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Fishing Methods (fishing + methods)
Selected AbstractsThe relationship between fishing methods, fisheries management and the estimation of maximum sustainable yieldFISH AND FISHERIES, Issue 4 2002Mark N Maunder Abstract The allocation of effort among fishing gears is as important as controlling effort with respect to both sustainable yield and ecosystem management. Differences in age-specific vulnerability to the fishing method can modify the maximum sustainable yield (MSY) that is obtainable from a fish stock. Different gears or methods are more or less selective for the species targeted, and MSY is rarely, if ever, attainable simultaneously for all species. The different fishing methods capture different types of nontarget species. Some methods will often be more profitable than others, and different user groups will prefer different methods. In many fisheries, it is unlikely that fishing can be limited to a single gear or method, so compromises among them will be required. Global MSY is discussed as a possible reference point for fisheries management. The yellowfin tuna fishery in the eastern Pacific Ocean (EPO) shows all the above characteristics and is used to illustrate effort allocation among fishing methods. [source] Recent evolution of the fishing exploitation in the Thau lagoon, FranceFISHERIES MANAGEMENT & ECOLOGY, Issue 1 2002V. CRESPI Fisheries activity in the Thau marine lagoon (Mediterranean coast of France) has an old tradition and involves different types of gears (set nets, traps and lines) that are used seasonally with varying frequencies in different areas. A survey of fishing activity, main fishing methods and main commercial species composition in the lagoon was carried out to assess the current fishing effort and seasonal yield. Many important changes in fishing effort and in the most important target species occurred during the last 10 years. A gradual decline in eel, Anguilla anguilla (L.), catches followed by an increase of other commercially-exploited species, particularly the gilthead sea-bream, Sparus aurata L., was observed. [source] Environmental variability and the fishery dynamics of the Okavango delta, Botswana: the case of subsistence fishingAFRICAN JOURNAL OF ECOLOGY, Issue 2009G. Mmopelwa Abstract The hydrological regime of the Okavango River Basin is the main driver of ecological change in the delta. The delta supports a small-scale fishery which is a source of livelihood for communities within its fringes. The fish resource is particularly important to subsistence fishers, who have limited access to socio-economic opportunities. However, fish availability is subject to ,concentration and dilution' effects because of the hydrological regime. As a copying strategy, fishers use a variety of fishing methods to effectively harvest the delta's fish community across all its trophic levels. This exploitation regime helps to maintain the delta's species diversity and only reduces fish biomass proportionally across the different trophical levels. Furthermore, fishers have developed different fish-processing techniques to preserve their harvest for low fishing season periods to cope with low food availability. The aim of this paper therefore, was to explore spatio-temporal variations in fish availability and to show how the delta's subsistence fishers cope with this dynamicity. [source] The status of fish conservation in South African estuariesJOURNAL OF FISH BIOLOGY, Issue 9 2010A. K. Whitfield Estuary-dependent fish species are defined as those taxa whose populations would be adversely affected by the loss of estuarine habitats. Of the 155 species regularly recorded in South African estuaries, only 32 (21%) are completely dependent on these systems, but this figure increases to 103 species (66%) if partially dependent taxa are included in the analysis. The conservation of fishes in estuaries on the subcontinent is threatened by a number of factors, including habitat degradation, disruption of essential ecological processes, hydrological manipulations, environmental pollution, overexploitation due to fishing activities and, more recently, climate change and the effects of introduced aquatic animals. Although major threats to fishes are usually linked to environmental degradation, there is increasing evidence that the stocks of certain fish species are overexploited or collapsed. Fish conservation and fisheries management does not depend on the implementation of a single action, but rather the co-ordination of a detailed plan, often in a multidisciplinary context. Some examples of innovative means of contributing to estuarine fish conservation in a South African context include the determination and implementation of the ecological freshwater requirements for estuaries, the zoning of estuaries for different uses and the recognition that the maintenance of ecological processes are vital to aquatic ecosystem health. Apart from the designation of protected areas, the main direct means of conserving fish species and stocks include habitat conservation, controls over fishing methods, effort, efficiency and seasonality, pollution control and the prevention of artificial manipulation of estuary mouths. Since becoming a democracy in 1994, environmental legislation, policy and institutional arrangements in South Africa have undergone some major changes, which, if fully implemented, will be very positive for fish conservation in estuaries on the subcontinent. [source] Previously spawned Atlantic salmon ascend a large subarctic river earlier than their maiden counterpartsJOURNAL OF FISH BIOLOGY, Issue 4 2006E. Niemelä Spawning migration timing of maiden Atlantic salmon Salmo salar and previous spawners was analysed in the catches in 1989,2004 in the large subarctic River Teno in the northernmost