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Fishing Activities (fishing + activity)
Selected AbstractsRole of Genetic Refuges in the Restoration of Native Gene Pools of Brown TroutCONSERVATION BIOLOGY, Issue 4 2009ROSA M. ARAGUAS introgresión de piscifactoría; pautas de manejo; acervos génicas nativas; refugios genéticos; repoblación de peces Abstract:,Captive-bred animals derived from native, alien, or hybrid stocks are often released in large numbers in natural settings with the intention of augmenting harvests. In brown trout (Salmo trutta), stocking with hatchery-reared non-native fish has been the main management strategy used to maintain or improve depleted wild brown trout populations in Iberian and other Mediterranean regions. This measure has become a serious threat to the conservation of native genetic diversity, mainly due to introgressive hybridization. Aware of this risk, the agency responsible for management of brown trout in the eastern Pyrenees (Spain) created "brown trout genetic refuges" to preserve the integrity of brown trout gene pools in this region. Within refuge areas, the prerefuge status with respect to fishing activities has been maintained, but hatchery releases have been banned completely. We evaluated this management strategy through a comparison of the stocking impact on native populations that accounted for stocking histories before and after refuge designations and fishing activities. In particular we examined the relevant scientific, cultural, and political challenges encountered. Despite agency willingness to change fishery policies to balance exploitation and conservation, acceptance of these new policies by anglers and genetic monitoring of refuge populations should also be considered. To improve management supported by genetic refuges, we suggest focusing on areas where the public is more receptive, considering the situation of local native diversity, and monitoring of adjacent introgressed populations. We recommend the use of directional supportive breeding only when a population really needs to be enhanced. In any case, management strategies should be developed to allow for protection within the context of human use. Resumen:,Animales criados en cautiverio derivados de individuos nativos, exóticos o híbridos a menudo son liberados en grandes cantidades en ambientes naturales con la intención de incrementar su explotación. En la trucha común (Salmo trutta), la repoblación con peces no nativos criados en granjas ha sido la principal estrategia de manejo utilizada para mantener o mejorar poblaciones naturales de trucha común en la Peninsula Ibérica y otras regiones Mediterráneas. Esta medida se ha convertido en una seria amenaza para la conservación de la diversidad genética nativa, debido principalmente a la hibridación introgresiva. Consciente de este riesgo, la agencia responsable del manejo de la trucha común en los Pirineos orientales (España) creó"refugios genéticos de trucha común" para preservar la integridad de las acervos genéticos de trucha común en esta región. Dentro de las áreas de refugio, se ha mantenido el estatus previo al refugio con respecto a las actividades pesqueras pero las liberaciones de peces de piscifactoría han sido completamente prohibidas. Evaluamos esta estrategia de manejo mediante la comparación del impacto de la repoblación sobre las poblaciones nativas que registraron historias de repoblación antes y después de la designación de refugios y de actividades pesqueras. En particular, examinamos los significativos retos científicos, culturales y políticos que encontramos. A pesar de la disponibilidad de la agencia para cambiar las políticas de pesca hacia un equilibrio entre la explotación y la conservación, también se debe considerar la aceptación de estas nuevas políticas por los pescadores y el monitoreo genético de las poblaciones en los refugios. Para mejorar el manejo en los refugios genéticos sugerimos centrarse en las áreas donde el público es más receptivo, considerando la situación de la diversidad nativa local y el monitoreo de las poblaciones introgresadas adyacentes. Recomendamos la utilización de la cría de apoyo direccional solo cuando una población realmente requiera ser mejorada. En cualquier caso, se deberían desarrollar estrategias de manejo para permitir la protección en el contexto del uso por el hombre. [source] Lessons from the past: the collapse of Jamaican coral reefsFISH AND FISHERIES, Issue 2 2009Marah J. Hardt Abstract Since Pre-Columbian times, humans have exploited Jamaican marine ecosystems with significant consequences for flora and fauna. This study focuses on the history of reef fish exploitation in Jamaica, from first human occupation to the present day, to determine how past fishing activities contributed to subsequent declines in the coral reef ecosystem. The pattern of declining