Showing papers on "Fishing published in 2004"

Coral decline threatens fish biodiversity in marine reserves.

Abstract: The worldwide decline in coral cover has serious implications for the health of coral reefs. But what is the future of reef fish assemblages? Marine reserves can protect fish from exploitation, but do they protect fish biodiversity in degrading environments? The answer appears to be no, as indicated by our 8-year study in Papua New Guinea. A devastating decline in coral cover caused a parallel decline in fish biodiversity, both in marine reserves and in areas open to fishing. Over 75% of reef fish species declined in abundance, and 50% declined to less than half of their original numbers. The greater the dependence species have on living coral as juvenile recruitment sites, the greater the observed decline in abundance. Several rare coral-specialists became locally extinct. We suggest that fish biodiversity is threatened wherever permanent reef degradation occurs and warn that marine reserves will not always be sufficient to ensure their survival.

The Role of Recreational Fishing in Global Fish Crises

Abstract: Exploitation of fishery resources has become a major conservation issue on a global scale. Commercial fisheries have been repeatedly blamed for the worldwide declines in fish populations. However, we contend that the recreational fishing sector also has the potential to negatively affect fish and fisheries. Here we present evidence to show that both recreational and commercial fishing sectors deserve consideration as contributors to the exploitation of fish in marine and inland waters. The lack of global monitoring and compiling of statistics on recreational fishing participation, harvest, and catch-and-release has retarded our ability to understand the magnitude of this fishing sector. Using data from Canada, we estimate that the potential contribution of recreational fish harvest around the world may represent approximately 12 percent of the global fish harvest. Failure to recognize the potential contribution of recreational fishing to fishery declines, environmental degradation, and ecosystem ...

Fisheries Sustainability via Protection of Age Structure and Spatial Distribution of Fish Populations

Abstract: Numerous groundfish stocks in both the Atlantic and Pacific are considered overfished, resulting in large-scale fishery closures. Fishing, in addition to simply removing biomass, also truncates the age and size structure of fish populations and often results in localized depletions. We summarize recent research suggesting that an old-growth age structure, combined with a broad spatial distribution of spawning and recruitment, is at least as important as spawning biomass in maintaining long-term sustainable population levels. In particular, there is evidence that older, larger female rockfishes produce larvae that withstand starvation longer and grow faster than the offspring of younger fish, that stocks may actually consist of several reproductively isolated units, and that recruitment may come from only a small and different fraction of the spawning population each year. None of these phenomena is accounted for in current management programs. We examine alternative management measures that addre...

The Impact of United States Recreational Fisheries on Marine Fish Populations

Abstract: We evaluated the commercial and recreational fishery landings over the past 22 years, first at the national level, then for populations of concern (those that are overfished or experiencing overfishing), and finally by region. Recreational landings in 2002 account for 4% of total marine fish landed in the United States. With large industrial fisheries excluded (e.g., menhaden and pollock), the recreational component rises to 10%. Among populations of concern, recreational landings in 2002 account for 23% of the total nationwide, rising to 38% in the South Atlantic and 64% in the Gulf of Mexico. Moreover, it affects many of the most-valued overfished species-including red drum, bocaccio, and red snapper-all of which are taken primarily in the recreational fishery.

The behavioural dynamics of fishers: management implications

Abstract: In pursuing their livelihood, fishers develop strategies when faced with changes in regulations and other fishery conditions. Changes involve each individual in a decision‐making process governed by his/her own goals or constraints. Despite this reality, the complex dynamics of fishing has usually been ignored in designing management initiatives, which has contributed to management failures in many parts of the world. Fishers have generally been treated as fixed elements, with no consideration of individual attitudes based on their operating scales (geographical, ecological, social and economic) and personal goals. We review existing research on the social, economic and behavioural dynamics of fishing to provide insight into fisher behaviour and its implications for fisheries management. Emphasis is placed on fisher perception, and how fishers develop dynamic fishing tactics and strategies as an adaptive response to changes in resource abundance, environmental conditions and market or regulatory constraints. We conclude that knowledge of these dynamics is essential for effective management, and we discuss how such information can be collected, analysed and integrated into fisheries assessment and management. Particular emphasis is placed on small‐scale fisheries, but some examples from industrial fleets are provided to highlight similar issues in different types of fisheries.

