Spatial separation of catches in highly mixed fisheries

Dolder, Paul J.; Thorson, James T.; Minto, Cóilín

doi:10.1038/s41598-018-31881-w

Cited by 38 publications

(35 citation statements)

References 45 publications

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“…This result is comparable to Khoukh and Maynou (), who found that full protection of an important nursery area in the Catalan coast would be equivalent, in terms of increased catches, to a reduction of 20% in fishing effort. These results confirm the difficulty of optimally managing several species simultaneously in mixed fisheries (Dolder, Thorson, & Minto, ).…”

Section: Discussionsupporting

confidence: 81%

“…Fisheries management must ideally address the simultaneous optimisation of often conflicting biological, social and economic objectives. Co-viability analysis studies the evolution of dynamic systems under constraints (Oubraham & Zaccour, 2018) and has been applied to bioeconomic fisheries models (Gourguet et al, 2013;Maynou, 2014;Tserpes, Nikolioudakis, Maravelias, Carvalho, & Merino, 2016) to help identify the management strategies that ensure that a fishery is viable (under some conditions) simultaneously for two or more criteria. When strong or absolute co-viability (Baumgärtner & Quaas, 2007) cannot be obtained, the analysis allows, at least, for the ranking of different management measures in terms of biological, social or economic viability.…”

Section: Introductionmentioning

confidence: 99%

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Co‐viability of a Mediterranean demersal fishery affected by the discard ban under alternative management scenarios

Maynou

2019

Fisheries Management Eco

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The joint viability, or co‐viability, of a Mediterranean Sea mixed demersal fishery was examined by applying a bioeconomic fisheries model to the main seven target stocks of the fishery under biological, social and economic constraints. The stocks of interest were hake, black‐bellied angler, deep‐water rose shrimp, red mullet, blue and red shrimp, Norway lobster and blue whiting, all of which were assessed as overexploited. Their combined production corresponds to 34% by volume and 52% by value of the landings of the demersal fishery studied. Simulation scenarios based on effort reduction, changes in the selectivity pattern and implementing a fisheries restricted area were compared over the simulation horizon of 2015–2030. The latter two scenarios were also examined in terms of full or partial compliance. The effect of a discard ban on the economy of the fleet was also analysed. The results show that the fishery is not co‐viable because some stocks are not viable in the projection period, but social and economic viability was ensured in all cases. As is often the case for mixed fisheries, a unique management measure is unlikely to improve the situation of all stocks simultaneously, but all the management measures tested are better than the status quo.

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Section: Discussionsupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Co‐viability of a Mediterranean demersal fishery affected by the discard ban under alternative management scenarios

Maynou

2019

Fisheries Management Eco

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“…Dolder, Thorson, & Minto, 2018). Joint dynamic species distribution models (JDSDM), which estimate population density including the degree of spatial autocorrelation, account for covariation in density and productivity among multiple species and incorporate changes in spatial distribution for multiple species over time .…”

Section: Me Thodsmentioning

confidence: 99%

“…Specifically, the MICE-in-space model identifies the predicted mix of species encountered at any given location, thereby providing an estimate of likely technical interactions (e.g. Dolder, Thorson, & Minto, 2018).…”

Section: Me Thodsmentioning

confidence: 99%

Spatio‐temporal models of intermediate complexity for ecosystem assessments: A new tool for spatial fisheries management

2019

Self Cite

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Multispecies models are widely used to evaluate management trade‐offs arising from species interactions. However, identifying climate impacts and sensitive habitats requires integrating spatial heterogeneity and environmental impacts into multispecies models at fine spatial scales. We therefore develop a spatio‐temporal model of intermediate complexity for ecosystem assessments (a “MICE‐in‐space”), which is fitted to survey sampling data and time series of fishing mortality using maximum‐likelihood techniques. The model is implemented in the VAST R package, and it can be configured to range from purely descriptive to including ratio‐dependent interactions among species. We demonstrate this model using data for four groundfishes in the Gulf of Alaska using data from 1982 to 2015. Model selection for this case‐study shows that models with species interactions are parsimonious, although a model specifying separate density dependence without interactions also has substantial support. The AIC‐selected model estimates a significant, negative impact of Alaska pollock (Gadus chalcogrammus, Gadidae) on productivity of other species and suggests that recent fishing mortality for Pacific cod (G. microcephalus, Gadidae) is above the biological reference point (BRP) resulting in 40% of unfished biomass; other models show similar trends but different scales due to different BRP estimates. A simulation experiment shows that fitting a model with fewer species at a coarse spatial resolution degrades estimation performance, but that interactions and biological reference points can still be estimated accurately. We conclude that MICE‐in‐space models can simultaneously estimate fishing impacts, species trade‐offs, biological reference points and habitat quality. They are therefore suitable to forecast short‐term climate impacts, optimize survey designs and designate protected habitats.

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“…The area accommodates a high diversity of marine species that support fisheries targeting different species assemblages from pelagic to demersal (Gerritsen and Lordan 2011;Martinez et al 2013;Mateo et al 2017;Dolder et al 2018). The mixed nature of these fisheries leads to high discard rates, especially in the mixed demersal trawl fishery where many species occupy similar habitats and display similar behaviours making it difficult to selectively fish for individual species.…”

Section: Introductionmentioning

confidence: 99%

Spatial distribution of discards in mixed fisheries: species trade-offs, potential spatial avoidance and national contrasts

Robert

Calderwood

Radford

et al. 2019

Rev Fish Biol Fisheries

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Since 2015, the European Union gradually implemented the landing obligation (LO). This prohibits at-sea discarding of species under total allowable catch management. Spatiotemporal avoidance strategies and increasing fishing gear selectivity are two complementary levers that could help fishers in reducing the amount of discards. The objective of this paper is to analyse discarding practices of demersal mixed fisheries in the central part of the Celtic Sea to inform on potential spatial avoidance strategies of unwanted catches in a multi-species context. This study provides the first international and fine scale discard maps based on combined observer at-sea data from Ireland, France and the UK, the main countries fishing in the area. Using a suite of multivariate analyses, we identified areas with similar discard profiles, accounting for the multi-species nature of the fisheries. The maps were also derived separately for the three countries to examine national versus general patterns. Strong spatial segregation in effort between the countries, combined with nationally distinct quotas constraints, fisheries targets and market preferences, resulted in limited differences in the species composition of discards, but considerable differences in spatial discard patterns between countries. In theory, the maps based on discards below and above the minimum conservation reference size could inform fishers on areas to avoid but in practice, the spatial ubiquity of some species involved and strong technical interactions between fishing gears limit the possibility of avoiding discards. Some species trade-offs could be identified that might help to minimize adverse impacts of the implementation of the LO.

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Spatial separation of catches in highly mixed fisheries

Cited by 38 publications

References 45 publications

Co‐viability of a Mediterranean demersal fishery affected by the discard ban under alternative management scenarios

Co‐viability of a Mediterranean demersal fishery affected by the discard ban under alternative management scenarios

Spatio‐temporal models of intermediate complexity for ecosystem assessments: A new tool for spatial fisheries management

Spatial distribution of discards in mixed fisheries: species trade-offs, potential spatial avoidance and national contrasts

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