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Elizabeth H. M. Tyler Andrea manica Narriman Jiddawi Martin R. Speight 《水产资源保护:海洋与淡水生态系统》2011,21(3):231-238
- 1. Completely banning fishing from coral reefs is now accepted to have significant benefits for marine biodiversity and in many cases, fisheries. However, the benefits of regulating fishing on coral reefs, by restricting the methods used, or the total amount of fishing, are less well understood, even though such regulations are much more likely to be supported by fishermen.
- 2. This study assesses whether banning illegal, destructive fishing methods and reducing the numbers of fishermen visiting from outside an area benefits a coral reef fishery, despite unregulated fishing by local fishermen using non‐destructive methods.
- 3. The abundance, biomass, mean length, and species richness of nine commercially important fish families are compared across ten independent patch reefs inside and outside the 470 km2 Menai Bay Conservation Area in Zanzibar, Tanzania.
- 4. Even after taking into account the effect of differences in habitat and the distance between reefs, 61% (±19.7%) more fish species were found in regulated than unregulated reefs. Fish abundance, biomass, and length were not affected, suggesting that banning destructive fishing may improve biodiversity, but that further regulations may be required to improve fish stocks.Copyright © 2011 John Wiley & Sons, Ltd.
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Janelle M. R. Curtis Joaquim Ribeiro Karim Erzini Amanda C. J. Vincent 《水产资源保护:海洋与淡水生态系统》2007,17(5):468-484
- 1. A 2‐year experimental seining programme and underwater visual censuses were undertaken to quantify the direct effects of active demersal fishing on the population structure and relative abundance of two sympatric seahorse species of conservation concern: the European long‐snouted seahorse, Hippocampus guttulatus Cuvier 1829 and the short‐snouted seahorse, Hippocampus hippocampus L. The influence of habitat preference on population‐level responses to changes in habitat structure following a reduction in fishing effort was also investigated.
- 2. It was predicted that the benthic habitat would be more structurally complex after fishing ceased and that seahorse densities would increase in response to reduced fishing mortality. Furthermore, it was predicted that the magnitude of the increase in density would be greater for H. guttulatus than for H. hippocampus, because the former species prefers complex vegetated habitats while the latter species uses sparsely vegetated habitats.
- 3. As predicted, the amount of habitat cover increased significantly when seining ceased, primarily through increases in the abundance of drifting macroalgae and unattached invertebrates. Despite similarities in life histories, the two seahorse species responded differently in terms of magnitude and direction to reduced fishing effort: the abundance of H. guttulatus increased significantly while H. hippocampus decreased in abundance.
- 4. Results suggest that active demersal fishing may influence the magnitude and direction of the responses of benthic marine fishes to exploitation through its impacts on habitat structure. An increase in habitat cover appeared to favour higher densities of H. guttulatus when seining effort was reduced. By contrast, repeated seining, which maintained less complex habitats, appeared to favour greater abundances of H. hippocampus.
- 5. Given differences in habitat preference among benthic marine fishes subject to incidental capture in fisheries, simultaneous attempts to manage populations of sympatric species may require complementary strategies that support the persistence of diverse habitat types.
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Fish landing data from the Mombasa Marine National Park (MNP) and a marine reserve exploited by various gears were studied over a 5‐yr period to determine the influence of the closed area and different gears in fisheries. The number fishing and boats per landing site was constant, but total and catch per unit effort progressively declined in all sites on an annual basis irrespective of the existence of a marine reserve, exclusion of the beach seines or use of gear. Differences between landing sites were most pronounced when analysed on a catch per area as opposed to the more standard catch per fisherman, suggesting compensation in human effort when catches decline. A marine reserve next to a closed area that excluded beach seines had the highest catch per area (5.5 kg ha?1 month?1) despite having the highest density of fishermen (0.07 ± 0.02 fishermen ha?1 month?1). The annual rate of decline in the catch was lower than the other sites at around 250 g day?1 compared with 310–400 g day?1 in the other sites. One landing site, which excluded beach seine landings for more than 20 yrs, had a high catch per area (～5.3 kg ha?1 month?1), but after experiencing a doubling in the effort of other gears (line, speargun and trap), the catch per fisherman and area were reduced. Environmental or habitat degradation and excessive effort remain the most likely explanation for the overall declines in catch from 1995 to 1999. Closed areas and beach seine exclusion have the potential to increase catch rates, but the first often reduces the total fishing area and possibly leads to a loss of total catch, at least on a time scale of less than 10 yrs. The exclusion of beach seines can lead to an increase in other gear types that can also cause reductions in catch. 相似文献
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Paolo Casale Lorenzo Cattarino Daniela Freggi Massimiliano Rocco Roberto Argano 《水产资源保护:海洋与淡水生态系统》2007,17(7):686-701
- 1. The fishing effort and turtle catch of vessels harbouring at Lampedusa island and fishing in the wider central Mediterranean area was monitored using a voluntary logbook programme. Two large trawlers were monitored between 2003 and 2005 and six small vessels using trawl nets, pelagic longline or bottom longline were monitored in the summer 2005.
