SHLOSSMAN and CHITTKNDEN: REPRODUCTION OF SAND SEATROUT 



from fisheries whose gear was biased seriously to 

 capture large fish about 12 mo and older. However, 

 even these fish averaged only 280 mm TL in recre- 

 ational catches and 343 mm in commercial 

 catches; and few were >330 mm and 406 mm TL, 

 respectively. 



The maximum lifespan of C. arenarius typically 

 is 1-2 yr at most for trawl-caught fish and possibly 

 as much as 2-3 yr for other gear. In the period 

 October 1977-April 1979, 90^r of the 3,988 fish that 

 we captured off Freeport were <215 mm TL (Fig- 

 ure 15), 999'f were <280 mm, and 99.5% were <300 

 mm. Similarly, of the 2,073 fish collected off Port 

 Aransas during February 1977- July 1978 (Figure 

 15), 90% were <210 mm TL, 99% were <260 mm, 

 and 99.5% were <275 mm. A t^ value of 1-2 yr at 

 most is reasonable for the Beverton-Holt model 

 parameter (Gulland 1969) for trawl-caught C. 

 arenarius because fish >260-300 mm TL made up 

 <0. 5-1.0% of our catch. This is about the average 

 size at age I (210-280 mm TL), which many indi- 

 viduals exceed, and approaches the maximum 

 sizes usually reported. Our trawling, moreover, 

 shows the scarcity offish with more than one an- 

 nulus, a disappearance of all fish by 14-18V2 mo of 

 age (Table 3), and agrees with Chittenden and 

 McEachran's (1976) suggestion that the typical 

 lifespan is no more than 1-2 yr. Even recreational 

 and commercial gear seriously selective for larger 

 sizes (references cited above) catch fish whose typ- 

 ical maximum age appears to be only 2-3 yr, at 

 most, because mean sizes at these ages predicted 

 by polynomial regression were 431 mm TL at age 

 II and 574 mm at age III for late summer fish and a 



o 



c 



c 

 I— 

 > 



< 



m 



3) 



O 



80 160 240 



TOTAL LENGTH (mm) 



320 



bays. Tex. Parks Wildl. Dep., Coastal Fish Branch, Proj. Rep. 

 2-231-R-l, 116 p. 



Figure 15. — Length frequency (moving average of threel and 

 cumulative percentage of all Cvno.sc;o/! arenarius collected in the 

 Gulf of Mexico off Freeport, Tex., October 1977-April 1979 and 

 off Port Aransas, Tex., February 1977-July 1978. 



probably unrealistically low 301 mm at age II for 

 spring fish. 



Sand seatrout has a total annual mortality rate 

 that approaches 100% and has a best estimate of 

 99.79% based on trawling data. Time-specific val- 

 ues of total annual mortality (1 - S) were calcu- 

 lated for each individual month from the expres- 

 sion S = N(/No where S = rate of survival and A^^ 

 and A^^ are the number offish collected from con- 

 secutive spring or late summer groups. Of the 20 

 mo when collections were made off Freeport, only 

 one spring group was present in 14 mo and only 

 one late summer group was present in 17 mo (Fig- 

 ure 4). Of the 14 mo when collections were made off 

 Port Aransas, only one spring group was present 

 in 13 mo and only one late summer group was 



Table 3. — Periods of time, sizes, and ages when spawned groups of Cynoscion arenarius were last captured off Freeport and Port 



Aransas, Tex. 



Spawned group 

 and location 



Disappeared in 

 the period 



TL(mm) 



Age (mo) 



Comments 



Spring 1976: 

 Port Aransas 



Late summer 1976: 

 Freeport 

 Port Aransas 



Spring 1976 

 Freeport 

 Port Aransas 



Late summer 1977: 

 Freeport 

 Port Aransas 



Spring 1978: 

 Freeport 

 Port Aransas 



Last summer 1978: 

 Freeport 



12-14 Few specimens ever captured 



14-15 Few specimens ever captured 

 14-15 



1 4V2-1 7'/? Few captured after December 1 977 



11-12 Few captured after November 1 977 



1 5V2- 1 8''2 Few captured after September 1 978 



11 



14V2 Few captured after April 1979 



4V2 Still being recruited when last collection was made 



13 Still abundant when last collection was made; sizes not distinct 



663 



