Interbreeding between local and translocated populations of a cleaner fish in an experimental mesocosm predicts risk of disrupted local adaptation

Abstract

Translocation of organisms within or outside its native range carries the risk of modifying the community of the recipient ecosystems and induces gene flow between locally adapted populations or closely related species. In this study, we evaluated the genetic consequences of large‐scale translocation of cleaner wrasses that has become a common practice within the salmon aquaculture industry in northern Europe to combat sea lice infestation. A major concern with this practice is the potential for hybridization of escaped organisms with the local, recipient wrasse population, and thus potentially introduce exogenous alleles and breaking down coadapted gene complexes in local populations. We investigated the potential threat for such genetic introgressions in a large seminatural mesocosm basin. The experimental setting represented a simulated translocation of corkwing wrasse (Symphodus melops) that occurs on a large scale in the Norwegian salmon industry. Parentage assignment analysis of mesocosm's offspring revealed 30% (195 out of 651 offspring) interbreeding between the two populations, despite their being genetically (FST = 0.094, p < 0.05) and phenotypically differentiated. Moreover, our results suggest that reproductive fitness of the translocated western population doubled that of the local southern population. Our results confirm that human translocations may overcome the impediments imposed by natural habitat discontinuities and urge for immediate action to manage the genetic resources of these small benthic wrasses.

The consequences of size‐selective fishing mortality for larval production and sustainable yield in species with obligate male care

“…While we do not have direct information on natural mortality rates for each life‐history type of corkwing wrasse, estimates of total mortality (natural mortality and fishing mortality) can be estimated from the frequency of each age class by life‐history type in the catch data (Halvorsen unpublished data ). The commercial fishery for live corkwing wrasse has grown rapidly since 2010 as the wrasse are used in louse biocontrol in salmon aquaculture (Blanco Gonzalez et al., 2019; Halvorsen, Larsen, et al, 2017; Halvorsen, Sørdalen, et al, 2017). The fishery is size‐selective, as the largest individuals fare better in salmon pens, and since nesting males grow faster and mature later than females and sneaker males, their life history is less protected by the current minimum size regulations.…”

The consequences of size-selective fishing mortality for larval production and sustainable yield in species with obligate male care

“…While we do not have direct information on natural mortality rates for each life-history type of corkwing wrasse, estimates of total mortality (natural mortality and fishing mortality) can be estimated from the frequency of each age class by life-history type in the catch data (Halvorsen unpublished data). The commercial fishery for live corkwing wrasse has grown rapidly since 2010 as the wrasse are used in louse biocontrol in salmon aquaculture (Blanco Gonzalez et al, 2019;Halvorsen et al, 2017). The fishery is size-selective, as the largest individuals fare better in salmon pens, and since nesting males grow faster and mature later than females and sneaker males, their life history is less protected by the current minimum size regulations.…”

Releases of Asian houbara must respect genetic and geographic origin to preserve inherited migration behaviour: evidence from a translocation experiment

“…But in many species, particularly where first migration occurs in the absence of experienced individuals, migratory traits are innate [4,8] with a strong heritable component [9][10][11]. For such species, translocation for reinforcement using individuals from an allopatric source population may disrupt the recipient population's migration strategy, potentially altering fitness [12][13][14], while translocation for reintroduction of extirpated populations may not replicate historic migration strategies [15]. Even where phylogeographic analyses suggest large-scale population genetic homogeneity this could mask finer-scale adaptation of behaviours under strong local selection.…”