Marine reserve benefits local fisheries

Abstract: The utility of no-take marine reserves as fisheries-management tools is controversial. It is hypothesized that marine reserves will help to sustain fisheries external to them by becoming net exporters of adults (the “spillover effect”) and net exporters of propagules (the “recruitment effect”). Local fishery benefits from spillover will likely generate support from fishing communities for marine reserves. We used underwater visual census to show that biomass of Acanthuridae (surgeonfish) and Carangidae (jacks), two families of reef fish that account for 40–75% of the fishery yield from Apo Island, Philippines, tripled in a well-protected no-take reserve over 18 years (1983–2001). Biomass of these families did not change significantly over the same period at a site open to fishing. The reserve protected 10% of the total reef fishing area at the island. Outside the reserve, biomass of these families increased significantly closer to (200–250 m) than farther away from (250–500 m) the reserve boundary over time. We used published estimates of fishery catch and effort, and fisher interviews (creel surveys) to show that the total catch of Carangidae and Acanthuridae combined at Apo Island was significantly higher after (1985–2001) than before (1981) reserve establishment. Hook-and-line catch per unit effort (CPUE) at the island was 50% higher during 1998–2001 (reserve protected 16–19 years) than during 1981–1986 (pre-reserve and early phases of reserve protection). Total hook-and-line effort declined by 46% between 1986 and 1998–2001. Hook-and-line CPUE of Acanthuridae was significantly higher close to (within 200 m) than far from the reserve. CPUE of Carangidae was significantly higher away from the reserve, possibly reflecting a local oceanographic effect. The benefits of the reserve to local fisheries at the island were higher catch, increased catch rate, and a reduction in fishing effort. The fishery and tourism benefits generated by the reserve have enhanced the living standard of the fishing community.

Fishing down the coast: historical expansion and collapse of oyster fisheries along continental margins.

Abstract: Estuarine ecosystems have changed dramatically from centuries of fishing, habitat disturbance, sedimentation, and nutrient loading. Degradation of oyster reefs by destructive fishing practices in particular has had a profound effect on estuarine ecology, yet the timing and magnitude of oyster-reef degradation in estuaries is poorly quantified. Here, I evaluate the expansion and collapse of oyster fisheries in 28 estuaries along three continental margins through the analysis of historical proxies derived from fishery records to infer when oyster reefs were degraded. Exploitation for oysters did not occur randomly along continental margins but followed a predictable pattern. Oyster fisheries expanded and collapsed in a linear sequence along eastern North America (Crassostrea virginica), western North America (Ostreola conchaphila), and eastern Australia (Saccostrea glomerata). Fishery collapse began in the estuaries that were nearest to a developing urban center before exploitation began to spread down the coast. As each successive fishery collapsed, oysters from more distant estuaries were fished and transported to restock exploited estuaries near the original urban center. This moving wave of exploitation traveled along each coastline until the most distant estuary had been reached and overfished.

Visualizing the Food-Web Effects of Fishing for Tunas in the Pacific Ocean

Abstract: We use food-web models to develop visualizations to compare and evaluate the interactions of tuna fisheries with their supporting food webs in the eastern tropical Pacific (ETP) and the central north Pacific (CNP) Oceans. In the ETP and CNP models, individual fisheries use slightly different food webs that are defined by the assemblage of targeted tuna species. Distinct energy pathways are required to support different tuna species and, consequently, the specific fisheries that target different tuna assemblages. These simulations suggest that catches of tunas, sharks, and billfishes have lowered the biomass of the upper trophic levels in both systems, whereas increases in intermediate and lower trophic level animals have accompanied the decline of top predators. Trade- offs between fishing and predation mortality rates that occur when multiple fisheries interact with their respective food webs may lead to smaller changes in biomass than if only the effect of a single fishery is considered. Historical simulations and hypothetical management scenarios further demonstrate that the effects of longline and purse seine fisheries have been strongest in upper trophic levels, but that lower trophic levels may respond more strongly to purse-seine fisheries. The apex predator guild has responded most strongly to longlining. Simulations of alternative management strategies that attempt to rebuild shark and billfish populations in each ecosystem reveal that (1) changes in longlining more effectively recover top predator populations than do changes in purse seining and (2) restrictions on both shallow-set longline gear and shark finning may do more to recover top predators than do simple reductions in fishing effort.

