| dc.description | Sessile colony-forming animals on the seafloor are susceptible to bottom fishing disturbances in marine ecosystems. Life histories of "colonial epifauna" affect the capacity for these animals to persist, however effects of bottom fishing on the richness, biomass, species composition and life histories of colonial epifauna are not well studied. A literature review demonstrated the high potential for regeneration from injuries inflicted by bottom fishing to impair sexual reproduction, growth and encounters with other individuals. A three year study with the Canadian Department of Fisheries and Oceans (DFO) on the impacts of experimentally pulsed otter trawling on the Scotian Shelf demonstrated significant changes in colonial epifauna species composition after trawling, and biologically relevant suppression of natural temporal dynamics in richness and biomass as well as impacts on biomass of sponges, bryozoans and soft corals. Inshore DFO scallop surveys in the Bay of Fundy demonstrated significant divergence between hydroid communities on heavily fished cobbles and those on relatively unfished live scallop substrata: divergence was mostly explained by the lack of large, long-lived arborescent taxa on cobbles. Dredging in the Bay of Fundy injured hydroids and significantly reduced sexual fecundity and induced colony fragmentation in the hydroid Sertularia cupressina. In vitro disturbance induced colonies of the soft coral Gersemia rubiformis to contract and prematurely release sexually-derived larvae to reduce injury and avoid expending resources associated with sexual reproduction. The importance of evaluating the potential for injuries to impair sexual reproduction in colonial epifauna is particularly emphasized throughout this thesis, as this may limit recruitment and recovery from bottom fishing and reduce genetic diversity in marine ecosystems. | en_US |
