SAND SEATROUT AND SILVER SEATROUT seatrout and silver seatrout ... (1929) presented a key to aid the ,identification of these species. Gunter (1945) ... Christmas and Waller 1973)

Biological Report 82( 1 1.72) TR EL-82-4 March 1987 -

00 b'p' - e , .. ,n , f !-?!-#7 !! t f ? 1 it)!- .< - -

Species Profiles: Life Histories and t i . - Environmental Requirements of Coastal ~ i s h e g ~ ~

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and Invertebrates (Gulf of Mexico) i -kte..~, LGU.;~JC)CI 70%

SAND SEATROUT AND SILVER SEATROUT

Coastal Ecology Group Fish and Wildlife Service Waterways Experiment Station U.S. Department of the lnterlor U S Army Corps of Engineers

Bio log ica l Report 82(11.72) TR EL-82-4 March 1987

Species Prof i les : L i f e H is to r ies and Environmental Requirements o f Coastal Fishes and Invertebrates (Gulf o f Mexico)


Frederick C. Sut ter and Thomas D. McIlwain Gul f Coast Research Laboratory

Fisher ies Research and Development East Beach Boulevard

Ocean Springs, MS 39564

Pro ject Manager Car ro l l Cordes Pro ject O f f i ce r

David Moran National Wetlands Research Center U.S. F ish and W i l d l i f e Service

1010 Gause Boulevard S l i d e l l , LA 70458

Performed f o r Coastal Ecology Group

Waterways Experiment S ta t ion U. S. Army Corps o f Engineers

Vicksburg, MS 39180

and

National Wet1 ands Research ten te r Research and Development Fish and W i l d l i f e Service

U.S. Department o f I n t e r i o r Washington, DC 20240

This ser ies may be referenced as fo l lows:

U.S. F i s h and W i l d l i f e Service. 1983-19-. Species p r o f i l e s : l i f e h i s t o r i e s and environmental requirements o f coasta l f i shes and inver tebra tes . U. S. F i sh Wi ld l . Serv. B i o l . Rep. 82(11). U. S. Army Corps o f Engineers, TR EL-82-4.

This p r o f i l e may be c i t e d as fo l lows:

Sut te r , F. C., and T. D. McIlwain. 1987. Species p r o f i l e s : l i f e h i s t o r i e s and environmental requirements o f coasta l f i shes and inver tebra tes (Gul f o f Mexico)--sand seat rou t and s i l v e r seatrout . U. S. F i sh W i l d l . Serv. B i o l . Rep. 82(11.72). U. S. Army Corps o f Engineers, TR EL-82-4. 16 pp.

PREFACE

Th is species p r o f i l e i s one o f a se r i es on coasta l aquat ic organisms, p r i n c i p a l l y f i s h , o f spor t , commerciaT, o r eco log ica l importance. The p r o f i l e s are designed t o prov ide coasta l managers, engineers, and b i o l o g i s t s w i t h a b r i e f comprehensive sketch o f t he b i o l o g i c a l c h a r a c t e r i s t i c s and environmental requirements o f t h e species and t o descr ibe how popu la t ions o f t h e species may be expected t o r e a c t t o environmental changes caused by coasta l development. Each p r o f i l e has sect ions on taxonomy, 1 i f e h i s t o r y , eco log ica l r o l e , environmental requirements, and economic importance, i f appl i cab le . A th ree - r i ng b inder i s used f o r t h i s ser ies so t h a t new p r o f i l e s can be added as they are prepared. Th is p r o j e c t i s j o i n t l y planned and f inanced by t h e U.S. Army Corps o f Engineers and the U.S. F i s h and W i l d l i f e Service.

Suggestions o r questions regarding t h i s r e p o r t should be d i r e c t e d t o one of t h e f o l l owing addresses.

I n fo rma t ion Trans fer S p e c i a l i s t Nat ional Wetlands Research Center U.S. F i sh and W i l d l i f e Serv ice NASA-Slidell Computer Complex 1010 Gause Boulevard S l i d e l l , LA 70458

U. S. Army Engineer Waterways Experiment S t a t i o n At ten t ion : WESER-C Post O f f i c e Box 631 Vicksburg, MS 39180

CONVERSION TABLE

Metr ic t o U.S. Customary

M u l t i p l y

m i l l ime te rs (mrn) centimeters (cm) meters (m) meters (m) k i lometers (km) ki lometers (km)

square meters (m2) 10.76 square k i 1 ometers ( km2) 0.3861 hectares (ha) 2.471

l i t e r s (1) cubic meters (m3)

cubic meters (m3)

mi l l ig rams (mg) grams (g) k i 1 ograms (kg) me t r i c tons (t) met r i c tons (t)

k i l o c a l o r i e s (kca l ) 3.968 Celsius degrees (OC) 1.8(OC) + 32

U. S. Customary t o Me t r i c

inches 25.40 inches 2.54 f e e t ( f t) 0.3048 fathoms 1.829 s t a t u t e mi les ( m i ) 1.609 nau t i ca l mi les (nmi) 1.852

square f e e t ( f t2) square mi les ( m i 2 )

acres

gal 1 ons (gal ) 3.785 cubic f e e t ( f t 3 ) 0.02831 acre- f e e t 1233.0

ounces (oz) ounces (oz) pounds ( l b ) pounds ( l b ) sho r t tons ( ton)

B r i t i s h thermal u n i t s (Btu) 0.2520 Fahrenheit degrees (OF) 0.5556(OF - 32)

