64 



Fishery Bulletin 94|l), 1996 



but rather in a continuum in size and age at matu- 

 rity from very small, precocious individuals to larger, 

 later-maturing individuals. Such variation appears 

 to be similar to phenotypic variation observed in 

 poeciliid fishes. Poeciliids show a large degree of plas- 

 ticity in size and age at maturity both within and 

 among populations (e.g. Trexler et al., 1992). Varia- 

 tion in size at maturity for male poeciliids has been 

 related to behavioral interactions such as matura- 

 tion inhibition due to the presence of larger males or 

 due to environmental stresses such as a limited food 

 supply or a decreased probability of survival 

 (Chapman and Chapman, 1992). Genetic control is 

 also thought to play an important role in variation 

 in size and age at maturity in fish species, with cer- 

 tain alleles causing early maturation in some spe- 

 cies of poeciliids (Campton and Gall, 1988). 



It is not known whether environmental, behav- 

 ioral, or genetic factors are influencing the variabil- 

 ity observed in size and age at maturity in Photololigo 

 sp. 1. It might be a combination of all three factors. 

 Squids exhibit complex behavioral communication 

 and courtship displays (Hanlon et al., 1983; Moyn- 

 ihan, 1985) which in many ways may be analogous 

 to mating strategies in the short-lived poeciliid fishes, 

 which have internal fertilization and the ability to 

 store sperm (Haynes, 1993) as do cephalopods. 



The statolith age analysis in this study has re- 

 vealed that the observed differences in size at matu- 

 rity were predominantly due to larger individuals 

 being older than their smaller counterparts rather 

 than due to profound differences in individual growth 

 rates. Future work incorporating larger sample sizes 

 of aged individuals will, no doubt, make the discern- 

 ment of size and age-based patterns of maturity 

 clearer in tropical loliginids. 



Acknowledgments 



We are most grateful to K. Sainsbury, C. Liron, and 

 the crew of the RV Southern Surveyor for their as- 

 sistance in collecting material from the northwest 

 shelf. We are thankful to Phil Davies for preparing 

 Figure 1 and to R. Black who assisted with Figure 2 

 and with statistical analysis. 



Literature cited 



Alford, R. R., and G. D. Jackson. 



1993. Do cephalopods and larvae of other taxa grow 

 asymptotically? Am. Nat. 141:717-728. 

 Arkhipkin, A., and A. Mikeev. 



1992. Age and growth of the squid Sthenoteuthis pteropus 

 (Oegopsida: Ommastrephidae) from the Central-East 

 Atlantic. J. Exp. Mar. Biol. Ecol. 163:261-276. 



Augustyn, C. J., M. R. Lipinski, and W. H. Sauer. 



1992. Can the Loligo squid fishery be managed effectively? 

 A synthesis of research on Loligo vulgaris reynaudii. S. 

 Afr. J. Mar. Sci. 12:903-918. 

 Boletzky, S. v. 



1983. Sepia officinalis. In P. R. Boyle (ed), Cephalopod 

 life cycles. Vol. I., p. 31-52. Acad. Press, London, England. 

 Brierley, A. S., and J. P. Thorpe 



1994. Biochemical genetic evidence supporting the taxo- 

 nomic separation of Loligo gahi from the genus Loligo. 

 Antarct. Sci. 6:143-148. 

 Brierley, A. S., J. P. Thorp, M. R. Clarke, and 

 H. R. Martins. 



1993a. A preliminary biochemical genetic investigation of the 

 population structure of Loligo forbesi Steenstrup, 1856, from 

 the British Isles and the Azores. In T Okutani, R. O'Dor, 

 and T. Kubodera (eds. I, Recent advances in cephalopod fish- 

 eries biology, p. 61-69. Tokai Univ. Press, Tokyo, Japan. 

 Brierley, A. S., P. G. Rodhouse, J. P. Thorpe, and 

 M. R. Clarke. 



1993b. Genetic evidence of population heterogeneity and 

 cryptic speciation in the ommastrephid squid Martialia 

 hyadesi from the Patagonian Shelf and the Antarctic Po- 

 lar Frontal Zone. Mar. Biol. 116:593-602. 

 Campton, D. E., and G. Gall. 



1988. Responses to selection for body size and age at sexual 

 maturity in the mosquitofish, Gambusia affinis. Aqua- 

 culture 68:221-241. 



Carvalho, G. R., and T. J. Pitcher. 



1989. Biochemical genetic studies on the Patagonian squid 

 Loligo gahi d'Orbigny. II: Population structure in Falkland 

 waters using isozymes, morphometries and life history 

 data. J. Exp. Mar. Biol. Ecol. 126:243-258. 



Carvalho, G. R., A. Thompson, and A. S. Stoner. 



1992. Genetic diversity and population differentiation of 

 the shortfin squid Illex argentinus in the south-west 

 Atlantic J. Exp. Mar. Biol. Ecol. 158:105-121. 



Chapman, L. J., and C. A. Chapman. 



1992. Variation in the structure of Poecilia gillii popu- 

 lations. Copeia 1992:908-914. 



Dunning, M. 



1982. Squid and cuttlefish resources of Australian 

 waters. FAO Fisheries Rep. 275:103-111. 



Dunning, M., S. McKinnon, C. C. Lu, J. Yeatman, and 

 D. Cameron. 



1994. Demersal cephalopods of the Gulf of Carpentaria, 

 Australia. Aust. J. Mar. Freshwater Res. 45:351-374. 

 Garthwaite, R. L., C. F. Berg Jr., and J. Harrigan. 



1989. Population genetics of the common squid Loligo pealei 

 LeSueur, 1821, from Cape Cod to Cape Hatteras. Biol. 

 Bull. 77:287-294. 



Hanlon, R. T, R. F. Hixon, and W. H. Hulet. 



1983. Survival, growth, and behavior of the loliginid squids 

 Loligo plei, Loligo pealei and Lolliguncula brevis ( Mollusca: 

 Cephalopoda) in closed sea water systems. Biol. Bull. 

 165:637-685. 



Hatfield, E. M. C, P. G. Rodhouse, and J. Porebski. 



1990. Demography and distribution of the Patagonian squid 

 {Loligo gahi d'Obigny) during the austral winter. J. Cons. 

 [nt. Explor. Mer 46:306-312. 



Haynes, J. L. 



1993. Annual reestablishment of mosquitofish populations 

 in Nebraska. Copeia 1993:232-235. 



Hixon, R. F. 



1980. Growth, reproductive biology, distribution and abun- 

 dance of three species of loliginid squid (Myopsida, 



