Linking extinction risk to the economic and nutritional value of sharks in small-scale fisheries.

To achieve sustainable shark fisheries, it is key to understand not only the biological drivers and environmental consequences of overfishing, but also the social and economic drivers of fisher behavior. The extinction risk of sharks is highest in coastal tropical waters, where small-scale fisheries are most prevalent. Small-scale fisheries provide a critical source of economic and nutritional security to coastal communities, and these fishers are among the most vulnerable social and economic groups. We used Kenya's and Zanzibar's small-scale shark fisheries, which are illustrative of the many data-poor, small-scale shark fisheries worldwide, as case studies to explore the relationship between extinction risk and the economic and nutritional value of sharks. To achieve this, we combined existing data on shark landings, extinction risk, and nutritional value with sales data at 16 key landing sites and information from interviews with 476 fishers. Shark fisheries were an important source of economic and nutritional security, valued at >US$4 million annually and providing enough nutrition for tens of thousands of people. Economically and nutritionally, catches were dominated by threatened species (72.7% and 64.6-89.7%, respectively). The most economically valuable species were large and slow to reproduce (e.g. mobulid rays, wedgefish, and bull, silky, and mako sharks) and therefore more likely to be threatened with extinction. Given the financial incentive and intensive fishing pressure, small-scale fisheries are undoubtedly major contributors to the decline of threatened coastal shark species. In the absence of effective fisheries management and enforcement, we argue that within small-scale fisheries the conditions exist for an economically incentivized feedback loop in which vulnerable fishers are driven to persistently overfish vulnerable and declining shark species. To protect these species from extinction, this feedback loop must be broken.

Conexión entre el riesgo de extinción y el valor nutricional de los tiburones en las pesquerías a pequeña escala Resumen Para lograr la sustentabilidad de las pesquerías de tiburones se deben entender los factores ecológicos y las consecuencias ambientales de la sobrepesca, así como los factores sociales y económicos del comportamiento del pescador. El riesgo de extinción de los tiburones es mucho mayor en las aguas tropicales costeras, en donde son más frecuentes las pesquerías a pequeña escala. Las pesquerías a pequeña escala, que además se encuentran entre los grupos con mayor vulnerabilidad social y económica, proporcionan una fuente importante de seguridad económica y nutricional para las comunidades costeras. Usamos las pesquerías de Kenia y Zanzíbar, las cuales representan muy bien a muchas de las pequeñas pesquerías de tiburones con deficiencia de datos, como estudios de caso para explorar la relación entre el riesgo de extinción y el valor económico y nutricional de los tiburones. Para lograr esto, combinamos los datos ya existentes de desembarques de tiburones, riesgo de extinción y valor nutricional con la información de ventas en 16 sitios clave de desembarque e información de las entrevistas a 476 pescadores. Las pesquerías de tiburones son una fuente importante de seguridad alimentaria y económica, valorada en más de US$4 millones anuales y que proporciona suficiente alimentación para miles de personas. En cuanto a la economía y la alimentación, las capturas estuvieron dominadas por especies amenazadas (72.7% y 64.6­89.7%, respectivamente). Las especies con mayor valor económico eran aquellas de gran tamaño y lenta reproducción, y, por lo tanto, con mayor probabilidad de estar en peligro de extinción. A causa del incentivo económico y la presión intensa de pesca, las pesquerías pequeñas sin duda son uno de los principales contribuyentes a la declinación de especies amenazadas de tiburones en las costas. Ya que no hay una aplicación ni un manejo efectivos de las pesquerías, argumentamos que en las pequeñas pesquerías existen las condiciones para un bucle de retroalimentación con incentivación económica en el que los pescadores vulnerables con frecuencia necesitan sobre pescar las especies de tiburones vulnerables y en declinación. Para proteger a estas especies de la extinción, este bucle de retroalimentación debe romperse.

Life-history, exploitation and extinction risk of the data-poor Baraka's whipray (Maculabatis ambigua) in small-scale tropical fisheries.

