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  • Articles  (1,063)
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  • Articles  (1,063)
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  • 11
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    Redefining environmental stewardship to deliver governance frameworks for marine biodiversity beyond national jurisdiction (2018)
    Oxford University Press
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    Publication Date: 2018-03-06
    Description: In 2015 the United Nations General Assembly decided to develop an international legally binding instrument (ILBI) under the United Nations Convention on the Law of the Sea (UNCLOS) on the conservation and sustainable use of marine biological diversity of areas beyond national jurisdiction. To that end, it established a Preparatory Committee (PrepCom), to make substantive recommendations to the General Assembly on the elements of a draft text of an ILBI. The PrepCom has identified the tension between the principle of the common heritage of mankind and high seas freedoms embodied in UNCLOS as one of the issues which must be addressed in such an international agreement. Some participants in the process have proposed a sui generis regime as a way of resolving any apparent clash of these international legal principles, particularly as it relates to marine genetic resources and their access and benefit sharing. This article argues that environmental stewardship may provide the framework for such a sui generis regime. For it to do so, however, it must be grounded in international legal principles and act as a balance between competing values, perspectives and interests in the conservation and sustainable use of marine biodiversity beyond national jurisdiction. If appropriately redefined in this way, environmental stewardship can deliver a governance framework which addresses some of the central issues with which the PrepCom will have to deal. These include the practical problems of access and benefit sharing of the marine genetic resources of areas beyond national jurisdiction, and reconciling the conflicting pressure for international decision-making for the conservation and sustainable use of marine biological diversity on the one hand, and the maintenance of existing regional and sectoral frameworks on the other. Environmental stewardship, redefined, can provide an intellectual framework for an ILBI under UNCLOS on marine biodiversity beyond national jurisdiction.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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  • 12
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    Multispecies acoustic dead-zone correction and bias ratio estimates between acoustic and bottom-trawl data (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: In this study, we extended the original work of Kotwicki et al. (2013. Combining bottom trawl and acoustic data to model acoustic dead zone correction and bottom trawl efficiency parameters for semipelagic species. Canadian Journal of Fisheries and Aquatic Sciences 70: 208–219) to jointly estimate the acoustic dead-zone correction, the bias ratio, and the gear efficiency for multiple species by using simultaneously collected acoustic and bottom-trawl data. The model was applied to cod ( Gadus morhua ) and haddock ( Melanogrammus aeglefinus ) in the Barents Sea and demonstrated a better or similar performance compared with a single species approach. The vertical distribution of cod and haddock was highly variable and was influenced by light level, water temperature, salinity, and depth. Temperature and sunlight were the most influential factors in this study. Increase in temperature resulted in decreasing catch and fish density in the acoustic dead zone (ADZ), while increasing sun altitude (surrogate for light level) increased the catch and fish density in the ADZ. The catch and density of haddock in the ADZ also increased at the lowest sun altitude level (shortly after midnight). Generally, the density of cod and haddock changed more rapidly in the ADZ than in the catch (from bottom to the effective fishing height) indicating the importance of modelling fish density in the ADZ. Finally, the uncorrelated variability in the annual residual variance of cod and haddock further strengthen the conclusion that species vertical distribution changes frequently and that there are probably many other unobserved environmental variables that affect them independently.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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  • 13
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    Connectivity among offshore feeding areas and nearshore spawning grounds; implications for management of migratory fish (2018)
    Oxford University Press
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    Publication Date: 2018-03-06
    Description: Knowing movement and structure of fish populations is a prerequisite for effective spatial fisheries management. The study evaluates migration patterns and connectivity of two groups of cod ( Gadus morhua ) associated with offshore feeding and nursery grounds. This was achieved by investigating (i) migration pathways of cod tagged at the feeding areas, (ii) immigration of cod to the areas based on mark-recapture data covering a period of two decades, and (iii) depth and temperature data from data storage tags (DSTs). Despite undertaking long-distance migrations after attaining sexual maturity, the cod aggregations in the two study areas appear to be largely separated from each other. This conclusion is supported by DSTs, indicating that mature fish associated with the two areas occupy different thermal-bathymetric niches. Low levels of connectivity suggest that effective spatial management in the two study areas would preserve fish of different origin. For the highly migratory adults, however, spatial management would need to focus on migration pathways and the areas where the fish are particularly vulnerable to fishing.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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  • 14
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    Disentangling the role of sea lice on the marine survival of Atlantic salmon (2018)
    Oxford University Press
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    Publication Date: 2018-03-06
    Description: The effects of sea lice on the marine survival of wild salmonids are widely debated. In Norway this debate has reached a crescendo as the Norwegian government has recently ratified a management system where the growth in the salmonid aquaculture industry will be conditional on regional estimated impact of salmon lice on wild fish. Sea lice have thus become the most prominent obstacle to the stated political aim of quintupling aquaculture production in Norway by 2050. Scientific documentation that salmon lice impact the marine survival of salmon is robust. However, it is also evident that marine survival of salmon is strongly impacted by other factors, and that the effect of salmon lice is most likely an integral part of these other mortality factors. In this paper, our goal is to discuss and give advice on how managers and policy makers should handle this complexity, and to identify the greatest challenges in using scientific results to construct robust management rules. Inadequate extrapolation from the scale of known effects to the scale of management implementation may initially give a false impression of scientific certainty, but will eventually fuel upsetting disagreements among stakeholders as they gradually uncover the shaky foundation of the implemented policy. Thus, using a single model and parameter to determine management advice is not warranted, as no single data point reflects the natural complexity of nature. Furthermore, robust management rules should be based on unambiguous definitions of key concepts. Finally, despite the scientific consensus that salmon lice are a risk to salmon, studies on wild populations in situ that accurately quantify the impact of salmon lice are still urgently needed. We give advice on how this can be accomplished.