Are circle hooks an effective tool for conserving marine and freshwater recreational catch-and-release fisheries?

Abstract: Circle hooks have rapidly become popular among recreational anglers, based largely on the assumption that their use aids in the conservation of fisheries resources by reducing gut hooking, and hence mortality. In addition, circle hooks are intended to facilitate jaw hooking. Unfortunately, these assumptions have been perpetuated by anecdotal reports with very little rigorous scientific information to support these assertions. 2. A number of recently published, forthcoming, and grey literature reports provide an opportunity to review briefly and synthesize research conducted on circle hooks. We surveyed literature databases and also used questionnaires to solicit information from unpublished or in- progress circle hook research. 3. Although among studies the results have been quite disparate, overall the mortality rates were consistently lower for circle hooks than J-style hooks. In addition, circle hooks were more frequently hooked in the jaw, and less frequently hooked in the gut than conventional hook types. There is no doubt that in some marine fisheries, such as tuna, billfish, and striped bass, capture efficiency remains high and injury and mortality rates are drastically reduced. However, in other species (e.g. bluegill), injury can actually be more severe from circle hooks relative to some other hook types. In other species, such as largemouth bass, circle hooks have minimal conservation benefit, but have reduced capture efficiency relative to conventional hook designs. 4. Factors such as hook size, fishing style, fish feeding mode, and mouth morphology all appear to affect the effectiveness of circle hooks. For these reasons, it is difficult to promote the adoption of the use of circle hooks as a panacea for all fish and fisheries. Instead, we recommend that management agencies focus on recommending circle hooks only for instances for which appropriate scientific data exist. 5. The recent interest in circle hooks has been beneficial for stimulating interest and research on the role of hook designs in reducing hooking-related injury and mortality. We encourage tackle manufacturers to continue to develop new hook designs that have the potential to provide conservation benefit to caught and released fish. This paper provides direction to management

Fish abundance with no fishing: Predictions based on macroecological theory

Abstract: 1. Fishing changes the structure of fish communities and the relative impacts of fishing are assessed usefully against a baseline. A comparable baseline in all regions is fish community structure in the absence of fishing. 2. The structure of unexploited communities cannot always be predicted from historical data because fisheries exploitation usually precedes scientific investigation and non-fisheries impacts, such as climate change, modify ecosystems over time. 3. We propose a method, based on macroecological theory, to predict the abundance and size-structure of an unexploited fish community from a theoretical abundance-body mass relationship (size spectrum). 4. We apply the method in the intensively fished North Sea and compare the predicted structure of the unexploited fish community with contemporary community data. 5. We suggest that the current biomass of large fishes weighing 4-16 kg and 16-66 kg, respectively, is 97.4% and 99.2% lower than in the absence of fisheries exploitation. The results suggest that depletion of large fishes due to fisheries exploitation exceeds that described in many short-term studies. 6. Biomass of the contemporary North Sea fish community (defined as all fishes with body mass 64 g-66 kg) is 38% lower than predicted in the absence of exploitation, while the mean turnover time is almost twice as fast (falls from 3.5 to 1.9 years) and 70% less primary production is required to sustain it. 7. The increased turnover time of the fish community will lead to greater interannual instability in biomass and production, complicating management action and increasing the sensitivity of populations to environmental change. 8. This size-based method based on macroecological theory may provide a powerful new tool for setting ecosystem indicator reference levels, comparing fishing impacts in different ecosystems and for assessing the relative impacts of fishing and climate change.

