Showing papers on "Fishing published in 1999"

Implications of fish home range size and relocation for marine reserve function

Abstract: Reserves are being used increasingly to conserve fish communities and populations under threat from overfishing, but little consideration has been given to how fish behavior might affect reserve function. This review examines the implications of how fish use space, in particular the occurrence and size of home ranges and the frequency and direction of home range relocations. Examples are drawn primarily from the literature on coral reef fishes, but the principles apply to other habitats. Reserves can protect fish species only if individuals restrict their movements to a localized home range during at least part of the life cycle. Home range sizes increase with body size. In small reserves, a significant proportion of fish whose home ranges are centered within the reserve can be exposed to fishing mortality because their home ranges include non-reserve areas. Relocation of home ranges following initial settlement increases exposure to the fishery, especially if habitat selection is frequency-dependent. Distance, barriers, and costs of movement counter such redistribution. These considerations lead to predictions that population density and mean fish size (1) will form gradients across reserve boundaries with maxima in the center of the reserve and minima outside the reserve away from the boundary; (2) will increase rapidly in newly established reserves, only later providing ‘spillover’ to adjacent fisheries as density-dependent emigration begins to take effect; and (3) will be higher in reserves that are larger and have higher area:edge ratios, more habitat types, natural barriers between reserve and non-reserve areas, and higher habitat quality inside than outside the reserve. (4) Species with low mobility and weak density-dependence of space use will show the greatest increase in reserves and the strongest benefit for population reproductive capacity, but those with intermediate levels of these traits will provide the greatest spillover benefit to nearby fisheries.

Structural change in an exploited fish community: a consequence of differential fishing effects on species with contrasting life histories

Abstract: 1. An understanding of the links between life histories and responses to exploitation could provide the basis for predicting shifts in community structure by identifying susceptible species and linking life-history tactics with population dynamics. 2. We examined long-term trends in the abundance of species in the North Sea bottom-dwelling (demersal) fish community. Between 1925 & 1996 changes in species composition led to an increase in mean growth rate, while mean maximum size, age at maturity and size at maturity decreased. The demersal fish community was increasingly heavily fished during this period. 3. Trends in mean life-history characteristics of the community were linked to trends in abundance of component species. An approach based on phylogenetic comparisons was used to examine the differential effects of fishing on individual species with contrasting life histories. 4. Those species that decreased in abundance relative to their nearest relative, matured later at a greater size, grew more slowly towards a greater maximum size and had lower rates of potential population increase. The phylogenetically based analyses demonstrated that trends in community structure could be predicted from the differential responses of related species to fishing. 5. This is the first study to link exploitation responses of an entire community to the life histories of individual species. The results demonstrate that fishing has greater effects on slower growing, larger species with later maturity and lower rates of potential population increase. The comparative approach provides a basis for predicting structural change in other exploited communities.

Ichthyofaunal assemblages in estuaries: A South African case study

Abstract: This review places the life-history styles of fishes associated with South African estuaries in a global context and presents a classification system incorporating all the major life-history categories for estuary-associated fish species around the world. In addition, it documents the early life histories of the major fish groups in South African estuaries, with particular emphasis on the differing modes of estuarine utilization by marine, estuarine and freshwater taxa. This review details factors influencing the ichthyofaunal community structure in South African estuaries. The availability of fish for recruitment into an estuary depends primarily upon the distributional range of euryhaline marine and estuarine species, with tropical and temperate taxa showing marked abundance trends. Within a particular biogeographic region, however, estuarine type and prevailing salinity regime have a major influence on the detailed ichthyofaunal structure that develops. There is an increasing preponderance of marine fish taxa when moving from a freshwater-dominated towards a seawater-dominated type of system, and a decline in species diversity between subtropical estuaries in the north-east and cool temperate systems in the south-west. Similar declines in fish species diversity between tropical and temperate estuaries in other parts of the world are highlighted. Fish assemblages in estuaries adjust constantly in response to changing seasons, salinities, turbidities, etc. Despite persistent fluctuations in both the biotic and abiotic environment, the basic ichthyofaunal structure appears to have an underlying stability and to be predictable in terms of the response of individual species to specific conditions. This stability seems to be governed by factors such as the dominance of eurytopic taxa within estuarine assemblages and the robust nature of food webs within these systems. The predictability arises from factors such as the seasonality associated with estuarine spawning cycles and juvenile fish recruitment patterns. These patterns, together with a well-documented resilience to a wide range of physico-chemical and biotic perturbations, appear to be an underlying feature of fish assemblages in estuaries around the world. In contrast to marine fish species, estuary-associated taxa have received little conservation attention. Apart from the designation of protected areas, the main direct means of conserving estuary-associated fish stocks include habitat conservation and controls over fishing methods, effort, efficiency and seasonality. Of these, the conservation of fish habitats, the most important, because healthy aquatic environments invariably support healthy fish populations. The use of estuarine sanctuaries for fish conservation is briefly reviewed, as well as the legislation governing the USA National Estuarine Research Reserve System (NERRS) and the Australian Marine and Estuarine Protected Area (MEPA) system. It is concluded that South Africa requires an expansion of the existing Estuarine Protected Area (EPA) network, as well as the upgrading of selected 'estuarine reserves' where fishing is permitted, into 'estuarine sanctuaries' where no exploitation of biological resources is allowed.

