804 



Fishery Bulletin 97(4), 1999 



Dry weight analysis 



M m 



3 n 



20 



To study the seasonal variation in 

 somatic and reproductive organs, 

 dry weight was used to correct for 

 differences in water content be- 

 tween different organs. The samples 

 for this study were collected from 

 November 1994 to April 1996. 

 From each monthly sample, a 

 subsample of 20 females and 20 

 males was selected with mantle 

 lengths within a 20-mm size range 

 encompassing the mean size at 

 maturity (the size at which 50% 

 of the individuals were maturing 

 or mature). This size was 122 and 

 61 mm ML ( calculated by using the 

 whole-year sample) for females and 

 males, respectively (Gabr et al., 

 1998). It is possible to treat speci- 

 mens from around the mean as 

 "standard" animals (sensii Gabbott, 1976) and so com- 

 pare cuttlefish at different degrees of maturity with- 

 out having to make statistical coiTections for size. There 

 were no cuttlefish of maturity stage I in this sub- 

 sample; however, stages II to IV were present. The 

 cuttlefish in the subsample were dissected in the 

 same way as those in the sample as a whole. The 

 same measurements of mass to two decimal places (in 

 grams) were taken, but dry rather than wet weight 

 was used. Tissues were dried to constant weight (for 

 48 h) at 80°C and then cooled in a desiccator 



The following indices were calculated for dry 

 weight tissues; gonadosomatic index for females 

 (GSI) - 100 OM/BM; gonadosomatic index for males 

 (GSI) = 100 TM/BM: nidamental gland index (NGI) 

 - 100 NGM/BM; spermatophoric complex index (SCI) 

 = 100 SCM/BM; mantle index (MI) = 100 MM/BM; 

 head index (HI) = 100 HM/BM; digestive gland in- 

 dex ( DGI ) = 100 DGM / BM, and viscera index ( VI ) = 

 100 VM/BM. 



Analysis of protein 



The dry tissue of mantle and whole head for 7 to 9 

 females of maturity stages II-IV was ground to a 

 fine powder with a mortar and pestle. The powdered 

 samples were placed in sealed plastic vials and stored 

 for further analysis. The Kjeldahl method for deter- 

 mination of nitrogen was used (see Giese, 1967). 

 % Protein = % nitrogen x 6.25 (Giese, 1967; Rigby, 

 1990; Dickey-Collas, 1991). Kruskal-Wallis ANOVA 

 was used to examine the significant variation in per- 

 centage of protein between maturity stages. 



Female 

 Male 



mmm aDD D OD D D 



iititm wi ri I (niDCKD O IDCO <E CD 



n m o m l I II mil iii III i n O dlD D C Q 

 "l atiHiii l on aiiiii » m i CJCXIDO O O O 



iiiiMinm «-M»M 

 O OCUD O 



Ml III 1 1 am D 



40 60 80 100 120 140 160 



Mantle length (mm) 



180 200 220 240 



Figure 1 



Relation between mantle length and maturity stages in female and male Sepia 

 pharaonis. 



Stomach content analysis 



Each specimen's stomach fioUness was estimated accord- 

 ing to a 5-level subjective scale: 0=empty; l=one-quarter 

 fuU; 2=halffijll; 3=three-quarters full; 4=fLiIl or distended. 



Length-weight relationship 



Equations of the form BW - aML^, where a and b 

 are constants of the regression, were fitted by trans- 

 forming the data into logjf, and deriving the regres- 

 sion line by the least squares method. Correlation 

 was expressed by the coefficient /•-, and comparisons 

 between males and females were made by ANCOVA. 



Results 



Growth and maturity 



Maturity generally increased with mantle length, but 

 each stage was represented by a very wide range of 

 mantle lengths with considerable overlap between 

 stages (Fig. 1). This finding suggests that there is no 

 strong relation between growth and maturation rate. 

 Males attained full maturity (stage III) at a smaller 

 size than females (stages III and IV). 



Maturity stages versus soma production and gonad 

 production 



In females (Table 1 ), there was a significant increase 

 in total somatic mass and mass of somatic organs 



