Carter and VanBlancom: Effects of experimental harverst on Stmngylocentrotus franascanus in nortfiern Washington 



671 



soa unliiiis were found to be associated with adult red sea 

 urchins (our study), juvenile abundance did not difTer by 

 harvest treatment (our study), refuge habitats (cobble, 

 crevices, kelp holdfasts) are abundant, and fast moving 

 sea urchin predators (e.g. fish, lobster) are rare or absent 

 (Breen et al., 1985; Sloan et al., 1987). 



Management implications 



The current hai-vest strategy in Washington, applied to 

 sea urchin beds in SJC, results in low yields in the second 

 year of harvest owing to the fishing down of the popula- 

 tion and slow recolonization of harvested areas. Annual 

 commercial har\'est of a single location is probably not 

 economically viable. Commercial hai-vests in Washington 

 and other areas of the west coast are well below levels 

 observed in the late 1980s, and biomass estimates are 

 not available to evaluate the status of stocks in Wash- 

 ington (Bradbury'-'). In such circumstances, options for 

 managing the fishery to conserve, and possibly increase, 

 stocks over the long term include artificially enhancing 

 stocks, redirecting or reducing harvest, and establishing 

 marine harvest refuges (Tegner, 1989; Quinn et al., 1993; 

 Rogers-Bennett et al., 1995). Stock enhancement efforts 

 often confer limited success (e.g. Tegner, 1989) and may 

 negatively impact behavioral and genetic diversity of wild 

 populations (Rogers-Bennett, 1997). 



Sea urchin harvest in Washington is currently controlled 

 by using harvest quotas, limited entry, and size limits; sea- 

 sonal closures and rotational harvests were also employed 

 until relatively recently (Pfister and Bradbury, 1996; Lai 

 and Bradbury, 1998). Washington also has two marine 

 harvest refuges (Fig. 2). Both rotational harvests and ma- 

 rine harvest refuges increase the probability of long-term 

 survivorship of populations, particularly when recruitment 

 is low and variable, as it appears to be in SJC (Botsford et 

 al., 1993; Quinn et al., 1993; Pfister and Bradbury, 1996). 

 Rotational harvests were discontinued in Washington in 

 1995, and the size of one of the two marine harvest refuges 

 was reduced substantially in 1998 (Fig. 2). Additional ma- 

 rine harvest refuges in Washington might be established in 

 areas difficult for harvesters to access (e.g. areas hazardous 

 to navigation and far from port) with little decrease in the 

 actual size of harvested areas (StaiT, 1998). Critical to the ef- 

 fectiveness of marine harvest refuges in enhancing recruit- 

 ment and fishery yields outside of refuge areas is the ability 

 of larvae produced in refuges to recruit to areas outside 

 of the refuge (Carr and Reed, 1992). The extended period 

 that sea urchin larvae spend in the plankton (9-19 weeks, 

 Strathmann, 1978) and the short residence time of water in 

 SJC (Thomson, 1981; Hickey et al., 1991 ) suggest that larval 

 dispersal from this and other refuge areas to areas outside 

 of the refuge is highly likely, probably occurring on a scale of 

 tens to hundreds of kilometers. Research on sea urchin re- 

 cruitment patterns (including larval dispersal, settlement, 

 and juvenile survival) in this region is needed to assess the 

 potential for marine harvest refuges in Washington to con- 

 tribute to recruitment of fished stocks in Washington. 



The current size limits in SJC protect a substantially 

 smaller proportion of the population than in SJDF (SO'X 



vs. 63"%, respectively). Because there are very few small 

 sea urchins in SJC, the lower size limit protects less than 

 5% of the population. The upper size limit, established to 

 protect larger "broodstock," currently protects 45% of the 

 population. Size limits in Washington were originally es- 

 tablished to protect the lower and upper 20% of the popu- 

 lation and to allow some individuals to grow through the 

 legal-size "window" under a three-year rotational harvest 

 policy (Pfister and Bradbury, 1996). Considering the small 

 number of juveniles in the population and the return to an 

 annual harvest in 1995, the existing size limits should be 

 reevaluated for their efficacy at protecting local stocks in 

 the context of other harvest control techniques. 



Acknowledgments 



This work was conducted as part of the requirements for 

 a Master of Science degree for S. K. Carter in the School 

 of Fisheries (now the School of Aquatic and Fishery Sci- 

 ences) at the University of Washington. David Duggins, 

 Terrie Klinger, Chris Foote, and Ken Chew provided 

 helpful suggestions and guidance on many aspects of the 

 project. Brian Allen cheerfully provided many hours of 

 expert assistance with diving work. Sam Sublett, Martin 

 Grassley, and many others also assisted with data col- 

 lection. Dennis Willows and the staff and faculty at 

 Friday Harbor Laboratories provided logistical support 

 and use of the facilities and equipment. David Duggins 

 and Terrie Klinger provided helpful comments on ear- 

 lier versions of the manuscript. Funding for the project 

 was provided by the U.S. Geological Survey-Biological 

 Resources Division, the Washington Department of 

 Fish and Wildlife, the North Pacific Universities Marine 

 Mammal Research Consortium, the Washington Coop- 

 erative Fish and Wildlife Research Unit, the H. Mason 

 Keeler Endowment for Excellence, the Egtvedt Endow- 

 ment Scholarship, the John N. Cobb Scholarship, and the 

 School of Fisheries, University of Washington. We offer 

 sincere thanks to all. 



Literature cited 



Andrew, N. L., and J. H. Choat. 



1985. Habitat related differences in the survivorship and 

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 Botsford, L. W., J. F. Quinn, S. R. Wing and J. G. Brittnacher. 



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 Bradbury. A. 



1991. Management and stock assessment of the red .sea 

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 Breen, P A., B. E. Adkins, and D. C. Miller 



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