Fishing Impact

Benthic cover, current strengths, and fish abundance and diversity were examined on 150 lagoonal patch reefs and mapped to determine their distribution, inter-relationships, and relationship to the fisheries closure in Glovers Reef Atoll. Current strength was highest at both the northern and southern ends of the atoll and largely controlled by local wind and weakly by tidal forcing. Benthic functional group distributions varied throughout the atoll and had distinct areas of dominance. In contrast, dominance of coral species was weaker, reflecting the lost cover and zonation of Acropora, Porites, and Montastraea that were reported in the 1970s. Hard and soft corals dominated the windward rim, while the central and leeward lagoon had lower current strengths and sea grass and fleshy green algae were relatively more abundant. Brown erect algae were relatively more common in the north and calcifying green and red algae the southern ends of the atoll. Only Montastraea-Agaricia agaricites distributions were similar to reports from the 1970s with high relative dominance in the southern and northeast atoll. The central-northern zone, which was described as an Acropora zone in the 1970s, was not recognizable, and Porites porites, P. astreoides, Millepora alcicornis, and Favia fragum were the most abundant species during this survey. Hard and soft coral cover abundance declined away from the reef rim and tidal channels and was associated with fast seawater turnover and high surgeonfish abundance. Consequently, the windward rim area has retained the most original and persistent hard-soft coral and surgeonfish community and is considered a priority for future management, if the goal is to protect coral from fishing impacts.

The NW Mediterranean has a number of structural features in common with upwelling ecosystems. Therefore, an ecological model representing a NW Mediterranean exploited ecosystem was standardized and compared with four previously standardized models from coastal upwelling ecosystems: the Northern and Southern Humboldt (Chile and Peru upwelling systems) and the Northern and Southern Benguela (Namibia and South Africa upwelling systems). Results from biomasses, flows and trophic levels indicated important differences between ecosystems, mainly caused by differences in primary production, which was smallest in the NW Mediterranean Sea. However, principal component analysis (PCA) of biomasses and flows suggested a similar pattern between the NW Mediterranean and the South African systems due to the inclusion of an important fraction of the continental shelf in both ecological models representing these areas. At the same time, diets of commercial species from the NW Mediterranean were more similar to Benguela than Humboldt species.However, the relatively heavy fishing pressure in the NW Mediterranean ecosystem was highlighted relative to its primary production, and was evident from the large catches and small primary production, largest flows from TL 1 required to sustain the fishery (%PPR), the low trophic level of the catch (TLc), high exploitation rates (F/Z), largest values in the trophic spectra portraying catch: biomass ratio, the FIB index and the demersal: total catch ration. Comparisons of %PPR, the trophic level of the community (TLco), the biomass of consumers and F/Z ratios seemed to capture the ecosystem effects of fishing: large in the NW Mediterranean, Namibia and Peru upwelling systems. Small pelagic fish were the most important component of the fisheries in the NW Mediterranean and Peruvian systems. However, the smaller production and biomass ratios from the NW Mediterranean could be an indirect indicator of intense fishing pressure on small pelagic fish, also in line with results from consumption of small pelagic fish by the fishery, F/Z ratios and trophic spectra. Moreover, similarities between the NW Mediterranean and Namibian systems were found, mainly related to the demersal: total catch ratios, the FIB index, the relevance of gelatinous zooplankton in the consumption of production and the importance of pelagic-demersal coupling, in remarkable contrast to the other ecosystems. These similarities should be interpreted in terms of dynamic trajectories that the Namibian system has shown due to the collapse of its pelagic ecosystem, partly due to fishing intensity, and the signs that the NW Mediterranean could follow suit in the future.

We analysed fisheries trends in the northern region of the Gulf of California, within the Biosphere Reserve of the Upper Gulf of California and Colorado Delta River and the Vaquita Refuge Area, and suggest measures to protect the vaquita, Phocoena sinus. We compiled and analysed catch reports of artisanal fishermen in the three fishing communities of the Upper Gulf of California (San Felipe in the State of Baja California, and Golfo de Santa Clara and Puerto Peñasco in the State of Sonora) from 1995 to 2007. This information was categorised with respect to geographic information systems, and all fishing sites within two marine protected areas in the region were identified. In addition, from a survey based on direct interviews with artisanal fishermen in each of the three ports, we identified that 23% of fishermen will continue fishing despite on-going fishing buy-out programmes in the region. We suggest several specific courses of action to decrease the fishing impact on this critically endangered cetacean. However, given the critical situation of this critically endangered species, it is very uncertain whether enforcing a no-take zone within the biosphere reserve and the Vaquita Refuge Area, or even a wider fishing moratorium, will be enough to save this endangered species from extinction.

