t i l i z a t i o n , a smal l i n d e n t a t i o n could be seen developing from t h e o u t s i d e of t h e egg i n t o t h e yolk. T h i s i n d e n t a t i o n was t h e a p p a r e n t p o i n t o f sperm e n t r a n c e and w i t h i n 5 t o 6 hours t h e b l a s t o d i s c developed from t h i s p o i n t , which i s o p p o s i t e t h e o i l g l o b u l e a t t h e v e g e t a l p o l e (Smith and Fahay, 1970). A f t e r 13 hours , t h e embryo extended halfway around t h e egg. The myomeres, unpigmented e y e s , and melanophores could be seen . A t 15 hours ,

3Sigma Chemical Company, S t . Louis , Missour i (F’MS Stock No. G-4877)

‘Sigma Chemical Company, S t . Louis , Missour i (HCGStock No. CG-10)

158 WORLD WICULTURE SOCIETY WORKSHOP

t h e embryo could move and t h e h e a r t could be s e e n pumping. A t 19 hours , t h e embryo extended t h r e e - f o u r t h s around t h e egg and t h e permordia l f i n was developed a s h a t c h i n g neared .

The PMS f i s h were s a c r i f i c e d 3 4 hours a f t e r i n j e c t i o n w i t h s t i l l no d i s c e r n i b l e development o f t h e eggs.

INCUBATION

The f i r s t eggs o b t a i n e d from c r o a k e r were p laced i n McDonald i n c u b a t i o n jars w i t h a 19 mn shad tube . An overhead r e s e r v o i r i n t r o d u c e d a c o n s t a n t w a t e r f low a t t h e bottom o f t h e j a r through t h e shad t u b e c r e a t i n g an upward c i r c u l a t i o n o f w a t e r t o t h e overf low a t t h e t o p o f t h e jar . The upward w a t e r flow was r e g u l a t e d so t h a t t h e eggs remained a f l o a t . n i t e x s c r e e n was a t t a c h e d t o t h e overf low o u t l e t t o prevent egg l o s s . Even an ex t remely s m a l l c u r r e n t of water running through t h e j a r p u l l e d t h e eggs and l a r v a e a g a i n s t t h e s c r e e n o v e r t h e overf low. The eggs developed and ha tched a g a i n s t t h e s c r e e n , b u t t h e l a r v a e were i n j u r e d and d i d n o t s u r v i v e .

A p i e c e of 2 5 0 ~

I n t h e second a t t e m p t , on ly t h e hormone HCG was g iven i n t r a - m u s c u l a r i l y a t t h e p r e v i o u s dosage. F i r s t p rocedure was fol lowed from i n j e c t i o n t o f e r t i l i z a t i o n except t h a t diatomaecous e a r t h was s u b s t i t u t e d f o r c o r n s t a r c h . The f e r t i l i z e d eggs were a g a i n p laced i n McDonald j a rs , b u t when t h e eggs hatched t h e c i r c u l a t - i n g w a t e r was s topped and a i r s t o n e s were p laced a t t h e bottom o f t h e j a r s . The r i s i n g a i r bubbles c r e a t e d an upflow and k e p t t h e l a r v a e a f l o a t and moving through t h e water. U n f o r t u n a t e l y , t h e a i r supply t o t h e jars f a i l e d and t h e l a r v a e sank and d i e d .

A t h i r d group o f c r o a k e r were brought t o t h e h a t c h e r y on November 1. Again HCG i n j e c t i o n s were g i v e n i n t r a m u s c a r i l y and p a s t p rocedures were fol lowed. Twenty-four hours a f t e r i n j e c - t i o n s t h e eggs had n o t developed. It was t h e n determined t h a t t h e HCG used f o r t h e i n j e c t i o n s was i n a c t i v e .

On November 3, a f o u r t h group was g iven i n t r a m u s c u l a r dosages from 100 I U / l O O g t o 600 IU/100 g of body weight t o de te rmine i f t h e r e was a maximum dosage l e v e l a t which HCG would become l e t h a l (Haydock, 197 1).

