NOTE Jackson: Seasonal influences on statolith growth in Loligo chinensis 



751 



Table 1 



Regression equations for the relationship between mantle length and statolith 

 length and for age and statolith length for individuals of Loligo chinensis 

 collected in both summer and winter. ML = mantle length. All regressions 

 were highly significant 'P<0.001). 



Season Relationship 



Equation 



Summer ML vs. statolith length 38 



Summer Age vs. statolith length 38 



Winter ML vs. statolith length 33 



Winter Age vs. statolith length 33 



y = -238.4+ 731.2 logx 

 y = -1585.8 + 1470.6 logx 

 y = 849.4 + 5.03x 

 y = 672.7 + 5.3x 



0.84 

 0.63 

 0.91 



0.67 



statoliths because they were in reality much older 

 than similar-sized, faster-growing squids (summer 

 population). Alternatively, when statolith length and 

 individual age were compared, faster-growing squids 

 had larger statoliths than slower-growing squids for 

 a given age because the individual itself was consid- 

 erably larger (e.g. in the summer, squids were reach- 

 ing adult sizes at around 80 days whereas in the 

 winter, 80-day squid were still juveniles). 



Morris andAldrich (1985) have suggested that sta- 

 tolith length may be a better indicator of squid age 

 than increment number because they observed less 

 variation in the mantle length:statolith length rela- 

 tionship than in the mantle length:age relationship 

 in Illex illecebrosus. However, the seasonal difference 

 in the relationship between the statolith and the 

 soma of L. chinensis suggests that this technique 

 should be used cautiously until further research into 

 temperature effects is conducted (see also Campana, 

 1990; Lipinski et al., 1993). On the basis of labora- 

 tory observations, Forsythe and Hanlon (1989) and 

 Forsythe ( 1993) have suggested that even fairly small 

 variations in ambient temperature can have a 

 marked effect on somatic growth rates. Temperature 

 has also been shown to be an important influence on 

 growth rates of Sepia australis in the field (Roeleveld 

 et al., 1993). This preliminary study withL. chinensis 

 suggests that temperature variation will not only 

 greatly influence somatic growth but statolith growth 

 as well. The uncoupling of statolith growth and so- 

 matic growth in squid is certainly an area that de- 

 serves further research (see Lipinski et al., 1993). 



Statoliths are structures which have accentuated 

 both the differences and similarities between cepha- 

 lopods and fish. The increment structure and the 

 growth of the statolith in relation to the squid soma 

 are remarkably similar to that of the otolith in fish. 

 In contrast, the enumeration of growth increments 

 in both otoliths and statoliths have accentuated very 

 different growth strategies and life histories (e.g. 

 Jackson and Choat, 1992; Alford and Jackson, 1993) 



of two organisms that are biologically 

 very different but nevertheless show 

 many similarities. 



Acknowledgments 



I would like to thank J. H. Choat for 

 comments throughout this project, C. 

 H. Jackson for reading the manu- 

 script, R. Black for assistance with 

 figure preparation, and the crew of 

 the research vessel James Kirby for 

 specimen collection. This research was 

 supported by grants from the James Cook University 

 of North Queensland Research Funding Panels. 



Literature cited 



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



1993. Do cephalopods and larvae of other taxa grow 

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

 Arkhipkin, A., and A. Mikheev. 



1992. Age and growth of the squid Sthenoteuthis pteropus 

 (Oegopsida: Ommastrephidae) from the Central-East 

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



Arkhipkin, A., and N. Nekludova. 



1993. Age, growth and maturation of the loliginid squids 

 Alloteuthis africana and A. subulata on the West African 

 Shelf. J. Mar. Biol. Assoc. U.K. 1993. 73:949-961. 



Bigelow, K. A. 



1992. Age and growth in paralarvae of the mesopelagic 

 squid Abralia trigonura based on daily growth increment 

 in statoliths. Mar. Ecol. Prog. Ser. 82:31-40 

 Campana, S. E. 



1990. How reliable are growth back-calculations based on 

 otoliths? Can. J. Fish. Aquat. Sci. 47:2219-2227. 

 Campana, S. E., and J. D. Neilson. 



1985. Microstructure of fish otoliths. Can. J. Fish. Aquat. 

 Sci. 42:1014-1032. 

 Campana, S. E., and C. M. Jones. 



1992. Analysis of otolith microstructure data. In D. K. 

 Stevenson and S. E. Campana (eds.), Otolith microstruc- 

 ture examination and analysis, p. 73-100. Can. Spec. 

 Publ. Fish. Aquat. Sci. 117. 



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. 



Forsythe, J. W. 



1993. A working hypothesis on how seasonal temperature 

 change may impact the field growth of young cepha- 

 lopods . In T. Okutani, R. K. O'Dor, and T. Kubodera ( eds. ), 

 Recent advances in cephalopod fisheries biology, p. 133- 

 143. Tokai Univ. Press, Tokyo. 



Forsythe, J. W., and R. T. Hanlon. 



1989. Growth of the Eastern Atlantic Squid, Loligo forbesi 

 Steenstrup (Mollusca: Cephalopoda). Aquacult. Fish. 

 Manage. 20:1-14. 

 Jackson, G. D. 



1990a. Age and growth of the tropical nearshore loliginid 