To Obtain

inches i nches f e e t fathoms s t a t u t e mi les nau t i ca l mi les

square feet square mi les acres

ga l 1 ons cub ic f e e t acre-feet

ounces ounces pounds pounds sho r t tons

B r i t i s h thermal u n i t s Fahrenheit degrees

m i 1.1 imeters cer:timeters meters meters k i lometers k i 1 ometers

square meters square k i lometers hectares

1 i t e r s cubic meters cub ic meters

mi l l ig rams grams k i 1 ograms met r i c tons me t r i c tons

k i l o c a l o r i e s Cels ius degrees

CONTENTS

PREFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i i i CONVERSIONTABLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . i v ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v i

NOMENCLATURE/TAXONOMY/RANGE . . . . MORPHOLOGY/IDENTIFICATION AIDS . . REASON FOR INCLUSION I N THE SERIES LIFE HISTORY . . . . . . . . . . .

Spawning . . . . . . . . . . . . Fecund i ty . . . . . . . . . . . Larvae . . . . . . . . . . . . . Juven i les . . . . . . . . . . . Adul ts . . . . . . . . . . . . .

GROWTH CHARACTERISTICS . . . . . . THE FISHERY . . . . . . . . . . . . ECOLOGICAL ROLE ( food h a b i t s ) . . . ENVIRONMENTAL REQUIREMENTS . . . .

Temperature . . . . . . . . . . S a l i n i t y . . . . . . . . . . . . Disso lved Oxygen . . . . . . . . Subst ra te . . . . . . . . . . .

LITERATURECITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

ACKNOWLEDGEMENTS

We a r e g r a t e f u l t o H.D. Hoese, U n i v e r s i t y o f Southwestern Louisiana, Lafayet te , and Thomas Linton, Texas A&M U n i v e r s i t y , Col lege S t a t i o n , f o r t h e i r review o f the manuscript and he1 p f u l suggestions.

Figure 1. Adult s i l v e r seatrout and sand seatrorrt. (from Fischer 1978).


NOMENC LATURE/TAXONOMY /RANGE

S c i e n t i f i c name . . . arenari us Gi nsburg

Preferred common name seatrout (Figure 1)

Other common names . S c i e n t i f i c name . .

nothus (Holbrook) Preferred common name

seatrout (Figure 1) Class . . . . . . . . Order . . . . . . . . Family . . . . . . .

. . . Cynoscion

. . . . . . Sand

. . White t r o u t . . . Cynoscion

. . . . . S i l ve r

. . Osteichthyes . . Perciformes

. . . Sciaenidae

Geographical range: Sand seatrout are endemic t o the Gulf o f Mexico (Figure 2), and are found from southwest F lo r ida (Roessler 1970) t o the Bay o f Campeche (Hildebrand 1955). The range o f the s i l v e r sea- t r o u t (Figure 3) extends from Chesapeake Bay t o the Bay o f Campeche (Hildebrand and Schroeder 1928; Hildebrand 1955). It i s common on the g u l f coast, the east coast o f F lor ida, and as f a r nor th as North Carolina.

CORPHOLOGY/ID€WTIFICATION AIDS

The f o l lowing morphological descrfp- t i o n s o f sand seat rout and s i l v e r sea- t r o u t were given by Guesr and Gunter (1958).

Cynoscion arenar i us C i nsburg

Vertebrae 25. S o f t anal rays 11, sometimes 10 o r 12. Dorsal s o f t rays modal number 26, commonly 25 o r 27. Total number o f g i l l rakers usua l l y 14 o r 13, b u t f requent ly 15. The usual number o f g i l l rakers on the two l imbs o f t he f i r s t arch i s 4 + 10 o r 3 + 10. Caudal no t emarginate i n i n d i v i d u a l s over 300 m long, t h e middle rays being somewhat 1 onger. Least depth o f caudal peduncle usua l l y shor ter than snout; 1.57 t o 1.82 i n maxi1 l a ry . Color pale, w i thou t we l l - def ined spots, ye1 lowi sh above, s i l v e r y below, t h e center o f t h e scales above l e v e l o f g i l l opening sometimes having f a i n t ob l ique rows o f cloudy areas. Back cloudy i n young, the cloudy areas tending t o form i n d e f i n i t e cross bands.

Cynoscion nothus (Holbrook)

Vertebrae near ly always 27, r a r e l y 26. Anal s o f t rays predominately 9, sometimes 8 and in f requen t l y 10 i n specimens from the A t l a n t i c coast. Dorsal r a t h e r long, t he usual number o f s o f t rays 28 o r 29, f requen t l y 27, less f requent ly 30; t he number o f rays increas ing i n more northern l a t i t u d e s , t he mode being 28 i n g u l f specimens. Tota l number o f g i l l rakers on the f i r s t arch i n specimens 30 t o 130 mm long have a mode of 13, f requent ly 12 o r 14, r a r e l y 15. Most common number o f g i l l rakers on f i r s t arch 3 + 10. Snout shor ter than the l e a s t depth o f caudal peduncle. Caudal peduncle shor t , the length o f t he m a x i l l a r y greater than the distance from p o s t e r i o r end o f i n s e r t i o n o f dorsal t o base o f caudal on mid1 ine. Eye conspicuously l a r g e r than i n sand seatrout . Color pale, w i thout conspicuous pigmentation, the

upper p a r t usua l l y straw o r walnut, t he lower p a r t l i g h t e r s i l v e r y ; sometimes an i n d i c a t i o n o f i r r e g u l a r rows o f f a i n t spots. I n small ind iv idua ls , up t o about 85 nun standard length (SL), t he upper p a r t i s more o r l ess f a i n t l y clouded, t h e cloudy areas tending t o form transverse bands.