reef fish populations was nonlinear. Reef fish first declined in prehistoric times but then potentially recovered, following genocide of the native human population. Reduced fishing pressure lasted until the mid-19th century. At that time, depletion of reef fish populations again occurred with a precipitous decline from the 1850s to the 1940s. The final shift from relatively abundant to overfished marine fauna corresponded to subtle changes in fish trap design as well as development of recreational fishing. Government subsidies throughout the second half of the 20th century exacerbated the declines. This analysis shows that local artisanal fisheries with relatively low levels of effort and seemingly subtle shifts in technology can significantly impact the coral reef ecosystem and that declines occurred decades to centuries before modern ecological studies began. This research shows how historical analysis can be a powerful tool to minimize shifted baselines and establish realistic targets for recovery and sustainable management of marine ecosystems. [source] Small fish, big fish, red fish, blue fish: size-biased extinction risk of the world's freshwater and marine fishesGLOBAL ECOLOGY, Issue 6 2007Julian D. Olden ABSTRACT Aim, In light of the current biodiversity crisis, there is a need to identify and protect species at greatest risk of extinction. Ecological theory and global-scale analyses of bird and mammal faunas suggest that small-bodied species are less vulnerable to extinction, yet this hypothesis remains untested for the largest group of vertebrates, fish. Here, we compare body-size distributions of freshwater and marine fishes under different levels of global extinction risk (i.e. listed as vulnerable, endangered or critically endangered according to the IUCN Red List of Threatened Species) from different major sources of threat (habitat loss/degradation, human harvesting, invasive species and pollution). Location, Global, freshwater and marine. Methods, We collated maximum body length data for 22,800 freshwater and marine fishes and compared body-size frequency distributions after controlling for phylogeny. Results, We found that large-bodied marine fishes are under greater threat of global extinction, whereas both small- and large-bodied freshwater species are more likely to be at risk. Our results support the notion that commercial fishing activities disproportionately threaten large-bodied marine and freshwater species, whereas habitat degradation and loss threaten smaller-bodied marine fishes. Main conclusions, Our study provides compelling evidence that global fish extinction risk does not universally scale with body size. Given the central role of body size for trophic position and the functioning of food webs, human activities may have strikingly different effects on community organization and food web structure in freshwater and marine systems. [source] Chronic fishing disturbance has changed shelf sea benthic community structureJOURNAL OF ANIMAL ECOLOGY, Issue 3 2000M. J. Kaiser Summary 1.,Bottom fishing using towed nets and dredges is one of the most widespread sources of physical disturbance to the continental shelf seas throughout the world. Previous studies suggest that degradation and ecosystem changes have occurred in intensively fished areas. Nevertheless, to date it has been difficult to attribute habitat and benthic community changes to fishing effort at a spatial scale that is truly representative of commercial fishing activities. 2.,In this study we present convincing evidence that chronic bottom-fishing disturbance has caused significant and widespread changes in the structure of two distinct soft-sediment benthic assemblages and habitats. 3.,Our study compared the benthic fauna found in areas that have been exposed to either high or low levels of bottom-fishing disturbance over the past 10 years. We were able to validate the fishing effort data in some areas using scars in the shells of a long-lived bivalve mollusc (Glycymeris glycymeris) which result from fishing disturbance. Shell scars occurred most frequently in bivalves collected from the area of highest fishing effort. 