A l l i n j e c t e d c r o a k e r s were h e l d i n t h e open a i r and t h e water t e m p e r a t u r e could n o t be c o n t r o l l e d . (A c o l d f r o n t dropped the water t e m p e r a t u r e t o 1 7 C compared t o tempera tures o f 2 4 t o 28 C a t which t h e p r e v i o u s l y i n j e c t e d f i s h had been h e l d . ) Due t o t h i s low vater tempera ture and longer h y d r a t i o n p e r i o d , t h e egg8 never r i p e n e d .

On November 7 , a f i f t h group of c r o a k e r s caught a t P o r t I s a b e l were brought t o t h e h a t c h e r y where HCG i n j e c t i o n s were given. Tho injected f i s h were placed i n a smaller 378 l i t e r t a n k and w a t e r h e a t e r s were used t o c o n t r o l water tempera ture .

Marine F i s h Propagat ion 159

The f i s h developed v i a b l e eggs which were f e r t i l i z e d and placed i n round 1 0 - l i t e r g l a s s jars. A i r s t o n e s were u s e d ’ t o c r e a t e w a t e r c i r c u l a t i o n necessary t o keep eggs and l a r v a e a f l o a t .

These eggs ha tched i n 24 hours , but t h e l a r v a e surv ived o n l y u n t i l t h e second day.

Eggs were obta ined from a s i x t h and seventh group of c roakers and a d i f f e r e n t procedure was used . A f t e r f e r t i l i z a t i o n , t h e eggs were water hardened i n a l a r g e j a r and t h e n skimmed from t h e s u r f a c e of t h e water, b e f o r e they begun t o s i n k . Viable eggs f l o a t e d whi le t h e nonviable eggs s e t t l e d o u t a long w i t h vascu- l a r i z e d o v a r i a n t i s s u e . I n prev ious exper iments , a f t e r water hardening f o r about a n hour i n t h e i n c u b a t o r s , t h e water c i r c u l a - t i o n was begun and good and bad eggs l e f t t o g e t h e r . It was f e l t t h a t t h e d e t e r i o r a t i o n o f nonviable eggs o v a r i a n t i s s u e could produce s u b s t a n c e s d e t r i m e n t a l t o t h e l a r v a l c r o a k e r s . By p l a c i n g t h e v i a b l e eggs i n c l e a n s a l t w a t e r , it was hoped t h a t t h i s d i f f i c u l t y would be avoided. I n a d d i t i o n , many of t h e h a t c h i n g l a r v a e were s iphoned o u t and p laced i n i n c u b a t o r s wi th c l e a n s a l t w a t e r . A round i n c u b a t o r system, c p n s i s t i n g of a c i r c u l a r g l a s s j a r w i t h an a i r r i n g around t h e bottom, was c o n s t r u c t e d a f t e r t h e method of Houde and Ramsay (1972) . A i r r i s i n g around t h e i n n e r edge o f t h e j a r , it was hoped, would provide water c i r c u l a t i o n t h a t would keep t h e l a r v a e a f l o a t wi thout i n j u r i n g them.

The i n c u b a t o r s were p laced indoors so t h a t t h e water tempera- t u r e could be c o n t r o l l e d .

LARVAL DEVELOPMENT

A t h a t c h i n g , t h e l a r v a e were approximately 1 . 5 mm long and had unpigmented eyes. The newly hatched l a r v a e had no f i n buds, mouth p a r t s , o r d i g e s t i v e system. The o t o c y s t , notochord, myomeres, and c r a n i a l a r e a could be d i s t i n g u i s h e d through t h e t r a n s p a r e n t body. The y o l k s a c was s t i l l a t t a c h e d t o t h e head w i t h a p o s t e r i o r l y l o c a t e d o i l g l o b u l e . The premordia l t a i l and most o f t h e body and head had d e n d r i t i c melanophores.