Sand seat rout and s i l v e r seat rout are sometimes d i f f i c u l t t o d i s t i n g u i s h (Guest and Gunter 1958; Daniels 1977). Ginsburg (1929) presented a key t o a i d the , i d e n t i f i c a t i o n o f these species. Gunter (1945) noted t h a t the s i l v e r seat rout has c teno id scales, which make i t f e e l rougher t o the touch t k r a ~ ~ sand seatrout .

REASON FOR INCLUSION IN THE SERIES

The sand seat rout i s one o f the most abundant f i shes i n t h e es tuar ine and nearshore waters o f t he g u l f (Gunter 1945; Christmas and Waller 1973). It i s a valuable recreat iona l species (Mo f fe t t e t a l . 1979) and a major component o f t he i n d u s t r i a l bottom fisher-y and shrimp bycatch (Roi thmayr 1965; Sheridan e t a l . 1984). Although s i l v e r seat rout are abundant i n the nearshore waters o f t h e northern Gu l f o f Mexico (Hi ldebrand 1954; Moore e t a l . 1970), l i t t l e study o f t h i s species has been done.

LIFE HISTORY

Spawning

Sand seatrc,gt mature a t 140 t o 180 mm tota: length (TL) as they approach age I i n g u l f waters o f f Freeport, T <as (Shlossman and Chittenden 19 1). Sheridan e t a l . (1984), work i w i t h specimens taken gulf-wide, we e able t o d i s t i n g u i s h males a t 84 mm SL and females a t 82 mm. The ima l l es t maturing male was 129 mm SL dnd the smal lest female was 140 mm.

Shl ossman and Chi t tenden (1981) i d e n t i f i e d two spawning peaks f o r sand seat rout i n Texas g u l f waters using in format ion from gonad development studies and c o l l e c t i o n s o f small f i s h (20 t o 80 mm TL). They proposed a f i r s t spawning peak i n e a r l y March t o May (spring), and a second i n l a t e summer (August and September). Sheridan e t a l . (1984) found matur ing and r i p e f i s h p r i m a r i l y du r ing March and A p r i l , al though r i p e females were taken i n August and males dur ing October. Other s tud ies o f sand sea- t r o u t have ind i ca ted a broad pe r iod o f spawning dur ing spr ing and l a t e summer (Franks e t a l . 1972; Gallaway and Strawn 1974; M o f f e t t e t a l . 1979).

Sand seat rout spawn i n lower es tuar ine environments o r inshore g u l f waters. Shlossman and Chi t tenden (1981) i d e n t i f i e d spawning loca t i ons by analyz ing 1 ength- f requency gradients from upper es tuar ine areas (Cedar Bayou, Texas) t o Galveston Bay and shal low g u l f areas; they found t h a t spawning took place a t depths o f 7-22 m. Sheridan e t a l . (1984) c o l l ec ted a h igher percentage o f r i p e and mature f i s h from samples taken i n 56- t o 73-m depth s t r a t a (38%) than from any o ther (9 t o 17 m, 14%; 18 t o 36 m, 15%; 37 t o 55 m, 24%; and 79 t o 9 1 m, 21%). Ripe sand seat rout were co l l ec ted a t depths o f 73-91 m o f f M iss i ss ipp i by Franks e t a l . (1972). Va r ia t i on i n spawning depths may be due t o d i f f e rences i n depths o f habi- t a t s o f f Texas and the M iss i ss ipp i De l ta (Sheridan e t a l . 1984).

Simmons (1951) and Simmons and Hoese (1959) found t h a t mature sand seat rout from Aransas Bay migrated i n t o the g u l f through Cedar Bayou dur ing May-August, and t h a t ~ o s t l arvae and spent adu l ts entered Aransas Bay on incoming t ides . Shl ossman and Chittenden (1981) noted t h a t t he inshore movement o f young sand sea- t r o u t , i n l i g h t o f t he proposed b i - modal spawning, coincided w i t h peri,ods of r i s i n g sea l e v e l i n the nor thern

g u l f due t o sur face cur rents and pre- v a i 1 i ng inshore winds . The spawning s t ra tegy o f sand seat rout may be t o take advantage o f t h i s phenomenon t o f a c i l i t a t e the t ranspor t o f eggs and/or la rvae from inshore g u l f spawning areas t o es tuar ine and g u l f nurser ies.

DeVri es and Chi t tenden (1982) reported t h a t s i l v e r seat rout mature a t 140 t o 170 m SL (age I) i n g u l f waters o f f Texas; they a l so determined t h a t females entered e a r l y develop- mental stages a t 100, t o 135 mm SL. Sheridan e t a l . (1984) were ab le t o i d e n t i f y males a t 77 nun SL and females a t 80 mm, no t i ng an SL o f 140 mm f o r the smal lest maturing female.

DeVries and Chittenden (1982) r e p o r t t h a t spawning o f s i l v e r seat rout occurs from e a r l y May t o October i n Texas g u l f waters and inc ludes two peak per iods o f spawning a c t i v i t y , one i n sp r ing and another i n l a t e summer. Each year c lass may produce th ree i n t ra -yea r cohorts, two o f which occur i n l a t e sununer. I n o ther studies i n the g u l f region, r i p e f i s h were noted i n mid-May ( M i l l e r 1965) and throughout August (Gunter 194.5; Hi ldebrand 1954). Stuck and Perry (1981) analyzed surface nekton and concurrent bottom t r a w l samples t o determine t h a t spawning o f s i l v e r seat rout i n waters o f f M i s s i s s i p p i occurred dur ing l a t e summer and f a l l .

