Macchi and Acha: Spawning frequency and batch fecundity of Brevoortia aurea 



285 



YO 



S— ^\ 



5v " , .^.«i.>■^<sV^:i. *•.._ 



\ 







YO 



■4 



-■  y 





Figure 2 



Postovulatoty follicles from female Brazilian menhaden at different stages: ( A and B ) day-0, 

 cordlike appearance of the granulosa layer can be observed; (C and D) day-1, reduction 

 in size and degeneration of follicles are evident. T = thecal layer; G = granulosa layer: 

 L = lumen; YO = yolked oocytes; PO = postovulatory follicles. Bar = 50 jim 



Batch fecundity (BF; number of oocytes released 

 per spawning) was estimated gravimetrically by the 

 hydrated oocyte method (Hunter et al., 1985) for 

 112 females (44 from 1994, 38 from 1995, and 30 

 from 1997). The hydrated ovaries showed no evi- 

 dence of recent spawning (no POFs). Three pieces of 

 ovary, approximately 0.1-0.2 g each, were removed 

 from the anterior, middle, and posterior parts of 

 one gonad, weighed (±0.1 mg), and the number of 

 hydrated oocytes were counted. Batch fecundity for 

 each female was the product of the mean number 



of hydrated oocytes per unit of weight and the 

 total weight of the ovaries. Relative fecundity (RF; 

 hydrated oocytes per gram of body weight ) was deter- 

 mined as the batch fecundity divided by female 

 weight (without ovary). The relationships of batch 

 fecundity to fork length and to total weight (ovary 

 free) were described by regression analysis (Draper 

 and Smith, 1981), and the significance evaluated by 

 testing whether the slope of the regression was sig- 

 nificantly different from zero. Interannual compari- 

 sons were based on coincident length ranges in the 



