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Comparative vulnerability to predators, and induced defense responses, of eastern oysters Crassostrea virginica and non-native Crassostrea ariakensis oysters in Chesapeake Bay
Newell, R.I.E.; Kennedy, V.S.; Shaw, K.S. (2007). Comparative vulnerability to predators, and induced defense responses, of eastern oysters Crassostrea virginica and non-native Crassostrea ariakensis oysters in Chesapeake Bay. Mar. Biol. (Berl.) 152(1): 449-460. hdl.handle.net/10.1007/s00227-007-0706-0
In: Marine Biology. Springer: Heidelberg; Berlin. ISSN 0025-3162, more
Peer reviewed article  

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Keyword
    Marine

Authors  Top 
  • Newell, R.I.E.
  • Kennedy, V.S.
  • Shaw, K.S.

Abstract
    Management agencies are considering introducing the Suminoe oyster Crassostrea ariakensis into Chesapeake Bay, USA. It is unknown if the growth of feral populations of this non-native oyster would be regulated by the same predators that once controlled the abundance of the native eastern oyster C. virginica. In laboratory studies, we compared the relative susceptibility of juvenile diploids (shell height < 25 mm) of both oyster species to invertebrate predators of eastern oyster juveniles. Predators included four species of mud crabs [Rhithropanopeus harrisii (carapace width 7–11 mm), Eurypanopeus depressus (6–21 mm), Dyspanopeus sayi (8–20 mm), and Panopeus herbstii (9–29 mm)], the blue crab Callinectes sapidus (35–65 mm), and two sizes of polyclad flatworms (Stylochus ellipticus and possibly Euplana gracilis; planar area ?5 mm2 and ~14 to 88 mm2). All four species of mud crab and the blue crab preyed significantly (ANOVA, P = 0.05) more on C. ariakensis than on C. virginica, but predation by flatworms of both sizes did not differ significantly between oyster species. The greater susceptibility of C. ariakensis to crab predation was likely due to its shell compression strength being 64% lower than that of C. virginica (P = 0.005). To test for predator-induced enhancement of shell strength, we held oysters of both species for 54 days in the presence of, but protected from, C. sapidus and R. harrisii. Crabs were fed congeneric oysters twice weekly within each aquarium. Compared to controls, shell strength of C. virginica exposed to R. harrisii increased significantly (P < 0.043), as did shell strength of both oyster species exposed to C. sapidus (P < 0.01). Despite the changes in shell strength by both oyster species in the presence of C. sapidus, the shell of C. ariakensis remained 57% weaker than C. virginica. We conclude that, because C. ariakensis exposed to predators continued to have a weaker shell relative to C. virginica, the natural suite of crab and flatworm predators in Chesapeake Bay will likely serve to control the abundance of feral C. ariakensis. We caution that the situation in the natural environment may be sufficiently different in some locations that C. ariakensis may be able to compensate for its greater vulnerability to crab predation and hence become a nuisance species.

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