FISHERY BULLETIN: VOL. 70. NO. 3 



7.1 _ 4.8 = 2.3 and Ce (5.9) = 2.3 for a rec- 

 ommended yield of 3.4 million pounds (Table 1). 

 It was assumed the Oregon fleet's catch from 

 Oregon waters would be negligible. 



A more radical strategy such as harvesting 

 all of the surplus stock could be employed, but 

 the attendant risks would be higher. These 

 risks would include a possible disturbance of 

 whatever stability exists in the population, par- 

 ticularly with reference to age structure. It 

 might also be argued that the observed catch- 

 per-effort should be used to adjust P(t) before 

 making the quota calculation described above. 

 Here again, a substantial risk would be involved 

 if the observed catch-per-effort were much high- 

 er than the expected since with our methods it 

 could not be determined whether such an anom- 

 aly was due to abnormal catchability or to a real 

 increase in the stock size. The quota-setting 

 procedure we recommended above does res])ond 

 in a limited way to a higher than expected catch. 

 Since the fishery operates under a quota, a catch- 

 per-eflFort which is higher than expected will 

 result in the quota being filled with a lower than 

 expected amount of eflfort and usually in a short- 

 er time period. An examination of (2) shows 

 that this will increase P(t) and thus result in 

 a larger quota for the season beginning at time t. 



This fishery must be carefully followed in the 

 future to observe how well the model based up- 

 on current parameters describes the observed 

 catch and effort pattern. An equation such as 

 this which is fitted to data from only 16 years 

 cannot be considered definitive from a statistical 

 estimation viewpoint and, in addition, there is 

 a chance the population parameters will actually 

 be changing. For example, one cannot avoid 

 speculating about the effect of the large Pacific 

 coast hake fishery on the shrimp natural mor- 

 tality rate. Since hake may be a substantial 

 predator upon shrimp (Gotshall, 1969), a reduc- 

 tion of the hake population due to a large fishery 

 might increase the abundance of ocean shrimp. 



Beyond the technical management problems 

 which we have discussed at length, there is the 

 institutional problem of a single state attempting 

 to manage an interstate fishery. While the catch 

 from Oregon waters by Oregon-based vessels has 

 usually been so small that it affects the popula- 



tion negligibly, at times it has been substantial. 

 A sustained change in conditions could nullify 

 the effect of California's quota mechanism. 



ACKNOWLEDGMENTS 



Many biologists of the Department of Fish 

 and Game collected the data used in this paper. 

 Daniel W. Gotshall and Walter A. Dahlstrom 

 were of special help to us in obtaining the data 

 and in freely passing on to us their knowledge 

 of this shrimp fishery and of shrimp life history. 

 We also wish to thank Catherine L, Berude for 

 programming and computing assistance. 



LITERATURE CITED 



Abramson, N. J. 



1968. A probability sea survey plan for estimating 

 relative abundance of ocean shrimp. Calif. Fish 

 Game 54:257-269. 



Abramson, N. J. (compiler). 



1971. Computer programs for fish stock assess- 

 ment. FAO Fish. Tech. Pap. 101, [149 p.] 



Berude, C. L., and N. J. Abramson. 



1972. Relative fishing power, CDC 6600, FOR- 

 TRAN IV. Trans. Am. Fish. Soc. 101-133. 



Dahlstrom, W. A. 



1961. The California ocean shrimp fishery. Pac. 

 Mar. Fish. Comm., Bull. 5:17-23. 



1970. Synopsis of biological data on the ocean 

 shrimp Pandalus jordani Rathbun, 1902. In M. N. 

 Mistakidis (editor). Proceedings of the world 

 scientific conference on the biology and culture 

 of shrimps and prawns, Mexico City, Mexico, 12- 

 14 June 1967, p. 1377-1416. FAO Fish. Rep. 57. 



Dahlstrom, W. A., and D. W. Gotshall. 



1969. Will the shrimp boats keep a comin'? Out- 

 door Calif. 30(3): 1-4. 



Fox, W. W., Jr. 



1971. Random variability and parameter estima- 

 tion for the generalized production model. Fish. 

 Bull., U.S. 69:569-580. 



Gotshall, D. W. 



1969. The use of predator food habits in estimating 

 relative abundance of the ocean shrimp, Pandalus 

 jordani Rathbun. In M. N. Mistakidis (editor). 

 Proceedings of the world scientific conference on 

 the biology and culture of shrimps and prawns, 

 Mexico City, Mexico, 12-14 June 1967, p. 667-685. 

 FAO Fish. Rep. 57. 



In press. Estimates of population size, mortality 

 rates and growth rates of northern California 

 ocean shrimp, Pandalus jordani 1965 - 1968. Calif. 

 Dep. Fish Game, Fish Bull. 155. 



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