Effects of local fisheries and ocean productivity on the northeastern Ionian Sea ecosystem

To better understand the effects of fisheries and ocean productivity on the northeastern Ionian Sea we constructed an Ecopath with Ecosim model with 22 functional groups. Data on biomass, production/biomass, consumption/biomass, and diet for each group were estimated or extrapolated from the literature. Fisheries landings and discards were also included. Temporal trajectories were simulated using Ecosim. The model was fitted with time-series data for the most important groups from 1964 to 2006. Simulations highlighted a decline of top predators and of most of the commercial species since the late 1970s. The model shows that the decline of fish resources was mainly caused by an intensive fishing pressure that occurred in the area until the end of the 1990s and also by changes in primary production that impacted the trajectories of the main functional groups. In particular, simulated changes through time in PP impacted the abundance trends of all the commercial species, showing a cascade-up effect through the ecosystem. The application of Ecopath with Ecosim was a useful tool for understanding the trends of the main functional groups of the northeastern Ionian Sea. The model underlined that management actions are needed to restore and protect target species including marine mammals, pelagic and demersal fishes. In particular, measures to reduce overfishing, illegal fishing activities and to respect existing legislations are in need. Moreover, the adoption of marine protected areas could be an effective management measure to guarantee prey survival and to sustain marine predators.     

Variability of epifauna and temperature in the northern North Sea

Benthic epifauna in three areas of the northern North Sea was studied from 1999 to 2007 to investigate the effect of temperature changes on community structure and species abundance and biomass. Abundance and/or biomass of 16 epifauna species was significantly correlated with temperature anomalies of the mean sea surface temperature (SST) from 1971 to 2000. The response of species to SST changes was different in the study areas depending on species life history and, most likely on food supply, which in turn is strongly influenced by the timing and duration of primary production and regional hydrographical conditions (e.g. stratification). Also, changes in community structure were obvious in the three areas between 2002 and 2003 coinciding with high temperature anomalies and SST. On the other hand, these changes were mainly caused by the variability in abundance of dominant species and altogether no clear trends in community structure were found. In contrast to epifauna communities in the shallow southern North Sea temperature changes in the northern North Sea affected only single epifauna species until now.     

Spatio-temporal patterns in the diversity of demersal fish communities off the south coast of South Africa

The diversity of ecological communities has been the focus of many studies. Because biodiversity provides several indicators used in an Ecosystem Approach to Fisheries (EAF) to track changes in fish communities, we investigated the spatial and temporal patterns in the diversity of some demersal fish communities subjected to varying fishing pressure. Depth and catch rate were the most important predictors in explaining changes in diversity followed by longitude and survey year. Diversity, as measured by the various indices except for taxonomic distinctness (∆*), initially declined with increasing depth to about a depth of 80 m, then increased to about 150 m after which it declined. Taxonomic distinctness index (∆*) showed an increase in the taxonomic heterogeneity of the demersal community below the 300-m isobath. Diversity remained relatively constant with increase in longitude to around 24°E (which has the lowest diversity) after which it increased. The assessment of the temporal trend in diversity indicates that survey year has a significant effect on all diversity indices except for ∆*. Diversity increased and dominance declined with time. This may be result of a decline in the abundance of dominant species or an increase in the abundance less dominant species, or a combination of both effects. Multivariate analysis of the set of diversity indices showed three groups of indices: those reflecting species richness (S, Margalef’s d), those measuring mainly taxonomic relatedness (∆*), and those balancing the richness and evenness components of diversity (J′, H′, λ, ∆, Hill’s N1, and Hill’s N2). The relationship between evenness, catch rate, and size was also investigated. Size classes with highest evenness were found to have lowest catch rate and vice versa. This highlights the need to consider the size and trophic level of species when linking diversity to the functioning of ecosystems.     

