80 



Fishery Bulletin 102(1 I 



Input 



number released 



(NR) 



' assign size-at-release (SAR) 

 * calculate cost of release 



(COR) 



<— 



Size-at-release 



N 



Density- 

 independent 



Julian day 



' assign date of release 

 (DOR) 



< 



I I 



* output 



- number of survivors 



- cost per survivor (CPS) 



\ 



/ 



Figure 1 



Model flowchart. Dashed arrows represent model "backloops" to the indicated compartment where 

 simulations continue with the next value of the arrow-labeled variable. Side graphs indicate the three 

 relationships between density and mortality (number offish consumed) that were considered, and the 

 general relationship between growth and Julian day. 



for the initial release scenario of fish size = 30 mm TL. 

 Julian day = 92, and an NFR input determined by the mod- 

 eler). The model then looped back to the "date-of-release" 

 step and simulated the release of the 30-mm-TL fish for 

 Julian release days 93-197, outputting a predicted number 

 of survivors and cost-per-survivor for each release date. The 

 model then repeated all previous steps under sequentially 

 larger size-at-release scenarios, looping back to the "size- 

 at-release" step and simulating the release of fish ranging 

 in size from 32-80 mm TL fish in steps of 2 mm TL. The 

 model output was a predicted number of survivors and 

 economic cost-per-survivor for each release day (92-197) 

 for each size-at-release (Fig. 1). Thus, for each input NFR, 

 there were 26 size-at-release possibilities x 105 Julian days 

 of release possibilities, which resulted in 2730 simulations, 

 each of which resulted in a predicted number of survivors 

 and cost-per-survivor for that particular release scenario. 

 For each input NFR, the results from the 2730 simulations 

 were plotted on two response surfaces, with an .v-axis of 



size-at-release, a y-axis of date-of-release, and a 2-axis of 

 either 1) predicted number of survivors (NOS), or 2) cost- 

 per-survivor ( CPS ), to identify release scenarios resulting in 

 the maximum predicted number of survivors and minimum 

 cost-per-survivor, respectively. The scenarios resulting in 

 the maximum predicted number of survivors and minimum 

 cost-per-survivor were not necessarily identical. 



Calculation of mortality, growth, survival, and economic 

 costs associated with release 



During each day at large (DAL), released fish were sub- 

 jected to a density-independent daily mortality rate of 

 0.02153, derived from postrelease mark-recapture data 

 of HR summer flounder (Kellison et al., 2003b). In deriv- 

 ing this value, mean postrelease densities were used to 

 estimate a total number of survivors from experimental 

 releases. Daily survival was then calculated with the 

 equation 



