114 



Fishery Bulletin 89(1), 1991 



alongshore southwestward flow: the young just need 

 to be entrained in waters already in the white shrimp 

 community, or enter them using the eastward counter- 

 flow, and be transported in a "downstream manner" 

 (see next paragraph). This interpretation is similar to 

 the current transport model Shaw et al. (1985) suggest 

 for B. patronus. 



Besides being offshore, spawning grounds for P. 

 burti found off Texas may lie towards or in thenorth- 

 central Gulf. We suggest some unknown combination 

 of offshore and spawning or postspawning movement 

 to the northcentral Gulf explains between-area popula- 

 tion dynamics differences. Such upcoast movement 

 may be required within the white shrimp community, 

 given the coincidence of spawning with downcoast cur- 

 rents. Mean alongshore surface current speed is 23 

 cm/second in water 22 m deep off Freeport, Texas from 

 September through June (Kelly et al. 1981), so spawn- 

 ing areas could lie 320 nmi upcoast assuming passive 

 transport for 30 days before the young recruit to the 

 bottom. This estimate depends on many poorly known 

 factors, including (1) routes followed, (2) alongshore 

 current speeds, (3) duration of the transport period, and 

 (4) behavior of the young. However, alongshore cur- 

 rents could transport young great distances— concep- 

 tually "downstream"— and Texas recruits could be 

 spawned off Louisiana where low-salinity waters prop- 

 agate along Texas when alongshore wind components 

 turn downcoast during August and September (Kelly 

 and Randall 1980, Kelly et al. 1981). Mature fish must 

 move toward spawning areas, conceptually in an up- 

 stream, contranatant direction from the northwestern 

 Gulf, to maintain a fixed, proven spawning ground 

 following Harden Jones (1968). 



Zoogeographic considerations 



Peprilus burti fill a niche in the Gulf similar to the one 

 P. triacanthus occupies on the Atlantic coast. However, 

 their population dynamics differ, and this may reflect 

 zoogeographic variation suggested for other taxa 

 whose ranges traverse the Cape Hatteras area, in- 

 cluding Micropogonias and Alosa (White and Chitten- 

 den 1977), Cynoscion (Shlossman and Chittenden 

 1981), and Stenotomus (Geoghegan and Chittenden 

 1982). It appears for P. burti that (1) maturity occurs 

 at 100- 160 mm in length as they approach age I and 

 spawn, (2) maximum size is only about 200 mm, but 

 most are much smaller, (3) maximum age is no more 

 than 2.5 years, and (4) total annual mortality rate is 

 not lower than about 82%. 



The life history of P. triacanthus north of Cape Hat- 

 teras is complicated by north-south and onshore- 

 offshore movements (Horn 1970), but they appear to 

 (1) mature at lengths of 110-130 mm in their second 



year (Hildebrand and Schroeder 1927, Bigelow and 

 Schroeder 1953, Horn 1970, DuPaul and McEachran 

 1973), (2) reach maximum sizes of 300 mm (Murawski 

 and Waring 1979), (3) have maximum ages of 3-6 years 

 (Draganik and Zukowski 1966, DuPaul and McEachran 

 1973, Waring 1975, Kawahara 1977), and (4) have total 

 annual mortalities of 67-84% (Murawski and Waring 

 1979). 



Little has been published for P. triacanthus south of 

 Cape Hatteras, but the largest fish collected in exten- 

 sive trawling in this area was 150mm (Wenner et al. 

 1979). This size range is more similar to P. burti than 

 P. triacanthus north of Cape Hatteras and may reflect 

 an intrageneric, Carolinian Province similarity in sizes, 

 maximum ages, and mortality. 



Acknowledgments 



We are much indebted to M. Burton, T. Crawford, 

 P. Geoghegan, J. Pavela, M. Rockett, J. Ross, P. Shloss- 

 man, B. Slingerland, G. Standard, H. Yette, and Cap- 

 tains Hollis, Mike, and Robby Forrester, P. Smirch, and 

 A. Smircic for assistance in field collections. T. Fehr- 

 man and R. Grobe recorded the data. R. Case was of 

 invaluable help for writing and assisting with computer 

 programs. B. Rohr and E. Gutherz allowed the senior 

 author to participate in NMFS groundfish survey 106. 

 R. Darnell, G. Grant, E. Klima, D. Stilwell, K. Strawn, 

 and K. Sulak reviewed drafts of the manuscript. Finan- 

 cial support was provided, in part, by the Texas 

 Agricultural Experiment Station; by the Strategic 

 Petroleum Reserve Program, Department of Energy; 

 and by the Texas A&M Sea Grant College Program, 

 supported by the NOAA Office of Sea Grant, U.S. 

 Department of Commerce. Final preparation and revi- 

 sions of this manuscript were made while the authors 

 were at Florida Marine Research Institute, Florida 

 Department of Natural Resources (MDM) and College 

 of William and Mary, Virginia Institute of Marine 

 Science (MEC). This manuscript was based on a thesis 

 submitted by the senior author as partial fulfillment 

 of the M.S. degree, Texas A&M University. 



Citations 



Allen, R.L., J.H. Render, A.W. Liebzeit. and G.W. Bane 



1986 Biology, ecology, and economics of butterfish and squid 

 off the northern Gulf of Mexico. Final Rep. LSU-CFI-86-30, 

 Coastal Fish. Inst., Center for Wetland Resources, Louisiana 

 State Univ., Baton Rouge, 175 p. 

 Alverson, D.L., and M.J. Carney 



1975 A graphic review of the growth and decay of population 

 cohorts. J. Cons. Cons. Int. Explor. Mer 36:133-143. 

 Bagenal, T.B., and E. Braum 



1971 Eggs and early life history. In Ricker, W.E. (ed.), 