4.,Multivariate analyses and the response of abundance/biomass curves indicated that chronic fishing has caused a shift from communities dominated by relatively sessile, emergent, high biomass species to communities dominated by infaunal, smaller-bodied fauna. Removal of emergent fauna has thus degraded the topographic complexity of seabed habitats in areas of high fishing effort. The communities within these areas currently may be in an alternative stable state. [source] The status of fish conservation in South African estuariesJOURNAL OF FISH BIOLOGY, Issue 9 2010A. K. Whitfield Estuary-dependent fish species are defined as those taxa whose populations would be adversely affected by the loss of estuarine habitats. Of the 155 species regularly recorded in South African estuaries, only 32 (21%) are completely dependent on these systems, but this figure increases to 103 species (66%) if partially dependent taxa are included in the analysis. The conservation of fishes in estuaries on the subcontinent is threatened by a number of factors, including habitat degradation, disruption of essential ecological processes, hydrological manipulations, environmental pollution, overexploitation due to fishing activities and, more recently, climate change and the effects of introduced aquatic animals. Although major threats to fishes are usually linked to environmental degradation, there is increasing evidence that the stocks of certain fish species are overexploited or collapsed. Fish conservation and fisheries management does not depend on the implementation of a single action, but rather the co-ordination of a detailed plan, often in a multidisciplinary context. Some examples of innovative means of contributing to estuarine fish conservation in a South African context include the determination and implementation of the ecological freshwater requirements for estuaries, the zoning of estuaries for different uses and the recognition that the maintenance of ecological processes are vital to aquatic ecosystem health. Apart from the designation of protected areas, the main direct means of conserving fish species and stocks include habitat conservation, controls over fishing methods, effort, efficiency and seasonality, pollution control and the prevention of artificial manipulation of estuary mouths. Since becoming a democracy in 1994, environmental legislation, policy and institutional arrangements in South Africa have undergone some major changes, which, if fully implemented, will be very positive for fish conservation in estuaries on the subcontinent. [source] Taxonomic sufficiency in two case studies: where does it work better?MARINE ECOLOGY, Issue 2009Tiziano Bacci Abstract In marine macrobenthos studies the identification of organisms at species level is the best entry to ecological and biological information about the animals. An accurate identification requires excellent conservation of the organisms, reliable fauna description, experts and lengthy work in the laboratory. The aim of this work is to test taxonomic sufficiency (TS) in two deliberately selected different case studies to understand whether and how the taxonomic complexity of a benthic assemblage influences the results of TS and where it works better. The first benthic settlement was collected in an area characterized by homogeneous depth and grain size composition (case study A) around an off-shore gas platform, while the second one was collected along a coast-wide transect in an area with human pressure limited to fishing activities (case study B). Univariate and multivariate statistical analysis was used to assess differences in the taxonomic structure of benthic assemblages and to test TS on the two different datasets. TS seems to work in both sites, from species to higher taxonomic levels, and the family taxonomic level appears the best compromise for taxonomic resolution when an accurate identification is not achievable. The application of TS does not indicate a significant difference between the two datasets and appears therefore to be a valid instrument to analyse and describe the structure of benthic settlements in the case of taxonomically complex communities. [source] Trawl-induced bottom disturbances off the south coast of Portugal: direct observations by the ,Delta' manned-submersible on the Submarine Canyon of PortimãoMARINE ECOLOGY, Issue 2007Paulo Morais Abstract The effects of marine fishing activities on benthic habitat and communities have become an important environmental issue. In addition to the direct removal of target species, effects include by-catch, damage to benthic organisms and alteration of habitat structure. The growing number of studies on the impact of fishing on bottom habitats indicates that the effects vary with the physical nature of the seabed and with the local natural disturbance regime. Several studies have been conducted on fisheries by-catch and discards off the south coast of Portugal since 1996. The results provide an idea of the impact on biodiversity: more than 60% of the species caught by the trawl fishery are discarded. The crustacean trawl captures the greatest number of species, probably due to the greater fishing depth range. In April 2004, the manned submersible ,Delta' (from DELTA Oceanographics, USA) conducted a sea campaign integrated in the SEMAPP programme (Science, Education, and Marine Archaeology Program in Portugal) to directly observe and assess the biological, geological, and archaeological aspects. A total of 15 dives were conducted mainly near the