Limited trophodynamics effects of trawling on three Mediterranean fishes

Trawling has a significant effect on the structure of marine communities, yet the ubiquity of trawling impacts makes testing such effects difficult. This study examines trawling impacts on trophodynamics of three fishes among the Gulfs of Castellammare and Termini Imerese (northern Sicily), the first of which has been subject to a trawling ban since 1990 that initially resulted in an eightfold increase in total fish biomass. The Gulf of Termini Imerese remains heavily fished and was treated as a control site. Nitrogen and carbon stable isotope data were used to assess fishing induced changes in trophic levels or source of production supporting three demersal fish species; Mullus barbatus, Merluccius merluccius and Lophius budegassa following a control-impact approach. The exclusion of trawling resulted in only small alteration of δ¹⁵N in two of the three-three species. There were no systematic changes in the δ¹³C of any species sampled. Thus, a large influence of trawling on the trophodynamics of the studied species at sampled size was discounted. Although stable isotopes do not have spatial or temporal resolution to identify detailed shifts in diet composition, their integrative nature highlights that the trophic role these species play is robust to fishing impacts at scales over which the fishery operates. This is despite a significant increase in the abundance of these species and of total fish biomass within the protected area.

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Documenting Loss of Large Trophy Fish from the Florida Keys with Historical Photographs

Abstract:  A loss of large vertebrates has occurred in aquatic and terrestrial ecosystems, but data to measure long-term population changes are sparse. Historical photographs provide visual and quantitative evidence of changes in mean individual size and species composition for groups of marine fish that have been targeted by sport fishing. I measured such trends for 13 groups of recreationally caught "trophy" reef fish with photographs taken in Key West, Florida, from 1956 to 2007. The mean fish size declined from an estimated 19.9 kg (SE 1.5) to 2.3 kg (SE 0.3), and there was a major shift in species composition. Landings from 1956 to 1960 were dominated by large groupers ( Epinephelus spp.), and other large predatory fish were commonly caught, including sharks with an average length of just <2 m. In contrast, landings in 2007 were composed of small snappers ( Lutjanus spp. and Ocyurus chrysurus ) with an average length of 34.4 cm (SE 0.62), and the average length of sharks declined by more than 50% over 50 years. Major declines in the size of fish caught were not reflected in the price of fishing trips, so customers paid the same amount for a less-valuable product. Historical photographs provide a window into a more pristine coral reef ecosystem that existed a half a century ago and lend support to current observations that unfished reef communities are able to support large numbers of large-bodied fish.     

Long-term changes in the Georges Bank food web: trends in stable isotopic compositions of fish scales

Fish scales from seven species of demersal fish in an archival collection were analyzed for stable isotopic compositions of carbon and nitrogen to study long-term changes in trophic structure of the Georges Bank food web. Nitrogen isotopic compositions are often used to infer trophic level. In the case of haddock, Melanogrammus aeglefinus (Linnaeus), there was a trend towards feeding at 2/3 of one trophic level (2.45% in ¹⁵N) lower in 1987 than in 1929. Values of °¹³C, frequently employed to identify sources of organic carbon to consumers, declined by 1.5 from 1929 to 1960, and then increased again toward the present, suggesting changes in the food web at the level of the primary producers. Superimposed on long-term isotopic trends were short-term variations (1 to 10 yr).To identify potential causes for these isotopic trends, canonical correlation analysis was performed between isotopic data and a suite of environmental and population factors including sea surface temperature, the Greenland Regional Pressure Anomaly (GRPA), the North Atlantic Oscillation (NAO), and the following haddock stock parameters; stock size, fishing mortality, recruitment, and weight-at-age-2 (a measure of growth rate). Isotopic variation was significantly correlated with a combination of environmental and population variables: GRPA, NAO, weight-at-age-2, stock size, and fishing mortality. On the basis of published gut content analyses, the seven fish species were predicted to vary in trophic level (TL) from American plaice, Hippoglossoides platessoides (Fabricius), (TL 2.9) to summer flounder, Paralichthys dentatus (Linnaeus), (TL 4.5), whereas measured °¹⁵N values suggested smaller differences in the trophic levels of these species (less than one TL). Four species showed good agreement between gut-predicted and measured ¹⁵N values, while three species did not. Inclusion of information on ontogenetic dietary shifts in our predictions improved the agreement in some cases but not in other. Differences between stable isotope analysis and gut content analysis in terms of what they measure, i.e., integrated assimilated diet vs short-term ingested diet, respectively, may account for some of the differences in results. Based on our analyses and previous studies, feeding habits of these fish may undergo considerable year-to-year and geographic variation, some of which may have been missed in gut content analyses. To the extent that these fish are representative members of the food web, trophic variation in these fish may indicate more general changes in the food web.     

