Assessment of the influence of finfish aquaculture on hard bottom habitats in a boreal/sub-arctic marine environment

Bungay, Terrence Ross (2012) Assessment of the influence of finfish aquaculture on hard bottom habitats in a boreal/sub-arctic marine environment. Masters thesis, Memorial University of Newfoundland.

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Abstract

Determining the extent of influence of marine salmonid farms on surrounding habitats is mandatory as an environmental monitoring procedure. In Newfoundland, environmental monitoring of salmonid farms relies on measuring geochemical properties of underlying sediment to assess the environmental impact of fish feces, mortalities, uneaten food and/or detached fouling organisms that deposit on the seafloor. This approach is problematic in coastal Newfoundland because it is difficult or impossible to obtain the intact sediment samples required for these analyses, given that the region has mostly hard bottom substrate. In this thesis, a new approach to habitat assessment, relying on indicator benthic species and habitat determinations based on benthic video droptransects, is used to determine the environmental impact of salmonid farms. All identifiable species were counted from a series of underwater video drop-transects from sample stations running through aquaculture lease boundaries, as well as control sites where depth did not exceed 1 00 meters. Abundances, proportions, and percent coverage of species were then used in a cluster analysis to determine spatial differences in sample stations. Sites characterized by high Beggiatoa, Opportunistic Polychaete Complexes, and deposit-feeding sea stars were identified as being influenced by aquaculture, the area of influence being larger under active cages with mid production. Non-production (control) sites and fallowed sites displayed no such assemblage but were dominated by suspension-feeding taxa (anemones and sponges). A decrease in the latter taxa along with the increase in deposition-tolerant species could be used for assessing the environmental influence of aquaculture on hard substrates.

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