An ecosystem model representing the continental shelf and upper slope of the South Catalan Sea (NW Mediterranean) is calibrated and fitted to the available time series data from 1978 to 2003. We use a process-oriented model to explore the extent to which changes in marine resources and the ecosystem were driven by trophic interactions, environmental factors and fishing activities. Fishing effort and fishing mortality are used to drive the model, while observed (absolute and relative) biomasses and catches are compared with the predicted results. A reduction in the sum of the squared deviations of the observed and predicted values of the biomass is used as a metric for calibrating and assessing the fit of the model. A posteriori trophodynamic indicators are used to explore the ecosystem's structural and functional changes from 1978 to 2003, and a generalized least squares regression is used to assess the significance of the predicted trends. In general, a high proportion of the variability in the time series data is explained by the main trophic interactions (37–53%), fishing activities (14%), and indirectly by considering the environment (6–16%), as driving factors. The model's predictions match satisfactorily with the yearly data on the biomass for anglerfish, adult hake, demersal sharks, anchovy and mackerel, which show a statistically significant decrease over time, while the biomass of flatfish and seabirds are observed to increase. Catch data show a significant decrease in anglerfish, demersal sharks, anchovy and sardine, while there is an increase in red mullet, flatfish, juvenile hake and horse mackerel. These changes in biomass are predicted to have direct and indirect impacts on the ecosystem mediated by the trophic web, such as the proliferation of non-commercial species with lower trophic levels (e.g., benthic invertebrates) or higher turnover rates (e.g., cephalopods and benthopelagic fish). This is consistent with anecdotal information from the Mediterranean and is likely caused by trophic cascades due to the removal of demersal and pelagic higher trophic level organisms (predator release), and a decrease in small pelagic fish (competitor release). Trophodynamic indicators suggest a degradation pattern over time: both the mean trophic level of the community (mTLco, excluding primary producers and detritus) and a modified version of Kempton's index of biodiversity decrease with time, while the total flow to detritus and the loss of production due to fishing increase from 1978 to 2003. Additionally, the demersal/pelagic ratio increases due to an overall decrease in the abundance of small pelagic fish in the ecosystem.

Towed bottom-fishing gears are thought to constitute one of the largest global anthropogenic sources of disturbance to the seabed and its biota. The current drive towards an ecosystem approach in fish- eries management requires a consideration of the im- plications of habitat deterioration and an understand- ing of the potential for restoration. We undertook a meta-analysis of 101 different fishing

Gascuel, D., Bozec, Y-M., Chassot, E., Colomb, A., and Laurans, M. 2005. The trophic spectrum: theory and application as an ecosystem indicator. e ICES Journal of Marine Science, 62: 443e452. Trophic spectra represent the distribution of biomass, abundance, or catch by trophic level, and may be used as indicators of the trophic structure and functioning of aquatic ecosystems in a

We analysed fisheries trends in the northern region of the Gulf of California, within the Biosphere Reserve of the Upper Gulf of California and Colorado Delta River and the Vaquita Refuge Area, and suggest measures to protect the vaquita, Phocoena sinus. We compiled and analysed catch reports of artisanal fishermen in the three fishing communities of the Upper Gulf of California (San Felipe in the State of Baja California, and Golfo de Santa Clara and Puerto Peñasco in the State of Sonora) from 1995 to 2007. This information was categorised with respect to geographic information systems, and all fishing sites within two marine protected areas in the region were identified. In addition, from a survey based on direct interviews with artisanal fishermen in each of the three ports, we identified that 23% of fishermen will continue fishing despite on-going fishing buy-out programmes in the region. We suggest several specific courses of action to decrease the fishing impact on this critically endangered cetacean. However, given the critical situation of this critically endangered species, it is very uncertain whether enforcing a no-take zone within the biosphere reserve and the Vaquita Refuge Area, or even a wider fishing moratorium, will be enough to save this endangered species from extinction.