Lake of flies, or lake of fish? A trophic model of Lake Malawi

Ecosystem-focused models have, for the first time, become available for the combined demersal and pelagic components of a large tropical lake ecosystem, Lake Malawi. These provide the opportunity to explore continuing controversies over the production efficiencies and ecological functioning of large tropical lakes. In Lake Malawi these models can provide important insight to the effect of fishing on fish composition, and the potential competition that the lakefly Chaoborus edulis may have with fisheries production. A mass-balanced trophic model developed for the demersal fish community of the southern and western areas of Lake Malawi was integrated with an existing trophic model developed for the open-water pelagic. Input parameters for the demersal model were obtained from a survey of fish distributions, fish food consumption studies, and from additional published quantitative and qualitative information on the various biotic components of the community. The model was constructed using the Ecopath approach and software. The graphically presented demersal food web spanned four trophic levels and was based primarily on consumption of detritus, zooplankton and sedimented diatoms. Zooplankton was imported into the system at trophic levels three and four through fish predation on carnivorous and herbivorous copepods and Chaoborus larvae. It is proposed that the primary consumption of copepods was by fish migrating into the pelagic zone. Chaoborus larvae in the demersal were probably consumed near the lakebed as they conducted a daily migration from the pelagic to seek refuge in the sediments. This evidence for strong benthic-pelagic coupling provided the opportunity for linking the demersal model to the existing model for the pelagic community so producing the first model for the complete ecosystem. Energy fluxes through the resulting combined model demonstrated that the primary import of biomass to the demersal system was detritus of pelagic origin (72.1%) and pelagic zooplankton (10.6%). Only 15.8% of the biomass consumed within the demersal system was of demersal origin. Lakefly production is efficiently utilised by the lake fish community, and any attempt to improve fishery production through introduction of a non-native plantivorous fish species would have a negative impact on the stability and productivity of the lake ecosystem.     

Decadal changes in a NW Mediterranean Sea food web in relation to fishing exploitation

We analysed changes in the ecological roles of species, trophic structure and ecosystem functioning using four standardized mass-balance models of the South Catalan Sea (North-western Mediterranean). Models represented the ecosystem during the late 1970s, mid 1990s, early 2000s, and a simulated no-fishing scenario. The underlying hypothesis was that ecosystem models should quantitatively capture the increasing exploitation in the ecosystem from the 1970s to 2000s, as well as differences between the exploited and non-exploited scenarios. Biomass showed a general decrease, while there was an increase in biomass at lower trophic levels (TL) from the 1970s to 2000s. The efficiency of energy transfer (TE) from lower to higher TLs significantly increased with time. The ecosystem during the 1990s showed higher biomass and flows than during the 1970s and 2000s due to an increase in small pelagic fish biomass (especially sardines). Exploited food webs also showed similarities in terms of general structure and functioning due to high intensity of fishing already in the 1970s. This intensity was highlighted with low trophic levels in the catch, high consumption of production by fisheries, medium to high primary production required to sustain the catches and high losses in secondary production due to fishing. Significant differences on ecosystem structure and functioning were highlighted between the exploited and no-fishing scenarios. Biomass of higher TLs increased under the no-fishing scenario and the mean trophic level of the community and the fish/invertebrate biomass ratios were substantially lower in exploited food webs. The efficiency of energy transfer (TE) from lower to higher TLs was lower under the no-fishing scenario, and it showed a continuous decrease with increasing TL. Marine mammals, large hake, anglerfish and large pelagic fish were identified as keystone species of the ecosystem when there was no fishing, while their ecological importance notably decreased under the exploited periods. On the contrary, the importance of small-sized organisms such as benthic invertebrates and small pelagic fish was higher in exploited food webs.     

