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Carrie Byron, Ph.D., assistant professor of Marine Sciences at the ³Ô¹Ï±¬ÁÏ and Alexia Morgan, Ph.D., associate researcher, recently published a paper investigating the role spiny dogfish play in the diets of gray and harbor seal’s in the Gulf of Maine. Until now there has been suggestion, but little evidence, that seals are eating spiny dogfish, which are currently an abundant species in the region.

According to the paper, harbor seal gray seal populations have increased by 28.7 percent and 8.6 percent respectively in the Gulf of Maine. Byron and Morgan investigated what seals are eating and how their diet influences the food web in the Gulf of Maine. They used a food web model to explore the potential of dogfish being a primary food source for seals and how this may be impacting the ecosystem, looking at various plausible diets for seals and the implications for other non-prey species in the ecosystem. In addition, white sharks have increased in abundance regionally and shark predation on seals is documented in the southern Gulf of Maine. The paper also explored top-down impacts of white shark predation on seals and other fish species.

Byron and Morgan concluded that dogfish could be contributing to the recovery of seal populations by providing an alternative prey base, there is a tipping point between 10 percent and 20 percent of dogfish in seal diet that elicits a linearly increasing trend in seal biomass over time and seals as prey will have a continued impact on the projected increase in white shark biomass.

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