The second is the ratio of total catches to total primary productivity, or how much fish can come from the plants at the base of the food chain. The first index used in the study is the total catch in an area, or how much fish a given patch of ocean can produce. Undue loss of value and shifting the catches in that ecosystem to one dominated by smaller fish and invertebrates could have been avoided, the authors say. In the North Sea, for example, declines in these indices suggested that total declines in fish catch indicative of ecosystem overfishing was occurring about 5-10 years earlier than what was pieced together by looking at sequential collapses in individual populations of cods, herrings and other species. ![]() “Detecting overfishing at an ecosystem level will help to avoid many of the impacts we have seen when managing fished species on a population-by-population basis, and holds promise for detecting major shifts in ecosystem and fisheries productivity much more quickly,” said Link. By their definition, ecosystem overfishing occurs when the total catch of all fish is declining, the total catch rate or fishing effort required to get that catch is also declining, and the total landings relative to the production in that ecosystem exceed suitable limits. Specific thresholds developed for each index make it possible, they say, to determine if ecosystem overfishing is occurring. They propose three indices, each based on widely available catch and satellite data, to link fisheries landings to primary production and energy transfer up the marine food chain. The authors suggest using large-scale ecosystem indices as a way to determine when ecosystem overfishing is occurring. ![]() “In simple terms, to successfully manage fisheries in an ecosystem, the rate of removal for all fish combined must be equal to or less than the rate of renewal for all those fish,” said Link, the senior scientist for ecosystem management at NOAA Fisheries and a former fisheries scientist at the Northeast Fisheries Science Center in Woods Hole, Massachusetts. In a paper published in Science Advances, NOAA Fisheries researcher Jason Link and colleague Reg Watson from the University of Tasmania’s Institute for Marine and Antarctic Studies suggest that scientists and resource managers need to focus on whole ecosystems rather than solely on individual populations. Population-by-population fishery management is more common around the world, but a new approach could help avoid damaging overfishing and the insecurity that brings to fishing economies. The smallest plants and creatures in the ocean power entire food webs, including the fish that much of the world’s population depends on for food, work and cultural identity.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |