750 



Fishery Bulletin 93(4), 1995 



ered seawater formalin and subsequently transferred 

 to 70% ethanol. Mantle length (ML) measurements 

 (nearest mm) were taken on the preserved individu- 

 als. Statoliths were removed shortly after preserva- 

 tion and mounted in Crystal Bond thermoplastic ce- 

 ment. 



Total increment number was determined (with a 

 camera lucida attached to an Olympus BH compound 

 microscope) as the mean of three consecutive counts 

 that differed less than 10% from the mean (see also 

 Jackson and Choat, 1992; Jackson, 1993). Statolith 

 length (to the nearest 10 urn) was measured with an 

 eyepiece micrometer (with an Olympus BH com- 

 pound microscope) along the longest axis from the 

 dorsal dome to the tip of the rostrum. 



Results 



For the summer population, the relationship between 

 statolith length and mantle length as well as sta- 

 tolith length and age was curvilinear. However, both 



1800 



■g 1600 

 3 



5 1400 



z 



UJ 



—I 



t 1200 

 o 



< 



U 1000 



800 



Winter 



Summer 



C 20 40 60 80 100 120 140 160 180 200 

 MANTLE LENGTH (mm) 



1800 



1600 



5 1400 



1200 



1000 



800 



B 



Summer 



Winter 



20 40 60 80 100 120 140 160 180 200 

 AGE (days) 



Figure 1 



The relationship between (A) statolith length and mantle 

 length and (B) statolith length and age for summer (Janu- 

 ary) and winter (July) samples of Loligo chinensis. 



relationships were linear for the winter population 

 (Fig. 1; Table 1). Because all relationships were not 

 linear, an analysis of covariance could not be applied 

 to these data sets. However, a paired £-test was used 

 to compare statolith lengths of similar-sized males 

 and females (mantle lengths between 90 and 110 mm, 

 rc=24) from both January (summer) and July (win- 

 ter). Squid statoliths from the July sample were sig- 

 nificantly longer than statoliths from the January 

 sample (P<0.05). 



The relationship between statolith length and 

 mantle length (Fig. 1A) suggested that somatic 

 growth was greater than statolith growth as size in- 

 creases (i.e. in larger squids the mantle was increas- 

 ing in length faster than was the statolith). More- 

 over, in general, for any given length, a winter squid 

 had larger statoliths than its summer counterpart. 



There were also considerable seasonal differences 

 in the growth of the statolith with age (Fig. IB). There 

 was a rapid increase in statolith length in summer 

 over a relatively short period from 60 to 100 days. In 

 contrast, statolith growth was much slower in the 

 winter; the statolith gradually increased in length 

 from 80 to 170 days. However, statoliths eventually 

 reached a greater length in the older, winter-popu- 

 lation squids. This feature was a factor of age be- 

 cause winter squids were not longer than summer 

 squids. In comparing similar-aged squids between 

 seasons, for any given age, a summer squid generally 

 had a larger statolith than its winter counterpart. 



Discussion 



Current research on fish somatic-otolith growth re- 

 lationships provides a background for the possible 

 mechanisms underlying somatic-statolith growth 

 relationships for L. chinensis. The relationship be- 

 tween both statolith length and mantle length and 

 statolith length and age shows striking similarities 

 to otolith length versus fish length and age studies. 

 Mosegaard et al. (1988), Secor and Dean (1989), 

 Reznick et al. ( 1989), Wright et al.( 1990), and Mugiya 

 and Tanaka ( 1992) have shown that slower-growing 

 fish have larger otoliths than similar-sized, faster- 

 growing fish. Furthermore, for striped bass, Morone 

 saxatilis, and Atlantic salmon, Salmo salar, slower- 

 growing fish have larger otoliths at any given size, al- 

 though faster-growing fish have larger otoliths at any 

 given age (Secor and Dean, 1989; Wright et al., 1990). 

 A similar relationship is evident between statolith 

 length and both mantle length and age for L. chinensis. 

 These teleost studies provide insights into the 

 growth dynamics of squid. The slower growing indi- 

 viduals of L. chinensis (winter population) had larger 



