Garcia-Diaz et al ; Spawning season, maturity sizes, and fecundity of Seiranus atncauda 



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Table 1 



Description of gonad stages according to Garci'a-Diaz et al. (1997, 2002). 



Maturity stage 



Histological appearance 



I. Immature 



II. Developing virgin, 

 or recovering-spent 



III. Developing, maturing 



IV. Ripe 



V. Spent 



Ovary contains oogoniaand oocytes from primary growth (stage I). Testis formed mainly by sperma- 

 togonia and primary spermatocytes. Ovary and testis joined by connective tissue. 



Ovary begins to acquire ovarian lamellae. Contains stage-I oocytes and yolk-vesicle-formation- 

 stage oocytes (stage II) in advanced phases. Testis arranged in tubules with spermatogonia and 

 primary and secondary spermatocytes. 



Ovary with oocytes at all previous stages and oocytes in vitellogenic stage (stage III). Seminiferous 

 tubules contain all spermatogenic cells. 



Ovary with oocytes at all previous stages and with maturation oocytes (stage IV), mature and 

 hydrated eggs (stage V). Atresic oocytes and postovulatory follicles appear. Testis completely 

 mature, tubules filled with spermatozoa (which accumulate in deferent duct next to gonadal wall) 

 to be expelled. 



Oocytes undergoing regression and reabsorption. Numerous atresic oocytes. Testis in regression; 

 cells appear fused, form semicontinuous mass. 



3 Hepatosomatic index (HSl={Uver weight I gutted 

 weight )y.lQO): this estimates the relative size of the 

 liver to body weight: 



4 Condition factor (Kn={total weight/ TL '•)x 1000): 

 this is as an overall measurement of robustness of 

 the fish, b being the exponential of the regression 

 TW = aTL^, which is 3.25 according to Tuset et al. 

 (2004); 



5 Oocyte diameter (DO): this gives information on the 

 cell development of each individual. To obtain this 

 value, often fish randomly chosen from the monthly 

 samples, the diameters of the first 50 oocytes encoun- 

 tered were measured with an ocular micrometer. 

 Measurements were taken only of oocytes sectioned 

 through the nucleus. 



Length at sexual maturity 



Total length of all individuals was used to estimate the 

 size at first maturity and size at mass maturity. These 

 are defined as the sizes (TL) at which 50% (TLj^y,^) and 

 95% (TLggtj) of all fish sampled are at the relevant 

 maturity stage (developing MS III, ripe MS IV, or spent 

 MS V) (Garcia-Diaz et al., 1997). The proportions were 

 estimated at length classes of 1 cm, and the data were 

 fitted to the logistic curve (Pope et al., 1983): 



p = WO/(l + exp{a+bTL)), 



where p = percentage of mature individuals as a func- 

 tion of size class (TL); and 



a and b = specific parameters that can change during 

 the life cycle. 



A logarithmic transformation was applied to the equa- 

 tion to calculate the parameters a and b by means of 

 linear regression. 



Reproductive potential 



The pattern of annual fecundity (indeterminate or deter- 

 minate) was assessed by oocyte size-frequency distribu- 

 tion (Hunter and Macewicz, 1985a). Ten fish ranging 

 between 18.1 and 31.5 cm TL in ripe stage were selected 

 for analysis of oocyte size-frequency distribution — five 

 fish in March and another five in July — to represent 

 early and late gonad development (White et al., 2003). 

 Because the mean size (^-test, P>0.05) was not signifi- 

 cantly different between both samples, one frequency 

 distribution was obtained for each month. The diameters 

 of the first 500 oocytes encountered were measured with 

 an ocular micrometer for each fish. Measurements were 

 taken only of oocytes sectioned through the nucleus. 



Gonads of individuals in MS III (developing) and 

 MS IV (ripe) were collected to estimate fecundity. One 

 lobule was fixed in 10% buffered formaldehyde (24 h) 

 for histological study, and the other was weighed and 

 preserved in Gilson's fluid to estimate fecundity. Gonads 

 with postovulatory follicles were omitted from batch 

 fecundity estimates (Hunter et al., 1985). 



The oocyte size-frequency method was applied to de- 

 termine the batch fecundity (Hunter et al., 1985). This 

 entails counting the number of oocytes in the most de- 

 veloped modal group of oocytes and plotting the size-fre- 

 quency. In each lobule 200 oocytes were measured with 

 the Nikon digital counter SC-112 and data processor DP- 

 201 connected to the micrometer stage of a profile projec- 

 tor (V-12A, Nikon, Melville, NY). The routine NORMSEP 

 (normal distribution separator) of FAO-ICLARM Stock 

 Assessment Tools (FISAT II, vers. 1.0.0, FAO, Rome, 

 Italy) program was used to separate the most developed 

 modal group of oocytes based on Hasselblad's maximum 

 likelihood method (Hasselblad, 1966). 



Batch fecundity was estimated gravimetrically by 

 using the oocyte size-frequency method (Hunter et 



