Seal‐Induced Injuries on Adult Atlantic Salmon Returning to Maine

Abstract

AbstractSeals (Phocidae) are known predators of Atlantic Salmon Salmo salar from their entry into the estuary as smolts until their return to freshwater as adults. We developed a written protocol for identifying seal‐induced injuries on adult Atlantic Salmon returning to Maine rivers. The protocol, which includes photos and category definitions, has been used since 2006 by Maine Department of Marine Resources biologists when handling adult Atlantic Salmon at the Veazie Dam fishway on the Penobscot River and at other adult capture facilities in Maine. The written protocol has ensured that reporting is consistent among years and rivers; photos of wounds serve as quality assurance for the protocol. For adults returning to the Penobscot River in 2006 and 2007, seal‐induced injuries were more likely to be found on two‐sea‐winter fish; to appear as gashes or arched wounds; to be open rather than healed; and to occur on the center third of the body below the lateral line. Larger two‐sea‐winter fish (>67 cm FL) returning to the Penobscot River early in the run (May–early July) were more likely to have a seal‐induced injury. Injury rates increased from 1978 to 2010; this increase was correlated with seal aerial counts for the Gulf of Maine and Penobscot Bay. From 2006 to 2010, the annual seal‐induced injury rate for Atlantic Salmon in six Maine rivers (including the Penobscot River) ranged from 0.00 to 0.30 across rivers. Rates of injury on Atlantic Salmon for all years combined did not differ among the six rivers, but low power likely affected our ability to detect any differences.Received July 25, 2013; accepted February 5, 2014