Fishing

About: Fishing is a research topic. Over the lifetime, 26543 publications have been published within this topic receiving 455552 citations. The topic is also known as: angling.

Potential pressure indicators for fishing, and their data requirements

Abstract: Indicators of fishing pressure are necessary to support an ecosystem approach to fisheries management (EAFM). We present a framework that distinguishes four levels of pressure indicators that move from being a simple description of anthropogenic activity to more precisely describing the actual pressure on the ecosystem and its components, but which require increasingly more information to be quantified. We use the example of the Dutch beam trawl fleet in the North Sea to compare these pressure indicators, as the level of information used is increased. The first level is that of fleet capacity (e.g. number of vessels), the second is fishing effort, usually expressed as the number of hours fishing or days at sea, the third incorporates fishing parameters such as the proportion of time actually spent fishing, fishing speed, or gear characteristics, e.g. the size of the beam trawl in order to determine the frequency with which an area is fished, and at the fourth level, the most informative measure of fishing pressure, annual fishing mortality, is available for a few commercial species from stock assessments. For other species, it can be calculated from the lower level pressure indicators through the incorporation of the chance of individuals of a species coming into contact with the fishing gear and the encounter mortality, which is the portion of mortality caused by the passing of the gear. Comparison of trends and absolute values shows that the pressure indicators at different levels differ considerably in their description of both present and historical fishing impact in the North Sea. Therefore, for an EAFM, we advise using the highest level pressure indicator that can be obtained with the data available.

Lake Trout, Sea Lampreys, and Overfishing in the Upper Great Lakes: A Review and Reanalysis

Abstract: To assess the role of commercial fishing in the destruction of lake trout Salvelinus namaycush in Lakes Huron, Michigan, and Superior in the 1940s and 1950s, we reviewed the literature and analyzed catch and effort data for U.S. waters by regression analysis. There is abundant evidence of the effect of the sea lamprey Petromyzon marinus in the destruction of lake trout, but some have claimed that fishing also was influential. We considered that a persistent, significant decrease in catch per unit of effort before and in the first few years after the sea lamprey was first found in a lake would be evidence of overfishing. We found no convincing evidence of overfishing in Lakes Huron and Michigan. Lake trout probably were overfished in Lake Superior before the sea lamprey became a major influence. We conclude that statements that lake trout were destroyed in Lake Huron or Lake Michigan by a combination of overfishing and the sea lamprey are not justified. The same claim applied simply to the Great L...

Evaluating effectiveness of time/area closures, quotas/caps, and fleet communications to reduce fisheries bycatch

Abstract: Designing effective bycatch mitigation programmes requires an understanding of the life histories of target and non-target species, interactions of fish and fishing gear, effects of spatial and temporal shifts in fishing effort, socio-economic impacts to the fishery, and incentives of fishery participants. The effects of mitigation measures (including fishing gear modification, time/area closures, bycatch quotas and caps, incentive programs, and fleet communication programs) have been evaluated with respect to reducing bycatch and discards. Less attention has been focused on evaluating unanticipated results related to shifts in fishing effort, changes in the size of non-target species caught, reduced catch of target species, and economic viability to fishing fleets. Time/area closures, bycatch quotas/caps, and fleet communication programmes were evaluated against a set of criteria to assess overall effectiveness in reducing bycatch without causing unintended biological and socio-economic impacts. The results suggest that wide-ranging studies of species’ life histories, potential changes in fleet behaviour, and individual incentives are important for developing and implementing mitigation programmes. Combining a suite of mitigation techniques has been successful in meeting biological and socio-economic fisheries goals. Additionally, collaborative programmes that utilize the skill sets of fishers, scientists, and managers have increased effectiveness in meeting bycatch reduction objectives.

Close the high seas to fishing

Abstract: The world's oceans are governed as a system of over 150 sovereign exclusive economic zones (EEZs, ∼42% of the ocean) and one large high seas (HS) commons (∼58% of ocean) with essentially open access. Many high-valued fish species such as tuna, billfish, and shark migrate around these large oceanic regions, which as a consequence of competition across EEZs and a global race-to-fish on the HS, have been over-exploited and now return far less than their economic potential. We address this global challenge by analyzing with a spatial bioeconomic model the effects of completely closing the HS to fishing. This policy both induces cooperation among countries in the exploitation of migratory stocks and provides a refuge sufficiently large to recover and maintain these stocks at levels close to those that would maximize fisheries returns. We find that completely closing the HS to fishing would simultaneously give rise to large gains in fisheries profit (>100%), fisheries yields (>30%), and fish stock conservation (>150%). We also find that changing EEZ size may benefit some fisheries; nonetheless, a complete closure of the HS still returns larger fishery and conservation outcomes than does a HS open to fishing.

Impact of fishing on the abundance of marine species

Abstract: The Census of Marine Life program aims to document the existence, distribution and abundance of marine organisms using all suitable data sources. In this study we analysed time series of catch data published by ICES and FAO in respect to trends in the resilience of species towards fishing. For this purpose we classified the fishing status of over 900 exploited species into undeveloped, developing, fully exploited, overfished, and collapsed or closed, where the sequence of the last three stages usually corresponds to a decline in species abundance. In world fisheries the percentage of species being overfished within 10 years after start of full exploitation increased from 26% in the 1950ies to 35% in the 1980ies. In 1999 the status of 50% of the exploited species was overfished, collapsed or closed. The number of species with low or very low resilience to fishing has been increasing from 80 (26%) in 1950 to 155 (32%) in 1999. Of 24 species reaching full exploitation in 1998 or 1999 for the first time, 8 had low and 8 had very low resilience to fishing. Of 25 species that had sustained 30 or more years of full exploitation before 1989, 11 species reached overfished or collapsed status thereafter. An analysis of length-frequency studies of commercial landings showed that in most cases mean length was below length at first maturity. In the ICES area 46% of the species were overfished within 10 years after start of full exploitation and in 1999 the status of 60% of the species were overfished, collapsed or closed. We suggest an alternative management regime that would allow fish to spawn at least once before being caught. A census of marine life conducted in an exploited area will still largely be able to detect the evolutionary species composition, but will not be able to determine the evolutionary relative abundance of species and their respective roles in the ecosystem.