S i l v e r seat rout from waters o f f Georgia a l so appear t o have two spawning peaks (Mahood 1974), t h e f i r s t i n o f fshore waters du r ing sp r ing and a second c lose r t o shore i n l a t e summer and f a l l .

Sheridan e t a l . (1984) found r i p e females on ly i n A p r i l and October i n c o l l e c t i o n s taken throughout the northern g u l f region; however, maturing females were c o l l e c t e d from March t o A p r i l and August t o October, and maturing males from March t o October. The i r ca l cu la t i ons o f t h e gonadal -somatic index (used t o

ind icate reproductive readiness) showed l i t t l e monthly var ia t ion; therefore, spawning may begin e a r l i e r than May, the month proposed by DeVri es and Chi ttenden (1982).

DeVries and Chi ttenden (1982) suggested t h a t s i l v e r seatrout use a mechanism o f egg o r l a r va l t ransport s im i la r t o t ha t discussed by Shlossman and Chittenden (1981) f o r sand sea- t rou t .

Fecundity

Sheridan e t a l . (1984) estimated mean fecundi ty f o r sand seatrout (140 t o 278 mm SL) t o be 100,990 eggs, and 73,900 f o r s i l v e r seatrout (140 t o 256 mm SL). They also provided the f o l lowing re la t ionsh ips between fecundi ty (F) and standard length i n mm (SL), weight i n g (W), and ovary weight i n g (OW):

Sand Seatrout

F = -198,665 + 1,480 SL; r2 = 0.36 F = -8,917 + 759 W; r2 = 0.51 F = 32,557 + 7,893 OW; r2 = 0.53

S i l ve r Seatrout

F = -362,882 + 2,570 SL; r2 = 0.76 F = -52,623 + 1,309 W; r2 = 0.84 F = 32,539 + 5,662 OW; r2 = 0.94.

Larvae - Daniels (1977) described sand sea-

t r o u t 1.75 t o 8 mm SL taken i n Loui- siana coastal waters, and Stender (1980) provided data on morphometrics, merist ics, pigmentation, and d i s t r i bu - t i o n f o r l a r v a l s i l v e r seatrout from South Carol ina waters. Despite t h e i r common occurrence and importance, the ear l y 1 i f e h i s to ry o f seatrouts from gu1.f waters has not been adequately studied. Stuck and Perry (1981) described the seasonal occurrence of l a r va l Cynoscion spp. as pa r t o f an ichthyoplankton survey o f Mississippi g u l f waters. They were unable t o separate sand and s i l v e r

seatrout 1 arvae because o f the 1 i.mi t ed data avai 1 able on l a r va l i d e n t i f ica- t ion.

Juveniles

The use o f estuarine areas as nursery grounds by sand seatrout was reported by Shlossman and Chi ttenden (1981). They noted t h a t groups spawned l a t e r i n the season returned t o estuar ies dur ing mid-spring a f t e r overwintering i n the g u l f and stayed u n t i l they returned t o deeper waters t o spawn. The use o f estuarine and nearshore waters by juveni le sand sea- t r o u t was also noted by Gunter (1945) and Christmas and Waller (1973). Gallaway and Strawn (1974) f i r s t observed young-of- the-year f i sh i n Galveston Bay dur ing A p r i l and continued t o col l e c t them u n t i 1 September. Immigration o f j uven i le sand seatrout ((30 mm SL) i n t o Mississippi nursery areas began i n Ap r i l o r May, and recruitment con- t inued through the sumer and f a l l (Warren and Sut ter 1981). Swingle (1971) noted t h a t young sand seatrout appeared i n Alabama g u l f waters i n May and were most abundant i n June.

Juvenile s i l v e r seatrout are taken i n the same general v i c i n i t y as adul ts o f f Mississippi ; the smallest specimens (under 28 mm SL) were taken i n June t o August and October (Christmas and Wal l e r 1973). The major r ec ru i t - ment o f juveni le f i s h (20 t o 80 mm SL) i n t o nursery areas o f f Miss iss ipp i Sound occurred i n September (Waller and Sutter 1981). Lengths increased t o 110 t o 160 mm SL by the fo l low ing June. I n Alabama, smallest f i s h (33 t o 74 mm SL) were taken i n September (Swi ngle 1971), whereas i n Texas, small f i s h were found i n June and September t o November (Gunter 1945).

Adults

Adult sand seatrout are most abundant i n bays, lagoons, and shallow open waters o f the g u l f (Gunter 1945). Ginsburg (1931) reported t h a t sand

seatrout were more common i n i nner bays, sounds, and sha l l ower o f f shore waters, wh i le s i l v e r seatrout were more abundant fa r ther offshore. M i 1 l e r (1965) be1 ieved t h a t the d i s t r i b u t i o n o f the two species overlapped a t water depths o f 5 t o 16 m.

Warren (1981) found sand seatrout t o be more than three times as abundant i n n i g h t samples as i n daytime c o l l e c t i o n s (taken a t the same 1 oca- t ions) dur ing May and June i n Miss iss ipp i Sound. Larger s i l v e r seatrout seem more suscept ib le t o t r a w l i n g dur ing the day; few f i s h longer than 100 mm SL are taken a t n i g h t (DeVries and Chi ttenden 1982).

Adul t s i l v e r seatrout are not taken o f f Texas dur ing win ter (December t o March). They reappear i n spring, which may i n d i c a t e o f fshore overwinter ing o f the la rge r f i s h (DeVries and Chi t tenden 1982). Chittenden and McEachran (1976) reported t h a t l a rge s i l v e r seatrout (>I40 mm) were most abundant i n deep g u l f waters o f f Texas i n mid-January, but M i l l e r (1965) found l a r g e r f i s h i n deep water from February t o Apr i 1. The abundance o f s i l v e r seatrout i n Texas g u l f waters increased w i t h distance from shore (Gunter 1938) ; the f i s h were common a t depths o f 10-20 m ( M i l l e r 1965) t o a t l e a s t 65 m (Hildebrand 1954).

GROWTH CHARACTERISTICS

Shl ossman and Chi t tenden (1981) aged sand seatrout co l l ec ted from Texas by length-frequency analysis. F ish t h a t were spawned i n the spr ing averaged 160 t o 190 mm TL a t 6 months and 220 t o 280 mm a t age I, whereas those spawned i n l a t e summer ranged from 120 t o 150 mm TL a t 6 months and 210 t o 250 mm TL a t age I. These mean lengths a t age I agree w i t h those o f Per re t and Cai 1 l oue t (1974), bu t exceed those given by Swingle and Bland (1974) and Hoese e t a l . (1968).

Shlossman and Chittenden (1981) a l so aged sand seatrout using scale samples. The f i r s t annulus formed from Apr i 1 through November, a1 though they noted t h a t f i s h spawned i n spr ing and l a t e summer may form annul i a t d i f f e r e n t times. Few f i s h examined had annul i (10%); however, t he propor- t i o n o f f i s h having annu l i increased w i t h length (from 8% a t 150 t o 199 mm TL, t o 24% a t 200 t o 249 mm, t o 52% a t 250 t o 299 mm, t o 71% a t 1300 mm).

Barger and Johnson (1980), who examined o t o l i ths, scales, and vertebrae from sand seat rout f o r ind ica- t i o n s o f annul i , found s i g n i f i c a n t co r re la t i ons between f i s h TL i n mm (X) and o t o l i t h r a d i i (Y=-1.13 + 0.22X, r=0.9), and TL(X) and number o f marks on o t o l i t h s (Y=178.79 + 87.05X, r=O. 68). The back-cal cu l ated mean lengths a t annu l i on o t o l i t h s were 200 mm TL f o r one annulus and 247 mm f o r two annul i .

Maximum s i z e f o r sand seatrout i n Texas g u l f waters was estimated t o be 342 mm TL (Shlossman and Chittenden 1981), bu t few f i s h longer than 300 mm were taken. These r e s u l t s agree w i t h o ther studies i n the g u l f (Gunter 1945; Chi t tenden and McEachran 1976; Christmas and Waller 1973; Per re t and Ca i l l oue t 1974). Some la rge r f i s h , however, have been reported f o r g u l f waters. Franks e t a l . (1972) and Adkins and Bowman (1976) found sand seat rout w i t h t o t a l lengths o f 425 t o 497 mm, wh i le Trent and Pr i s tas (1977) c o l l e c t e d f i s h o f 540 and 590 mm TL i n g i 11 net samples from northwest F lor ida.

The maximum l i f e span o f sand seatrout was estimated t o be 1 t o 2 years f o r f i s h taken w i t h t raw ls and 2 t o 3 years f o r those taken w i t h other gears (Shlossman and Chittenden 1981). Annual m o r t a l i t y (A) was ca lcu la ted t o be near 100% (A=99.79%).

Several studies i n the g u l f have provided estimates o f length-weight

re la t ionsh ips f o r sand seatrout (Table 1).

Monthly increase i n t o t a l length o f sand seatrout was greatest dur ing May t o October (35 mm TL/month) and 6lowest i n win ter (5-10 mm TL/month), according t o Shl ossman and Chi ttenden (1981). Warren (1981) estimated a weekly summer growth r a te o f 5.8 mm SL f o r sand seatrout from Mississippi Sound.

DeYries and Chittenden (1982) aged s i l v e r seatrout from g u l f waters o f f Texas by 1 ength- frequency and scale analyses. They found t ha t s i l v e r seatrout reached 130 t o 190 mm SL a t age I; f i s h from the dominant f a l l - spawned groups averaged 145 t o 150 mm SL (range 125-170 mm) a t 11 months and

the May-spawned groups averaged 130 t o 190 mm SL a t 11-14 months. These values o f length a t age I agree w i th those reported by Chi ttenden and McEachran (1976). Gunter (1945) estimated t ha t f i s h 75-110 mm SL taken i n May were about 1 year old. DeVries and Chittenden (1982) found few annul i on scales they examined. Time o f annulus formation f o r the group spawned i n May was the fo l lowing A p r i l t o June, a f t e r the f i s h were 130 t o 190 mm SL. The time o f annulus formation f o r f i s h seaward i n August o r September was not c lear , but poss ib ly was Ap r i l t o June as wel l . The smallest f i s h w i t h an annulus was 130 mm SL; the proport ion o f f i s h w i t h annul i increased w i t h length (16% a t 150-159 mm SL, 24% a t 160-169 mm, 60% a t 170-179 mm and 100% a t ,180 mm).

Table 1. Length-weight regression re la t ionsh ips f o r sand seatrout and s i l v e r seatrout from selected studies i n the Gul f o f Mexico. Log transformations were performed on 1 engths (mm) and weight (g); the in te rcep t i s a and the slope coe f f i c i en t i s b f o r the regression.

