624 



Fishery Bulletin 101(3) 



the depths over the year examined. Similarly, no latitudi- 

 nal differences in red sea urchin growth were found in a 

 large-scale growth study at 18 sites ranging from Alaska 

 to southern California where growth varied between 

 neighboring sites as between much as distant sites (Ebert 

 etal., 1999). 



Future studies could be longitudinal and examine tem- 

 poral patterns in sea urchin growth, for example during 

 and after warm water El Niiio years, as has been examined 

 for abalone in southern California (Haaker et al., 1998); 

 however these temporal patterns too would have to be 

 greater than individual variation to be detectable. 



Implications for fishery management 



Large old sea urchins (>125 mm test diameter) are fished 

 in California despite fishermen receiving lower prices 

 for these sea urchins compared with mid-size animals 

 (Rudie^). Many of the large, old urchins have high gonadal 

 weights (>100 g) (Carney, 1991; Rogers-Bennett et al., 

 1995), thereby potentially contributing more to repro- 

 duction than smaller urchins (Tegner and Levin, 1983; 

 Tegner, 1989; Kalvass and Hendrix, 1997). Similarly, large 

 coral-reef fish also have the potential to contribute more to 

 reproduction than smaller fish (Bohnsack, 1993). 



In fished areas, size-frequency distributions are heav- 

 ily skewed to smaller urchins indicating that the larger 

 size classes are absent (Kalvass and Hendrix, 1997). If 

 the abundance and density of red sea urchins is decreased 

 during fishing, this will decrease the chances of fertiliza- 

 tion success significantly (Levitan et al., 1992). Sufficient 

 numbers of large broodstock are critical because recruit- 

 ment does not appear to be successful every year (Ebert, 

 1983; Pearse and Hines, 1987; Sloan et al., 1987). In addi- 

 tion, fishing can impact recruitment success because the 

 spines of large urchins provide canopy shelter for juveniles; 

 therefore an Allee effect may be present (Tegner and Day- 

 ton, 1977; Sloan et al., 1987; Rogers-Bennett et al., 1995). 

 Size-structured red sea urchin models that include variable 

 recruitment or an Allee effect (positive density dependence) 

 resulted in a >50'7f decrease in estimated population size 

 even at low fishing mortality levels (Pfister and Bradbury, 

 1996). 



Harvest experiments conducted in northern California 

 have shown that management strategies that protect large 

 urchins (upper size limits and harvest reserves) improve 

 recovery and recruitment after six years compared with 

 strategies in which large urchins are harvested (lower size 

 limits only) (Rogers-Bennett et al., 1998). Upper size limits 

 and reserves have been used in the management of the 

 sea urchin fishery in Washington state (Bradbury, 2000) 

 and are currently being considered for California's red sea 

 urchin fishery (Taniguchi^). 



2 Rudie, n. 1994. Personal commun. Catalina Offshore Prod- 

 ucts Inc., 5202 Lovelock St., San Diego, CA 92110. 



' Taniguchi, I. 2002. Personal commun. Calif. Dep. Fish and 

 Game, 4665 Lampson Ave., Los Alamitos, CA. 90720. 



In conclusion, our work and that of others (Ebert and 

 Russell, 1992, 1993; Ebert et. al., 1999) suggest that red 

 sea urchins are slow growing, long-lived animals. Intense 

 harvest rates may have serious consequences because red 

 sea urchins require seven years to reach harvestable size 

 in northern California. Declines in red sea urchin landings 

 in northern California of more than 80% from the peak of 

 13,800 t in 1988 (Kalvass, 2000) demonstrate that harvest 

 rates are high. Our growth results suggest that proposed 

 alternative management strategies that would protect 

 large, slow growing broodstock inside reserves or upper 

 size limits for the fishery could be beneficial, in addition to 

 existing regulations, for sustaining the fishery. 



Acknowledgments 



Special thanks to H. C. Fastenau, D. Canestro and the 

 U. C. Santa Cruz research dive class (1992) for help tag- 

 ging and measuring red sea urchins. D. Cornelius and 

 the "Down Under" helped harvest urchins. P. Kalvass 

 shared his growth data from PIT tagged sea urchins. F. 

 McLafferty discussed models and "the most probable sea 

 urchin." W. Clark, S. Wang, and F. Griffin gave access to 

 and instruction on the confocal microscope. C. Dewees, H. 

 Blethrow, S. Bennett, and K. Rogers all contributed. This 

 research was funded in part by the California Department 

 Fish and Game, the PADI Foundation, UC. Davis Natu- 

 ral Reserve System, and the Bodega Marine Laboratory. 

 Comments from M. Lamare and M. Mangel improved the 

 manuscript. 



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