Showing papers on "Fishing published in 2006"

Documented and Potential Biological Impacts of Recreational Fishing: Insights for Management and Conservation

Abstract: While the impacts of high exploitation on fish populations and aquatic ecosystems are well-documented for commercial fishing, particularly in the marine environment, the potential biological impacts of angling received less attention. This paper discusses angling patterns within a framework of basic ecological and evolutionary literature and examines potential biological impacts of angling by focusing on study results associated with high exploitation rates and pronounced selective exploitation. The impacts range from impacts occurring directly on the exploited species (truncation of the natural age and size structure, depensatory mechanisms, loss of genetic variability, evolutionary changes), to those that occur on the aquatic ecosystem (changes in trophic cascades, trait-mediated effects). As a third category, impacts related to the angling activity per se are distinguished (habitat modifications, wildlife disturbance, nutrient inputs, loss of fishing gear). Although the main threats to fish often are l...

Global analysis of response and recovery of benthic biota to fishing

Abstract: Towed bottom-fishing gears are thought to constitute one of the largest global anthropogenic sources of disturbance to the seabed and its biota. The current drive towards an ecosystem approach in fish- eries management requires a consideration of the im- plications of habitat deterioration and an understand- ing of the potential for restoration. We undertook a meta-analysis of 101 different fishing impact manipu- lations. The direct effects of different types of fishing gear were strongly habitat-specific. The most severe impact occurred in biogenic habitats in response to scallop-dredging. Analysis of the response of differ- ent feeding guilds to disturbance from fishing re- vealed that both deposit- and suspension-feeders were consistently vulnerable to scallop dredging across gravel, sand and mud habitats, while the re- sponse of these groups to beam-trawling was highly dependent upon habitat type. The biota of soft-sedi- ment habitats, in particular muddy sands, were sur- prisingly vulnerable, with predicted recovery times measured in years. Slow-growing large-biomass biota such as sponges and soft corals took much longer to recover (up to 8 yr) than biota with shorter life-spans such as polychaetes (<1 yr). The results give a possi- ble basis for predicting the outcome of the use of dif- ferent fishing gears in a variety of habitats with poten- tial utility in a management context.

Fishing elevates variability in the abundance of exploited species

Abstract: The separation of the effects of environmental variability from the impacts of fishing has been elusive, but is essential for sound fisheries management. We distinguish environmental effects from fishing effects by comparing the temporal variability of exploited versus unexploited fish stocks living in the same environments. Using the unique suite of 50-year-long larval fish surveys from the California Cooperative Oceanic Fisheries Investigations we analyse fishing as a treatment effect in a long-term ecological experiment. Here we present evidence from the marine environment that exploited species exhibit higher temporal variability in abundance than unexploited species. This remains true after accounting for life-history effects, abundance, ecological traits and phylogeny. The increased variability of exploited populations is probably caused by fishery-induced truncation of the age structure, which reduces the capacity of populations to buffer environmental events. Therefore, to avoid collapse, fisheries must be managed not only to sustain the total viable biomass but also to prevent the significant truncation of age structure. The double jeopardy of fishing to potentially deplete stock sizes and, more immediately, to amplify the peaks and valleys of population variability, calls for a precautionary management approach.

Fishing down the deep

Abstract: Global landings of demersal marine fishes are demonstrated to have shifted to deeper water species over the last 50 years. Our analysis suggests deep-water fish stocks may be at serious risk of depletion, as their life histories render them highly vulnerable to overfishing with little resilience to over-exploitation. Deep-sea fisheries are exploiting the last refuges for commercial fish species and should not be seen as a replacement for declining resources in shallower waters. Instead, deep-water habitats are new candidates for conservation.

Climate Variability, Fish, and Fisheries

Abstract: Fish population variability and fisheries activities are closely linked to weather and climate dynamics. While weather at sea directly affects fishing, environmental variability determines the distribution, migration, and abundance of fish. Fishery science grew up during the last century by integrating knowledge from oceanography, fish biology, marine ecology, and fish population dynamics, largely focused on the great Northern Hemisphere fisheries. During this period, understanding and explaining interannual fish recruitment variability became a major focus for fisheries oceanographers. Yet, the close link between climate and fisheries is best illustrated by the effect of “unexpected” events—that is, nonseasonal, and sometimes catastrophic—on fish exploitation, such as those associated with the El Nino–Southern Oscillation (ENSO). The observation that fish populations fluctuate at decadal time scales and show patterns of synchrony while being geographically separated drew attention to oceanograph...

