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Fishery Bulletin 94(1). 1996 



However, culture conditions 

 do not reflect the natural en- 

 vironment, and although 

 benthic octopods can be raised 

 relatively easily in captivity, 

 this is not true for the pelagic 

 squids. The use of statolith 

 increments to age individual 

 squids is providing a means 

 both to disentangle the size- 

 age question and to deter- 

 mine the reproductive tactics 

 of squid. 



During the summer of 1990, 

 collections were made of 

 Photololigo sp. 1 from the 

 northwest shelf, western 

 Australia, as part of a popu- 

 lation genetic study of Aus- 

 tralian loliginids (see Yeat- 

 man and Benzie, 1994). This 

 species, which was first iden- 

 tified by using genetic mark- 

 ers, showed marked varia- 

 tion in size at maturity, some 

 individuals maturing at less 



than half the size of their counterparts. Photololigo 

 sp. 1, so named because of the presence of light or- 

 gans on the ink sac (see Natsukari, 1984), is one of 

 two species identified that fits the gross morphology 

 of Photololigo edulis documented from these north- 

 ern tropical waters (Dunning, 1982). After establish- 

 ing that the small and large mature individuals do 

 not represent different species ( Yeatman and Benzie, 

 1994), we used statolith ageing techniques on a 

 subsample of these individuals to explore how age is 

 related to the observed plasticity in size at maturity. 



Materials and methods 



Sample collection 



Individuals of Photololigo sp. 1 (37 males, 42 females) 

 were collected by bottom trawl during the 1990 Sep- 

 tember-October cruise of the RV Southern Surveyor 

 on the northwest shelf ( Fig. 1 ). After the removal and 

 subsequent freezing of tentacular tissue for electro- 

 phoresis, a random subsample (n=32) of squid heads 

 was taken from the 79 specimens and fixed in 70% 

 ethyl alcohol. Statoliths were removed from the fixed 

 specimens of Photololigo sp. 1 after a period of nearly 

 two years in ethanol. Statoliths of thirteen male squid 

 and nineteen female squid, captured at water depths 

 between 102 and 178 meters, were examined. 



Figure 1 



Capture localities for Photololigo sp. 1 from the northwest shelf of Australia. 



Maturity status 



Each squid was assigned a maturity status accord- 

 ing to Lipinski's universal scale (see Juanico, 1983; 

 Sauer and Lipinski, 1990) which recognizes six mac- 

 roscopic stages: 1 = juvenile; 2 = immature; 3 = pre- 

 paratory; 4 = maturing; 5 = mature; and 6 = spent. 

 For males, the definitions of the various categories 

 are the following: 1 = spermatophoric complex (SO 

 visible as a spot only; 2 = testes and parts of the SC 

 visible; 3 - spermatophoric organ visible with white 

 streak on vas deferens; 4 = vas deferens extended 

 and spermatophoric sac (SS) contains white particles, 

 testis structure present; 5 = SS contains tightly 

 packed spermatophores; and 6 = degenerating sper- 

 matophores and SC, and loss of testis structure. 



The categories (stages) in females are distin- 

 guished by the following criteria: 1 = nidamental 

 glands (NG) appear as fine transparent strips; 2 = 

 sexual organs translucent or whitish, oviduct mean- 

 der visible, ovary visible as homogenous structure; 3 

 = sexual organs not translucent, oviduct meander 

 extended, immature ova visible, NG enlarged; 4 = 

 NG large, covering most internal organs, mature ova 

 in ovary; 5 = same as 4 but mature eggs in oviduct; 

 6 = few, if any, eggs in the oviduct and ovary. 



Lipinski's maturity scale was used because it can 

 easily be used in the field. However, recently stages 

 1 through 4 have been validated by histological cri- 