parts of Finland and Norway. The hypothesis was that the migration timing of previous spawners and their maiden counterparts is similar, with the migration timing similar between sexes. In most cases, however, previous spawners were observed to migrate into the River Teno and its tributaries earlier than their maiden counterparts. The difference in run timing was especially evident between maiden one-sea-winter (1SW) Atlantic salmon and the corresponding group of previous spawners [1S1, 1 year at sea (1) followed by first spawning (S) and reconditioning period of 1 year (1) at sea and second spawning run] for both sexes in the River Teno and in its two tributaries. The same was also evident between 2SW maiden and 2S1 previous spawning female Atlantic salmon in the River Teno. Females showed earlier spawning migration than males both in previous spawners and maiden Atlantic salmon. Different maiden sea-age classes also showed differences in run timing as multi-sea-winter fish (2,4SW) ascended earlier than 1SW fish but the timing of 1S1 and 2S1 previous spawning females coincided. The results suggest that run timing of Atlantic salmon may not be strictly genetically fixed as previous spawners ascend earlier than they did on their first spawning migration as maiden fish, and indicated that the closeness of the reconditioning area of postspawners to the river of origin resulted in an early ascent. Run timing of different sea-age groups has major management implications if the populations are heavily exploited with numerous fishing methods in different periods of the fishing season, as in the River Teno system. [source] Management of the Nile tilapia (Oreochromis niloticus (L.)) fishery in the Kenyan portion of Lake Victoria, in light of changes in its life history and ecologyLAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 2 2008M. Njiru Abstract This study reports on the population parameters, catch distribution and feeding ecology of Nile tilapia (Oreochromis niloticus) from bottom trawls and commercial catches obtained in the Kenyan portion of Lake Victoria during 1997,2006. The population parameters were analysed using the FAO-ICLARM stock assessment tool (FISAT). The fish biomass and the food ingested by the fish were estimated using the swept area and point methods, respectively. Immature fish comprised ,70% of the total fish population. The asymptotic length, maximum weight, maximum age, exploitation rate (E) and length at 50% maturity of Nile tilapia have decreased, whereas the growth curvature and fishing mortality have increased. The commercial catches increased from 13.93 t in 1997, to 23.70 t in 1999, decreasing thereafter to 18.73 t in 2005. The bottom trawl catches increased from 46.90 kg ha,1 in 1997, to 401.48 kg ha,1 in 2000, decreasing thereafter to 15.57 kg ha,1 in 2006. The major food items ingested by the fish were algae, insects and other fish. Population parameters, and the catch and diet of O. niloticus, have changed over the years in Lake Victoria. The population characteristics suggest a population under stress, attributable to intense catch exploitation. Even under intense exploitation (E = 0.68), however, the mature fish constituted ,30% of the population. The commercial catches are still high, indicating a very resilient fishery. Nevertheless, despite this resilience, the future of Oreochromis fishery is threatened by increased fishing capacity in the lake, and there is need to re-evaluate the effectiveness of current fishery management measures, with the goal of possibly adopting new measures. Enactment of new fishery policies also should provide for co-management to enhance the management process. Furthermore, there is a need to reduce fishing capacity and illegal fishing methods, and to seek alternative livelihoods for lake fishers and other stakeholders. [source] Experimental sponge fishery in Egypt during recovery from sponge diseaseAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2005J. Castritsi-Catharios Abstract 1.A survey was undertaken (1995) on the Mediterranean coast of Egypt that investigated four sponge fishing grounds. These fishing banks suffered from sponge disease between 1987 and 1990, causing a mass mortality of commercial sponges in the eastern and central Mediterranean. 2.Adult commercial sponges (length >10 cm) were harvested by divers in the infralittoral zone (depth range 17,36 m). The substratum at most of the sampling stations was hard, consisting mainly of plaques, rocks and heavy stones, sometimes covered by Posidonia oceanica. 3.Two commercial sponge species were detected, Hippospongia communis and Spongia cfr zimocca; the former was more prevalent and abundant. Light penetration in the area surveyed was high. The two commercial sponge species detected seemed to be well adapted to these conditions, as indicated by the colour of their external membranes, which were almost black due to enhanced pigment formation. The absence of Spongia officinalis, in the area surveyed may also be related to light penetration, since S. officinalis is a more sciaphilous species. 4.The shape of H. communis was almost spherical, and the average dimensions (length, width, height, circumference) increased with increasing depth of the fishing grounds. At shallower depths (<30 m), adult H. communis occurred in lower densities, whereas young commercial sponges were abundant. No signs of sponge disease were found. 5.It is concluded that the recovery of the four sponge fishing grounds was in progress, and that the repopulation of commercial sponges in the infralittoral zone showed a gradient from deeper to shallower waters. It is recommended to prohibit destructive fishing methods in the deeper waters in order to protect the population and its ability to regenerate. Copyright © 2005 John Wiley & Sons, Ltd. [source] | |||||||||||||