In-press 1 Perspectives on pink salmon and sea lice: scientific evidence fails to support the extinction hypothesis

Using a Ricker (1975) model and escapement data for a subset of Broughton Archipelago, British Columbia watersheds, Krkošek et al. (2007) predicted that sea lice infections originating on Atlantic salmon (Salmo salar) farms will cause the extinction of pink salmon (Oncorhynchus gorbuscha) in the archipelago by 2010. The purpose of this paper is to examine this issue in the context of all of the escapement data available for the archipelago and to review additional scientific reports and information not discussed by Krkošek et al. (2007). Additional research during the last five years is not consistent with the Krkošek et al. (2007) conclusion that sea lice routinely cause in excess of 80 % mortality of fry. Rather the literature reviewed herein indicates that pink salmon fry mount an effective immune response at sizes as small as 0.7 grams resulting in the rapid shedding of lice within two weeks. Pink salmon returns are shown to be highly variable throughout the Northeast Pacific in areas without salmon farms. Following periods of high abundance, pink salmon populations typically fall to low levels and they may remain depressed for several generations. However, in most cases, the populations then gradually increase to begin the cycle anew. An examination of returns to all of the documented Broughton Archipelag