Vaughan and Prager Decline in abundance of Pagnis pagnis off the southeastern United States 



369 



o 3000  



S- 1000 



Primary matrix 



-«- Primary (Miss) 

 -a- Alternate matrix 



tr 

 9r so 



Primary matrix 



-*— Primary (Miss) 

 -e- Alternate matrix 



B 



Figure 8 



Annual estimates of (A) total spawning stock biomass, and IB) 

 static spawning potential ratio (SPR) for red porgy off the south- 

 eastern United States from calibrated VPA based on different 

 catch matrices and treatment of zeroes (alternative treatment of 

 zeroes as missing value is indicated as "Miss" after Primary) in 

 MARMAP hook-and-line CPUE. 



erage age of transition to male is unknown, as is the effect 

 of population density on transformation rate. 



Increased sex transformation due to reduced abundance 

 of males, as reported in other protogynous reef fish (Sha- 

 piro. 1979), would cause declines in mature female bio- 

 mass and egg production beyond those expected from fish- 

 ing alone. McGovern^ found a greater percentage of males 

 in smaller size classes in 1991-99 than in 1979-81 and 

 suggested that red porgy have compensated for the loss 

 of large individuals by becoming male at smaller sizes. If 

 so, a smaller change in sex ratio, but a greater reduction 

 in egg production, would be expected than implied by in- 

 creasing fishing mortality alone. 



New evidence suggests that red porgy are indetermi- 

 nate, serial spawners (Daniel"). That is, the size and num- 

 ber of batches of eggs are not fixed at the start of the 

 spawning season, but older, larger females spawn in larger 



^ McGovem, J. C. 2001. Personal commun. South Carolina 

 Department of Natural Resources, P.O. Box 12559. Charleston, 

 SC 29422. 



^ Daniel, E. A. 2001. Personal commun. University of Charles- 

 ton, Charleston, SC 29424. 



batches, more frequently, and possibly over a longer sea- 

 son than younger, smaller females. If so. SPR based on egg 

 production estimated from a fixed weight-fecundity rela- 

 tionship would be unrealistic, and SPR based on total ma- 

 ture biomass would underestimate the contribution of old- 

 er fish, and thus underestimate the effects of fishing. 



Huntsman and Schaaf (1994) proposed accounting for 

 sex-composition changes by multiplying total egg produc- 

 tion by a factor representing the probability of successful 

 fertilization. They calculated that probability (Q) for a giv- 

 en fishing mortality rate F' from the relative change in 

 male contribution of spawning products under fishing: 



^ jG^IGf)\F- 



^GJGf)\F = 



where G„, and G,= the gamete contributions of males and 

 females, respectively. 



Huntsman and Schaaf (1994) computed G,„ as total male 

 biomass and G. as total female egg production. When new 

 information on red porgy batch spawning becomes avail- 



