Jackson: Age and growth of Sepioteuthis lessoniana 



17 



250 



200 r 



150 - 



100 



50 



50 



100 150 



AGE (days) 



200 



250 



Figure 2 



Age-length relationship for field-captured male, female, and juvenile 

 Sepioteuth i'.s lesson ia na. 



than in the paralarvae or juveniles (Table 3). Maturity 

 was found to take place as young as 67 days and 69 

 days in males and females, respectively. 



Discussion 



Ageing research with Sepioteuthis lessoniana provides 

 further evidence that statolith growth rings in tropical 

 loliginids are a valuable tool that can be applied to 

 tropical squid demogi-aphy. Daily statolith ring periodi- 

 city has also been demonstrated to occur in Illex ille- 

 cebrosus (Hurley et al. 1985, Dawe et al. 1985), Allo- 

 teuthis subidata (Lipinski 1986), Loligo opalescens 

 (Yang et al. 1986), and Idiosepius pygmaeus (Jackson 

 1989). Furthermore, statolith ring sequences have been 

 observed and counted in other temperate-water squid 

 species (Kristensen 1980, Rosenberg et al. 1981, Nat- 

 sukari et al. 1988). 



The presence of subdaily rings within the statolith 

 microstructure of S. lessoniana illustrates the need for 

 validation when attempting to enumerate growth rings. 

 Validation is the only way to conclusively delineate 

 whether less-prominent rings are in fact subdaily rings. 



Statolith growth-ring analysis suggests that S. lesso- 

 niana in Australia has a short life cycle and rapid 

 growth. Estimates of age and growth of this species 



from size-frequency analysis at other localities suggest 

 a very different pattern of growth. Earlier work on 

 growth analysis in India (Rao 1954, Silas et al. 1982) 

 has estimated that S. lessoniana takes up to three years 

 to reach maximum size. This has also been further sup- 

 ported by ELEFAN 1 computer program analysis of 

 Rao's (1954) length-frequency data (Longhurst and 

 Pauly 1987). 



Data from these different tropical populations of S. 

 lessoniana suggest different patterns in the life cycle 

 and growth of this species. The question is raised as 

 to whether this is a locality difference or a reflection 

 of different methodologies in analysis of growth rate. 