Length Species Measurement range (m) Sex a b Location

Sand Seatrou

S i 1 ver S L Seatrout SL

S L

Male Fema 1 e A1 1 Femal e Male A1 1 A1 1

ex as^ a Texas,

Texas Texasb Texas ~ i s s i s s i ~ ~ i . ~ Northern&ul f

region

ex as^ Mississippi f

Northern .Gulf region

d

a Shlossman and Chittenden (1981). bMoffet t e t a l . (1979). 'warren (1981). d~he r i dan e t a1 . (1984). e DeVries and Chi ttenden (1982). f ~ a r r e n e t at. (1978).

Barger and Johnson (1980) examined o t o l i t h s , scales, and vertebrae from s i l v e r seat rout f o r i nd i ca t i ons o f annulus formation; they found t h a t t h e r e l a t i o n s h i p between t h e number o f marks on o t o l i t h s and TL i n mm ( X ) was Y=206.00+11.65X (r=O. 55). Back- ca lcu la ted mean lengths a t annu l i on o t o l i t h s were 160 mm TL a t t he f i r s t annulus, 207 mm a t t he second, and 216 mm f o r the t h i r d .

The maximum s i ze o f 190 mm (SL) f o r s i l v e r seat rout repor ted by DeVries and Chittenden (1982) concurred w i t h f indings of previous s tud ies (Hi ldebrand and Cable 1934; Gunter 1945; Christmas and Wal ler 1973). However, Franks ,et a l . (1972) c o l l e c t e d a specimen o f 315 nun SL (380 m r TL) o f f M iss i ss ipp i coastal waters.

DeVries and Chi t tenden (1982) e s t i - mated the maximum l i f e span o f s i l v e r seat rout t o be 1-1.5 years, although f i s h may l i v e t o 2 years i n the north- cen t ra l gul f region. Annual morta l i ty was ca l cu la ted t o be 99.83% (Table 1).

Length-weight re la t i onsh ips have been developed f o r s i l v e r seat rout from several areas o f t he g u l f (Table 1).

S i l v e r seat rout spawned i n August and September grew f a s t e s t i n June and September, averaging 25 t o 30 mm SL/ month (DeVries and Chittenden 1982). Growth slowed t o 5 mm SL/month dur ing December t o March, b u t increased again by March through June t o 15 t o 20 mm SL/month. Wal ler and Su t te r (1981) est imated f a l l and w in te r growth t o be approximately 10 mm SL/month f o r s i l v e r seat rout i n M iss i ss ipp i waters, acce lera t ing t o 15 mm SL/month as water temperatures increased du r ing spring.

THE FISHERY

Sand and s i l v e r seat rout a re among the most common species caught i n the

northern Gu l f o f Mexico i n d u s t r i a l bottom f i s h e r y (Roithmayr 1965; Warren 1981). Approximately 50,000 me t r i c tons (t) o f groundf ish are landed annual ly f o r t he product ion o f p e t food. I n add i t ion , about 300,000 t a re harvested and discarded by commercial shrimpers from Pt. au Fer, Louisiana, t o Perdido Key, F lo r i da , and rec rea t iona l shrimpers take an add i t i ona l 50,000 t (Warren 1981). Commercial land ing s t a t i s t i c s (Bureau o f Commercial F isher ies , Nat ional Marine F isher ies Service) f o r sand seat rout and s i l v e r seat rout a re combined and 1 i s t e d as "wh i te t r o u t . " However, M o f f e t t e t a l . (1979) l i s t e d average landings f o r Texas, and range values f o r F lo r i da , Alabama, M iss i ss ipp i and Louisiana f o r 1952 t o 1974.

The sand seat rout i s an important rec rea t i ona l species throughout the g u l f ; however, data f o r t he s i l v e r seat rout a re l i m i t e d . Recreational 1 andi ng s t a t i s t i c s f o r sand seat rout and s i l v e r seat rout (1979 only) are summarized i n Table 2.

ECOLOGICAL ROLE ( food hab i ts )

F i sh predominate i n the d i e t s o f sand seat rout from the Gu l f o f Mexico (Reid 1954, 1955; Reid e t a l . 1956; Darnel1 1958; Springer and Woodburn 1960; Sheridan and L iv ings ton 1979; and Sheridan 1979). Several i n v e s t i - gators have noted changes i n d i e t r e l a t i v e t o growth i n length. Sheridan (1979) and Sheridan and L iv ings ton (1979) found t h a t mysid shrimp and ca lano id copepods were the main d i e t o f f i s h l e s s than 40 mm SL i n F l o r i d a waters, b u t f i s h became a more important p a r t o f t he d i e t as sand seat rout grew la rge r . They a l so noted t h a t l o c a t i o n was important t o sand seat rout d i e t ; f i s h were heav i l y consumed near passes o f t he estuary, whereas mysidaceans were eaten more f requen t l y i n 1 ower sa l i n i t y areas.

Table 2. Summary o f rec rea t i ona l f i s h i n g s t a t i s t i c s f o r sand and s i l v e r seat rou t i n t h e G u l f o f Mexico.

To ta l Percent o f U.S. ca tch t o t a l ca tch Catch by G u l f States

Species and t ime frame

(thousands taken from (thousands o f f i s h ) o f f i s h ) G u l f o f Mexico FL AL MS LA TX

Sand Seatrout Jan-Dec 197ga

Mar-Dec 1981b

Jan-Dec 1982~ Jan-Dec 1983' Jan-Dec 1984'

Jan-Dec 1985~

S i 1 ve r Seatrout Jan-Dec 197ga

a U. S. Nat iona l Marine F i she r ies Serv ice (1980).

b ~ . S. Nat iona l Marine F i she r ies Serv ice (1985a). C

U. S. Nat iona l Marine F i she r ies Serv ice (1985b).

d ~ . S. Nat iona l Marine F i she r ies Serv ice (1986).