Fishing through marine food webs

Abstract: A recurring pattern of declining mean trophic level of fisheries landings, termed “fishing down the food web,” is thought to be indicative of the serial replacement of high-trophic-level fisheries with less valuable, low-trophic-level fisheries as the former become depleted to economic extinction. An alternative to this view, that declining mean trophic levels indicate the serial addition of low-trophic-level fisheries (“fishing through the food web”), may be equally severe because it ultimately leads to conflicting demands for ecosystem services. By analyzing trends in fishery landings in 48 large marine ecosystems worldwide, we find that fishing down the food web was pervasive (present in 30 ecosystems) but that the sequential addition mechanism was by far the most common one underlying declines in the mean trophic level of landings. Specifically, only 9 ecosystems showed declining catches of upper-trophic-level species, compared with 21 ecosystems that exhibited either no significant change (n = 6) or significant increases (n = 15) in upper-trophic-level catches when fishing down the food web was occurring. Only in the North Atlantic were ecosystems regularly subjected to sequential collapse and replacement of fisheries. We suggest that efforts to promote sustainable use of marine resources will benefit from a fuller consideration of all processes giving rise to fishing down the food web.

Maladaptive changes in multiple traits caused by fishing: impediments to population recovery.

Abstract: Some overharvested fish populations fail to recover even after considerable reductions in fishing pressure. The reasons are unclear but may involve genetic changes in life history traits that are detrimental to population growth when natural environmental factors prevail. We empirically modelled this process by subjecting populations of a harvested marine fish, the Atlantic silverside, to experimental size-biased fishing regimes over five generations and then measured correlated responses across multiple traits. Populations where large fish were selectively harvested (as in most fisheries) displayed substantial declines in fecundity, egg volume, larval size at hatch, larval viability, larval growth rates, food consumption rate and conversion efficiency, vertebral number, and willingness to forage. These genetically based changes in numerous traits generally reduce the capacity for population recovery.

Estimating Collateral Mortality from Towed Fishing Gear

Abstract: More than 50% of the world’s total marine catch (approximately 81 million tonnes) is harvested using towed fishing gears (i.e. Danish seines, dredges and otter and beam trawls). As for all methods, the total fishing mortality of these gears comprises the reported (landed) and unreported catch and other unaccounted, collateral deaths due to (i) avoiding, (ii) escaping, (iii) dropping out of the gear during fishing, (iv) discarding from the vessel, (v) ghost fishing of lost gear, (vi) habitat destruction or subsequent (vii) predation and (viii) infection from any of the above. The inherent poor selectivity of many towed gears, combined with their broad spatial deployment, means that there is considerable potential for cumulative effects of (i)‐(viii) listed above on total fishing mortality, and subsequent wide-scale negative impacts on stocks of important species. In this paper, we develop a strategy for minimizing this unwanted exploitation by reviewing all the primary literature studies that have estimated collateral, unaccounted fishing mortalities and identifying the key causal factors. We located more than 80 relevant published studies (between 1890 and early 2006) that quantified the mortalities of more than 120 species of escaping (26 papers) or discarded (62 papers) bivalves, cephalopods, crustaceans, echinoderms, elasmobranches, reptiles, teleosts and miscellaneous organisms. Seven of these studies also included the estimates of mortalities caused by dropping out of gears, predation and infection [(iii), (vii) and (viii) listed above]. Owing to several key biological (physiology, size and catch volume and composition), environmental (temperature, hypoxia, sea state and availability of light) and technical (gear design, tow duration and speed) factors, catch-and-escape or catch-and-discarding mechanisms were identified to evoke cumulative negative effects on the health of most organisms. We propose that because the mortalities of discards typically are much greater than escapees, the primary focus of efforts to mitigate unaccounted fishing mortalities should concentrate on the rapid, passive, size and species selection of nontarget organisms from the anterior sections of towed gears during fishing. Once maximum selection has been achieved and demonstrated to cause few mortalities, efforts should be made to modify other operational and/or post-capture handling procedures that address the key causal factors listed above.