Which forcing factors fit? Using ecosystem models to investigate the relative influence of fishing and changes in primary productivity on the dynamics of marine ecosystems

Fishing mortality and primary production (or proxy for) were used to drive the dynamics of fish assemblages in 9 trophodynamic models of contrasting marine ecosystems. Historical trends in abundance were reconstructed by fitting model predictions to observations from stock assessments and fisheries independent survey data. The model fitting exercise derives values for otherwise unknown parameters that specify the relative strength of trophic interactions and, in some instances, a time series anomaly for changes in primary production. We measured how much better or worse were model predictions when bottom-up forcing by primary production were added to top-down forcing by fishing. Searching for cross system patterns, the relative contribution of fishing and changes in primary production, mediated through trophic interactions, are evaluated for the ecosystems as a whole and for selected similar species in different ecosystems. The analysis provides a simple qualitative way to explain which forcing factors have most influence on modeled dynamics. Both fishing and primary production forcing were required to obtain the best model fits to data. Fishing effects more strongly influenced 6 of 9 of the ecosystems, but primary production was more often found to be the main factor influencing the selected pelagic and demersal fish stock trends. Examination of sensitivity to ecological and model parameters suggests that the results are the product of complex food-web interactions rather than simple deterministic responses of the models.     

Shifts in a Pacific Ocean Fish Assemblage: the Potential Influence of Exploitation

Abstract:  As in many regions of the world, marine fishes and invertebrates along the Pacific coast of the United States have long been subjected to overexploitation. Despite this history, however, we lack basic information on the current status of many fishes along this coastline. We used data from a quarter century of fishery-independent, coast-wide trawl surveys to study systematically the demersal fish assemblages along the U.S. Pacific coast. We documented fundamental shifts in this fish assemblage. Average fish size, across a diversity of species, has declined 45% in 21 years. There have been major shifts in the constituent species of the assemblage, with some species achieving annual population growth rates of >10% and others declining in excess of 10% per year. Annual rate of change in population size appeared to be a function of life history interacting with fishing pressure. Negative trends in population size were particularly apparent in rockfish ( Sebastes spp.). However, across all taxa examined, trends in population size were associated with size of maturity, maximum size, and growth rate. Trends in population size were associated inversely with harvest levels, but stocks that mature late tended to decline faster than would be predicted by catch rates alone. Our results are disquieting because they raise the possibility that fishing-induced phase shifts in fish communities may affect the recovery of fishes, even after the implementation of severe fishing restrictions.     

Breaking Bergmann's rule: truncation of Northwest Atlantic marine fish body sizes

A strictly species-centric view of human impacts on ecological communities may conceal important trait changes key to ecosystem functioning and stability. Analyses of body size and community composition data for 326 Northwest Atlantic fish species sampled across > 900000 km2 over three decades revealed a rapid and widespread reduction of body sizes driven by declines within species and changes in relative abundances. The changes were unrelated to species richness but of sufficient magnitude to eliminate biogeographic scale gradients of increasing body size with latitude commonly characterized as Bergmann's rule. These changes have persisted despite reduced potential for intraspecific competition and favorable bottom water temperatures, both of which should lead to increased growth rates. The aggregate body sizes in these Northwest Atlantic fish communities may now represent a mismatch between the environmental variability characteristic of the Northwest Atlantic and the historical body size, life history traits, and productivity of species across this region. We discuss how these changes may jeopardize the potential for recovery of these important temperate/subarctic ecosystems.     

Nahrung aus dem Meer

Background and Scope

There is a multitude of uses in the seas worldwide: fishing, shipping, tourism, exploitation of oil and gas, sea-bed mining, waste disposal, etc. They all compete for space and resources. Each of them has its specific impact on marine ecosystems. Furthermore, they interact with each other and with the marine environment. Fisheries are the most deleterious interactions of man with marine ecosystems by withdrawing a major part of the annual production of large fish, molluscs and crustacea. Many marine habitats are destroyed by fishing, particularly by heavy bottom trawling.