* means none reported.

--means l ess than 30,000 reported; however, t h e f i g u r e i s inc luded i n row and

column t o t a l s .

M o f f e t t e t a l . (1979) found t h a t t he stomachs o f sand sea t rou t 45-159 mm SL contained 38% crustaceans and 30% f i s h , whereas those specimens o f 160-375 mm SL contained 46% f i s h (mostly t he bay anchovy, Anchoa m i t c h i 11 i), 10% crustaceans, and 1% annel ids (percentages are frequencies o f occurrence i n f i s h w i t h food items). Overs t ree t and Heard (1982) examined t h e stomach contents o f sand seat rou t taken from M i s s i s s i p p i Sound, f i n d i n g the f o l 1 owing percentages o f occurrence ( i n f i s h w i t h food items): stomatopods 3%, penaeids 53%, carideans 7%, and f i shes 55% (most ly bav anchovies and - a u l f menhaden. ~ r e v o o r t i a patronus). Sher idan e t a1 .' (1984) examined sand sea t rou t taken

throughout t he nor thern g u l f reg ion and found t h a t f i s h were the pr imary food, w i t h the bay anchovy being the most f requen t l y u t i 1 i zed species. Shrimp were a l so eaten, w i t h Trachypenaeus and Acetes being most commonly observed.

L i t e r a t u r e on t h e feeding hab i t s o f s i l v e r sea t rou t i s n o t as extensive as t h a t f o r sand seatrout . Rogers (1977) found t h a t s i l v e r seat rou t from west F l o r i d a and Texas consumed (by volume) 56% f i s h and 19% shrimp. Rogers a l s o noted a s h i f t i n d i e t from 40% shrimp and 18% mysids f o r s i l v e r seat rou t 26 t o 50 mm long, t o 77% f i s h and 8% shrimp f o r t r o u t 76 t o 175 mm long. Overstreet and Heard

(1982) reported t ha t s i lver seatrout taken from Mississippi Sound consumed 83% f i sh and 41% penaeids (values indicate percent occurrence i n f i s h w i t h food items). Sheridan e t a l . (1984) found f i sh o r shrimp t o be the primary foods fo r s i l v e r seatrout in the northern gulf .

ENVIRONMENTAL REQUIREMENTS

Temperature

Larval and juvenile sand seatrout have been collected in water temperatures of 5 t o 35 OC, but most a re taken a t temperatures above 10 O C

(Christmas and Wall e r 1973). Small f i s h ( l e s s than 20 mm SL) were taken most frequently in Mississippi a t temperatures of 25 t o 30 OC, b u t were a l so found a t temperatures as low as 15 O C (Warren and Sut te r 1981). Copeland and Bechtel (1974), who examined catch records of sand sea- t r ou t from gulf coast es tuar ine systems concomitantly with several environmental fac to rs , found a temperature range of 5 t o 30 O C ;

optimum catches were made a t 20 t o 30 O C . Gallaway and Strawn (1974) noted t h a t most sand seatrout in Galveston Bay were caught a t temperatures of 29-32 O C (seines) and 25-32 O C ( t rawls) , but some were taken a t temperatures as high as 40 O C .

Adult s i l v e r seatrout a r e taken between 10 O C (Christmas and Waller 1973) and 30 O C (Gunter 1945), and juveniles are taken over the wider range of 5 t o 30 O C (Swingle 1971). Si lver seatrout were caught in Mississippi waters a t temperatures between 10 and 30 OC; catches peaked a t 25-30 O C (Wal l e r and Sut ter 1981).

Sal i ni t y

Small sand seatrout ( l e s s than 20 mm SL) were collected in Mississippi

waters a t s a l i n i t i e s of 0-30 ppt (Warren and Sut te r 1981). Christmas and Waller (1973) found larval and juvenile sand seatrout i n s a l i n i t i e s of 0-26 ppt. Warren and Sut ter (1981) reported t h a t the highest catches of larger young-of-the-year (20 t o 90 mm SL) in Mississippi waters were a t s a l i n i t i e s of l ess than 15 ppt, the majority being taken in l ess than 10 ppt; larger f i s h (90 t o 220 mm SL) were most frequently taken in s a l i n i t i e s above 15 ppt. Adult sand seatrout have been taken in s a l i n i t i e s up t o 45 ppt (Simmons 1957; Roessler 1970).

Preferred s a l i n i t i e s are higher f o r s i l v e r seatrout areas than fo r sand seatrout ; adu l t s i l v e r seatrout have been taken q t 7.5 ppt (Swingle 1971) t o 38.6 ppt (Franks e t a l . 1972), but a re most commonly found above 25 ppt (Swingle 1971; Warren e t a l . 1978).

Dissolved Oxygen

Information on re la t ionships between dissolved oxygen and sand and s i l v e r seatrout tolerance o r preferences i s scarce. Benson (1982) noted an unreferenced study s t a t i ng t h a t sand seatrout tend t o avoid water with less than 4.6 t o 5.0 mg/l of dissolved oxygen.

Substrate

Early l i f e stages of sand seatrout prefer s o f t organic bottom (Conner and Truesdale 1972), but adul ts a r e found over most substra tes in es tuar ies and offshore. Gal laway and Strawn (1974) s ta ted t ha t habi ta t preferences of sand seatrout i nc1 ude oyster-reef substra tes and water depths greater than 1 m.

