Effects of Warming Temperatures on the Feeding Interactions of an Omnivorous Crab, Pugettia producta (Crustacea: Brachyura: Epialtidae)1

The Northern kelp crab (Pugettia producta) is a common omnivore that inhabits bull kelp (Nereocystis luetkeana) beds in the Salish Sea (Washington, USA). Rising ocean temperatures associated with ongoing environmental changes have the potential to alter organismal physiology and consequently change their feeding strategies, especially in organisms with high feeding flexibility such as omnivores. In this study, we performed feeding trials with P. producta at ambient and elevated temperatures to determine if elevated temperatures characteristic of short-term heat waves induce changes in feeding rate or preferred food type. We offered crabs N. luetkeana blades, Lacuna vincta snails, or a combination of both as food options in choice and no-choice feeding trials. Our results showed that elevated temperatures did not change crab feeding rates or their preference for algal tissue versus animal tissue. When offered the two food options in choice feeding trials, crabs consistently chose to incorporate both into their diet, demonstrating that they are opportunistic consumers across a range of temperatures. The feeding behaviors of grazers and omnivores in kelp beds are impactful in shaping the habitat around them. Thus, studies such as this are essential to improving our understanding of how elevated temperatures may affect trophic interactions among kelp forest inhabitants and ecosystems. Further work to investigate the effects of elevated temperatures on P. producta feeding, including how diet may shift across ontogeny, is needed to understand and accurately predict how elevated temperatures will affect future trophic interactions within Salish Sea bull kelp ecosystems.