Effects of Artisanal Fishing on Caribbean Coral Reefs

Abstract: Although the impacts of industrial fishing are widely recognized, marine ecosystems are generally considered less threatened by artisanal fisheries. To determine how coral reef fish assemblages and benthic communities are affected by artisanal fishing, we studied six Caribbean islands on which fishing pressure ranged from virtually none in Bonaire, increasing through Saba, Puerto Rico, St Lucia, and Dominica, and reaching very high intensities in Jamaica. Using stationary-point fish counts at 5 m and 15 m depth, we counted and estimated the lengths of all noncryptic, diurnal fish species within replicate 10-m-diameter areas. We estimated percent cover of coral and algae and determined reef structural complexity. From fish numbers and lengths we calculated mean fish biomass per count for the five most commercially important families. Groupers (Serranidae), snappers (Lutjanidae), parrotfish (Scaridae), and surgeonfish (Acanthuridae) showed order-of-magnitude differences in biomass among islands. Biomass fell as fishing pressure increased. Only grunts (Haemulidae) did not follow this pattern. Within families, larger-bodied species decreased as fishing intensified. Coral cover and structural complexity were highest on little-fished islands and lowest on those most fished. By contrast, algal cover was an order of magnitude higher in Jamaica than in Bonaire. These results suggest that following the Caribbean-wide mass mortality of herbivorous sea urchins in 1983–1984 and consequent declines in grazing pressure on reefs, herbivorous fishes have not controlled algae overgrowing corals in heavily fished areas but have restricted growth in lightly fished areas. In summary, differences among islands in the structure of fish and benthic assemblages suggest that intensive artisanal fishing has transformed Caribbean reefs.

Choerodon schoenleinii. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2

Abstract: Choerodon schoenleinii is a highly sought after food fish throughout its distribution. It is high on the list of regularly caught species by recreational fishers at surveyed locations in Western Australia and is a prized species in many areas of south-east Asia, including Sabah, Japan and Hong Kong. There has been a severe decline in its abundance in Hong Kong since the 1940s and it is now considered rare in that location (A. Cornish, pers. comm.; Cornish 2003). Choerodon schoenleinii is a large species, reaching up to 100 cm, and it is a monandric protogynous hermaphrodite, with very low numbers of males recorded in Shark Bay, Western Australia (Ebisawa et al. 1995, Fairclough in prep.). Those two studies demonstrated that male fish occur only in the largest size classes, i.e., > ca. 50 cm, and these are commonly the target of fishers, e.g., in Hong Kong (Cornish 2003). Heavy fishing pressure for local and live reef fish trade use would have rapidly reduced the numbers of males in assemblages of this species and would have undoubtedly contributed to its rapid decline in locations such as Hong Kong. It is also considered to be overexploited in Japan (Ebisawa et al. 1995). Thus, heavy fishing pressure coupled with the large scale use of destructive fishing practices in south-east Asia and overall low abundances in that region (Werner and Allen 2000, Allen and McKenna 2001) put this species at risk in a substantial proportion of its range. Choerodon schoenleinii should be considered to be Near Threatened and it almost meets the criteria for Vulnerable: VU A2cd and/or VU A3cd and/or VU A4cd. This species should be monitored regularly for further evidence of population decline/ or fragmentation and every effort made to obtain information on its fishery, especially in southeastern Asia and Japan.

Using an individual-based model of fish assemblages to study the response of size spectra to changes in fishing

Abstract: For most fish species, strong environmental constraints imposed by living in an aquatic medium have produced converging streamlined body forms without prehensile appendices. This similarity in body...

Mapping global fisheries: sharpening our focus

Abstract: Mapping global landings is an important prerequisite for examining causal relationships between fishing and ecological change. Landing statistics, typically provided with poor spatial precision, can be disaggregated into a grid system of spatial cells (30 min ·30 min) using a rule-based approach and ancillary data about distributions of fished taxa and fishing access of reporting countries. Presentation of time series catch composition is then possible for many types of marine areas including biogeochemical provinces, large marine ecosystems and exclusive economic zones.

Size structural change in lightly exploited coral reef fish communities: Evidence for weak indirect effects

Abstract: Exploitation influences community structure directly through preferential removal of larger-bodied fishes and indirectly because larger-bodied fishes may exert top-down control upon other community...