head and in the flanks inside Portimão canyon, down to 300 m. Observations showed variations in bottom type, the sedimentary framework and biological communities. These dives (150,300 m depth) also revealed a heavily trawled canyon bottom and erosion structures leading to changes in habitat structure and biodiversity. Of special interest was the occurrence of low-relief boulder substrates with relatively high densities of demersal finfish and shellfish. These sites served as a refuge for several species, whose abundance here was greater than on the surrounding areas of fine-grained substrates. Strong marks on the bottom are apparently caused by the doors of the trawl nets. Their impact will be examined in greater detail in future studies. [source] Fishing and the Sexual Division of Labor among the MeriamAMERICAN ANTHROPOLOGIST, Issue 3 2007REBECCA BLIEGE BIRD Do men and women forage differently because they are cooperatively responding to children's requirements for care or because they are differentially sensitive to variance? In this article, I examine how care trade-offs and variance contribute to gender differences in fishing strategies among Torres Strait Islanders (Meriam). Women's fishing had lower failure rates, coefficients of variation, and frequencies of sharing than men's fishing. Men and women responded to trade-offs between mean and variance differently: Women spent less time on high mean,high variance activities, men less time on high mean,low variance activities. Although child-care trade-offs affected time allocation to different fishing activities among women, they did not affect differences in time allocation between the sexes. These results support previous work implicating variance and sharing frequency as important resource currencies shaping gender differences in subsistence decisions, and they offer challenges to a general model of the division of labor predicated on economic notions of specialization as increasing production efficiency. [source] FISH, FISHERS, SEALS AND TOURISTS: ECONOMIC CONSEQUENCES OF CREATING A MARINE RESERVE IN A MULTI-SPECIES, MULTI-ACTIVITY CONTEXTNATURAL RESOURCE MODELING, Issue 4 2002JEAN BONCOEUR ABSTRACT. This paper investigates some economic consequences of creating a marine reserve on both fishing and ecotourism, when the range of controllability of fishing effort is limited and the impact of the reserve on ecosystem is considered. The issue is illustrated by the example of creating a no-take zone in part of a region where fishing is managed through a limited entry license system, and which is inhabited by two interacting stocks: a stock of prey (fish) and a stock of predators (seals). While the former is targeted by commercial fishing, the latter is not subject to harvest but is a potential basis for a commercial non-extractive activity (seal watching). Analysis is conducted with the help of a bioeconomic model combining the features of marine reserve modeling and of multispecies modeling. Following a description of the model, results of several simulation runs are presented. These show that creating a marine reserve has more complex economic implications than predicted in studies focused exclusively on one stock and/or commercial fisheries. More specifically, the model shows that the dynamics of the two interacting stocks reduces the benefits of the no-take zone for the fishing industry, while it makes the creation of this zone provide an opportunity for the development of ecotourism. Due to this dynamics, the model suggests that the optimal size of the reserve is larger when ecotourism is taken into account along with fishing activities. [source] A method to assess the sensitivity of sedimentary communities to fishing activitiesAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2009Harvey Tyler-Walters Abstract 1.Methods of sensitivity assessment to identify species and habitats in need of management or protection have been available since the 1970s. 2.The approach to sensitivity assessment adopted by the Marine Life Information Network (MarLIN) assumes that the sensitivity of a community or biotope is dependent on the species within it. However, the application of this approach to sedimentary communities, especially offshore, is complex because of a lack of knowledge of the structural or functional role of many sedimentary species. 3.This paper describes a method to assess the overall sensitivity of sedimentary communities, based on the intolerance and recoverability of component species to physical disturbance. A range of methods were applied to identify the best combinations of abundant, dominant or high biomass species for the assessment of sensitivity in the sedimentary communities examined. 