Matching Social and Ecological Systems in Complex Ocean Fisheries

Abstract: This paper considers ocean fisheries as complex adaptive systems and addresses the question of how human institutions might be best matched to their structure and function. Ocean ecosystems operate at multiple scales, but the management of fisheries tends to be aimed at a single species considered at a single broad scale. The paper argues that this mismatch of ecological and management scale makes it difficult to address the fine-scale aspects of ocean ecosystems, and leads to fishing rights and strategies that tend to erode the underlying structure of populations and the system itself. A successful transition to ecosystem-based management will require institutions better able to economize on the acquisition of feedback about the impact of human activities. This is likely to be achieved by multiscale institutions whose organization mirrors the spatial organization of the ecosystem and whose communications occur through a polycentric network. Better feedback will allow the exploration of fine-scale science and the employment of fine-scale fishing restraints, better adapted to the behavior of fish and habitat. The scale and scope of individual fishing rights also needs to be congruent with the spatial structure of the ecosystem. Place-based rights can be expected to create a longer private planning horizon as well as stronger incentives for the private and public acquisition of system relevant knowledge.

Reducing sea turtle by-catch in pelagic longline fisheries

Abstract: Reducingby-catchofseaturtlesinpelagiclonglinefisheries,inconcertwithactivitiesto reduce other anthropogenic sources of mortality, may contribute to the recovery of marine turtle populations. Here, we review research on strategies to reduce sea turtle by-catch. Due to the state of management regimes in most longline fisheries, strategies to reduce turtle interactions must not only be effective but also must be commercially viable. Becausemostresearchhasbeeninitiatedonlyrecently,manyresultsarenotyet peer-reviewed, publishedor readily accessible. Moreover, mostexperiments havesmall sample sizes and have been conducted over only a few seasons in a small number of fisheries; many study designs preclude drawing conclusions about the independent effectofsinglefactorsonturtleby-catchandtargetcatchrates;andfewstudiesconsider effects on other by-catch species. In the US North Atlantic longline swordfish fishery, 4.9-cm wide circle hooks with fish bait significantly reduced sea turtle by-catch rates and the proportion of hard-shell turtles that swallowed hooks vs. being hooked in the mouth compared to 4.0-cm wide J hooks with squid bait without compromising commercial viability for some target species. But these large circle hooks might not be effective or economically viable in other longline fisheries. The effectiveness and commercialviabilityofaturtleavoidancestrategymaybefishery-specific,dependingon thesizeandspeciesofturtlesandtargetfishandotherdifferencesbetweenfleets. Testing of turtle avoidance methods in individual fleets may therefore be necessary. It is a priority to conduct trials in longline fleets that set gear shallow, those overlapping the most threatened turtle populations and fleets overlapping high densities of turtles such as those fishing near breeding colonies. In addition to trials using large 4.9-cm wide circlehooksinplaceofsmallerJandJapantunahooks,otherfishingstrategiesareunder assessment. These include: (i) using small circle hooks (£ 4.6-cm narrowest width) in place of smaller J and Japan tuna hooks; (ii) setting gear below turtle-abundant depths; (iii) single hooking fish bait vs. multiple hook threading; (iv) reducing gear soak time and retrieval during daytime; and (v) avoiding by-catch hotspots through fleet communication programmes and area and seasonal closures.

Socioeconomic factors that lead to overfishing in small-scale coral reef fisheries of Papua New Guinea

Abstract: The coral reefs of Papua New Guinea are among the most species diverse in the world, support an important artisanal fishery, but lack an effective national conservation programme. Increased commercialization, population growth, promotion of fisheries development projects, and the live reef food fish trade are expected to increase demand for the country's reef fish. This paper examines how socioeconomic factors affect the condition of the artisanal multi-species coral reef fishery in six sites in Papua New Guinea. Catch characteristics such as diversity, trophic level and body size by landing site were examined along a fishing pressure gradient. Both exogenous factors such as markets and endogenous factors such as fishing pressure were related to the condition of fish catch. In general, the trophic level and lengths of fish captured in Papua New Guinea were relatively high, but were reduced on reefs with high fishing effort near fish markets. Fisheries showed signs of depletion above c. 25 fishing trips per km2 per day and the proximity of markets was a better indicator of overfishing than human population size. A cross-scale approach to fisheries management is required in Papua New Guinea to coordinate decentralized local management, limit the intrusion of extractive enterprises, and develop policies that seek to minimize exogenous pressures on marine resources.

The Worldwide Crisis in Fisheries: Economic Models and Human Behavior

Abstract: The world's marine fisheries are in trouble, as a direct result of overfishing and the overcapacity of fishing fleets. Despite intensive management efforts, the problems still persist in many areas, resulting in many fisheries being neither sustainable nor profitable. Using bio-economic models of commercial fisheries, this book demonstrates that new management methods, based on individual or community catch quotas, are required to resolve the overfishing problem. Uncertainty about marine systems may be another factor contributing to overfishing. Methods of decision analysis and Bayesian inference are used to discuss risk management and the precautionary principle, arguing that extensive marine reserves may be the best way to protect fisheries, alongside a controlled catch quota system. This book will be of interest to environmental scientists, economists and fisheries managers, providing novel insights into many well-known but poorly understood aspects of fisheries management.

