380 



Fishery Bulletin 88(2), 1990 



0.68-kg isopleth over the higher observed levels of 

 fishing mortality, it appears that management for full 

 stock replacement would not involve a very great loss 

 of yield per recruit. In fact, assuming an F of 0.2 and 

 an age of first capture of 10 years, which equates to 

 a 100-cm (40-inch) size limit, yield per recruit is less 

 than 10% below the maximum shown in Figure 4. 

 And given any F between the mean estimated value 

 of 0.084 and the maximum estimate of F, the yield with 

 the 100-cm size limit is within 10% of the maximum 

 for that F. 



However, in terms of numbers caught per recruit 

 there is a substantial decline as the size limit increases. 

 AtF= 0.2, numbersper recruit values are 0.126, 0.192, 

 and 0.292 for size limits of 100, 84, and 63 cm respec- 

 tively; corresponding mean weights of fish comprising 

 the retained catch are 5.8, 4.0, and 2.4 kg. All of these 

 estimates assume that mortalities due to hooking and 

 releasing undersized fish are negligible. 



Based on the above information, a viable manage- 

 ment strategy for the leopard shark would appear to 

 be a size limit of 40 inches (100 cm). Although this size 

 limit results in a 34% decline in numbers caught com- 

 pared with a 33-inch (84 cm) limit, the fish which can 

 be kept are almost 50% larger. Further, stock replace- 

 ment is at the 100% level as compared with only 55% 

 at the smaller size limit. 



We stress, however, that our mortality and fecund- 

 ity estimates were based on data from studies in only 

 one area within the animal's geographic range, and the 

 extent to which these can be extrapolated to the en- 

 tire coastal population is not known. 



Acknowledgments 



We wish to thank David Holts, Mark Helvey, and 

 Nancy Lo for reviewing the manuscript and making 

 useful suggestions, and we are especially grateful to 

 Patrick Tomlinson for pointing out a number of errors 

 and omissions in his review of the manuscript and for 

 providing a very insightful discussion of the contents. 

 Also, we are indebted to an anonymous reviewer for 

 detecting an important quantitative error. We would 

 also like to thank Susumu Kato for providing valuable 

 advice during all phases of the tagging project, and to 

 others who helped tag and recover the fish. John Wit- 

 zig and Joyce Underbill generously supplied leopard 

 shark catch data, and Lorraine Prescott provided 

 editorial assistance. 



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