Fishing impacts and the degradation or loss of habitat structure

Abstract: The wider effects of fishing on marine ecosystems have become the focus of growing concern among scientists, fisheries managers and the fishing industry. The present review examines the role of habitat structure and habitat heterogeneity in marine ecosystems, and the effects of fishing (i.e. trawling and dredging) on these two components of habitat complexity. Three examples from New Zealand and Australia are considered, where available evidence suggests that fishing has been associated with the degradation or loss of habitat structure through the removal of large epibenthic organisms, with concomitant effects on fish species which occupy these habitats. With ever-increasing demands on fish-stocks and the need for sustainable use of fisheries resources, new approaches to fisheries management are needed. Fisheries management needs to address the sustainability of fish-stocks while minimizing the direct and indirect impacts of fishing on other components of the ecosystem. Two long-term management tools for mitigating degradation or loss of habitat structure while maintaining healthy sustainable fisheries which are increasingly considered by fisheries scientists and managers are: (1) protective habitat management, which involves the designation of protected marine and coastal areas which are afforded some level of protection from fishing; and (2) habitat restoration, whereby important habitat and ecological functions are restored following the loss of habitat and/or resources. Nevertheless, the protection of marine and coastal areas, and habitat restoration should not be seen as solutions replacing conventional management approaches, but need to be components of an integrated programme of coastal zone and fisheries management. A number of recent international fisheries agreements have specifically identified the need to provide for habitat protection and restoration to ensure long-term sustainability of fisheries. The protection and restoration of habitat are also common components of fisheries management programs under national fisheries law and policy.

Hyperaggregation of fish and fisheries: how catch-per-unit-effort increased as the northern cod (Gadus morhua) declined

Abstract: Misinterpretations of elevated catch-per-unit-effort (CPUE) in the northern cod (Gadus morhua) fishery contributed to overestimations of stock size, inflated quotas, and unsustainable fishing morta...