Western Africa: A Fish Basket of Europe Past and Present

Abstract: This article shows that despite increasing catches by foreign fishing fleets, the economic growth and social benefits from marine resources have not been met for many western African countries that host these fleets. A meta-analysis of changes in catches, market values, exports, imports, employment, access, and domestic supplies in western Africa since 1960 illustrates the impact of the expansion of distant-water fleets on not only the status of the marine resources and their ecosystems but also on the economic and social conditions of the people of western Africa. Finally, recommendations are made on appropriate management options for foreign fishing fleets and the key initiatives that could be considered by regional fish bodies and governments in western Africa.

The decline of a regional fishing nation: The case of Ghana and West Africa

Abstract: Inadequate trade policies, globalization of the fishing industry, dominance of Europe’s distant water fleets, declarations of exclusive economic zones (EEZs) by neighbouring West African nations, overfishing and a lack of good governance contributed to the decline of Ghana as a regional fishing nation, a position it had held since the 18 th century. The prohibitive cost of access arrangements limited Ghana’s access to distant waters. The country’s marine environments have been impacted by overexploitation of stocks and the use of destructive methods. Subsistence fishing has become the sole means of survival for many fishers. The decline of the fishing sector has limited the country’s ability to meet domestic demand and threatened the economic and food security of many Ghanaians. The article traces the early history of Ghana’s fisheries, their gradual decline during the last four decades, and outlines recommendations for policy changes to address the situation and steer the nation on a course towards sustainable fisheries.

The origins of intensive marine fishing in medieval Europe: the English evidence.

Abstract: The catastrophic impact of fishing pressure on species such as cod and herring is well documented. However, the antiquity of their intensive exploitation has not been established. Systematic catch statistics are only available for ca. 100 years, but large-scale fishing industries existed in medieval Europe and the expansion of cod fishing from the fourteenth century (first in Iceland, then in Newfoundland) played an important role in the European colonization of the Northwest Atlantic. History has demonstrated the scale of these late medieval and post-medieval fisheries, but only archaeology can illuminate earlier practices. Zooarchaeological evidence shows that the clearest changes in marine fishing in England between AD 600 and 1600 occurred rapidly around AD 1000 and involved large increases in catches of herring and cod. Surprisingly, this revolution predated the documented post-medieval expansion of England's sea fisheries and coincided with the Medieval Warm Period-when natural herring and cod productivity was probably low in the North Sea. This counterintuitive discovery can be explained by the concurrent rise of urbanism and human impacts on freshwater ecosystems. The search for 'pristine' baselines regarding marine ecosystems will thus need to employ medieval palaeoecological proxies in addition to recent fisheries data and early modern historical records.

HIV and AIDS among fisherfolk: a threat to 'responsible fisheries'?

Abstract: Fishing communities are often among the highest-risk groups in countries with high overall rates of HIV/AIDS prevalence Vulnerability to HIV/AIDS stems from complex, interacting causes that may include the mobility of many fisherfolk, the time fishermen spend away from home, their access to daily cash income in an overall context of poverty and vulnerability, their demographic profile, the ready availability of commercial sex in fishing ports and the subcultures of risk taking and hypermasculinity among some fishermen The subordinate economic and social position of women in many fishing communities in low-income countries makes them even more vulnerable HIV/AIDS in fishing communities was first dealt with as a public health issue, and most projects were conducted by health sector agencies and NGOs, focusing on education and health care provision More recently, as the social and economic impacts of the epidemic have become evident, wider social service provision and economic support have been added In the last 3 years, many major fishery development programmes in Africa, South/South-East Asia and the AsiaPacific region have incorporated HIV/AIDS awareness in their planning The HIV/ AIDS pandemic threatens the sustainability of fisheries by eclipsing the futures of many fisherfolk The burden of illness puts additional stresses on households, preventing them from accumulating assets derived from fishing income Premature death robs fishing communities of the knowledge gained by experience and reduces incentives for longer-term and inter-generational stewardship of resources Recent projects championing local knowledge and resource-user participation in management need to take these realities into account If the fishing communities of developing countries that account for 95% of the world’s fisherfolk and supply more than half the world’s fish are adversely impacted by HIV/AIDS, then the global supply of fish, particularly to lower-income consumers, may be jeopardized

