Mackie et al.: Variability in reproductive development of Spanish mackerel (Scomberomorus commerson) 



347 



Females 



150-, 



400 600 



1 1 1 r 



000 1200 1400 1600 



I 1 1 1 1 1 1 1 1 1 — 



100 200 300 400 500 600 700 800 900 1000 



O 



1 I 



c 



- 4 



1200 



1400 



Length 



Figure 2 



Proportion of mature female and male S. commerson within samples. 

 The number offish within each length class is indicated by the verti- 

 cal bars and the left v-axis and the proportion of mature fish by the 

 black circles and the right y-axis. The length at which 50% of fish 

 within the samples were mature is indicated on the fitted maturity 

 curve (±95% CI). Lengths are fork length in mm. Note that data for 

 juvenile fish of undifferentiated sex are included in both graphs. The 

 dashed lines indicate the length at 50% mature (P=0.5). 



FL (±14.5 SE) for data taken during the reproductive 

 period. The size at which 10% of females were mature 

 was 638 mm FL (±19.6 SE), with 90% mature by 981 

 mm FL (±7.2 SE) (Fig. 2A). 



There was also considerable overlap between the 

 lengths of immature and mature males. The largest im- 

 mature male was 1140 mm FL (11.3 kg WW), whereas 

 the smallest mature male (stage 3) was 491 mm FL (1.0 

 kg WW). The size at which 10% of males were mature 

 was 465 mm FL (±24.9 SE), the size at which 50% of 

 males were mature was 628 mm FL (±13.8 SE) or 706 

 mm TL, and the size at which 90% were mature was 

 791 mm FL (±10.5 SE) (Fig. 2B). 



Development of oocytes is asynchronous and all stag- 

 es of oocytes are present at the same time within re- 

 productively active ovaries. This reproductive feature, 

 along with the maturation of multiple batches of oocytes 

 (as evidenced by presence of both POFs and hydrated 

 or MNS oocytes in spawning ovaries), confirms that 

 female S. commerson are serial or partial spawners 

 (Hunter et al., 1985). 



Relationships between batch fecundity and body 

 parameters were obtained from counts of hydrated 

 oocytes within prespawning (stage 5a) ovaries. Size 

 of females for which batch fecundity was determined 

 ranged from 857 to 1143 mm FL and from 5.3 to 



