FISHERY BULLETIN: VOL. 81, NO. 4 



The offshore commercial catch cannot be ac- 

 curately calculated from commercial fishery statis- 

 tics. In the Carolinas in 1973 and 1974 the headboat 

 catch of snappers and groupers appeared to be 3 or 5 

 times greater (depending on the inclusion of ver- 

 milion snapper) than the commercial catch (Hunts- 

 man 1976b). Beginning in 1975 the commercial 

 landings in the Carolinas increased greatly and were 

 836 t of snappers and groupers in 1980. Commercial 

 snapper- grouper landings for the entire bight were 

 1,308 t for 1980. 4 



Both commercial and recreational fishermen prefer 

 groupers and any of three species known in the trade 

 as red snapper — Lutjanus campcchanus, L. vivanus, 

 and L. buccanella. Recreational fishermen and 

 trawlers usually take whatever species is most avail- 

 able, but commercial handline fishermen often leave 

 white grunts or red porgies and seek red snappers 

 and groupers. Since 1976, however, commercial hand- 

 line fishermen have responded to an improved mar- 

 ket for small species by being less selective. 



Potential Management Problems 



Public Law 94-265 requires that fisheries within the 

 United States extended jurisdiction zone (the area 

 between 3 and 200 mi seaward of the U.S. coast) be 

 managed so that an optimum yield is attained. 

 Optimum yield is an allocation of the yearly harvest 

 to recreational, commercial, and nonexploitive users 

 that is usually equal to, or less than, the maximum 

 sustainable yield (MSY). Minor conflicts and 

 polarized viewpoints have arisen between the 

 various users, primarily because of differing goals 

 and differing methods of fishing. At present there is 

 no objective way of allocating the catch among the 

 various groups, because there is an insufficient 

 understanding of stock productivity. Institutional 

 provisions for the allocation of the catch exist, but the 

 understanding of stock productivity necessary for 

 the allocation is lacking. 



Insight into stock productivity may be achieved 

 through mathematical models. But neither the 

 dynamic pool (Beverton and Holt 1957) nor the 

 surplus-yield (Schaefer 1957) population models is 

 presently useful to us because both require data that 

 do not exist. The dynamic pool model requires 

 parameter estimates (such as the relationship of 

 stock size to recruitment) that are unavailable for the 

 stocks involved and the surplus yield model requires 



4 Unpublished data, Southeast Fisheries Center Miami Laboratory, 

 National Marine Fisheries Service, NOAA, Miami, FL 33149- 

 1099. 



a fairly long series of annual catch and effort 

 measurements. 



Despite initiation of fishery censuses in 1880, there 

 is a lack of interpretable records of annual commer- 

 cial catches for the South Atlantic snapper-grouper 

 fishery. Serious problems in the data series include, 

 among others: 



1) Missing or faulty species distinctions. At least 

 10 species of grouper are listed only as grouper, 

 and porgies include both inshore estuarine- 

 dependent and oceanic reef species. The red 

 snapper listing includes at least three species 

 of Lutjanus and, depending on the year, may or 

 may not include vermilion snapper, Rhom- 

 boplites aurorubens. 



2) Missing records, often covering decades, in the 

 series of records begun in 1880. 



3) Catches reported by area of landing instead of 

 by area of fishing (e.g., snappers landed on 

 Florida' s east coast may have come from North 

 Carolina or the Bahamas). 



4) No useful or reliable effort data. 



Matching catch and effort data available for the 

 headboat fishery from 1972 to 1980 in North Caroli- 

 na and South Carolina (Huntsman 1976a, b; footnote 

 3) and from 1976 to 1980 in Georgia and North Flo- 

 rida, (footnote 3) are nearly useless for yield-model 

 construction without concurrent commercial data. 



Enough information is available to develop an 

 abbreviated version of the full dynamic pool model — 

 the yield per recruit model (Beverton and Holt 1957). 

 The yield per recruit model, which can be used for 

 partial analysis, is especially useful if one must pre- 

 pare management schemes from incomplete infor- 

 mation. An advantage of the yield per recruit model is 

 that it has minimal requirements of parameter 

 estimates but allows easy evaluation of the response 

 of yield to changes in fishing mortality and recruit- 

 ment age. Even if the exact relationship between 

 effort and fishing mortality is unknown, one can 

 derive general information on which to base manage- 

 ment regulations. 



The yield per recruit model predicts the ratio of the 

 weight or numbers of fish caught during the life span 

 of a cohort to the initial number of individuals of the 

 cohort that enter the fishing grounds. It expresses 

 these yields as a surface responding to the indepen- 

 dent variables F (instantaneous fishing mortality 

 rate) and t r (age at recruitment to the gear). The 

 growth rate, natural mortality rate, and longevity of 

 the species are the principal parameters influencing 

 the shape of the surface. 



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