Fisheries benefits and optimal design of marine reserves

Abstract: We used fishery population models to assess the potential for ma- rine fishery reserves, areas perma- nently closed to fishing, to enhance long-term fishery yields. Our models included detailed life history data. They also included the key assumptions that adults did not cross reserve boundaries and that larvae mixed thoroughly across the boundary but were retained sufficiently to produce a stock-recruit- ment relationship for the management area. We analyzed the results of these models to determine how reserve size, fishing mortality, and life history traits, particularly population growth poten- tial, affected the fisheries benefits from reserves. We predict that reserves will enhance catches from any overfished population that meets our assumptions, particularly heavily overfished popula- tions with low population growth po- tential. We further predict that re- serves can enhance catches when they make up 40% or more of fisheries man- agement areas, significantly higher proportions than are typical of existing reserve systems. Finally, we predict that reserves in systems that meet our assumptions will reduce annual catch variation in surrounding fishing grounds. The fisheries benefits and optimal design of marine reserves in any situation de- pended on the life history of the spe- cies of interest as well as its rate of fish- ing mortality. However, the generality of our results across a range of species suggest that marine reserves are a vi- able fisheries management alternative. ies have generally demonstrated that fish stocks build up within a protected area (Roberts and Polunin, 1991; Dugan and Davis, 1993; Rowley, 1994; Bohnsack, 1996, and references within) but much less information exists on fishery enhancements. In theory, reserves can maintain productive fisheries by protecting a critical stock within their borders. These stocks may enhance catches through adults that grow larger in the reserve and then migrate to fishing areas (adult spillover), or through enhanced recruitment in fishing areas due to increased popu- lation fecundity from the reserve (larval transport). In practice, fish- eries benefits from reserves have rarely been demonstrated or even measured. This lack of field evi- dence reflects the difficulty of per- forming controlled and replicated experiments in unpredictable politi- cal and biological systems. The few existing field studies ad- dressing fisheries benefits from re- serves show promise. A marine fish- ery reserve encompassing over 60% of the former fishing grounds north of Mombasa, Kenya, showed a 110% increase in catch per unit of effort after only two years (McClanahan and Kaunda-Arara, 1996). Total catches had not yet met those prior to reserve establishment, but trends looked favorable. On Apo Island, Philippines, total fish density and

An empirical model of fleet dynamics in New England trawl fisheries

Abstract: Regulations and changes in market and environmental conditions that change the profitability of one fishery or area will result in a redistribution of fishing effort among alternative fisheries or ...

A Case History of Effective Fishery Management: Chesapeake Bay Striped Bass

Abstract: Stocks of anadromous striped bass Morone saxatilis of the Atlantic coast have supported important fisheries since colonial times. Commercial landings reached a record high in 1973, then declined by almost 90% during the following decade. Juvenile production by the Chesapeake Bay stock, a major contributor to coastal fisheries, was depressed during the 1970s. These patterns prompted efforts to identify why striped bass had declined and to rebuild the Chesapeake Bay stock. We review the history of the striped bass decline and the science, management, and legislation that led to its recovery. Historical data and modeling results indicated that recruitment overfishing was a major factor in the decline. Juvenile production may have been further depressed by water quality problems that reduced survival of early life stages. Mathematical models demonstrated that reducing fishing mortality would immediately increase population growth rate, regardless of the decline's cause. An Interstate Fishery Manageme...

Management histories of Sumilon and Apo Marine Reserves, Philippines, and their influence on national marine resource policy

Abstract: The histories of management of the Sumilon and Apo marine reserves in the Philippines provide a stark contrast. Both began with marine conservation and education programs at the community level, initiated by the Marine Laboratory of Silliman University in 1973 at Sumilon, and in 1976 at Apo. At both islands community support for the “no take” reserve concept evolved gradually, via perceived benefits of increased local fish yields and income from tourism. However, Sumilon reserve has been fished down twice (in 1984,1992), and was still being fished in December 1998. Apo reserve has been protected from fishing successfully for 16 y (1982–1998). The management histories of these two marine reserves are the longest and most detailed available for coral reefs. Scientific data spanning 1976–1993 for Sumilon and 1980–1993 for Apo have provided some of the best available evidence of the utility of such reserves as management tools in coral reef fisheries. At Sumilon, collapse of reserve protection in 1984, after 9.5 y of restrictions on fishing, led to significant declines in reef fisheries yields in areas adjacent to the reserve. At Apo, continuous protection from 1982 to 1993 has led to consistent build up of fish in the reserve and some evidence that local fish yields have increased. The unique time series of scientific data obtained from Sumilon and Apo islands are the result of their distinct management histories. The greater success of management at Apo was due to community support for the reserve concept being actively maintained for the past 16 y. Socio-political factors caused the level of community support for the Sumilon reserve to wax and wane over this period. Both case histories have had a profound effect on marine resource management in the Philippines. As marine reserve models they had substantial influence on the design of the National Integrated Protected Area System (NIPAS). Policy now encourages co-management between the National government and local communities, with a strong emphasis on decentralization of decision making and recognition of local territorial use rights in fisheries.

