HABITAT VALUE OF NATURAL VERSUS RECENTLY TRANSPLANTED 



EELGRASS, ZOSTERA MARINA, FOR THE BAY SCALLOP, 



ARGOPECTEN IRRADIANS 



Ingrid Smith,' Mark S. Fonseca,^ Jose A. Rivera,^ and 

 Keith A. Rittmaster'' 



ABSTRACT 



Bay scallops, Argopecten irradians, were used in a mark and recapture experiment to determine the 

 habitat value of recently transplanted eelgrass. Zostera marina, meadows for fishery restoration and 

 enhancement through stocking. The study site, adjacent to an island formed from dredge material, con- 

 sisted of natural and transplanted eelgrass and of unplanted areas. Seventy-five marked bay scallops 

 were placed in plots at a density of 2.2 scallops per m" on 20 February 1986. A month later, only 18 

 marked scallops were recovered; of these. 15 were found in the natural eelgrass beds. On the study site, 

 94% of 207 unmarked naturally occurring bay scallops were found in the natural eelgrass beds. Recovery 

 of marked adult bay scallops was not affected by the distance from the dredge island; rather densities 

 of natural scallop populations increased with distance from the island. A second, modified survey (30 

 March to 7 April 1986) was conducted specifically to examine the recovery of marked bay scallops; this 

 survey again showed a high rate of loss both in the transplanted and unplanted areas. 



The two surveys showed that recently transplanted eelgrass meadows do not provide the same habitat 

 functions as natural meadows for bay scallops. Stocking of adult scallops in early stage eelgrass transplants 

 to enhance or restore that fishery does not appear to be feasible. A protracted period of time may pass 

 before habitat function is returned for the bay scallops in transplanted eelgrass meadows. Results from 

 these surveys also illustrate the need for careful consideration in the placement of dredge material in 

 the coastal environment. 



Seagrass meadows form an essential habitat for a 

 variety of marine organisms (Thayer et al. 1975, 

 1984; Kenworthy et al. 1988). These highly produc- 

 tive ecosystems provide refuge, food resources, and 

 nursery grounds for a number of commercially and 

 recreationally harvested species. 



Recent concerns about loss of seagrass habitat in 

 general (Thayer et al. 1984, 1985; Fonseca et al. 

 1985, 1987, 1988) have prompted research into ways 

 in which that loss can be reduced. Since mitigation 

 measures often require the creation of new seagrass 

 meadows to replace damaged ones, it is critical that 

 this trade-off provide a persistent habitat that is the 

 functional equivalent of the one that is lost. Given 

 our approach to creating seagrass beds by install- 

 ing widely spaced planting imits that coalesce in 1-2 



'Duke University Marine Laboratory, Beaufort, NC 28516. 



^Southeast Fisheries Center Beaufort Laboratory, National 

 Marine Fisheries Service, NOAA, Beaufort. NC 28516. [To whom 

 correspondence and reprint requests should be addressed.] 



'NOAA Corps, on assignment to Southeast Fisheries Center 

 Beaufort Laboratory, National Marine Fisheries Service. NOAA, 

 Beaufort, NC 28516. 



'Southwest Fisheries Center La Jolla Laboratory, National 

 Marine Fisheries Service, NOAA, P.O. Box 271, La Jolla, CA 

 92038. 



years, it is possible that an artificially propagated 

 bed will require a certain time interval before it will 

 attain natural meadow functions. If these created 

 beds do not provide similar functional values as 

 natural ones or if they require a very long time to 

 do so, then the entire concept of seagrass bed miti- 

 gation will have to be reexamined. These are critical 

 questions, especially when seagrass restoration pro- 

 jects have not produced more acreage than was lost 

 (Fonseca et al. 1988). 



In the temperate zone, the dominant seagrass spe- 

 cies is eelgrass, Zostera marina. Eelgrass has been 

 utilized in many seagrass restorations (Fonseca et 

 al. 1988). Recent losses of eelgrass and scallops in 

 Long Island Sound due to a "brown tide" (Chris 

 Smith pers. commun.^), and losses of scallops in 

 Bogue and Back Sounds, Carteret County, NC, 

 apparently due to a Ptychodiscus bloom, have 

 prompted questions regarding seagrass and scallop 

 restoration. Given the paucity of information on 

 faunal recovery in restored or created seagrass beds, 



Manuscript accepted October 1988. 

 Fishery Bulletin, U.S. 87:189-196. 



^Chris Smith, Cooperative Extension Association of Suffolk 

 County, Sea Grant Program, 39 Sound Avenue, Riverhead, NY 

 11901, pers. commun. June 1987. 



189 



