Publication Abstract

Commercial fishing: the wider ecological implications

G. Moore and S. Jennings

Fishing provides food, income ($80 billion/year) and employment for 200 million people. However, fishing can have environmental costs which threaten marine ecosystems and the sustainability of the fished resource.

The greatest impacts of fishing tend to occur when an unfished environment is first exploited. The relative impacts of fishing depend on the balance between fishing and natural disturbance.

Fishing gears are designed to maximise yields of target species while minimizing the costs of the capture. These gears have direct and indirect effects on the marine environment, resulting in by-catches of unwanted species and damage to marine habitats.

Sand and gravel seabeds in shallow water are relative resilient to the effects of towed gears, such as trawl nets, because they are adapted to natural disturbance. Habitats most at risk are coral reefs, maerl beds and seagrass meadows. Recovery may take many years, especially in the deep sea.

Species most as risk from the direct and indirect effects of fishing are characterized by late maturity, large body size and low potential rates of population increase. Species least at risk have high population recovery rates and morphologies that can withstand contact with fishing gears.

The populations most at risk from pelagic gears are those of some seabirds (especially albatrosses), turtles, sharks and marine mammals. By-catches of birds or marine mammals are high in some long-line, gill or seine net fisheries but mitigation measures can reduce by-catches without reducing catches of target species.

Lost nets and traps may continue to catch fish. Such `ghost fishing' will continue until the gears are broken up or overgrown with fouling organisms.

Fishery discards provide important food material for surface-feeding seabirds, whose populations will inevitably suffer if discarding practices are reduced. Discards that sink provide food for benthic scavengers.

Fishing can have indirect effects on the structure of marine communities and ecosystems. Some coral reefs have shifted from coral- to algal-dominated phases following fishing. In many other ecosystems, however, fishing does not have clear effects on interactions and changes are largely due to the loss of vulnerable species.

Fishing, as with other human activity that provides food, income and employment, has some undesirable impacts on the environment. Managers have to balance the costs of these impacts against the benefits derived from the food, income and employment that fishing provides and against the costs of producing protein in other ways.

Effective fisheries conservation will maximise the long-term yields of protein and income from fisheries while minimising environmental impacts. Marine reserves can help to protect vulnerable habitats and species of conservation concern.

Reference:

G. Moore and S. Jennings, 2000. Commercial fishing: the wider ecological implications. Blackwells Scientific Publications, Oxford. 66pp