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Wal l e r , R. S. , and F. C. Sut te r . 1981. Other t a r g e t species-moni t o r i n g and assessment. Pages V-2-1 - V-2-59 i n T.D. McIlwain, ed. F ishery - moni tor ing and assessment. Comple- t i o n Rep. PL 88-309 P ro j . 2-296-R. Gu l f Coast Research Laboratory, Ocean Springs, Miss.

Warren, J. R. 1981. Populat ion analyses o f t he j u v e n i l e g roundf ish on the t r a d i t i o n a l shrimping grounds i n M iss i ss ipp i Sound before and a f t e r t he opening o f t he shrimp season. 1979. M.S. Thesis. U n i v e r s i t y o f Southern M iss i ss ipp i , Hat t iesburg. 93 pp.

Warren, J.R. and F.C. Sut te r . 1981. I n d u s t r i a l bo t tomf ish - moni to r ing and assessment. Pages 11-1-1 t o 11-1-69 T.D. McIlwain, ed., F ishery moni to r ing and assessment. Completion Rep. PL88-309, Pro j . 2-296-R. Gulf Coast Research Lab- o ra tory , Ocean Springs , Miss.

Warren, J.R., H.M. Perry, and B. L. Boyes. 1978. F i she r ies assessment and moni tor ing. Pages 25-118 J.Y. Christmas, H.M. Perry, and T.M. Van Devender, eds. I n d u s t r i a l bot tomf ish, M iss i ss ipp i . Completion Rep. PL88-309, Pro j . 2-215H. Gu l f Coast Research Laboratory, Ocean Springs, Miss.

lo771 -101

12. Soom.#cn# Or8anhclm Namm and l d b m a Nat ional Wetlands Research Center U.S. Army Corps of Engineers Fish and W i l d l i f e Service Waterways Experiment S t a t i o n

REPORT DOCUMENTATION . I - "Emnr -- &

PAGE I B io log i ca l Report 82(11.72) * 1 I

4. n a e and S,WI~I.

Species P r o f i l e s : L i f e H is to r i es and Environmental Requirements of Coastal Fishes and Invertebrates (Gul f o f Mexi co)--Sand Seatrout and S i l v e r Seatrout

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F. C. Su t te r and T. D. McIlwain b. hdorm1n8 Oqmlart~mn Name an# A b d r . ~

Gulf Coast Research Laboratory East Beach Ocean Springs, MS 39564

U.S. Dep. o f the I n t e r i o r P.O. B& 631. Was h i ngton , DC 20240 Vicksburg, MS 39180

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Species p r o f i l e s are 1 i te ra tu re sumnaries o f the taxonomy, morphology, range, 1 i f e h i s to ry , and environmental requirements o f coastal aquat ic species. They are designed t o a s s i s t i n environmental impact assessment. Sand seat rout are one o f the most abundant f i shes i n the es tuar ine and nearshore areas o f the Gul f o f Mexico. A1 though s i 1 ver seat rout a re a1 so abundant, l i t t l e research has been conducted f o r t h i s species. Sand seat rout spawn i n lower es tuar ine environments o r i n nearshore g u l f waters w i t h two spawning peaks; one i n spr ing, and another i n l a t e summer. S i l v e r seat rout f o l l o w a s i m i l a r reproduct ive pat te rn . Sand seat rout a re common i n bays, sounds, and shal low o f fshore g u l f water, w h i l e s i l v e r seat rout are more abundant i n deeper waters. Both seat rout are important components i n the indus tri a1 bottom f i she r ies ; sand seat rout a1 so are a valuable rec rea t iona l species. Shrimp and o ther crustaceans are most commonly eaten. by small sand and s i l v e r seat,rout, wh i l e l a r g e r f i s h s h i f t t o a more pisc ivorous d i e t . Small sand seat rout a re usua l l y found i n waters w i t h temperatures greater than 15°C and s a l i n i t y values less than 15 ppt, wh i l e l a r g e r f i s h are found over a wider temperature range (5" t o 30°C), and i n s a l i n i t i e s greater than 15 ppt. S i l v e r seat rout genera l ly p r e f e r waters w i t h s a l i n i t i e s greater than 25 p p t w i t h temperatures ranging from 5" t o 30°C.

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Estuar ies Temperature S a l i n i t y

Growth D i ssol ved oxygen L i f e cycles F isher ies Food habi t s F i shes b IdeM1fiemlek.n-Wed Temm

Sand sea t rou t Habi t a t requirements Cynoscion arenar i us I S i l v e r sea t rou t Cynoscion nothus Spawn1 ng r cuun n . c a ~ ~ ~ ~ u o

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TAKE A PRIDE 212 Amerzcd

DEPARTMENT OF THE INTERIOR U.S. ASH AND WILDLIFE SERVICE

As the Nation's principal conservation agency, the Department of the Interior has responsibility for most of our .nationally owned public lands and natural resources. This includes fostering the wisest use of our land and water resources, protecting our fish and wildlife, preserving thsenvironmentai and cultural values of our national parks and hlstorical places, and providing for the enjoyment of life through outdoor recreation. The Department as- sesses our energy and mineral resources and works to assure that their development is in the best interests of all our people. The Department also has a major responsibility for American Indian reservation communities and for people who live in island territories under U.S. administration.

Documents

SAND SEATROUT AND SILVER SEATROUT seatrout and silver seatrout ... (1929) presented a key to aid the ,identification of these species. Gunter (1945) ... Christmas and Waller 1973)