Fishing under low productivity conditions is further delaying recovery of Northwest Atlantic cod (Gadus morhua)

Abstract: Excessive and unsustainable fishing mortality was the predominant factor in the depletion of Northwest Atlantic cod (Gadus morhua) stocks. However, despite imposition of severe catch restrictions for over a decade, stocks have mostly failed to recover at predicted rates. A number of explanations have been considered. Our analysis of demographic characteristics of 12 of these stocks indicates that recent productivity over the northern portion of the range is much lower than 20 years previous when several stocks recovered from less severe declines. Main contributing factors are, in rank order, increased natural mortality, decreased body growth, and in a few cases, reduced recruitment rates. Continued fishing in directed and bycatch fisheries is also an important factor. Under current conditions, we estimate negative or very low ( 5% would be expected in six stocks, with >10% in four of these. Although productivity is low, we conclude that fishing mortality is further delaying recovery.

Southern Chile, trout and salmon country: invasion patterns and threats for native species

Abstract: In order to evaluate the present distribution patterns of salmonids and their potential effects on native fish, we sampled 11 large lakes and 105 streams, encompassing a total of 13 main hydrographic watersheds of southern Chile (39° to 52°S). Overall, trout (Salmo trutta and Oncorhynchus mykiss) accounted for more than 60 % of total fish abundance and more than 80 % of total biomass, while 40 % of the streams sampled did not have native fish. Salmon, introduced for aquaculture, such as O. kisutch, Salmo salar, and O. tshawytscha, were only present in lakes with salmon farming and did not seem to be reproducing naturally in affluent streams. We tested the effect of river geographic origin (Andes mountains, central valley, or Coastal range) on fish abundance and found that rainbow trout was more restricted to the Andean streams with higher water discharge, while brown trout was widely distributed and did not relate to any of several catchment attributes measured. The abundance of native fish was greater in lakes than in streams and the highest native fish biodiversity occurred in streams of the central valley. The most common native species were Galaxias maculatus, G. platei, Brachygalaxias bullocki, Aplochiton zebra and Basilichthys australis. Streams with higher conductivity, larger pool areas, more fine sediments, and low brown trout densities were more suitable for native fish. Thus, catchments with higher anthropogenic disturbance appeared as refuges for native species. Given the descriptive nature of our study we can only presume the negative impacts of trout and salmon on native fish; an effect which should be superimposed on biogeographical conditioning of present distribution. Yet based on the present abundance and distribution patterns of salmonids and native fish, negative effects are very likely. Conservation of native fish biodiversity in central valley streams, far from protected areas or national parks and fully exposed to human perturbations represents a great challenge. We propose to enhance conservation by exerting a stronger sport fishing pressure on trout in those streams

When does this fish spawn? Fishermen's local knowledge of migration and reproduction of Brazilian coastal fishes

Abstract: Fishermen’s local knowledge of fishing resources may be an important source of information to improve artisanal tropical fisheries management, such as those found in Brazil, where most data on fish biology is lacking. We aim to study the local ecological knowledge that Brazilian coastal fishers have about reproductive aspects (season, places and migration) of 13 coastal fish species of commercial importance. We selected fishermen with more than 30 years of fishing practice and we interviewed a total of 67 fishermen: 29 from the southeastern coast, from the communities of Puruba, Almada, Picinguaba and Bertioga, and 38 from the northeastern coast, from the communities of Valenca, Arembepe and Porto Sauipe. In the interviews, we used standardized questionnaires and showed photos of fish species. Our results indicate some general patterns in fishes’ reproduction according to fishermen knowledge: fish species spawn in open ocean, near reefs or in coastal rivers (estuaries); some fishes reproduce during the summer and others in winter, while some have more defined spawning months. The main fish migratory patterns mentioned by interviewees were: long migrations along the coast, usually in the South to North direction, short migrations among reefs, fishes that do not migrate, migrations between the shore and open ocean and migrations between the sea and coastal rivers. Fishermen’s knowledge differed among fish species: most fishermen did not know spawning places or seasons of large pelagic fishes, which raised concerns of their possible depletion. We compared such ethnoichthyological information with available scientific data, indicating promising insights about reproduction and migration of Brazilian coastal fishes. Data gathered from local fishermen may provide inexpensive and prompt information, potentially applicable to fisheries management. Our approach might be useful to several other small-scale fisheries, especially the tropical ones, where there is a high diversity of target species and a low biological and ecological knowledge about these species.