Basics of Fisheries

The production of a fish stock can be increased by removing the old fish. Fishing is sustainable as long as it is restricted to the removal of the surplus production. Subventions and market forces are opposed the rational way of effort reduction aiming at the recovery of overexploited stocks. Fishing has collateral effects on target species. Heavy selective fishing of large, slow-growing predatory fish will favour small, fast-growing species of a lower level in the trophic pyramid. Fishing in marine ecosystems is a complex process in which biological and economic factors interact. At different scales of space and time they are superimposed by changes in the oceanic environment. Climatic variations and global warming of the Ocean differ in their effects from region to region, and they affect distribution, composition and fishing yield of the various exploited fish stocks. Politics has a major impact on the development of fisheries; historical examples are the collapse of the Eastern Bloc with its big distant water fishing fleets, or the introduction of the 200 nm Economic Zones, putting most fish stocks under national jurisdiction.

Discussion

Fishery science is still striving to understand the variability of year-class strength in fish stocks. In the foreground of modern research, however, are the interactions in multi-species communities in relation to changes in the abiotic and biotic environment and to different kinds of management. We have no possibility to study the complex interactions in marine fish communities by controlled experiments. The only information we have are records on landings and fishing efforts. They provide the basis for sophisticated mathematical models. Ecosystem modelling is a relatively young field in marine ecology. In Europe and North America fishery science is more than hundred years old. It is not possible, however, to apply the methods and models of, e.g., North Sea research to low latitude ecosystems and fisheries.

Conclusions

The sustainable use and protection of the marine living resources and biodiversity are global challenges. Each Large Marine Ecosystem calls for specific solutions in terms of research and management. Problems have to be tackled not only by computer models and remote sensing, but also by field research in all parts of the world. The further development of marine and fisheries research in developing countries is a matter of north-south-partnerships with high win-win spin-offs. Over the past decades some excellent groups of marine scientists from several tropical countries have been established who are very open for partnership projects in the true sense. They offer great opportunities to jointly study the richness of marine fauna, flora, and ecosystems in tropical and subtropical shelf seas and up-welling regions.     

Sea ice retreat alters the biogeography of the Bering Sea continental shelf.

Seasonal ice cover creates a pool of cold bottom water on the eastern Bering Sea continental shelf each winter. The southern edge of this cold pool, which defines the ecotone between arctic and subarctic communities, has retreated approximately 230 km northward since the early 1980s. Bottom trawl surveys of fish and invertebrates in the southeastern Bering Sea (1982-2006) show a coincident reorganization in community composition by latitude. Survey catches show community-wide northward distribution shifts, and the area formerly covered by the cold pool has seen increases in total biomass, species richness, and average trophic level as subarctic fauna have colonized newly favorable habitats. Warming climate has immediate management implications, as 57% of variability in commercial snow crab (Chionoecetes opilio) catch is explained by winter sea ice extent. Several measures of community distribution and structure show linear relationships with bottom temperature, suggesting warming climate as the primary cause of changing biogeography. However, residual variability in distribution not explained by climate shows a strong temporal trend, suggesting that internal community dynamics also contribute to changing biogeography. Variability among taxa in their response to temperature was not explained by commercial status or life history traits, suggesting that species-specific responses to future warming will be difficult to predict.     

Seasonal and annual variability in an epifaunal community in the German Bight

While the benthic infauna of the North Sea has been studied intensively over the past decades, few studies have focused on the larger mobile epifauna. Studies carried out to date have described the distribution of epifaunal communities over the whole of the North Sea, but variability within the identified communities, which occurs on a much smaller scale, has so far remained unstudied. This is the first study to describe seasonal and annual variability of an epifaunal assemblage in the German Bight area, where environmental conditions are highly variable. The benthic community was sampled with a 2 m beam trawl from 1998 to 2001. The echinoderms Ophiura albida and Asterias rubens and the crustacean Pagurus bernhardus were the dominant species caught throughout the study period. Overall the species composition of the catches was relatively consistent, while abundances of dominant species fluctuated considerably between sampling periods. Differences between sampling periods were not only influenced by the abundances of dominant species, but also by less dominant species such as Ophiura ophiura, Astropecten irregularis, Corystes cassivelaunus, Crangon crangon and Aphorrahis pespelicani. The abundances of these species varied annually and seasonally in the assemblage. Clear differences between summer and winter in the species composition, abundance and biomass were identified. Annual and seasonal changes were most likely linked to migratory movements of epifauna into and out of the area under investigation. Temporal changes in species composition and abundance correlated best with water temperatures, while the spatial distribution of the total biomass over the whole sampling period was correlated with sediment characteristics. Anthropogenic influences such as fishing activity and chronic large-scale eutrophication are thought to have influenced the community on a long-term basis, but have been considered unlikely causes for the short-term variability described by this study.Communicated by J.P. Thorpe, Port Erin     