The Baraka's whipray (Maculabatis ambigua) is a major constituent of small-scale fisheries catch in the south-western Indian Ocean. Despite this, little is known of its life-history or exploitation status. We provide the first estimates of crucial life-history parameters and the maximum intrinsic population growth rate rmax , using specimens collected from small-scale fisheries landings in Kenya, Zanzibar and Madagascar (with northern Madagascar representing a range extension for this species). We assess the relative risk of overexploitation by combining rmax with estimates of total Z, fishing F, and natural M mortality, and an estimate of the exploitation ratio E. The data indicate that Baraka's whipray is a medium-sized, fast-growing, early maturing species, with a relatively long lifespan. This results in a high rmax relative to many other elasmobranchs, which when combined with estimates of F suggests that the species is not at imminent risk of extinction. Yet, estimates of exploitation ratio E indicate likely overfishing for the species, with full recruitment to the fishery being post-maturation and exploitation occurring across a broad range of age and size classes. Thus, Baraka's whipray is unlikely to be biologically sustainable in the face of current fisheries pressures. This paper makes an important contribution to filling the gap in available data and is a step towards developing evidence-based fisheries management for this species. Further, it demonstrates a simple and widely applicable framework for assessment of data-poor elasmobranch exploitation status and extinction risk.

Correction: To Fish or Not to Fish: Factors at Multiple Scales Affecting Artisanal Fishers' Readiness to Exit a Declining Fishery.

[This corrects the article DOI: 10.1371/journal.pone.0031460.].

Profiling bacterial communities associated with sediment-based aquaculture bioremediation systems under contrasting redox regimes.

Deposit-feeding invertebrates are proposed bioremediators in microbial-driven sediment-based aquaculture effluent treatment systems. We elucidate the role of the sediment reduction-oxidation (redox) regime in structuring benthic bacterial communities, having direct implications for bioremediation potential and deposit-feeder nutrition. The sea cucumber Holothuria scabra was cultured on sediments under contrasting redox regimes; fully oxygenated (oxic) and redox stratified (oxic-anoxic). Taxonomically, metabolically and functionally distinct bacterial communities developed between the redox treatments with the oxic treatment supporting the greater diversity; redox regime and dissolved oxygen levels were the main environmental drivers. Oxic sediments were colonised by nitrifying bacteria with the potential to remediate nitrogenous wastes. Percolation of oxygenated water prevented the proliferation of anaerobic sulphate-reducing bacteria, which were prevalent in the oxic-anoxic sediments. At the predictive functional level, bacteria within the oxic treatment were enriched with genes associated with xenobiotics metabolism. Oxic sediments showed the greater bioremediation potential; however, the oxic-anoxic sediments supported a greater sea cucumber biomass. Overall, the results indicate that bacterial communities present in fully oxic sediments may enhance the metabolic capacity and bioremediation potential of deposit-feeder microbial systems. This study highlights the benefits of incorporating deposit-feeding invertebrates into effluent treatment systems, particularly when the sediment is oxygenated.

Patterns of Coral-Reef Finfish Species Disappearances Inferred from Fishers' Knowledge in Global Epicentre of Marine Shorefish Diversity.

In the Philippines, very high fishing pressure coincides with the globally greatest number of shorefish species, yet no long-term fisheries data are available to explore species-level changes that may have occurred widely in the most species rich and vulnerable marine ecosystem, namely coral reefs. Through 2655 face-to-face interviews conducted between August 2012 and July 2014, we used fishers' recall of past catch rates of reef-associated finfish to infer species disappearances from catches in five marine key biodiversity areas (Lanuza Bay, Danajon Bank, Verde Island Passage, Polillo Islands and Honda Bay). We modeled temporal trends in perceived catch per unit effort (CPUE) based on fishers' reports of typical good days' catches using Generalized Linear Mixed Modelling. Fifty-nine different finfish disappeared from catches between the 1950s and 2014; 42 fish were identified to species level, two to genus, seven to family and eight to local name only. Five species occurring at all sites with the greatest number of fishers reporting zero catches were the green bumphead parrotfish (Bolbometopon muricatum), humphead wrasse (Cheilinus undulatus), African pompano (Alectis ciliaris), giant grouper (Epinephelus lanceolatus) and mangrove red snapper (Lutjanus argentimaculatus). Between the 1950s and 2014, the mean perceived CPUE of bumphead parrotfish declined by 88%, that of humphead wrasse by 82%, African pompano by 66%, giant grouper by 74% and mangrove red snapper by 64%. These declines were mainly associated with excess and uncontrolled fishing, fish life-history traits like maximum body size and socio-economic factors like access to market infrastructure and services, and overpopulation. The fishers' knowledge is indicative of extirpations where evidence for these losses was otherwise lacking. Our models provide information as basis for area-based conservation and regional resource management particularly for the more vulnerable, once common, large, yet wide-ranging reef finfish species.