Wild Profusion: Biodiversity Conservation in an Indonesian Archipelago

Abstract: Preface vii Acknowledgments xiii List of Abbreviations xvii INTRODUCTION: Between the Human and the Wild Profusion 1 PART ONE: Diversity as Milieu 27 CHAPTER ONE: Making the Monkey 33 CHAPTER TWO: The Social Turn 53 PART TWO: Togean Cosmopolitics 75 CHAPTER THREE: Extraterrestrial Others 81 CHAPTER FOUR: On the (Bio)logics of Species and Bodies 106 PART THREE: Integrating Conservation and Development 129 CHAPTER FIVE: Fishing with Cyanide 135 CHAPTER SIX: The Sleep of Reason 154 Appendix: Scientific, Military, and Commercial Explorations in the Togean Islands and Vicinity: 1680-1999 167 Notes 171 References 181 Index 193

LCA of Danish Fish Products. New methods and insights (9 pp)

Abstract: Goal, Scope and Background This article presents the main results from a PhD dissertation about environmental impacts from Danish fish products. The focus is on LCA results for flatfish, but the article also gives an overview of screenings of other fish species. Furthermore, it includes an analysis of the energy consumption in the fishing stage – as a function of fish species and fishing methods. Alternative impact categories that have not been included in the quantitative LCA and policy perspectives are elaborated in the discussion part of the paper.

Predicting the effects of area closures and fishing effort restrictions on the production, biomass, and species richness of benthic invertebrate communities

Abstract: To effectively implement an Ecosystem Approach to Fisheries (EAF), managers need to consider the effects of management actions on the fishery and the ecosystem. Methods for assessing the effects on target stocks are generally well developed, but methods for assessing the effects on other components and attributes of the ecosystem are not. Area closures and effort controls are widely used fishery management tools that affect the distribution of fishing effort and may therefore have consequences for a range of species and habitats. An approach is developed to predict the effects of area closures and effort control on the biomass, production, and species richness of benthic communities in the North Sea. The redistribution of beam trawling effort as a result of management action was modelled with a random utility model, assuming that fishers selected fishing grounds on the basis of their knowledge of past catch rates. The effects of trawling on benthic invertebrates were predicted using a size-based model that accounted for differences in habitat among fishing grounds. Our simulations demonstrated that closures of different sizes and in different locations could have positive or negative effects on benthic communities. These predicted effects resulted from the trade-off between recovery in the closed areas and additional trawling effects in the open areas that arose from displaced fishing activity. In the absence of effort controls, closure of lightly fished areas had the strongest positive effect on benthic communities. Effort reduction also had a positive effect. Therefore, area closures in lightly fished areas, coupled with effort reduction, are expected to minimize the effects of fishing on benthic communities. As it was not possible to access full international data for the North Sea beam trawl fleet, the results of the analyses are illustrative rather than complete. Nevertheless, what is demonstrated is an effective approach for assessing the environmental consequences of fishery management action that can be used to inform management decision-making as part of an EAF.

A length-based multispecies model for evaluating community responses to fishing

Abstract: Quantitative ecosystem indicators are needed to fulfill the mandate for ecosystem-based fisheries management. A variety of community metrics could potentially be used, but before reference levels f...

Overcoming human obstacles to conservation of recreational fishery resources, with emphasis on central Europe