Movements of adult Atlantic salmon in relation to a hydroelectric dam and fish ladder

Abstract: The movements of adult Atlantic salmon were recorded as they approached, entered and ascended the pool-and-orifice fish ladder at Pitlochry Dam, Scotland. Thirty-nine returning salmon were captured in the River Tummel by rod-and-line angling, radio-tagged and released near where they were caught. The subsequent movements of each fish were then monitored. An electronic fish counter collected additional data on movements of untagged fish past a fixed point in the ladder. Of the 39 fish that were radio-tagged, 29 individuals were recorded approaching and ascended the ladder. The remaining fish either did not approach the dam (three fish), approached the dam after detailed tracking had ended (two fish), were recaptured by anglers (three fish), or the radio tags failed (two fish). Salmon released earlier in the year delayed longer before first approaching the dam. Delays between first approaching the dam and ascent of the ladder were greater for fish that approached the dam earlier. The majority of salmon visited the ladder entrance more than once (maximum 10 visits) before ascending. Having entered, all but four salmon ascended the fish ladder successfully on their first attempt. The four individuals that failed to do so succeeded on their second attempt. The rate at which salmon ascended the ladder was related directly to temperature. The shortest ascent time of a radio-tagged salmon was 5·25 h. Movements of eight of 11 tagged fish through the ladder ceased with the onset of darkness but continued on the following morning. No radio-tagged fish entered the ladder at temperatures below 9) C. Similarly, few untagged fish were recorded ascending the ladder by the electronic fish counter at water temperatures below 8·5) C. Records from the fish counter indicated that 92% of upstream movements were made during daylight.

A review of a model for qualitative evaluation of exploitation levels in multi-species fisheries

Abstract: The fauna of inland waters, especially in the tropics, consist of complex assemblages of numerous species, which are not accessible to analysis by conventional stock assessment methods. The formulation of policies for management and conservation requires alternative models which are capable of predicting the ways in which such assemblages change in response to fishing or other stresses. Historically, models which group species according to simple parameters have proved adequate to provide the level of advice needed to indicate ecosystem health and sustainability of yield from the fishery. Such models have received relatively little attention, and can be profitably further developed and refined. The present review concludes that, out of the various explanatory variables, the mean length of fish caught is one of the most significant together with the numbers of species in the catch and the time taken for catches in fluctuating systems to respond to floods. More complex indicators are based on emergent characteristics of the system such as the production:biomass or predator:prey ratios. Three major strategies are identified for management based on responses of fish assemblages to increases in effort.

Skipper skill and panel data in fishing industries

Abstract: Skipper skill or managerial ability plays a central role in the harvesting of fish and fishing power. Examining the influences of managerial ability on catch rates, however, may be complicated, since managerial ability is generally unobservable. Using panel data on production activities in the Pacific Coast trawl fishery, we examine the use of the fixed- and random-effects panel data models to depict managerial skill by intervessel differences, representing differences in technical efficiency. The random-effects production model is selected over the fixed-effects model. We conclude that skipper skill is more related to finding fish, dealing with unforseen events, and handling inclement weather than it is to managing the economic inputs.

An economic analysis of blast fishing on Indonesian coral reefs

Abstract: Characteristics, impacts and economic costs and benefits of blast fishing have been little investigated and they were therefore studied in Indonesia, at the scale of individual fishing households and of Indonesian society as a whole. Although illegal and highly destructive to coral reefs, blast fishing provides income and fish to a vast number of coastal fishers who claim that they have no alternative to make a living. Crew members in small-, medium- and large-scale blast fishing operations earned net incomes per month of US33 900 per km2 of coral reef where there is a low potential value. The main quantifiable costs are through loss of the coastal protection function, foregone benefits of tourism, and foregone benefits of non-destructive fisheries. The economic costs to society are four times higher than the total net private benefits from blast fishing in areas with high potential value of tourism and coastal protection. This analysis of characteristics, impact and economics of blast fishing should help to raise the political will to ban blast fishing from Indonesian waters. Moreover, it allows for an evaluation of possible management solutions, taking into account their costs and the socio-economic framework that caused coastal fishers to start using explosives.