Larval fishes in the zooplankton community of the North Pacific Central Gyre

Patterns of species structure are described for the larval fish assemblage in the North Pacific Central Gyre. About 30,000 larvae, primarily of mesopelagic fish species, were identified for 7 cruises. Samples were collected using Isaacs-Kidd plankton trawls on 6 cruises over a 4 1/2 year period; stratified samples were taken with an opening/closing bongo net on one late-summer cruise. Data on absolute and relative abundances, size ranges and summertime depth distributions of over 150 species of larvae are presented. The depth distribution and abundance of the ichthyoplankton are compared to those of the total zooplankton community. The larval assemblage is also examined with respect to the known adult mesopelagic fish assemblage. Seasonal changes in ichthyoplankton species structure occur but, within seasons, species structure is remarkably constant from year to year. Despite seasonal changes in species abundance and rank order of abundance, a constant cumulative frequency structure was found to exist in the ichthyoplankton, both between seasons and between years. The implications of this result are discussed in light of similar findings in a terrestrial community and with respect to possible mechanisms of regulation.     

Comparison of Modern and Historical Fish Catches (AD 750–1400) to Inform Goals for Marine Protected Areas and Sustainable Fisheries

Abstract: We tested the unsustainable fishing hypothesis that species in assemblages of fish differ in relative abundance as a function of their size, growth rates, vagility, trophic level, and diet by comparing species composition in historical bone middens, modern fisheries, and areas closed to fishing. Historical data came from one of the earliest and most enduring Swahili coastal settlements (approximately AD 750–1400). Modern data came from fisheries near the archeological site and intensively harvested fishing grounds in southern Kenya. The areas we sampled that were closed to fishing (closures) were small (<28 km²) and permanent. The midden data indicated changes in the fish assemblage that are consistent with a weak expansion of fishing intensity and the unsustainable fishing hypothesis. Fishes represented in the early midden assemblages from AD 750 to 950 had longer life spans, older age at maturity, and longer generation times than fish assemblages after AD 950, when the abundance of species with longer maximum body lengths increased. Changes in fish life histories during the historical period were, however, one‐third smaller than differences between the historical and modern assemblages. Fishes in the modern assemblage had smaller mean body sizes, higher growth and mortality rates, a higher proportion of microinvertivores, omnivores, and herbivores, and higher rates of food consumption, whereas the historical assemblage had a greater proportion of piscivores and macroinvertivores. Differences in fish life histories between modern closures and modern fishing grounds were also small, but the life histories of fishes in modern closures were more similar to those in the midden before AD 950 because they had longer life spans, older age at maturity, and a higher proportion of piscivores and macroinvertivores than the modern fisheries. Modern closures and historical fish assemblages were considerably different, although both contained species with longer life spans.     

A simulation model to explore the response of the Gulf of Maine food web to large-scale environmental and ecological changes

A dynamic simulation model was constructed using outputs from a balanced Gulf of Maine (GOM) energy budget model as the initial parameter set. The model was structured to provide a recipient control set of dynamics, largely based off of flows to and from different biological groups. The model was used to produce Monte Carlo simulations that were compared (percent change in biomass) with basecase simulations for a variety of scenarios. Changes in primary production, large increases in pelagic and demersal fish biomass, increases in fishing mortality, and large increases in top predators such as baleen whales and pinnepids were simulated. These scenarios roughly simulated the potential impacts of climate change, altered fishing pressure, additional protected species mitigations, and combinations thereof. Results suggest that the GOM system is primarily influenced by bottom-up processes involving phytoplankton, zooplankton, and bacterial biomass. Pelagic and demersal fish were important in determining trends in some of the scenarios. Marine mammals, large pelagic fish, and seabirds have a minor role in the GOM system in terms of biomass flows among the ecosystem components. The system is resilient to large-scale change due, in part to many predator–prey linkages. However, major alterations could occur from sustained climate change, high fishing rates, and by combinations of these types of external forcing mechanisms.     

