FISHERY BULLETIN: VOL. 82, NO. 3 



800 



O 600 



o 



c 400 

 IB 



o 



2 200 

 4) 



2 4 6 8 10 12 14 16 18 



Fishing Effort (thousand boat months) 



FIGURE 3. — Catch versus a nominal effort index 

 for the California Pacific sardine fishery (after 

 Fox 1974). 



IMPLICATIONS 



In this simple treatment, I have shown how 

 some available estimates of fishing effort are in- 

 adequate to describe a fishery where searching 

 time is stock-density dependent. More realistic 

 models can be based upon an examination of de- 

 tailed log-book data for inferences as to the rela- 

 tionships between searching time, stock abun- 

 dance, prey and fleet distribution, and cooperation 

 among the fleet. Hassel (1978) offers a comprehen- 

 sive review of current approaches. 



Even with better estimates of fishing effort a 

 catastrophic collapse may be unavoidable because 

 of parameters that cannot be measured or con- 

 trolled (e.g., Clark and Manguel 1979). These es- 

 timates are important, however, in order to use 

 surplus-production models for estimating the 

 causes of such catastrophic collapses as that of the 

 Pacific sardine fishery. Such estimates may also be 

 necessary to suggest whether existing fisheries 

 such as the Atlantic menhaden are actually being 

 overfished. 



ACKNOWLEDGMENTS 



I am indebted to the captain and crew of the Sea 

 Wolf, Wallace Menhaden Company, for allowing 

 me to participate in a fishing expedition off Cam- 

 eron, La.; the Menhaden Advisory Committee of 

 the Gulf States Marine Fisheries Commission; 

 and T. B. Ford, W. W. Fox, Jr., J. Geaghan, and an 

 anonymous reviewer for their interest and advice. 



This report resulted from research supported by 

 the Louisiana Sea Grant Program, Gulf States 

 Marine Fisheries Commission, and Louisiana 

 Board of Regents. 



452 



400 500 600 700 800 900 1000 1100 1200 1300 

 EFFORT IN "1971" VESSEL-WEEKS 



400 800 1200 1600 1000 2400 2800 



EFFORT IN VESSEL-WEEKS 



FIGURE 4. — Comparing the difference between fitting catch data 

 for Atlantic menhaden when the effort is measured as (A) 

 Schaaf's (1975a) 1971-vessel weeks and (B) vessel weeks. Curves 

 were fit after the technique of Marchesseault et al. (1976). 



LITERATURE CITED 



BANNEROT, S. E, AND C. B. AUSTIN. 



1983 . Using frequency distributions of catch per unit effort 

 to measure fish-stock abundance. Trans. Am. Fish. Soc. 

 112:608-617. 

 BEDDINGTON, J. R. 



1979. On some problems in estimating population abun- 

 dance from catch data. Rep. Int. Whal. Comm. 29:149- 

 154. 

 CLARK, C. W, AND M. MANGEL. 



1979. Aggregation and fishery dynamics: a theoretical 

 study of schooling and the purse seine tuna fisheries. 

 Fish. Bull., U.S. 77:317-337. 



FOWLER, C. W. 



1980. A rationale for modifying effort by catch, using the 



