Submitted to: Estuaries and Coasts - Journal of the Estuarine Research Federation
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/31/2006
Publication Date: 2/28/2007
Citation: Mcdonald, P., Holsman, K.K., Beauchamp, B.R., Dumbauld, B.R., Armstrong, D.A. 2007. Bioenergetics modeling to investigate habitat use by the non-indigenous crab, Carcinus maenas, in Willapa Bay, Washington, USA. Estuaries and Coasts - Journal of the Estuarine Research Federation.29(6B):1132-1149. Interpretive Summary: The European green crab, Carcinus maenas, is one of the most conspicuous and widely introduced invasive marine species around the world and was introduced to the West coast of the United States in the mid 1980’s with recent rapid expansion from the estuaries in California, U.S.A. to British Columbia, Canada. Green crabs display relatively broad physiological tolerances to salinity and temperature and inhabit a wide range of habitats in their native environment. They can also play a significant role in structuring the benthic community due to their aggressive behavior as predators and ability to disturb the sedimentary environment. The spread of these crabs has led to myriad predictions about their potential impact on the native fauna in estuaries where they have established. A bioenergetics model was developed using existing data on this crab’s physiological tolerances and ecology. Several simulations were run to test where these crabs would most likely be found in Willapa Bay, Washington and similar estuaries along the U.S. west coast. These results were compared with monthly trapping efforts which showed that the crabs responded to other factors including interspecific interactions with native Dungeness crabs which inhabit sublittoral channels causing green crabs to choose littoral habitats neglected by native crabs, such as meadows of the introduced cordgrass, Spartina alterniflora. This result suggests that impacts to the sublittoral benthic community may be less than those to the higher littoral areas where the crabs spend most of their time.
Technical Abstract: A bioenergetics model was developed and applied to questions of habitat use and migration behavior of non-indigenous European green crab (Carcinus maenas) in Willapa Bay, Washington, USA. The model was parameterized using existing data from published studies on the ecology and physiology of C. maenas and allied brachyuran crabs. Simulations of the model were run describing four scenarios of habitat use and behavior during a 214 d simulation period (April – October) including crabs occupying (1) mid-littoral habitat, (2) high littoral habitat, (3) sublittoral habitat, and (4) sublittoral habitat but undertaking intertidal migrations. Monthly trapping was done along an intertidal gradient in Willapa Bay to determine the actual distribution of crabs for the same time interval as the simulation period, and model results were compared to the observed pattern. Model estimates suggest no intrinsic energetic incentive for crabs to occupy littoral habitats since metabolic costs were ~ 6% higher for these individuals than their sublittoral counterparts. Crabs in the littoral simulations were also less efficient at converting consumed energy into growth than sublittoral crabs. Yet monthly trapping revealed that C. maenas are abundant in mid-littoral habitats of Willapa Bay and there is no evidence of resident sublittoral populations. The discrepancy intimates the significance of other factors, including interspecific interactions that are not incorporated.