SMITH ET AL.: TRANSPLANTED EELGRASS FOR BAY SCALLOPS 



mollusc shells onto the island repeatedly to fracture 



the shell and feed on the contents. A marked shell 

 from the HPA treatment (survey II, block 1) was 

 found in the intertidal zone of the island, and one 

 from a natural edge plot in survey I was found at 

 a high, central point on the island during a random- 

 ized search of the island. Other potential predators, 

 blue crabs {Callinectes sp.. A'' = 3) and whelks 

 (Busycon sp., A'' = 12), also were observed in the 

 grassbeds during the surveys. 



Eelgrass cover and density in the natural meadow 

 remained relatively constant throughout the study 

 period. Natural bed experimental units had a con- 

 sistent 77% cover, while shoot densities ranged 

 between 441 and 1,148 shoots/m', with an average 

 of 635 shoots/m- over the time between 20 Feb- 

 ruary and 7 June 1986. Seedlings of eelgrass were 

 observed among the natural and transplanted 

 eelgrass in late March and early April. No eel- 

 grass seedlings were recorded in the randomly 

 chosen unplanted plots, although some were ob- 

 served nearby. Throughout this time, transplanted 

 treatments generally increased in number of shoots 

 and area covered. By early June 1986, planting units 

 averaged 0.02 m^, or approximately 15 cm in 

 diameter with an average of 25 shoots/planting 

 unit. 



After 34-38 days (survey I), 18 of 75 marked bay 

 scallops (24%) were recovered (Fig. 3) and all were 

 located in the plot in which they had been deployed. 

 Fifteen of these 18 bay scallops were recovered in 

 the natural grassbeds, with 9 located in the natural 

 interior (NI) treatments and 6 in the natural edge 

 (NE) treatments. Of the three remaining scallops, 

 two were found in HPA treatments and one in a B, 

 unplanted treatment. Three scallops were recovered 

 from block 1 (farthest from the dredge island), 8 

 from block 3 (intermediate), and 7 from block 5 

 (closest). 



A total of 207 unmarked, naturally occurring bay 

 scallops were counted and measured during survey 

 I (Fig. 4). There were 77 from the natural interior, 

 119 from the natural edge, 3 from LPA, 6 from 

 HPA, and 2 from B, unplanted area treatments. One 

 hundred and twenty-five bay scallops were found in 

 block 1 (farthest from land), 50 in block 3, and 32 

 in block 5. 



Our second, shorter survey recovered 10 out of 

 the 45 (22%) bay scallops deployed in the trans- 

 planted grassbeds and B, unplanted areas (Fig. 

 3). Five of those recovered were located in LPA 

 areas, 4 in HPA, and 1 in a B treatment. Five 

 scallops were found in block 1, 2 in block 3, and 3 

 in block 5. 



DISCUSSION 



The greater recovery of marked as well as un- 

 marked, naturally occurring bay scallops from the 

 natural beds as compared to the transplanted and 

 bare areas (Figs. 3, 4) indicated that natural bed 

 treatments provided a more suitable habitat for 

 adult bay scallops. Bay scallops in the transplanted 

 areas apparently suffered a higher mortality than 

 occurred in denser, natural vegetation as suggested 

 by the low recovery of marked scallops and our ob- 

 servations of seabird predation. None of the bay 

 scallops deployed in the transplants or bare areas 

 were found in the natural beds, although in some 

 instances the natural bed was only a few meters dis- 

 tant. The few scallops recovered from these trans- 

 plant and bare treatments were found in the plot 

 of their deployment. Either there was little move- 

 ment of the deployed bay scallops, and they were 

 preyed upon, or the ones that moved were preyed 

 upon. Whichever the mechanism of loss, it was ap- 

 parent that few survived the 34 d deployment in 

 these treatments. 



Neither treatment (LPA, HPA) of 5-6 mo old 

 transplanted areas or bare areas provided the same 

 habitat resource as adjacent, natural grassbeds 

 (survey I); transplants did, however, provide a slight- 

 ly better habitat for adult bay scallops than bare, 

 unplanted areas over a short time (results from 

 survey II). Twenty-two percent of the marked bay 

 scallops were recovered from the transplant and 

 bare treatments in survey II (8 day) deployment as 

 opposed to 7% over the same area in survey I (34 

 days), suggesting a steady decline in numbers as a 

 function of time. The extensive dense vegetation of 

 the natural beds likely provides better refuge from 

 predators such as gulls or blue crabs, along with in- 

 creased protection from physically disruptive fac- 

 tors such as wave action. 



Recovery of marked bay scallops from the treat- 

 ment areas could not be attributed to the distance 

 from the dredge island (Fig. 3). In survey I, the 

 number of marked bay scallops recovered decreased 

 with distance from the island, while in survey II, the 

 opposite was observed. Distances from the island 

 may not have been great enough to record a notic- 

 able difference in seabird predation upon adult bay 

 scallops as a function of distance. The natural scallop 

 population, however, did demonstrate a fivefold in- 

 crease in numbers with increasing distance from the 

 dredge island (Fig. 4). There is no bottom elevation 

 gradient across this distance. Tidal flow and wave 

 energy patterns around dredge island conceivably 

 could interfere with recruitment of water-borne 



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