Fishing Down Coastal Food Webs in the Gulf of California

Abstract: We used information from interviews with fishers, fisheries statistics, and field surveys to document changes in fisheries and fish assemblages in shallow coastal habitats in the Gulf of California, Mexico. Coastal food webs in the Gulf of California have been “fished down” during the last 30 years–fisheries shifted from large, long-lived species belonging to high trophic levels to small short-lived species from lower trophic levels. In addition, the maximum individual length of the landings has decreased about 45 cm in only 20 years. Although some catches are stagnant or still increasing for some species groups, catch-per-unit-effort declined for most species groups after 1980. These declines were associated to a dramatic increase in fishing effort in the region in the late 1970s-early 1980s, mostly in the number of gillnets. Fishing not only impacted target species, but also caused community-wide changes. These results suggest that coastal fisheries in the Gulf of California are unsustainable a...

Ecosystem effects of fishing in the mediterrean: an analysis of the major threats of fishing gear and practices to biodiversity and marine habitats

Abstract: Most of the major impacts of fishing on the ecosystems recorded around the world occur in the Mediterranean. They vary from local effects on the sea bottom caused by trawler gears to large-scale impacts on cetacean populations driven by driftnet bycatch. This variety – which makes the Mediterranean a unique global model for the implementation of the Ecosystem Approach to Fisheries – is due to four main interrelated factors: the huge diversity of fishing gears and practices, the very high intensity of fishing, a high diversity of habitats distributed from the shallow-waters to the deep-sea and the oceanic domain, and an important biological diversity. The latter is demonstrated by the Mediterranean presence of a vast array of vulnerable species, many of them listed in international protection agreements that include emblematic sharks, turtles, whales and seals. Mediterranean fisheries are not an exception in the context of the general declining trend shown by elasmobranch populations and their fisheries around the world. Information indicating to unsustainable catch rates of rays (including the disappearance of certain taxa from commercial catches) and other demersal species deserves special concern. The high elasmobranch bycatches – and even commercial catches – achieved in many pelagic fisheries, notably longlining and driftnetting, also appear to be a potential danger for several species. Longline fishing is also the main cause of seabird mortality in Mediterranean fisheries. Indirect effects of fishing on seabirds related to food availability, driven by discards, are particularly important. Fishing in the Mediterranean basin is clearly a major threat to marine turtle populations, which are massively bycaught. Longline fleets are a major threat in the whole region, particularly on the Loggerhead turtle population, as are trawlers and small-scale gears in particular areas, such as the Gulf of Gabes. The special vulnerability of marine turtles to high mortality rates of adults and sub-adults makes the maximization of the survival of individuals at sea a conservation priority. As for marine mammals, the information available describes a wide variety of interactions between cetacean populations and fishing fleets in the Mediterranean, involving almost every kind of major fishing gear commonly in use. However, driftnet fisheries and, to a much lesser extent, small-scale fisheries using fixed nets and purse seine fisheries appear to account for the highest impact and are also responsible for the highest rates of direct human-induced mortality. The reduced population of monk seal in the Mediterranean is also victim of both direct mortality by artisanal fishing gears and an increasing scarcity of food resources driven by overfishing. The impact of fishing on the seabed concerns mostly the use of bottom-trawling gears, namely otter trawls, beam trawls and dredges, together with some aggressive practices affecting rocky bottoms such as dynamite fishing and fishing for coral and date mussels. Trawling impacts on seagrass beds by both suspending sediments and directly damaging the vegetal mass, have the most dramatic consequences on Posidonia beds. As for particular fishing gears, bottom trawling, longlining and driftnets arise as those with most impact on marine ecosystems in the whole Mediterranean region. Evidence shows that the effects of fishing in the Mediterranean go far beyond the isolated impacts on overfished target species, vulnerable non-commercial groups or sensitive habitats. The ecosystem effects of fishing in the Mediterranean are also conspicuous at the systemic level, as highlighted by the massive ecological footprint of fishing or the marked effects on the foodweb structure. A holistic approach should therefore be adopted if the overall changes to the structure and the functioning of marine ecosystems caused by fishing are to be remedied.

