Olivia P.

ABSTRACT: Fish often escape from aquaculture operations, raising concerns of interactions with wild individuals. Farmed fish from genetically diverse populations grown outside their native range create the threat of outbreeding depression if they escape and interbreed with wild fish. Atlantic cod (Gadus morhua) spawn within cages, releasing millions of embryos into the environment, some of which may live to reproduce. Due to selective breeding, fewer breeding individuals are used in culture… Show more

ABSTRACT: Fish often escape from aquaculture operations, raising concerns of interactions with wild individuals. Farmed fish from genetically diverse populations grown outside their native range create the threat of outbreeding depression if they escape and interbreed with wild fish. Atlantic cod (Gadus morhua) spawn within cages, releasing millions of embryos into the environment, some of which may live to reproduce. Due to selective breeding, fewer breeding individuals are used in culture relative to wild populations, potentially leading to inbreeding within single cages. If inbreeding reduces survival, this could reduce the likelihood of outbreeding depression if maturing escaped cod mate with wild cod. Forced inbreeding could be used to mitigate some effects of aquaculture on the environment. We aimed to determine if cod inbreed and, if so, what short-term effects inbreeding has on offspring. Spawned embryos from tanks of sister− brother−unrelated male trios underwent microsatellite analysis to determine parentage. Inbreeding occurred, and females did not prefer one type of male over the other. Percent hatch, deformities, larval size, and mortality were monitored in artificially fertilized inbred and unrelated crosses. Percent hatch was higher in non-inbred offspring, but inbreeding had no significant effect on the other factors. Show less

ABSTRACT: The linkages between biological communities and ecosystem function remain poorly understood along gradients of human-induced stressors. We examined how resource provisioning (nutrient recycling), mediated by native freshwater mussels, influences the structure and function of benthic communities by combining observational data and a field experiment. We compared the following: (1) elemental and community composition (algal pigments and macroinvertebates) on live mussel shells and… Show more

ABSTRACT: The linkages between biological communities and ecosystem function remain poorly understood along gradients of human-induced stressors. We examined how resource provisioning (nutrient recycling), mediated by native freshwater mussels, influences the structure and function of benthic communities by combining observational data and a field experiment. We compared the following: (1) elemental and community composition (algal pigments and macroinvertebates) on live mussel shells and on nearby rocks across a gradient of catchment agriculture and (2) experimental colonisation of benthic communities on live vs. sham shells controlling for initial community composition and colonisation duration. We show that in near pristine systems, nutrient heterogeneity mediated by mussels relates to greater biodiversity of communities, which supports the notion that resource heterogeneity can foster biological diversity. However, with increased nutrients from the catchment, the relevance of mussel-provisioned nutrients was nearly eliminated. While species can persist in disturbed systems, their functional relevance may be diminished or lost.
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Canadian Technical Report of Fisheries and Aquatic Sciences 2925.
Cat. No. Fs 97-6/2925 ISSN 0706-6457 (print version)
Cat. No. Fs 97-6/2925-PDF ISSN 1488-5387 (online version)