Downloaded By: [Canadian Research Knowledge Network] At: 22:02 4 May 2008 Reviews in Fisheries Science, 16(4):403–412, 2008 Copyright C  Taylor and Francis Group, LLC ISSN: 1064-1262 print DOI: 10.1080/10641260801937131 Perspectives on Pink Salmon and Sea Lice: Scientific Evidence Fails to Support the Extinction Hypothesis KENNETH M. BROOKS 1 and SIMON R. M. JONES 2 1 Aquatic Environmental Sciences, Port Townsend, Washington, USA 2 Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, British Columbia, Canada Using a Ricker (1975) model and escapement data for a subset of Broughton Archipelago, British Columbia watersheds, Krkoˇ sek et al. (2007a) 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 article 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 Krkoˇ sek et al. (2007a). Additional research during the last five years is not consistent with the Krkoˇ sek et al. (2007a) 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 g, 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 Archipelago watersheds indicates that following exceptionally high returns in 2000 and 2001, the populations declined to very low numbers in 2002 and 2003. Contrary to the conclusions reached by Krkoˇ sek et al. (2007a), Broughton pink salmon returns have steadily increased since then, with no indication that they are threatened with extinction. Other unsubstantiated assumptions used in Krkoˇ sek et al. (2007a) are also discussed in light of additional scientific reports and theoretical considerations. Keywords Atlantic salmon, aquaculture, netpens, pink salmon fry, sea lice INTRODUCTION Following the release in 2002 of the Pacific Fisheries Re- source Conservation Council Advisory document (PFRCC, 2002), intensive research on sea lice and their interaction with wild and farmed fish in the Broughton Archipelago of British Columbia has been underway. A series of studies claiming that salmon farms are the cause of sea lice (Lepeophtheirus salmonis and Caligus clemensi) infections on pink salmon (Oncorhynchus gorbuscha) fry in the archipelago have been published (Morton et al., 2004; Krkoˇ sek et al., 2005, 2006, 2007b). Krkoˇ sek et al. (2007a) now claim that sea lice originating on salmon farms Address correspondence to Kenneth M. Brooks, Aquatic Environmen- tal Sciences, 644 Old Eaglemount Road, Port Townsend, Washington, USA. E-mail: brooks@olympus.net will result in the extinction of Broughton pink salmon stocks in the near future. This review, which is intended to expand the discussion by describing other peer-reviewed papers and public information important to understanding the interaction between pink salmon, farmed fish, and sea lice, includes the following considerations: 1. The variability of pink salmon returns throughout the North Pacific with particular emphasis on the Broughton Archipelago. 2. The general absence of mortality among juvenile pink salmon following controlled laboratory exposure to Lepeophtheirus salmonis. 3. The absence of a cause-and-effect relationship between sea lice infecting pink salmon fry and larval lice released from salmon farms. 4. A reevaluation of trends in pink salmon abundance. 403