- 2. The observed turtle catch rates of pelagic longline and bottom trawl were among the highest recorded in the basin, and high catch rates by bottom longline were observed too. This suggests that the area contains major oceanic and neritic habitats for the loggerhead turtle Caretta caretta in the Mediterranean Sea.
- 3. When fishing effort is considered, these results suggest a very high number of captures by Italian trawlers and longliners in the area, as well as by fleets from other countries. This is reason of concern for the conservation of the loggerhead turtle within the Mediterranean Sea.
- 4. Different fishing gear have different technical/operational characteristics affecting turtle catch and mortality and the present knowledge about associated parameters of these gear varies too.
- 5. All this considered, specific actions are recommended: (i) an awareness campaign to fishermen to reduce post‐release mortality, (ii) technical modifications to pelagic longline gear to reduce turtle catch, (iii) further investigation into turtle bycatch in all fishing gear, with priority given to bottom longline fishing and quantification of mortality caused by trawlers, (iv) assessment of the turtle populations affected by fishing activity in the area, and (v) international cooperation in undertaking threat assessments, and implementing regulations, management measures and monitoring.
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- 1. Dolphins are often blamed for reducing fisheries catches and may be killed in retaliation. Depredation of fishing gear in coastal Mediterranean waters is normally caused by bottlenose dolphins. Economic impact, however, may be modest even within areas of reportedly acute conflict.
- 2. Boat surveys and interviews were conducted to investigate dolphin occurrence and interactions with fisheries within the 167 km2 Porto Cesareo Marine Protected Area (MPA) in southern Italy. Based on 69 interviews with fishermen using bottom‐set trammel and gill nets, there was reportedly a high occurrence of depredation by bottlenose dolphins. Depredation was reported by 92% of the fishermen operating in or near the MPA, and 67% of them claimed an economic cost in excess of €1000 per year, with a mean reported cost of €2561: a higher impact than in other Mediterranean studies.
- 3. According to local fishermen, dolphin occurrence and depredation peaked in spring and autumn, coincident with the study's surveys at sea. Dedicated visual surveys totalling 1255 km of effort, however, resulted in no encounters with cetaceans. Information from interviews and boat surveys was therefore contradictory, suggesting that reports of acute depredation do not imply a constant presence of dolphins within the MPA.
- 4. While depredation in the MPA might be caused by wide‐ranging dolphins or incursions occurring overnight, damage may well be overestimated or over‐reported. As local fishermen had previously benefited from subsidies, interviews made during this study could be perceived by some as an opportunity to influence future decision‐making regarding monetary compensation for the impact of depredation.
- 5. Evidence from interviews also indicated that species and factors other than dolphins were responsible for part of the damage. Copyright © 2011 John Wiley & Sons, Ltd.