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    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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  • 15
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    Clarifying the concept of climate change refugia for coral reefs (2018)
    Oxford University Press
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    Publication Date: 2018-03-06
    Description: Refugia can facilitate the persistence of biodiversity under changing environmental conditions, such as anthropogenic climate change, and therefore constitute the best chance of survival for many coral species in the wild. Despite an increasing amount of literature, the concept of coral reef refugia remains poorly defined; so that climate change refugia have been confused with other phenomena, including temporal refuges, pristine habitats and physiological processes such as adaptation and acclimatization. We propose six criteria that determine the capacity of refugia to facilitate species persistence, including long-term buffering, protection from multiple climatic stressors, accessibility, microclimatic heterogeneity, size, and low exposure to non-climate disturbances. Any effective, high-capacity coral reef refugium should be characterized by long-term buffering of environmental conditions (for several decades) and multi-stressor buffering (provision of suitable environmental conditions with respect to climatic change, particularly ocean warming and acidification). Although not always essential, the remaining criteria are important for quantifying the capacity of potential refugia.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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  • 16
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    Population-specific mortality in coho salmon (Oncorhynchus kisutch) released from a purse seine fishery (2018)
    Oxford University Press
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    Publication Date: 2018-03-06
    Description: Coastal commercial fisheries targeting Pacific salmon inevitably capture a mix of co-migrating species and genetically distinct populations within each species, only some of which are sufficiently abundant to sustain exploitation. Species-specific release measures are implemented as a conservation measure, but there remains little understanding of the resulting mortality. A purse seine fishery for Pacific salmon in British Columbia, Canada, was simulated with the goal of estimating post-release mortality for coho salmon, a species commonly released from commercial fisheries. Landed coho salmon ( n = 220) were tagged with acoustic transmitters and tracked along their coastal approach and into freshwater. Survival analyses accounting for variable migration pathways among populations revealed population-specific survival, with the population of greatest conservation concern having the best survival. Condition assessments revealed scale loss to be the strongest predictor of success. Physically exhausted fish, identified via reflex impairment tests, also experienced higher mortality. Results highlight the complexity of estimating release mortality in mixed-population commercial fisheries and are discussed in the context of management implications.
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    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
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  • 17
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    Commercial fisheries interactions with oil and gas pipelines in the North Sea: considerations for decommissioning (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: Commercial fisheries and oil and gas extraction are both spatially extensive industries in the North Sea (NS), and inevitably there is physical interaction where the two activities coincide. Regular contact between fishing gear and pipelines may risk pipeline integrity and could lead to gear snagging. It is also known, anecdotally, that some vessels target pipelines, potentially benefiting from local artificial reef effects. The impacts of pipeline decommissioning options (removal vs. in situ ) on commercial fisheries must be evaluated as part of the consenting process, but the degree of interaction between the two is presently unknown in the NS. Vessel Monitoring System (VMS) data for the Scottish demersal fleet were analysed with spatial data on pipelines. Approximately one-third (36.1%) of trips fished within 200 m of a pipeline over a 5-year period, suggesting that pipelines are subjected to regular interaction with fishing gear. The fishing effort (in hours) associated with pipelines was 2.52% of the total effort, compared to 1.33% in an equivalent area of seabed 1 km away, implying modest aggregation of fishing around pipelines. Only a small percentage (0.93%) of fishing trips actively targeted pipelines as fishing grounds. The highest level of fishing around pipelines occurred in the northeast NS. Pipeline sections with 〉100 h of fishing were typically larger diameter pipelines. The results suggest that pipeline decommissioning may have both negative (displacement of aggregated effort) and positive (reduced snagging potential) outcomes for commercial fisheries. It is recommended that where there is little or no fishing activity associated with pipelines, receptors other than fishing should be prioritized when selecting decommissioning strategies. Additionally, the intensity of fishing around pipelines should be used to inform the frequency of post-decommissioning integrity monitoring for any pipelines left in situ.
