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Marine Ecology Progress Series

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MEPS 684:69-78 (2022)  -  DOI:

Effects of perceived competition and water temperature on the functional responses of invasive and native crabs

Brett R. Howard1,2,*, Dickson T. S. Wong2, Veronica Aguiar2, Jessica Desforges3, Elizabeth M. Oishi2, Jordan Stewart2, Isabelle M. Côté2

1Pacific Biological Station, Department of Fisheries and Oceans Canada, Nanaimo, BC V9T 6N7, Canada
2Earth to Ocean Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
3Department of Biology and Institute of Environmental and Interdisciplinary Science, Carleton University, 1125 Colonel Bay Dr., Ottawa, ON K1S 5B6, Canada
*Corresponding author:

ABSTRACT: As the frequency of species introductions increases globally, the need for predicting the ecological impacts of invaders becomes ever more urgent. Functional responses, i.e. how resource uptake by consumers changes as a function of resource density, describe the species-specific ability to deplete resources under standardized conditions, and their shape has been used as a tool to predict the impact of non-native species. However, functional responses are usually derived from individuals foraging alone, which overlooks the important roles of intra- and interspecific interactions in shaping per capita consumption rates. We tested the extent to which the functional responses of invasive European green crab Carcinus maenas and native graceful rock crab Metacarcinus gracilis are affected by the perceived presence of con- and heterospecific individuals. Overall, crabs did not consume significantly more prey in the perceived presence of either a conspecific or novel heterospecific, but did demonstrate significantly higher attack rates in warmer water in the presence of a conspecific. Regardless of competitor type, green crabs consumed, on average, 16% more prey than the native crabs. This was largely due to their higher attack rate and lower prey handling time in warmer water. Green crab prey consumption increased significantly with increasing water temperature while that of the native crab species was unaffected (12 vs. 3.5% per 1°C increase, respectively). Higher maximum feeding rates are congruent with green crab impacts throughout their invaded range and suggest that green crabs might be undeterred from feeding in the presence of this co-occurring native crab species.

KEY WORDS: Non-native species · Comparative functional response analysis · CFRA · Resource use · Impact prediction · Population stability · Climate change

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Cite this article as: Howard BR, Wong DTS, Aguiar V, Desforges J, Oishi EM, Stewart J, Côté IM (2022) Effects of perceived competition and water temperature on the functional responses of invasive and native crabs. Mar Ecol Prog Ser 684:69-78.

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