Factors in Exposure Assessment: Ethnic and Socioeconomic Differences in Fishing and Consumption of Fish Caught along the Savannah River

Abstract: South Carolina has issued fish consumption advisories for the Savannah River based on mercury and radionuclide levels We examine differences in fishing rates and fish consumption of 258 people interviewed while fishing along the Savannah River, as a function of age, education, ethnicity, employment history, and income, and test the assumption that the average consumption of fish is less than the recreational value of 19 kg/year assumed by risk assessors Ethnicity and education contributed significantly to explaining variations in number of fish meals per month, serving size, and total quantity of fish consumed per year Blacks fished more often, ate more fish meals of slightly larger serving sizes, and consumed more fish per year than did Whites Although education and income were correlated, education contributed most significantly to behavior; people who did not graduate from high school ate fish more often, ate more fish per year, and ate more whole fish than people who graduated from high school Computing consumption of fish for each person individually indicates that (1) people who eat fish more often also eat larger portions, (2) a substantial number of people consume more than the amount of fish used to compute risk to recreational fishermen, (3) some people consume more than the subsistence level default assumption (50 kg/year) and (4) Blacks consume more fish per year than Whites, putting them at greater risk from contaminants in fish Overall, ethnicity, age, and education contributed to variations in fishing behavior and consumption

Habitat-mediated survivorship of juvenile (0-year) Atlantic cod Gadus morhua

Abstract: Fishing activity can impact fish populations in 2 ways. The first is the immediate effect on population demographics by the removal of fish. Second is the impact of fishing (e.g. bottom trawls and dredges) on the seafloor which can reduce habitat structure and thus increase the vulnerability of juvenile fish to predation by older conspecifics and other predators. We conducted laboratory experiments to investigate the role of variability in seafloor habitat structure on the survivorship of post-settlement juvenile (0-yr) Atlantic cod Gadus morhua. Groups of 0-yr cod were exposed to a foraging predator (3+ cod) over 5 seafloor habitats of varying complexity (sand, cobble, minimum density short sponge, maximum density short sponge, and tall sponge). These habitats were selected to mimic the range of impacts of mobile fishing gear given a gradient in fishing effort. Emergent epifauna resulted in a significant decrease in 0-yr mortality when compared to flat sand, the least complex habitat. Epifaunal density was shown to be more significant than epifaunal height in reducing 0-yr mortality. Predator reaction distance decreased with increasing habitat complexity, presumably due to the obstruction of visual cues by complex relief. Latency to first and second capture did not differ statistically between habitats. Alteration of seafloor habitat by fishing activity in the northwest Atlantic could magnify the effects of overfishing by limiting juvenile survivorship.

A history of change: causes of miombo woodland decline in a protected area in Malawi

Abstract: 1. Tropical dry woodlands are thought to be declining as a result of human activity. Aerial photograph analysis showed measurable conversion of closed canopy miombo* to sparse woodland in Lake Malawi National Park, Malawi, from 1982 to 1990. This multi-disciplinary study investigates the possible contributions to these impacts by local use of domestic fuelwood, construction poles and fuelwood for commercial fish smoking. 2. Domestic fuelwood use was measured in 30 households over an 11-month period. Domestic fuelwood is collected by women and is headloaded to the village. It comprises a large biomass of mainly dead wood and small branches over a wide species range. Mean total annual domestic fuelwood consumption by the total enclave population was less than half the mean annual production of fallen dead wood in the Park, estimated from three quadrats harvested monthly over an 11-month period. 3. Construction poles are mostly small, have extended durability and come from a broad species range. Fencing poles frequently take root to form live hedges. Eucalyptus trees are commonly grown for poles. Construction pole use appears sustainable and shows signs of substitution. 4. The 305 commercial fish smoking stations in the enclaves used less fuelwood annually than domestic fuelwood users. However, the men who undertake this activity target large branches and logs from a narrow species range, involving destructive felling of canopy species. 95% of men collecting fuel for fish smoking use cutting tools and three-quarters transport the wood by boat or bicycle. 5. The scale, size classes and species involved in commercial fish smoking suggest that this activity drives the observed degradation of closed canopy to sparse woodland. Traditional local fishing focused on small species sun-dried for preservation. Commercial fish smoking was introduced relatively recently by immigrants, along with gill netting that harvests larger fish requiring smoking for preservation. Demand for fish by ever-increasing urban populations underpins the continuing growth of the fish smoking industry. 6. Disaggregation of different wood use practices allows informed management policy for the Park. Currently, management targets and penalizes domestic fuelwood collectors. While seeking to reduce demand and provide alternative fuelwood sources, law enforcement and forestry extension should be reorientated to address the extraction of fuelwood for fish smoking.