Diverging strategies to planning an ecologically coherent network of MPAs in the North Sea: the roles of advocacy, evidence and pragmatism in the face of uncertainty.

The North Sea is one of the most economically important seas in the world due to productive fisheries, extensive oil and gas fields, busy shipping routes, marine renewable energy development and recreational activity. Unsurprisingly, therefore, the use of marine protected areas (here defined widely to include fisheries closed areas and no-take marine reserves) in its management has generated considerable controversy-particularly with regards to the design of a regional ecologically coherent MPA network to meet international obligations. Drawing on three MPA processes currently occurring in the UK North Sea, we examine the real-world problems that make the designation of MPA networks challenging. The political problems include: disagreement among (and within) sectors over policy objectives and priorities, common access to fisheries resources at the EU level increasing the scale at which decisions have to be made and lack of an integrated strategy for implementing protected areas in the North Sea. The scientific problems include the patchy knowledge of benthic assemblages, limited knowledge of fishing gear-habitat interactions, and the increased risk of unforeseen externalities if human activity (predominantly fishing) is displaced from newly protected sites. Diverging stakeholder attitudes to these problems means that there is no consensus on what ecological coherence actually means. Ultimately, we caution against 'quick-fix' solutions that are based on advocacy and targets, as they create confusion and undermine trust in the planning process. We argue for a more pragmatic approach to marine protection that embraces the complexity of the social and political arena in which decisions are made.

Perceptions of rule-breaking related to marine ecosystem health.

Finding effective solutions to manage marine resources is high on political and conservation agendas worldwide. This is made more urgent by the rate of increase in the human population and concomitant resource pressures in coastal areas. This paper links empirical socio-economic data about perceptions of marine resource health to the breaking of marine management rules, using fisheries as a case study. The relationship between perceived rule-breaking (non-compliance with regulations controlling fishing) and perceived health of inshore marine environments was investigated through face-to-face interviews with 299 heads of households in three Tanzanian coastal communities in November and December 2011. Awareness of rules controlling fishing activity was high among all respondents. Fishers were able to describe more specific rules controlling fishing practices than non-fishers (t = 3.5, df = 297, p<0.01). Perceived breaking of fishing regulations was reported by nearly half of all respondents, saying "some" (32% of responses) or "most" (15% of responses) people break fishing rules. Ordinal regression modelling revealed a significant linkage (z= -3.44, p<0.001) in the relationship between respondents' perceptions of deteriorating marine health and their perception of increased rule-breaking. In this paper, inferences from an empirical study are used to identify and argue the potential for using perceptions of ecosystem health and level of rule-breaking as a means to guide management measures. When considering different management options (e.g. Marine Protected Areas), policy makers are advised to take account of and utilise likely egoistic or altruistic decision-making factors used by fishers to determine their marine activities.

To fish or not to fish: factors at multiple scales affecting artisanal fishers' readiness to exit a declining fishery.

Globally, fisheries are challenged by the combined impacts of overfishing, degradation of ecosystems and impacts of climate change, while fisheries livelihoods are further pressured by conservation policy imperatives. Fishers' adaptive responses to these pressures, such as exiting from a fishery to pursue alternative livelihoods, determine their own vulnerability, as well as the potential for reducing fishing effort and sustaining fisheries. The willingness and ability to make particular adaptations in response to change, such as exiting from a declining fishery, is influenced by economic, cultural and institutional factors operating at scales from individual fishers to national economies. Previous studies of exit from fisheries at single or few sites, offer limited insight into the relative importance of individual and larger-scale social and economic factors. We asked 599 fishers how they would respond to hypothetical scenarios of catch declines in 28 sites in five western Indian Ocean countries. We investigated how socioeconomic variables at the individual-, household- and site-scale affected whether they would exit fisheries. Site-level factors had the greatest influence on readiness to exit, but these relationships were contrary to common predictions. Specifically, higher levels of infrastructure development and economic vitality - expected to promote exit from fisheries - were associated with less readiness to exit. This may be due to site level histories of exit from fisheries, greater specialisation of fishing households, or higher rewards from fishing in more economically developed sites due to technology, market access, catch value and government subsidies. At the individual and household scale, fishers from households with more livelihood activities, and fishers with lower catch value were more willing to exit. These results demonstrate empirically how adaptive responses to change are influenced by factors at multiple scales, and highlight the importance of understanding natural resource-based livelihoods in the context of the wider economy and society.