By t h e second day , t h e y o l k sac had been absorbed l e a v i n g only t h e o i l g lobule . The r e n a l t r a c t had begun t o deve lop from near t h e o i l g lobule . The f i n f o l d a t h a t c h i n g was c o n s i d e r a b l y behind t h e o t o c y s t , b u t by t h e second day extended t o t h e eye. The mala- nophores were n o t e v i d e n t and t h e eye was s t i l l unpigmented. The o t o c y s t wi th two o t o l i t h s could be noted d o r s o - p o s t e r i o r t o t h e e y e .

On t h e t h i r d day, eye p igmenta t ion had s t a r t e d and t h e o i l g l o b u l e was s t i l l l a r g e ; t h r e e t i m e s t h e s i z e of t h e eye. The f i n f o l d had begun t o move p o s t e r i o r l y and t h e anus was develop- i n g , bu t no opening was p r e s e n t . p o s i t i o n behind t h e e y e . The a n t e r i o r a l i m e n t a r y t rac t had begun t o form wi th an i n d e n t a t i o n d o r s o - a n t e r i o r t o t h e eye where t h e mouth was forming, and a t u b e had developed from t h e o i l g lobule

The o t o c y s t had moved t o a

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t o t h e v i c i n i t y o f t h e eye.

No d e s c r i p t i o n o f t h e l a r v a e p a s t t h e t h i r d day i s a v a i l a b l e because a l l b u t one group d i e d d u r i n g t h i s day.

DISCUSSION

I f female c r o a k e r s a r e caught when eggs a r e i n t h e g r a n u l a t e d s t a g e , egg r i p e n e s s can be induced by hormone i n j e c t i o n s o f HCG. Although PMS was used d u r i n g t h e f i r s t exper iment , i t s use was d i s c o n t i n u e d a f t e r i t proved i n e f f e c t i v e . S t u d i e s on t h e Gulf c r o a k e r showed PMS a t 50 t o 100 I U / l O O g of body weight caused o v u l a t i o n , w h i l e HCG caused t h e f i s h t o h y d r a t e b u t no t o v u l a t e . HCG caused b l o a t i n g and d e a t h i n Gulf c r o a k e r (Haydock, 1971) . I n t h e p r e s e n t s t u d y , HCG caused b l o a t i n g , but v i a b l e eggs could be o b t a i n e d a t any dosage from 100 t o 600 I U / l O O g of body weight . Only one f i s h o u t o f f o u r developed eggs which could be f e r t i l i z e d .

Once i n j e c t i o n s were g iven , v i a b l e eggs could be obta ined i n 2 8 t o 36 h o u r s , depending on t h e w a t e r tempera ture i n which t h e i n j e c t e d f i s h were h e l d . During t h e f i r s t two exper iments , water tempera ture ranged from 24 t o 2 8 C and eggs were o b t a i n e d i n 2 8 t o 3 0 hours . On subsequent a t t e m p t s , when t h e w a t e r was k e p t a t 2 1 t o 2 3 C , eggs were obta ined i n 3 3 t o 36 hours w h i l e a t a tempera ture of 17 t o 2 0 C t h e f i s t : d i d n o t deve lop v i a b l e eggs. Three groups of f i s h h e l d i n a 3 7 8 l i t e r t a n k w i t h water h e a t e r s m a i n t a i n i n g t h e w a t e r a t 2 1 t o 2 3 C produced v i a b l e eggs i n 3 3 hours .

Viable eggs were c h a r a c t e r i z e d by a s i n g l e o i l g l o b u l e w i t h no yel low mass enveloping them. The eggs were f e r t i l i z e d by adding sperm, thoroughly s t i r r e d , t h e n adding s a l t w a t e r . Sperm remain a c t i v e f o r o n l y a couple o f minutes a f t e r a c t i v a t i o n . S i n c e some t r o u b l e was exper ienced i n o b t a i n i n g sperm, one male was i n j e c t e d w i t h 100 IU o f HCG. This dose caused t h e sperm t o flow *

Nonviable eggs were o b t a i n e d from g r o s s l y b l o a t e d f i s h . These clumped t o g e t h e r and surrounded w i t h yellow v a s c u l a r i z e d o v a r i a n t i s s u e . Many eggs conta ined f r a c t i o n a t e d o i l g l o b u l e s w i t h blood s t r e a k s running throughout t h e egg mass.