Comanagement Practices Enhance Fisheries in Marine Protected Areas

Abstract:  Fishing activities worldwide have dramatically affected marine fish stocks and ecosystems. Marine protected areas (MPAs) with no-take zones may enhance fisheries, but empirical evidence of this is scant. We conducted a 4-year survey of fish catches around and within an MPA that was previously fully closed to fishing and then partially reopened under regulated comanaged fishing. In collaboration with the fishers and the MPA authority, we set the fishing effort and selected the gear to limit fishing impact on key fish predators, juvenile fish stage, and benthic communities and habitats. Within an adaptive comanagement framework, fishers agreed to reduce fishing effort if symptoms of overfishing were detected. We analyzed the temporal trends of catch per unit of effort (CPUE) of the whole species assemblages and CPUE of the four most valuable and frequent species observed inside the opened buffer zone and outside the MPA investigated. After the comanaged opening, CPUE first declined and then stabilized at levels more than twice that of catches obtained outside the MPA. Our results suggest that working closely with fishers can result in greater fisheries catches. Partial protection of coastal areas together with adaptive comanagement involving fishers, scientists, and managers can effectively achieve conservation and fishery management goals and benefit fishing communities and alleviate overfishing.     

Increased primary production shifts the structure and composition of a terrestrial arthropod community

Numerous studies have examined relationships between primary production and biodiversity at higher trophic levels. However, altered production in plant communities is often tightly linked with concomitant shifts in diversity and composition, and most studies have not disentangled the direct effects of production on consumers. Furthermore, when studies do examine the effects of plant production on animals in terrestrial systems, they are primarily confined to a subset of taxonomic or functional groups instead of investigating the responses of the entire community. Using natural monocultures of the salt marsh cordgrass Spartina alterniflora, we were able to examine the impacts of increased plant production, independent of changes in plant composition and/or diversity, on the trophic structure, composition, and diversity of the entire arthropod community. If arthropod species richness increased with greater plant production, we predicted that it would be driven by: (1) an increase in the number of rare species, and/or (2) an increase in arthropod abundance. Our results largely supported our predictions: species richness of herbivores, detritivores, predators, and parasitoids increased monotonically with increasing levels of plant production, and the diversity of rare species also increased with plant production. However, rare species that accounted for this difference were predators, parasitoids, and detritivores, not herbivores. Herbivore species richness could be simply explained by the relationship between abundance and diversity. Using nonmetric multidimensional scaling (NMDS) and analysis of similarity (ANOSIM), we also found significant changes in arthropod species composition with increasing levels of production. Our findings have important implications in the intertidal salt marsh, where human activities have increased nitrogen runoff into the marsh, and demonstrate that such nitrogen inputs cascade to affect community structure, diversity, and abundance in higher trophic levels.     

Zooplankton community structure and water flow in the lee of Helix Reef (Great Barrier Reef, Australia)

To investigate which physical processes contribute most in moulding zooplankton community structure in the waters close to coral reefs, light traps moored in a grid pattern were used to collect zooplankton from the sea surface at 16 stations on the downstream side of Helix Reef during three time periods (2100-2200, 2400-0100, and 0300-0400 hours) over three consecutive nights covering the new moon period in January 1992. Two distinct zooplankton communities were present: a community composed primarily of reef-resident, demersal plankton immediately to the south of the reef in an area of reduced flushing, and a community containing coastal and shelf-seas taxa at the more exposed sites in the open flow field. The fauna composition at a number of exposed stations was as rich as that at sheltered stations both in terms of number of taxa and diversity indices but was almost an order of magnitude less abundant. The reef-resident, demersal plankton community was dominated by gammarid amphipods, mysids, and polychaetes, whereas only transient, meroplanktonic forms such as echinoderm and echinopluteus larvae and shelf-seas, holoplanktonic forms such as doliolids and larvaceans were significantly more abundant in the exposed community. Zooplankton associations were apparently formed by a combination of hydrodynamic processes, spatial and temporal distribution patterns of individual taxa, specific behaviours of certain taxa, and the interactions among taxa at different trophic levels.