The Bioeconomics of Marine Sanctuaries

Abstract: Consider an offshore fishing grounds of size K. Suppose the grounds has been overfished to the point that net revenue has been driven to zero and the fishery is in open access equilibrium at (X∞, Y∞). A marine sanctuary, where fishing is prohibited, is then created. Suppose the marine sanctuary is of size K2 and that fishing is allowed on a smaller grounds, now of size K1, where K1 + K2 = K. In the first, deterministic, model, the present value of net revenue from the grounds-sanctuary system is maximized subject to migration (diffusion) of fish from the sanctuary to the grounds. The size of the sanctuary is varied, the system is re-optimized, and the populations levels, harvest, and value of the fishery is compared to the 'no-sanctuary' optimum, and the open access equilibrium. In the deterministic model, a marine sanctuary reduces the present value of the fishery relative to the 'ideal' of optimal management of the original grounds. In the second model net growth is subject to stochastic fluctuation. Simulation demonstrates the ability of a marine sanctuary to reduce the variation in biomass on the fishing grounds. Variance reduction in fishable biomass is examined for different-sized sanctuaries when net growth on the grounds and in the sanctuary fluctuate independently and when they are perfectly correlated. For the stochastic model of this paper, sanctuaries ranging in size from 60 to 40% of the original grounds (0.6 ≥ K2/K ≥ 0.4) had the ability to lower variation in fishable biomass compared to the no sanctuary case. For a sanctuary equal to or greater than 70% of the original grounds (K2 ≥ 0.7K), net revenue would be nonpositive and there would be no incentive to fish.

Fishing in urban New Jersey: ethnicity affects information sources, perception, and compliance.

Abstract: Recreational and subsistence angling are important aspects of urban culture for much of North America where people are concentrated near the coasts or major rivers. Yet there are fish and shellfish advisories for many estuaries, rivers, and lakes, and these are not always heeded. This paper examines fishing behavior, sources of information, perceptions, and compliance with fishing advisories as a function of ethnicity for people fishing in the Newark Bay Complex of the New York–New Jersey Harbor. We test the null hypothesis that there were no ethnic differences in sources of information, perceptions of the safety of fish consumption, and compliance with advisories. There were ethnic differences in consumption rates, sources of information about fishing, knowledge about the safety of the fish, awareness of fishing advisories or of the correct advisories, and knowledge about risks for increased cancer and to unborn and young children. In general, the knowledge base was much lower for Hispanics, was intermediate for blacks, and was greatest for whites. When presented with a statement about the potential risks from eating fish, there were no differences in their willingness to stop eating fish or to encourage pregnant women to stop. These results indicate a willingness to comply with advisories regardless of ethnicity, but a vast difference in the base knowledge necessary to make informed risk decisions about the safety of fish and shellfish. Although the overall median income level of the population was in the $25,000–34,999 income category, for Hispanics it was on the border between $15,000–24,999 and $25,000–34,999.

Modeling the effects of land use and climate change on riverine smallmouth bass

Abstract: Anthropogenic changes in temperature and stream flow, associated with watershed land use and climate change, are critical influences on the distribution and abundance of riverine fishes. To project the effects of changing land use and climate, we modeled a smallmouth bass (Micropterus dolomieu) population in a midwestern USA, large river–floodplain ecosystem under historical (1915–1925), present (1977–1990), and future (2060, influenced by climate change) temperature and flow regimes. The age-structured model included parameters for temperature and river discharge during critical seasonal periods, fish population dynamics, and fishing harvest. Model relationships were developed from empirical field data collected over a 13-yr period. Sensitivity analyses indicated that discharge during the spawning/rearing period had a greater effect on adult density and fishing yield than did spawning/rearing temperature or winter discharge. Simulations for 100 years projected a 139% greater mean fish density under a historical flow regime (64.9 fish/ha) than that estimated for the present (27.1 fish/ha) with a sustainable fishing harvest under both flow regimes. Simulations under future climate-change-induced temperature and flow regimes with present land use projected a 69% decrease in mean fish density (8.5 fish/ha) from present and an unstable population that went extinct during 56% of the simulations. However, when simulated under a future climate-altered temperature and flow regime with historical land use, the population increased by 66% (45.0 fish/ha) from present and sustained a harvest. Our findings suggest that land-use changes may be a greater detriment to riverine fishes than projected climate change and that the combined effects of both factors may lead to local species extinction. However, the negative effects of increased temperature and precipitation associated with future global warming could be mitigated by river channel, floodplain, and watershed restoration.