S u c c e s s f u l i n c u b a t i o n o f t h e c r o a k e r eggs r e s u l t e d i n up t o 50% h a t c h i n g s u c c e s s . The water tempera ture i n which t h e eggs were h e l d was t h e c o n t r o l l i n g f a c t o r i n h a t c h i n g t i m e . With t h e f i r s t and second group o f eggs , t h e w a t e r tempera ture ranged between 24 t o 27 C , and h a t c h i n g began i n 20 hours . I n t h e f i f t h and s i x f h group o f eggs , t h e water tempera ture ranged between 2 1 t o 23 C , and t h e eggs hatched i n 2 4 - 2 6 hours w h i l e i n t h e seventh group t h e water tempera ture ranged between 26 t o 2 9 C , and h a t c h i n g began a t 16 hours .

Marine F i s h Propagat ion 161

Although eggs were hard and could w i t h s t a n d c o n s i d e r a b l e t u r b u l e n c e i n t h e i n c u b a t o r s , s u r v i v a l o f l a r v a l c r o a k e r s was minimal . S e v e r a l t y p e s of i n c u b a t i o n systems were used , none of which provided l a r v a l s u r v i v a l f o r more than 5 days . Consider- a b l e e f f o r t was made t o c o n t r o l t h e s a l i n i t y , t empera ture , and p u r i t y of t h e water i n t h e i n c u b a t o r s , bu t most o f t h e l a r v a e d i e d w i t h i n 2 days . A t f i r s t t h e i n c u b a t o r s were out -of -doors where a tempera ture f l u x a t i o n o f 100 was exper ienced by t h e l a r v a e . It was thought t h a t moving t h e i n c u b a t o r s indoors where t h e tempera ture could be c o n t r o l l e d would i n c r e a s e l a r v a l s u r - v i v a l , bu t t h i s d i d not happen.

Varying s a l i n i t y from 32 ppt t o 40 ppt had no n o t i c e a b l e e f f e c t on t h e i n c u b a t i o n of t h e eggs o r l a r v a l s u r v i v a l .

Apparent ly t h e t u r b u l e n c e c r e a t e d by t h e water c i r c u l a t i o n i n t h e i n c u b a t o r s i n j u r e s t h e l a r v a e and k i l l s them. A t t h e time of h a t c h i n g , t h e l a r v a e a r e ex t remely s m a l l , wi th unpigmented eyes and no f i n development. They d a r t v i g o r o u s l y through t h e w a t e r , bu t cannot s w i m f o r more t h a n a second, and a r e completely a t t h e mercy o f t h e water c u r r e n t s i n t h e i n c u b a t o r s . This sub- j e c t s them t o c o n s i d e r a b l e t o s s i n g and tumbling.

LITERATURE CITED

Haydock, I rwin . 1971. Gonad m a t u r a t i o n and hormone-induced spawning o f t h e Gulf c r o a k e r , B a i r d i e l l a i c i s t i a . U . S . Department o f Commerce F i s h e r i e s B u l l e t i n 69(1):157-180.

Henderson, George G. 1972. Marine i n t r o d u c t i o n s , F-18-R-5, Job N o . 8, Texas Parks and W i l d l i f e Department Job Comple- t i o n Report . 33 p.

Houde, Edward D . , and Andrew J. Ramsay. 1971. A c u l t u r e system f o r marine f i s h l a r v a e . P r o g r e s s i v e F i s h - C u l t u r i s t 3 3 ( 3 ) : 156-157.

Smith, W . G . , and Michael P. Fahay. 1970. D e s c r i p t i o n of eggs and l a r v a e of t h e sununer f l o u n d e r , P a r a l i c h t h y s d e n t a t u s . U . S . F i s h and W i l d l i f e S e r v i c e Research Report No. 75. i v - 2 1 p.

S t e v e n s , Robert E . 1966. Hormone-induced spawning of s t r i p e d b a s s f o r r e s e r v o i r s t o c k i n g . P r o g r e s s i v e F i s h - C u l t u r i s t 28(1):19-28.