4.Results showed that reporting the most frequent species' sensitivity assessment, irrespective of the four methods used to select species, consistently underestimated the total sensitivity of the community. In contrast, reporting the most sensitive assessment from those species selected resulted in a range of biotope sensitivities from very low to very high, that was better able to discriminate between the sensitivities of the communities examined. 5.The assumptions behind the methodology, its limitations and potential application are discussed. © Crown copyright 2008. Reproduced with permission of Her majesty's stationery office. Published by John Wiley & Sons, Ltd. [source] Conserving a subpopulation of the northern Atlantic cod metapopulation with a marine protected areaAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2009Liuming Hu Abstract 1.Marine reserves can play an important role in the conservation of subpopulations of marine fish metapopulations. The population spatial structure of northern Atlantic cod of Newfoundland and Labrador has characteristics of a metapopulation. Subpopulations of northern Atlantic cod on the continental shelf were decimated by decades of overfishing, and have not recovered. The remaining northern cod are concentrated in coastal areas. 2.A Marine Protected Area (MPA) was established in Gilbert Bay, Labrador by the Government of Canada in 2005 to protect the bay's resident subpopulation of northern Atlantic cod. Conservation of Gilbert Bay cod will help protect the genetic diversity of the northern cod metapopulation. 3.Unlike some other MPAs, Gilbert Bay is not a harvest refugium or ,no-take' reserve. Aboriginal subsistence fisheries for salmonids with a bycatch of cod are allowed in designated areas of the MPA. A recreational fishery for Atlantic cod by angling open to all people is under consideration. Management of the MPA must ensure that fishing activities do not endanger the local cod population. 4.The population dynamics of Gilbert Bay cod were simulated using an age-structured Leslie matrix model to estimate the total mortality under various recreational fishing scenarios. The level of sustainable harvest by a recreational fishery depends on the natural mortality of the Gilbert Bay cod population, which is unknown. Therefore, there is risk in permitting a recreational fishery in the MPA. 5.There may be benefits to the northern cod metapopulation, if the Gilbert Bay subpopulation is allowed to rebuild to the carrying capacity of the bay. If the abundance of Gilbert Bay cod exceeds the level which the local marine ecosystem can support, some cod may emigrate from the bay and recolonize adjacent coastal areas. The potential for Gilbert Bay cod to recolonize continental shelf areas is less certain. Copyright © 2008 John Wiley & Sons, Ltd. [source] An Evaluation of the Cod Fishing Policies of Denmark Iceland and NorwayEUROCHOICES, Issue 3 2004R. Arnason Summary An Evaluation of the Cod Fishing Policies of Denmark, Iceland and Norway Many ocean fisheries are subject to a fundamental economic problem generally referred to as the common property problem. This problem manifests itself as excessive fishing fleets and fishing effort, depressed fish stocks and little or no profitability of the fishing activity, irrespective of the richness of the underlying marine resources. European fisheries represent some of the most dramatic examples of the common property problem. This article employs simple empirical models and recently developed mathematical techniques to examine the economic efficiency of three European fisheries, namely the Danish, Icelandic and Norwegian cod fisheries, The optimal harvesting policies for each of these fisheries are calculated. Comparing these optimal policies with actual harvests provides a measure of the relative efficiency in these three cod fisheries. The comparison confirms the widely held impression that the cod harvesting policies of ail three countries have been hugely inefficient in the past. Moreover, it appears that the inefficiency has been increasing over time. Only during the last few years of our data are there indications that this negative trend may have been halted. Somewhat more surprisingly, in spite of radically different fisheries management systems, we find relatively little difference in the level of stock over-exploitation between these three countries. Politiques compareées de pêhe à la morue au Danemark, en Islande et en Norvège Beaucoup de pêcheries océaniques sont confrontées au problème nique fondamental de la "propriété collective". Celui-ci se manifeste par des flottes de taille excessive, au service d' efforts de péche exagérés, qui aboutissent à détruire les stocks de poisson et la rentabilité des pécheries, en dépit de la richesse des ressources marines sousjacentes. Les pêcheries européennes constituent actuellement l'un des exemples les plus dramatiques des problèmes associés a la propriété collective. On présente ici un