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Leandro Castello Laura L Hess Ram Thapa David G McGrath Caroline C Arantes Vivian F Renó Victoria J Isaac 《Fish and Fisheries》2018,19(3):431-440
Inland fisheries underpin food security in many tropical countries. The most productive inland fisheries in tropical and subtropical developing countries occur in large river–floodplain systems that are often impacted by land cover changes. However, few studies to date have assessed the effects of changes in floodplain land cover on fishery yields. Here, we integrated fisheries and satellite‐mapped habitat data to evaluate the effects of floodplain deforestation on fishery yields in 68 floodplain lake systems of the lower Amazon River, representing a wide range in relative amounts of woody, herbaceous and non‐vegetated land cover. We modelled relative fish yields (fish capture per unit effort [CPUE]) in the floodplain lakes as a function of the relative amounts of forest, shrub, aquatic macrophyte and bare/herbaceous habitats surrounding them. We found that forest amount was positively related (p = .0003) to multispecies CPUE. The validity of these findings was supported by rejection of plausible alternative causative mechanisms involving habitat‐related differences in amount of piscivores, fishing effort, lake area, and habitat effects on CPUE of the nine taxa dominating multispecies yields. Our results provide support to the idea that removal of floodplain forests reduces fishery yields per unit effort. Increased protection of floodplain forests is necessary to maintain the food, income and livelihood security services provided by large river–floodplain fisheries. 相似文献
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Giovanni Bearzi Stefano Agazzi Joan Gonzalvo Silvia Bonizzoni Marina Costa Annalise Petroselli 《水产资源保护:海洋与淡水生态系统》2010,20(5):549-559
- 1. Dolphins are often claimed to compete with fisheries, including through removal of substantial biomass. To calculate the biomass removed by fisheries and the degree of resource overlap with dolphins in a coastal area of Greece, estimates of dolphin abundance based on photographic capture–recapture were combined with an assessment of fishing effort and catch.
- 2. The estimated total biomass consumed annually by local dolphin populations – 15 short‐beaked common dolphins and 42 common bottlenose dolphins – was 15.5 and 89.8 tonnes, respectively. The total biomass removed by the local fishing fleet (307 fishing boats) was 3469.2 tonnes, i.e. about 33 times greater than that removed by dolphins.
- 3. Dolphins removed 2.9% of the total biomass, fisheries 97.1%. Nine purse seiners (representing only 3% of the active fishing fleet) were responsible for 31.9% of biomass removal. Similarity of biomass composition between dolphins and fisheries was expressed by a Pianka index of 0.46 for common dolphins and 0.66 for bottlenose dolphins.
- 4. Overlap differed according to fishing gear. Common dolphin overlap was higher with purse seiners (0.82), and lower with beach seiners (0.31), bottom trawlers (0.11) and trammel boats (0.06). There was virtually no overlap with longliners (0.02). Bottlenose dolphin overlap was higher with trammel boats (0.89) and bottom trawlers (0.75), and lower with longliners (0.38), purse seiners (0.24) and beach seiners (0.18). There was minimal overlap (0.12) between the two dolphin species.
- 5. This study suggests that ecological interactions between dolphins and fisheries in this coastal area have minor effects on fisheries. Conversely, prey depletion resulting from overfishing can negatively affect dolphins. Fisheries management measures consistent with national and EU legislation are proposed to ensure sustainability and to protect marine biodiversity. Copyright © 2010 John Wiley & Sons, Ltd.
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- 1. The present study characterizes the macro‐epibenthic assemblages, and the relationships between demersal species and benthic habitats on the shelf trawl fishing grounds off the Balearic Islands (western Mediterranean).
- 2. The data used were collected during experimental bottom trawl surveys from 2002 to 2005. A total of 157 samples from 38–255 m depth were analysed.
- 3. Three macro‐epibenthic assemblages were identified in both the shallow (at 38–91 m) and deep shelf (90–255 m). Macroalgae bathymetric distribution was identified as the main factor explaining the segregation between shallow and deep shelf assemblages.
- 4. Two especially sensitive habitats were identified: maërl and crinoid beds; a third habitat was identified as Peyssonnelia beds, which represented the highest biomass on the whole shelf, with a similar species richness to the maërl beds. On the deep shelf, crinoid beds represented the highest biomass.
- 5. Habitat type had a significant effect on the distribution of demersal commercial species, most of them being more abundant in the two sensitive habitats mentioned and in the Peyssonnelia beds. Some species showed size‐specific habitat preferences.
- 6. Fisheries management in the area should take into account the resilience of these benthic habitats, and their importance from both ecological and sustainable fisheries management perspectives.
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