FISHERY BULLETIN: VOL. 87, NO. 2, 1989 



FISHING MORTALITY RATE 



Figure 7.— Yield-per-recruit (g) as a function of minimum legal size and instantaneous fishing 

 mortality rate, determined by the method of Beverton and Holt (Ricker 1975). For red abalones, 

 parameters were K = 0.269, L^ = 201 mm, W_ = 1,500 g. and M = 0.10 (A) and M = 0.15 (B). 



M = 0.20, then the best minimum size is 140 mm. 

 Both are substantially lower than the present mini- 

 mum legal size. 



Fecundity 



Regression constants for the power curves re- 

 lating fecundity to shell length in the four data sets 

 are shown in Table 2. This table also shows the con- 

 stants from the combined analysis, which were used 

 in egg-per-recruit analysis. 



Egg-Per-Recruit Analysis 



Results for red abalones using M = 0.10 and M 

 328 



= 0.15 are shown in Figure 8A and B respectively. 

 Three points should be noted. First, egg production 

 estimates are sensitive to the natural mortality rate, 

 decreasing as M decreases. Second, even at the 

 smaller recreational size limit and very high rates 

 of fishing, egg production estimates are reasonably 

 high. With M = 0.10, egg production by abalones 

 below the recreational size limit should be more than 

 35% of the virgin population egg production. At 

 higher values of M, large size limits, or lower fishing 

 intensities, the estimate is higher. At the more 

 realistic point of using M = 0.15, ii' = 1.0, and 

 the recreational size limit, egg production would 

 be 48%. Third, combinations of F and size limits 

 that produce the best yield-per-recruit lead to 