Fisheries and Energy Use

Abstract: active fishing gear Equipment used for fishing in which the aquatic organisms being targeted encounter the gear primarily through movement of the gear itself. Examples include cast nets, dredges, harpoons, jigs, and all forms of seine and trawl fishing. animate energy Energy dissipated through the application of human or animal muscles to do work. artisanal fisheries Small-scale fisheries that are typically executed by members of fishing households (as opposed to commercial companies) in which relatively small amounts of capital and energy and relatively small, if any, fishing vessels are employed. culturally mediated energy All forms of energy dissipated through the application of technologies in the process of human activities. energy intensity The amount of culturally mediated energy required to provide a given quantity of a product or service of interest. In the current context, energy intensity is expressed either as the total joules of energy required to land a live weight or ‘‘round’’ tonne of fish or shellfish harvested, or in terms of fuel use intensity, the total liters of fuel burned directly on fishing vessels per tonne of fish or shellfish landed. energy return on investment (EROI) ratio A dimensionless ratio calculated by dividing the amount of useful energy provided by a given activity by the culturally mediated energy dissipated in providing it. In the case of food production systems, a common energy output used to calculate the EROI is the edible protein energy yield from the system being evaluated. fishing Any activity that results in the catching, collecting, or harvesting of fish, and or aquatic invertebrates for any purpose other than scientific research. In the current context, the harvesting of aquatic plants and mammals is not considered as fishing, nor is aquaculture. industrial fisheries Those fisheries typically undertaken by commercial companies in which relatively large quantities of capital and energy are deployed. net primary productivity (NPP) The difference between the total amount of carbon taken up by plants via photosynthesis and the amount of carbon lost by living plants via respiration. passive fishing gear Equipment used for fishing in which the aquatic organisms being targeted encounter the gear primarily through their own movement or as a result of the movement of the surrounding waters. Examples include all forms of hook and line gears, drift nets, gillnets, traps, and weirs.

The effects of size-selective fisheries on the stock dynamics of and sperm limitation in sex-changing fish

Abstract: Fisheries models have traditionally focused on patterns of growth, fecundity, and survival of fish. However, reproductive rates are the outcome of a variety of interconnected factors such as life-history strategies, mating patterns, population sex ratio, social interactions, and individual fecundity and fertility. Behaviorally appropriate models are necessary to understand stock dynamics and predict the success of management strategies. Protogynous sex-changing fish present a challenge for management because size-selective fisheries can drastically reduce reproductive rates. We present a general framework using an individual-based simulation model to determine the effect of life-history pattern, sperm production, mating system, and management strategy on stock dynamics. We apply this general approach to the specific question of how size-selective fisheries that remove mainly males will impact the stock dynamics of a protogynous population with fixed sex change compared to an otherwise identical dioecious population. In this dioecious population, we kept all aspects of the stock constant except for the pattern of sex determination (i.e. whether the species changes sex or is dioecious). Protogynous stocks with fixed sex change are predicted to be very sensitive to the size-selective fishing pattern. If all male size classes are fished, protogynous populations are predicted to crash even at relatively low fishing mortality. When some male size classes escape fishing, we predict that the mean population size of sex-changing stocks will decrease proportionally less than the mean population size of dioecious species experiencing the same fishing mortality. For protogynous species, spawning-per-recruit measures that ignore fertilization rates are not good indicators of the impact of fishing on the population. Decreased mating aggregation size is predicted to lead to an increased effect of sperm limitation at constant fishing mortality and effort. Marine protected areas have the potential to mitigate some effects of fishing on sperm limitation in sex-changing populations.

Endangered species: where leatherback turtles meet fisheries.

Abstract: The dramatic worldwide decline in populations of the leatherback turtle (Dermochelys coriacea) is largely due to the high mortality associated with their interaction with fisheries, so a reduction of this overlap is critical to their survival. The discovery of narrow migration corridors used by the leatherbacks in the Pacific Ocean raised the possibility of protecting the turtles by restricting fishing in these key areas. Here we use satellite tracking to show that there is no equivalent of these corridors in the North Atlantic Ocean, because the turtles disperse actively over the whole area. But we are able to identify a few 'hot spots' where leatherbacks meet fisheries and where conservation efforts should be focused.