NOTE Bishop et al Effects of harvest methods on sustainability of a bay scallop fishery 



717 



Before 



Control 



12 



6 

 



12 

 >, 



o 



c 



d 6 



<p 



l£ 







12 

 6 

 



bCLTHl 



10 20 30 40 



Hand-harvested 



-r 



fk 



10 20 30 40 



Dredged 



I 



10 



20 30 



40 



12 

 6 

 



12 

 6 

 



Shell height (mm) 



After 



tt_a 



10 20 30 40 



10 20 30 40 



fil Ul 



10 



20 



30 



40 



Figure 4 



Size-frequency distribution of juvenile bay scallops (<40 mm in shell height) 

 collected from control, hand-harvested, and dredged plots immediately before 

 and one month after the 10-minute treatments were applied. 



In our study, just 10 minutes of dredging resulted in 

 the removal of approximately 9% of the total biomass of 

 seagrass in the experimental plot. Repeating this fish- 

 ing disturbance over large spatial scales could, there- 

 fore, have substantial detrimental effects on seagrass 

 habitat and, as an indirect result, the abundance of bay 

 scallops that comprise the next generation. In addition, 

 other habitat functions of seagrass are likely compro- 

 mised until regrowth occurs. Peterson et al. (1987) dem- 

 onstrated in this same system that a one-time reduction 

 of 65% in seagrass biomass from gear disturbance dur- 

 ing clam harvesting was not replaced over a subsequent 

 2-year period free of additional fishing. 



The results of our study raise doubt about the sus- 

 tainability of a bay scallop fishery in which the harvest 

 method is dredging. Because this species, which lives 

 only 12-24 months, is recruitment-limited (Peterson 

 and Summerson, 1992; Peterson et al., 1996), reductions 

 in densities of juvenile bay scallops by dredging will not 

 only diminish that year's harvest but also presumably 

 result in less spawning-stock biomass. Without restric- 

 tions on scallop dredging, impacts of dredging distur- 

 bance compounded across years may lead to the gradual 

 collapse of the fishery. Re-imposing gear restrictions 

 in shallow areas where hand harvest is practical may, 

 therefore, pay big dividends. When use of the less de- 

 structive hand method carries little or no penalty of re- 

 duced fishing success, restricting scallop dredging from 

 shallow SAV represents an appropriate ecosystem-based 



management choice (Botsford et al., 1997) that may 

 sustain SAV habitat and restore a bay scallop fishery 

 now in serious decline (Burgess and Bianchi 3 ). 



Acknowledgments 



We thank Ted Willis of Salter Path for advice and collab- 

 oration on harvesting methods and intensities. This work 

 was funded by the North Carolina Fishery Resource 

 Grant Program administered by North Carolina Sea- 

 Grant (to C. H. Peterson). This manuscript benefitted 

 from the comments of two anonymous reviewers. 



Literature cited 



Belding, D. L. 



1910. The scallop fishery of Massachusetts, 51 p. The 

 Commonwealth of Massachusetts, Boston, MA. 

 Botsford, L. W., J. C. Castilla, and C. H. Peterson. 



1997. The management of fisheries and marine ecosys- 

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 Caddy, J. F. 



1973. Underwater observations on tracks of dredges 

 and trawls and some effects of dredging on a scallop 

 ground. J. Fish. Res. Board Can. 30:173-80. 

 Castagna, M. 



1975. Culture of the bay scallop, Argopecten irradians, 

 in Virginia. Mar. Fish. Rev. 37:19-24. 