modèle empirique assez simple mais associéà de nouvelles techniques mathématiques récemment développé es pour mesurer l' efficacitééconomique de trois types de politiques de pêche à la morue, au Danemark, en Norvège et en Islande. On commence par calculer le volume optimal des prises pour chacun de ces pays. La comparaison entre le niveau optimal et le niveau réel des prises permet de mesurer le degré d' efficacité des politiques suivies. Elle permet de confirmer l'opinion largement répandue selon laquelle les politiques passées ont été extrêmement peu efficaces. En outre, il apparaît que l'inefficacité est croissante avec le temps. C'est seulement dans les toutes dernières années des séries de données que l' on observe un infléchissement de cette tendance négative. Enfin, et c'est le plus surprenant, on trouve peu de differences entre les trois pays en ce qui conceme le degré de surexploitation du stock, et cela, bien que les principes de gestion des pêcheries y soient entiArement différents. Eine Bewertung der Kabeljaufischereipolitik in Dänemark, Island und Norwegen ahlreiche Hochseefischereien tehen einem grundlegenden ftliehen Problem gegenüber, das allgemein als Problem des kollektiven Eigentums bezeichnet wird. Dieses Problem zeigt sich in übermäßig großen Fangflotten und beträchtlichem Fischereiaufwand, geschrumpften Fischbeständen und geringer oder fehlender Rentabilität der Fischerei; dabei ist die Höhe der Fischressourcen unbedeutend für das Problem. Die europäischen Fischereien stellen einige der drastischsten Beispiele für das Problem des kollektiven Eigentums dar. In diesem Beitrag werden einfache empirische Modelle und kürzlich entwickelte mathematische Verfahren angewendet, um die wirtschaftliche Effizienz von drei europäischen Fischereien zu untersuchem der dänischen, der isländischen und der norwegischen Kabeljaufischerei. Für jede dieser Fischereien wird die optimale Nutzungsstrategie berechnet. Aus dem Vergleich dieser optimalen Nutzungsstrategie mit den tatsächlichen Erträgen ergibt sich ein Maß fur die relative Effizienz, die bei diesen drei Kabeljaufischereien vorliegt. Der Vergleich bestätigt den weit verbreiteten Eindruck, dass die Strategien zum Kabeljaufang in alien drei Ländern in der Vergangenheit enorm ineffizient waren. Darüber hinaus wird deutlich, dass die Ineffizienz im Laufe der Zeit zugenommen hat. Lediglich die Daten der letzten jahre enthalten Hinweise darauf, dass dieser negative Trend zum Stillstand gekommen sein könnte. Obwohl sich die Fischwirtschaft in jedem dieser drei Länder sehr stark unterscheidet, lassen sich erstaunlich wenige Unterschiede im Maß der Übernutzung des Fischbestandes finden. [source] Interpreting the Viking Age to Medieval period transition in Norse Orkney through cultural soil and sediment analysesGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 4 2005Ian A. Simpson The transition from the Viking Age (ca. A.D. 800,1050) to the Medieval period (ca. A.D. 1050,1500) saw the development of widening trade activities that incorporated peripheral North Atlantic polities into mainstream Europe and contributed to the intensification of marineresource exploitation and agricultural production in these localities. As yet, there is only limited understanding of these intensification processes and their interrelationships, particularly at a local, site-based level. Through the micromorphological analysis of cultural soils and sediments at Quoygrew, Westray, Orkney, we explore the characteristics of farming and fishing activity during the Viking Age,Medieval transition period and establish their chronological relationships. The study demonstrates: (1) that intensification took place from ca. A.D. 966,1162 on an already existing Viking Age settlement, (2) that intensification of fishing activity occurred prior to the intensification of arable agriculture, and (3) that the Quoygrew site continued throughout this period as an economically diverse permanent settlement. When viewed in a wider North Atlantic context, these findings indicate that intensification of different economic activities proceeded at different rates and that intensification of specialized economic activities during the transition from the Viking Age to the Medieval period was dependent on existing knowledge of local environments. © 2005 Wiley Periodicals, Inc. [source] IS FISHING COMPATIBLE WITH ENVIRONMENTAL CONSERVATION: A STOCHASTIC MODEL WITH AN ELEMENT OF SELF-PROTECTIONNATURAL RESOURCE MODELING, Issue 3 2008D. AMI Abstract The purpose of this paper is to introduce the impact of fishing activity on a marine ecosystem. The fishing activity is considered not only through annual harvest but also through a second component, called the degree of protection of the fishery environment. This characterizes the environmental impact of fishing. A stochastic dynamic programming