We review studies of the early ocean period of salmon life history conducted in the coastal areas off Canada's West Coast. The role of the ocean in the dynamics of salmon popula- tions has received considerably less study than their life cycle in fresh water, even though Pacific salmon in general spend more time in the ocean than in fresh

The Gulf of California is unique because of its geographical location and conformation. It hosts diverse ecosystems and important fisheries that support industry and provide livelihood to coastal settlements. It is also the site of interests and problems, and an intense interaction among managers, producers, and conservationists. In this report, we scrutinize the abiotic (hydrography, climate, ocean circulation, and chemistry)

An exploited ecosystem from the continental shelf and upper slope of the Northwestern Mediterranean Sea was described by means of an Ecopath mass-balance model with the aim of characterising its functioning and structure and describing the ecosystem impacts of fishing. This application included some complexities added to the general modelling methodology due to the high biodiversity of the Mediterranean Sea and the multispecific nature of the fishery, and to the difficulties of working with fishing data which are usually irregularly or imprecisely collected. The model comprised 40 functional groups including primary producers, the main species of benthic, demersal and pelagic invertebrates, fishes and non-fish vertebrates and three detritus groups. In addition, trawling, purse seine, longline and troll bait fishing fleets were included.Results showed that the functional groups were organized into four trophic levels with the highest levels corresponding to anglerfish, dolphins, large pelagic fishes and adult hake. The system was dominated by the pelagic fraction, where sardine and anchovy prevailed in terms of fish biomasses and catches. Detritus and detritivorous groups also played key roles in the ecosystem and important coupled pelagic-demersal interactions were described. Considering Odum's theory of ecosystem development, the ecosystem was placed on an intermediate-low developmental stage due, at least partially, to the impact of fishing activity. This highlighted the high intensity of fishing in the ecosystem, in accordance with the general assessment of western Mediterranean marine resources, and fishing fleets were ranked as top predators of the system. The low trophic level of the catch was in line with the long history of exploitation in the area. However, the steady decline of pelagic landings between 1994 and 2003, coupled with a decrease of the pelagic biomass within the system, underlined the low resistance of the system in front of perturbations. This decline was reproduced under Ecosim dynamic simulations combining different scenarios of moderate increase of fishing effort and an environmental forcing affecting the availability of preys to small and medium-sized pelagic fishes under wasp-waist flow control.

We used a process-oriented model (Ecosim) to characterize changes in marine resources in the north-central (NC) Adriatic Sea (Mediterranean) from 1975 to 2002, and to explore the extent to which these changes were driven by trophic interactions, environment and fishing. Fishing efforts and fishing mortalities were used to drive the ecosystem model, and available biomass and catch data were compared

A trophic mass-balance model was developed to characterise the food web structure and functioning of the Northern and Central Adriatic Sea and to quantify the ecosystem impacts of fishing during the 1990s. Forty functional groups were described, including target and non-target fish and invertebrate groups, and three detritus groups (natural detritus, discards and by-catch of cetaceans and marine turtles). Results highlighted that there was an important coupling between pelagic–benthic production of plankton, benthic invertebrates and detritus. Organisms located at low and medium trophic levels, (i.e. benthic invertebrates, zooplankton and anchovy), as well as dolphins, were identified as keystone groups of the ecosystem. Jellyfish were an important element in terms of consumption and production of trophic flows within the ecosystem. The analysis of trophic flows of zooplankton and detritus groups indirectly underlined the importance of the microbial food web in the Adriatic Sea.Fishing activities inflicted notable impacts on the ecosystem during the 1990s, with a high gross efficiency of the fishery, a high consumption of fishable production, high exploitation rates for various target and non target species, a low trophic level of the catch and medium values of primary production required to sustain the fishery. Moreover, the analysis of Odum's ecological indicators highlighted that the ecosystem was in a low-medium developmental stage. Bottom trawling (Strascico), mid-water trawling (Volante) and beam trawling (Rapido) fleets had the highest impacts on both target and non target ecological groups. On the contrary, purse seining (Lampara) showed medium to low impacts on the ecosystem; cetaceans, marine turtles and sea birds were not significantly involved in competition with fishing activity.