The Ecological Impact of Marine Plant Harvesting in the Canadian Maritimes, Implications for Coastal Zone Management

ABSTRACT: The harvest of algae in Eastern Canada has been active for over 50 years. Benthic ecology studies by the 1950’s had established the value of the algal thallus and algal populations as habitats for many species of animals. However, for the first 35 years of marine plant harvests the primary concern of resource scientists was the sustainability of the resource. The incidental removal (bycatch) of non-targeted species was recognized by fisheries managers in the Chondrus crispus Stackhouse (Irish Moss) harvest but bycatch limits were not a part of the management plans. The implications of removing algal biomass and the potential of changing the structure of the algal habitat were only recently realized and integrated in resource management plans. A managed Ascophyllum nodosum L. Le Jolis harvest removes 17 % of the harvestable standing crop and less than 7.5 % of the total biomass. In terms of the total productivity of attached macrophytes in the Bay of Fundy ecosystem this is less than 1 % removals. In general the degree of complexity of an algal thallus is directly related to invertebrate abundance on a per unit biomass basis Ascophyllum nodosum harvests can change the relative spatial distribution of the biomass and the complexity of the plant structure. However harvesting is not homogeneous and hence, it increased the patchiness in the habitat. At an exploitation rate of 17 % it was not possible to detect changes in the structure of A. nodosum beds at a landscape scale. Precautionary management measures incorporated in the management plan for this harvest has made it a model in coastal zone management