problem is presented in infinite horizon, where a sole owner seeks to maximize a discounted expected profit. The main hypothesis states that the stock,recruitment relationship is stochastic and that both components of the fishing activity have an impact on the probability law of the state of the fishery environment. The optimal fishing policy is obtained and compared with standard models. This optimal policy has the following properties: is not a constant escapement policy and indicates an element of self-protection by the fishery manager. The paper ends with a discussion on the existence of degrees of protection of the fishery environment that take into account the environmental conservation and preservation of economic activity. [source] Chagos feels the pinch: assessment of holothurian (sea cucumber) abundance, illegal harvesting and conservation prospects in British Indian Ocean TerritoryAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2010A. R. G. Price Abstract 1.Data are analysed from visual censuses of shallow-water holothurians (sea cucumbers) in 72 shallow water transects 100,m×2,m within four atolls of Chagos. Mean holothurian abundance in Diego Garcia, where harvesting is absent, was 18.5 individuals/transect (all transects) and 55.4 individuals/transect (only those containing holothurians). In the three exploited atolls, mean abundance did not exceed 3.5 and 5.2 individuals/transect, respectively. 2.Comparison with data collected during this study and an earlier investigation reveals a marked decline over four years in both mean and maximum density of commercially valuable Stichopus chloronotus and Holothuria atra in Salomon and Peros Banhos, both exploited atolls, and also for Holothuria nobilis in the latter. 3.Holothurian counts were also made along an extensive transect (21,km×4,m) encircling Salomon atoll. Abundance showed highly significant negative correlation with fishing pressure, the latter estimated using an ordinal (0,3) scale (Rs=,0.605, P,0.01). Harvesting effects were not discernible using data from 200,m2 transects. 4.While recent studies have shown Chagos is virtually pristine regarding contaminant levels, its holothurian resources are under increasing pressure. Results from this study, and examination of Sri Lanka's fishing activity in distant waters, point to heavy and illegal harvesting. 5.Stronger measures are needed to control the illegal fishery, to prevent holothurian abundances falling to the non-sustainable levels now prevalent across much of the Indo-Pacific, and to ensure that Chagos remains a biodiversity hotspot and environment of international renown. Use of smaller surveillance vessels would facilitate this.Copyright © 2009 John Wiley & Sons, Ltd. [source] Community patterns generated by human harvesting on Chilean shores: a reviewAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2001Carlos A. MorenoArticle first published online: 21 FEB 200 Abstract 1.,The Chilean rocky coast has been exploited for food by coastal gatherers for at least 8500 years BP and probably was an important factor in how prehistoric people were able to colonize the South Americas Pacific Rim. The main species targeted in the past were the same as those today except that now the gatherers are resident and the fishing activity is more intense and persistent. 2.,With many pertinent studies from around the world having been published on this topic, mostly conducted in Marine Reserves, this review tries to identify the main patterns that can help us recognize, in the Chilean intertidal, the degree of exploitation on wave exposed and wave protected rocky shore habitats. 3.,Three clear patterns were identified depending on the trophic level adopted by the human gatherers in the food chain of the intertidal zone. First, when the humans act as herbivores, collecting the large laminarian Durvillaea antarctica, adult plants disappear from the accessible sites, especially the midlittoral, semi-exposed and exposed habitats. 4.,Second, when humans harvest the ecologically important herbivorous archeogastropoda Fissurella spp., this results in the red alga Mazzaella laminarioides covering almost 100% of the midlittoral rocks. Third, when humans become top predators by collecting the muricid carnivore Concholepas concholepas, then bivalves, mainly Perumytilus purpuratus, cover the rocks in multiple layers. 5.,These patterns contribute to the evaluation of the state of conservation of the Chilean rocky intertidal shores, especially because the north and the south are beginning to be connected by a new coastal road. Thus it is necessary to evaluate urgently, on a large spatial scale, the state of conservation of these communities, in order to help select the appropriate places for establishing Marine Reserves. Copyright © 2001 John Wiley & Sons, Ltd. [source] | |||||||||||||