cover) are confounded in our study, we cannot dis- 

 tinguish between them. However, because most 

 studies have consistently demonstrated higher den- 

 sities of marine benthic infauna, including hard 

 clams, in seagrass meadows than in nearby unvege- 

 tated bottom (e.g., O'Gower and Wacasey 1967; San- 

 tos and Simon 1974; Oith 1977; Brook 1978; Stoner 

 1980; Peterson 1982), we suspect that our habitat- 

 specific differences in rake effectiveness can be gen- 

 eralized. Nevertheless, exceptions are likely to exist, 

 implying that our results on relative catch efficiency 

 should be applied only where hard clam abundances 

 are known to be greater in the seagrass habitat. 



We chose to estimate the dry weight of seagrass 

 removed as a measure of environmental damage be- 

 cause many studies have identified, and most coastal 

 resource managers now recognize, the value of pre- 

 serving meadows of seagrass. For instance, sea- 

 grasses have been identified as locally significant 

 producers of fixed carbon to fuel estuarine and coastal 

 food chains and as providers of nursery habitat for 

 juvenile finfishes and shellfishes, many of which are 

 either commercially harvested or else serve as signifi- 

 cant food items for commercially harvested species 

 (e.g., Thayer et al. 1975). Our raking and seagrass 

 harvest results demonstrate that the bull rake re- 

 moved more seagrass than the pea digger per unit 

 time of use and per unit area raked. Furthermore, dif- 

 ferences between rakes in estimated seagrass removal 

 tended to be greater for the belowground than the 

 aboveground components of the seagrass. Because 

 roots and rhizomes probably provide the source 

 of vegetative propagation, a potentially important 

 mode of spread in seagrasses, the bull rake may have 

 more long-lasting effects on seagrass cover than the 

 pea digger, as well as a greater immediate impact. 

 Seagrass that is removed by raking probably enters 

 the detrital pool and thus continues to fulfill one of its 

 important functions. However, the loss of seagrass 

 may reduce the value of the grass bed as a nursery 

 habitat. We did not collect any data to test this 

 possibility, but the dependence of bay scallops on 

 seagrass surface area for juvenile attachment sites 

 and the dependence of various juvenile fishes on 

 seagrass cover for predator protection and on sea- 

 grass surface for foraging habitat (e.g., Thayer et al. 

 1975) imply that the value of a seagrass bed is dimin- 

 ished by uprooting significant amounts of seagrass. 



This study was designed to provide estuarine re- 

 source managers with some of the biological informa- 

 tion needed to manage and regulate clamming in 

 shallow estuarine habitats. We have demonstrated 

 that the superior effectiveness of the more massive 

 bull rake in a seagrass habitat is accompanied by sub- 





stantially more uprooting of seagrass than is caused 

 by raking with a pea digger. However, environmental 

 planners and resource managers must apply these 

 results with caution in their attempts to weigh the 

 benefits of permitting bull rake usage in seagrass 

 beds against the potential costs associated with in- 

 creased uprooting of seagrasses. Our experiments 

 were restricted to a single seagrass system; changing 

 the seagrass type or the sediment grade may yield 

 different results. More importantly, we made no 

 direct measurements of the cost of seagrass removal. 

 It is likely that, because the amount of uprooted sea- 

 grass appears to be an increasing function of clam- 

 ming intensity, the impact of removal could be 

 negligible in some areas where clamming intensity is 

 low relative to the areal extent of the seagrass 

 habitat. Thinning of seagrass may even be beneficial 

 under some conditions by stimulating growth of the 

 plants left behind. Recovery by growth may be rapid 

 enough at certain seasons to render the impact of 

 seagrass removal insignificant to the production of 

 associated vertebrate and invertebrate species. 



Although we calculate the seagrass removal per unit 

 resource harvested (Table 3), quantitative estimates 

 of the cost of seagrass removal are necessary to con- 

 vert these biological data into a management crite- 

 rion. Even if resource managers choose to prohibit the 

 use of bull rakes inside seagrass beds on the basis of 

 the enhanced loss of seagrass biomass per unit time, 

 per unit area, and per unit resource (clam) collected 

 (Table 3), this prohibition should probably be re- 

 stricted to seagrass meadows. Even though the bull 

 rake is not as effective as the pea digger in harvesting 

 clams on an unvegetated sand flat (Table 1), it may 

 well be a superior implement in other habitats, such 

 as soft muds. It is also used in deeper waters (Glude 

 and Landers 1953), where short-handled rakes with- 

 out baskets are ineffective and where seagrass is 

 sparse or absent. We are aware that any habitat- 

 specific regulation of a fishery requires more intense 

 enforcement to be effective than an outright prohibi- 

 tion of certain gear, but the deeper water and un- 

 vegetated mud-bottom usages of bull rakes (Glude 

 and Landers 1953) suggest that the bull rake de- 

 serves a place in the repertoire of legal clamming 

 gear, despite its threat to seagrass. 



Acknowledgments 



We thank D. Cecelski of Duke University Marine 

 Laboratory for carrying out a pilot study of these two 

 clam rakes in spring 198 1. M. E. Colby, S. A. Hughes, 

 C. A. Peckham, K. C. Pierce, and G. W. Safrit pro- 

 vided assistance in the field and laboratory. The 



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