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    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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  • 18
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    Size-based indicators show depth-dependent change over time in the deep sea (2018)
    Oxford University Press
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    Publication Date: 2018-03-06
    Description: Size-based indicators are well established as a management tool in shelf seas as they respond to changes in fishing pressure and describe important aspects of community function. In the deep sea, however, vital rates are much slower and body size relationships vary with depth, making it less clear how size-based indicators can be applied and whether they are appropriate for detecting changes through time. The deep-sea fish stocks of the North Atlantic underwent a period of exploitation followed by management and conservation action that relieved this pressure. We used data from a deep-water bottom trawl survey in the Rockall Trough, at depths of 300–2000 m, to test whether size-based indicators changed over a 16-year period, during which fishing pressure decreased. We applied four indicators to these data: mean body length, mean maximum length, large fish indicator (LFI), and the slope of the biomass spectrum. Patterns were analysed within four different depth bands. The LFI and slope of the biomass spectrum showed positive change over time, suggesting recovery from fishing pressure. This response was generally most apparent in the shallowest depth band, where most fishing activity has been distributed. Values of the LFI were much higher overall than in shelf seas, so the same reference points cannot be applied to all marine ecosystems. These findings imply that size-based indicators can be usefully applied to the deep sea and that they potentially track changes in fishing pressure in the medium term.
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    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
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  • 19
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    Automatic fish species classification in underwater videos: exploiting pre-trained deep neural network models to compensate for limited labelled data (2018)
    Oxford University Press
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    Publication Date: 2018-03-06
    Description: There is a need for automatic systems that can reliably detect, track and classify fish and other marine species in underwater videos without human intervention. Conventional computer vision techniques do not perform well in underwater conditions where the background is complex and the shape and textural features of fish are subtle. Data-driven classification models like neural networks require a huge amount of labelled data, otherwise they tend to over-fit to the training data and fail on unseen test data which is not involved in training. We present a state-of-the-art computer vision method for fine-grained fish species classification based on deep learning techniques. A cross-layer pooling algorithm using a pre-trained Convolutional Neural Network as a generalized feature detector is proposed, thus avoiding the need for a large amount of training data. Classification on test data is performed by a SVM on the features computed through the proposed method, resulting in classification accuracy of 94.3% for fish species from typical underwater video imagery captured off the coast of Western Australia. This research advocates that the development of automated classification systems which can identify fish from underwater video imagery is feasible and a cost-effective alternative to manual identification by humans.
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    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
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  • 20
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    Migration patterns and putative spawning habitats of Atlantic halibut (Hippoglossus hippoglossus) in the Gulf of St. Lawrence revealed by geolocation of pop-up satellite archival tags (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: Characterizing migratory behaviours contributes to the sustainable management of marine fishes by resolving stock structure and identifying the timing and locations of events within fish life cycles. The migratory behaviour of Atlantic halibut ( Hippoglossus hippoglossus ) in the Gulf of St. Lawrence (GSL), Canada was characterized over an annual cycle using pop-up satellite archival tags ( n  = 15). Daily probability density functions of individual halibut positions were estimated using a geolocation model specifically developed to track demersal fish species in the GSL. Reconstructed migration routes ( n  = 8) revealed that Atlantic halibut displayed seasonal migrations, moving from deeper offshore waters in the winter to shallower nearshore waters in the summer. Variability in migratory behaviours was observed among individuals tagged at the same location and time. One individual resided year round in the vicinity of the tagging site, three individuals displayed homing behaviour, and four individuals did not return to the tagging site. The identification of presumed spawning rises for two individuals suggested that spawning of Atlantic halibut occurred in the GSL. Although based on a limited number of individuals, these results suggest that Atlantic halibut in the GSL forms a philopatric population, supporting the current separate management of this stock from the adjacent Scotian Shelf and southern Grand Banks stock.
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    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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