Anthropogenically induced changes in the environment: effect on fisheries.

Abstract

AbstractIn considering 'responsible fisheries', the focus usually is on potential effects of fisheries on ecosystems and habitats (i.e. effects of fisheries on the environment). For most, the term 'responsible fisheries' implies a need for a change in fishing practices to protect or improve the state of the environment. The state of the environment, however, also inevitably affects fish and, thus, fisheries. Many societal activities influence the state of aquatic environments. Thus, in moving towards 'responsible fisheries', changes in other societal activities rather than fisheries alone may also need to be considered. The indirect (i.e. non-fishing) effects on fish and fisheries can be divided into two types: those that affect ecosystem structure or population processes such that recruitment to the fishable stock is reduced, and those that affect the quality (and, hence, marketability) of the fish product. Environmental changes that can influence recruitment include land use changes that may alter habitats for fish. Damming and re-routing of streams and rivers may reduce access to spawning grounds for fishes that migrate between salt and freshwaters. Erosion (leading to increased turbidity) and eutrophication also lead to changes in habitats and food availability that can affect recruitment. Intentional and non-intentional introductions of new species to a region can alter ecosystems to the point that fisheries are severely affected. All of these influences are well described for individual stocks or local regions. However, a global assessment of the quantitative impact of such changes on fisheries is lacking. Chemical contamination of aquatic ecosystems can influence the physiology of organisms and accumulate in body tissues. Thus, both the recruitment and the marketability of fish products may be affected by contaminants. Many studies dealing with the potential toxicity of contaminants to physiological processes at the cell and organism level have been carried out. However, few studies have dealt with the effect of contaminants at the population level and thus attempted to quantify the effects of environmental contamination on fisheries. Monitoring of contaminant concentrations in fish meat is, in many regions of the world, standard protocol as part of public health protection measures, and some fisheries, especially in fresh and semi-enclosed marine waters, have been restricted as a result of such contamination. Although, in most cases, contaminant concentrations in wild fishes have been found to be below the levels considered to be safe for human consumption, recent studies have shown that, for example, dioxin contaminant levels in the muscle of wild fishes in the EU is higher than those found in meat produced in commercial agriculture. As knowledge concerning the effects of contaminants on human physiological processes increases, the contaminant concentrations considered as safe for human consumption are being reconsidered and, in some cases, reduced. Thus, the fact that wild fish meat is among the most contaminated with respect to dioxin of the common meat protein sources for the human population suggests that environmental effects on fisheries will be an area of increasing concern in coming years.