Abstract: Recreational fisheries are the dominant or sole user of many coastal and most inland fish stocks in industrialized societies Recreational angling can negatively affect fish populations, but appropriate management approaches to address these impacts are often lacking Overall, privately-governed European recreational fisheries systems offer suitable conditions to reconcile resource use with resource conservation because access restriction is possible, decision-making structures are simple and management scales are small This increases the hope that the race to fish may be less pronounced than in open-access commercial fisheries To achieve harmony between use and conservation values, a thorough understanding of the human dimension is paramount, yet approaches including this are underrepresented in contemporary recreational fisheries science and management Based on theoretical considerations, literature review and personal experiences, this paper presents key human obstacles to the reconciliation of recreational fishery resource use and resource conservation, with emphasis on private fishing rights regimes of central Europe Nine obstacles are identified: (1) lack of social priority; (2) lack of integrated approaches; (3) lack of cooperative institutional linkages; (4) lack of systems thinking; (5) lack of research and monitoring; (6) lack of shared values and dominance of stereotyped perceptions; (7) lack of consideration for regional fish-angler dynamics; (8) lack of objective communication of scientific findings; and (9) lack of critical self-reflection among individual anglers Potential solutions to overcome the identified constraints briefly discussed include: (1) evaluation of the socioeconomic benefits of angling; (2) rehabilitation of ecosystem structure and function on larger scales; (3) facilitation of structured cooperation between stakeholders and management units; (4) application of complex systems approach; (5) increased funding for long-term monitoring; (6) fostering of common values of different stake-holders; (7) active adaptive management of angling effort on regional scales; (8) intensified communication of research findings; and (9) conviction of anglers to meet personal targets by more restrictive regulations Increasing research and management efforts related to the social component of recreational fisheries will improve reconciliation of resource use and resource conservation in traditional recreational fisheries management It is a matter of societal values whether it is judged necessary to do so on a broader scale

Modelling an exploited marine fish community with 15 parameters - results from a simple size-based model

Abstract: To measure and predict the response of fish communities to exploitation, it is necessary to understand how the direct and indirect effects of fishing interact. Because fishing and predation are size-selective processes, the potential response can be explored with size-based models. We use a simulation approach to describe the relationship between size spectrum slope and overall fishing mortality and to try to understand how a linear spectrum might be maintained. The model uses 15 parameters to describe a 13-‘‘species’’ fish community, where species are defined by their maximum body size and the general relationship between size and life-history characteristics. The simulations allow us to assess the role of changes in the strength and type of density dependence in controlling the response to fishing, and to investigate the trade-off between catches and stock status of the different species. The outputs showed that the linear slope of the size spectrum was a function of community exploitation rate. Density-dependent controls, specifically predation mortality and the extent of compensation in the stock-recruit relationship, were key mechanisms in maintaining a linear spectrum. A linear spectrum emerged independent of the rate of compensation in the stockrecruit relationship. When this rate was low, the effects of changes in fishing mortality on predator abundance dominated those on spawning-stock biomass, whereas the dominance was reversed when the compensation rate in the stock-recruit relationship was high. The approach allows us to explore the effects of different fishing mortality schedules on properties of the fish community, to assess how fishing affects species with different life histories in mixed fisheries, and to assess the effects of selectively fishing different size classes. The simulations indicate that the size classes to be included when developing and interpreting size-based metrics must be carefully considered in relation to the trophic structure and likely strength of predatory interactions in the community. Runs with different fishing mortality by size suggest that the dynamics of predation cannot compensate fully for changing rates and patterns of exploitation, implying that the effects of selectively fishing different size classes should be assessed on a case-by-case basis.

Linking Angling Catch Rates and Fish Learning under Catch-and-Release Regulations

Abstract: Many recreational fisheries are subject to varying degrees of catch-and-release fishing through regulations and conservation-minded anglers. Clearly, releasing a proportion of the catch improves conservation of the fishery, yet it is not clear how the released catch contributes to angling quality. If fish change their behavior to lower their individual catchability after they have been caught, then angler catch rates may not be proportional to fish density. Therefore, even catch-and-release fisheries could exhibit poor angling quality if there is sufficiently high angler effort. We tested this idea by experimentally fishing five small lakes that contained rainbow trout Oncorhynchus mykiss in the interior of British Columbia. We found that with sustained effort of 8 angler-hours · d−1 · ha−1 and complete release of the catch, catch rates quickly dropped within 7–10 d. Given the individual capture histories of tagged fish, the most parsimonious catchability model incorporated learning and heterogen...

Vulnerability of seamount fish to fishing: Fuzzy analysis of life-history attributes

Abstract: Despite rather broad definitions, global analysis showed that seamount fishes, particularly seamount-aggregating fishes, had higher intrinsic vulnerability than other groups of fishes. The pattern was similar when considering only commercially exploited species. Biological characteristics leading to greater vulnerability included a longer life span, later sexual maturation, slower growth and lower natural mortality. The results supported the contention that seamount fishes, especially those that aggregate on seamounts, are highly vulnerable to exploitation and that fishing on seamounts may not be sustainable at current levels and with current methods. A number of seamount populations have already been depleted; more depletion, extirpations, and even species extinctions may follow if fishing on seamounts is not reduced.