Reduced growth in wild juvenile sockeye salmon Oncorhynchus nerka infected with sea lice

Abstract

Daily growth rings were examined in the otoliths of wild juvenile sockeye salmon Oncorhynchus nerka to determine whether infection by ectoparasitic sea lice Caligus clemensi and Lepeophtheirus salmonis was associated with reduced host body growth, an important determinant of survival. Over 98% of the sea lice proved to be C. clemensi and the fish that were highly infected grew more slowly than uninfected individuals. Larger fish also grew faster than smaller fish. Finally, there was evidence of an interaction between body size and infection status, indicating the potential for parasite-mediated growth divergence.

Sea trout adapt their migratory behaviour in response to high salmon lice concentrations

“…For example, Birkeland (1996) found a median decrease of 23.5% in body mass among sea trout recovering from a severe louse attack, after spending a median of 37.5 days in FW before sea re-entry. Based on our In addition to losing growth opportunities due to delousing behaviour, the fish also grow less at sea when infested (Godwin, Dill, Krkosek, Price, & Reynolds, 2017;Shephard et al, 2016). Growth is a particularly important component of fitness for juveniles, because it both expands their prey size range and reduces predation risk (Sogard, 1997).…”

Oust the louse: leaping behaviour removes sea lice from wild juvenile sockeye salmon Oncorhynchus nerka

“…) and our results indicate that the leaping behaviour of juvenile O. nerka dislodges motile stages of these ectoparasites. The vast majority of the sea lice infecting O. nerka in our study were C. clemensi (just 4% of motiles were L. salmonis ) which is consistent with the emerging consensus that C. clemensi are the dominant louse species in the Inside Passage of BC (Godwin et al ., , ; Price et al . ; Hunt , 2016) despite the current focus of sea louse research and management on L. salmonis .…”

“…The trade-offs underlying the leaping behaviour of juvenile salmonids imply that the costs of leaping yield a benefit of alleviating juvenile salmonids from the costs of sea-lice infestation. For example, heavy sea-louse infestation (primarily by C. clemensi) is correlated with reduced growth (Godwin et al, 2017) and competitive foraging ability (Godwin et al, 2015) in O. nerka and with decreased survival in other Oncorhynchus spp. (Ford & Myers, 2008;Krkošek & Hilborn, 2011;Morton & Routledge, 2005).…”

“…Sea lice have been the subject of extensive research due to their adverse effects on both farmed and wild salmonids (reviewed in Costello , ). These effects include direct mortality (Wooten & Smith, ; Krkošek et al ., ), but mounting evidence suggests that sub‐lethal effects, such as effects on host susceptibility (Peacock et al ., ), competitive ability (Godwin et al ., ) and growth (Godwin et al ., ), may play an important role in determining survival of wild juvenile Oncorhynchus spp. infected with sea lice.…”

The coast-wide collapse in marine survival of west coast Chinook and steelhead: slow-moving catastrophe or deeper failure?

“…25% of FCRPS annual revenues (including foregone clean power generation), or >$0.5 Billion per year [148]. Similarly, in British Columbia, where dams are not present in the migration paths, much effort has focused on removing salmon farms to help restore Fraser River salmon populations [149-151]. Clearly, it is important to understand the impact of various anthropogenic impacts on poor salmon returns, but it is also important that the real prospects for improvement as a result of these region-specific actions are carefully assessed.…”