Potential effects of maternal factors on spawning stock-recruitment relationships under varying fishing pressure

Abstract: The use of spawning stock biomass as a direct measure of reproductive potential may not be valid because of age- or size-specific differences in fecundity and the effect of maternal size and condition on offspring viability. In this study, we examine the potential significance of these effects using modelled Atlantic cod (Gadus morhua) populations. We quantify how changes in the age composition of the spawning stock, due to a range of fishing pressures and under different stock-recruitment relationships, could influence the reproductive output. Quantitative comparisons were made between a "standard" population where all age-classes only suffer natural instantaneous mortality (M = 0.2) and populations that suffer increasing levels of fishing pressure (F = 0.0-1.0). The results of the modelling exercise suggests that if the effects of the loss of more fecund older/larger individuals in the population are not considered, the number of potential recruits produced by populations under higher levels of fishing ...

Bony fishes part 2 (mugilidae to carangidae)

Abstract: This multivolume field guide covers the species of interest to fisheries of the major marine resource groups exploited in the Western Central Pacific. The area of coverage includes FAO Fishing Area 71 and the southwestern portion of Fishing Area 77 corresponding to the South Pacific Commission mandate area. The marine resource groups included are seaweeds, corals, bivalves, gastropods, cephalopods, stomatopods, shrimps, lobsters, crabs, holothurians, sharks, batoid fishes, chimaeras, bony fishes, estuarine crocodiles, sea turtles, sea snakes and marine mammals. The introductory chapter outlines the environmental, ecological and biogeographical factors influencing the marine biota as well as the basic components of the fisheries in the Western Central Pacific. Within the field guide, the sections on the resource groups are arranged phylogenetically according to higher taxonomic levels such as class, order and family. Each resource group is introduced by general remarks on the group, an illustrated section on technical terms and measurements and a key or guide to orders or families. Each family generally has an account summarising family diagnostic characters, biological and fisheries information, notes on similar families occurring in the area, a key to species, a checklist of species and a short list of relevant literature. Families that are less important to fisheries include an abbreviated family account and no detailed species information. Species in the important families are treated in detail (arranged alphabetically by genus and species) and include the species name, frequent synonyms and names of similar species, an illustration, FAO common name(s), diagnostic characters, biology and fisheries information, notes on geographical distribution and a distribution map. For less important species, abbreviated accounts are used. Generally, this includes the species name, FAO common name(s), an illustration, a distribution map and notes on biology, fisheries and distribution. Each volume concludes with its own index of scientific and common names.

Effectiveness of an Existing Estuarine No-Take Fish Sanctuary within the Kennedy Space Center, Florida

Abstract: Approximately 22% of the waters of the Merritt Island National Wildlife Refuge, which encompasses the Kennedy Space Center, Florida, have been closed to public access and fishing since 1962. These closed areas offer an opportunity to test the effectiveness of “no-take” sanctuaries by analyzing two replicated estuarine areas. Areas open and closed to fishing were sampled from Nov 1986 to Jan 1990 with 653 random trammel-net sets, each enclosing 3,721 m2. Samples from no-fishing areas had significantly (P < 0.05) greater abundance and larger fishes than fished areas. Relative abundance (standardized catch per unit effort, CPUE) in protected areas (6.4 fish/set) was 2.6 times greater than in the fished areas (2.4 fish/set) for total game fish, 2.4 times greater for spotted seatrout Cynoscion nebulosus, 6.3 times greater for red drum Sciaenops ocellatus, 12.8 times greater for black drum Pogonias cromis, 5.3 times greater for common snook Centropomus undecimalis, and 2.6 times greater for striped mul...