We describe the temporal and spatial patterns of three tetrapod groups (sea turtles, seabirds, an... more We describe the temporal and spatial patterns of three tetrapod groups (sea turtles, seabirds, and cetaceans) stranded in southeast Brazil, based on daily beach surveys of over >800 km of coastline between 2015 and 2020. Patterns were analysed by stranding rates (individuals/1000 km of coastline) of groups and species; for the 14 most numerous species, we also fitted generalized additive models for location, scale, and shape (GAMLSS) using temporal and spatial explanatory variables. We recorded 53850 animals (22738 sea turtles, 28155 birds, and 2957 cetaceans) of 78 species. Higher stranding numbers were observed during winter/spring for all groups, and could be an effect of a higher occurrence/abundance at the region, driven by productive waters, jointly with higher stranding probabilities due to stronger drifting forces. Most modelled species showed temporal and spatial stranding patterns most likely related to their general occurrence/abundance cycles in southeast Brazil, but ...
<p>Estimated smooth function (solid line) with 95% confidence interval (dashed lines) for t... more <p>Estimated smooth function (solid line) with 95% confidence interval (dashed lines) for the fitted GAM by year (A) and month (B) from 1992 to 2013. Y-axis = fitted function with estimated degrees of freedom in parentheses.</p
<p>Estimated smooth function (solid line) with 95% confidence interval (dashed lines) for t... more <p>Estimated smooth function (solid line) with 95% confidence interval (dashed lines) for the fitted GAM by year (A) and month (B) from 1992 to 2013. Y-axis = fitted function with estimated degrees of freedom in parentheses.</p
<p>The total stranding events for each species is given as number and as percentage. Mean a... more <p>The total stranding events for each species is given as number and as percentage. Mean annual stranding rates are shown in the last column.</p
<p>Estimated smooth function (solid line) with 95% confidence interval (dashed lines) for t... more <p>Estimated smooth function (solid line) with 95% confidence interval (dashed lines) for the fitted GAM by year and month from 1992 to 2013. Neonates (A and B) and juveniles/adults (C and D). Y-axis = fitted function with estimated degrees of freedom in parentheses.</p
Bycatch is one of the main causes of mortality of marine megafauna over the world. In the coastal... more Bycatch is one of the main causes of mortality of marine megafauna over the world. In the coastal waters of southern Brazil, bycatch in gillnet fisheries affects threatened species that use this region as a breeding and feeding area. The identification of hotspot areas of bycatch is necessary to design and prioritize efficient spatial-temporal closures that protect the largest possible number of threatened species of marine megafauna. In this context, the use of a multispecies approach is an important step towards planning effective fisheries management measures. This study has two main objectives: 1) to identify hotspot areas of bycatch in gillnet fisheries for the most threatened marine megafauna species on the continental shelf of Rio Grande do Sul (RS); 2) compare single species and multispecies mapping methods for the identification of these areas. To meet these objectives, data collected by onboard observers during fishing trips in the coastal commercial RS-based gillnet fleet...
<p>Estimated smooth function (solid line) with 95% confidence interval (dashed lines) for t... more <p>Estimated smooth function (solid line) with 95% confidence interval (dashed lines) for the fitted GAM by year (A) and month (B) from 1992 to 2013. Y-axis = fitted function with estimated degrees of freedom in parentheses.</p
Franciscana dolphin Pontoporia blainvillei bycatch has been high for near six decades in western ... more Franciscana dolphin Pontoporia blainvillei bycatch has been high for near six decades in western South Atlantic, with large regional variation. In 2012, the Brazilian Government‐regulated gillnet fisheries in south and southeast Brazil by reducing fishing effort and establishing no‐fishing zones. However, there is evidence that the magnitude of franciscana bycatch remains high and unsustainable. The aims of this study were to identify hotspot areas of franciscana bycatch associated with two main gillnet fisheries and to propose no‐fishing zones combined with limited total allowable fishing effort (i.e. total net length per season) in order to meet management objectives in southern Brazil. A hierarchical Bayesian model using integrated nested Laplace approximation (INLA) was employed based on 1427 reported settings from 1999 to 2003 and 2006 to 2009. Hotspot zones were detected and are proposed as no‐fishing zone during the white croaker Micropogonias furnieri and striped weakfish Cynoscion guatucupa gillnet fishing seasons. Their extents represent 6% (1466.8 km2) and 19% (4493.7 km2) of the fishing ground (23 204.1 km2) during croaker and weakfish fishing seasons respectively. The total allowable fishing effort estimated outside the no‐fishing zones were estimated at 541 km (95% credible interval (CrI) [339; 940]) during croaker and 688 km (CrI [312; 2,166]) during weakfish fishing seasons, one order of magnitude lower than the current total fishing effort. The drastic reduction of total fishing effort estimated in this study is largely due to weak protection measures since the gillnet fisheries became the major conservation concern for franciscana by the end of 1970s in southern Brazil. Although the implementation of the proposed exclusion zones and limiting fishing effort will strongly impact the status quo, they were based on the best scientific evidence and on a clearly defined management goal to reduce the risk of the franciscana population’s collapse in southern Brazil.
We describe the temporal and spatial patterns of three tetrapod groups (sea turtles, seabirds, an... more We describe the temporal and spatial patterns of three tetrapod groups (sea turtles, seabirds, and cetaceans) stranded in southeast Brazil, based on daily beach surveys of over >800 km of coastline between 2015 and 2020. Patterns were analysed by stranding rates (individuals/1000 km of coastline) of groups and species; for the 14 most numerous species, we also fitted generalized additive models for location, scale, and shape (GAMLSS) using temporal and spatial explanatory variables. We recorded 53850 animals (22738 sea turtles, 28155 birds, and 2957 cetaceans) of 78 species. Higher stranding numbers were observed during winter/spring for all groups, and could be an effect of a higher occurrence/abundance at the region, driven by productive waters, jointly with higher stranding probabilities due to stronger drifting forces. Most modelled species showed temporal and spatial stranding patterns most likely related to their general occurrence/abundance cycles in southeast Brazil, but ...
<p>Estimated smooth function (solid line) with 95% confidence interval (dashed lines) for t... more <p>Estimated smooth function (solid line) with 95% confidence interval (dashed lines) for the fitted GAM by year (A) and month (B) from 1992 to 2013. Y-axis = fitted function with estimated degrees of freedom in parentheses.</p
<p>Estimated smooth function (solid line) with 95% confidence interval (dashed lines) for t... more <p>Estimated smooth function (solid line) with 95% confidence interval (dashed lines) for the fitted GAM by year (A) and month (B) from 1992 to 2013. Y-axis = fitted function with estimated degrees of freedom in parentheses.</p
<p>The total stranding events for each species is given as number and as percentage. Mean a... more <p>The total stranding events for each species is given as number and as percentage. Mean annual stranding rates are shown in the last column.</p
<p>Estimated smooth function (solid line) with 95% confidence interval (dashed lines) for t... more <p>Estimated smooth function (solid line) with 95% confidence interval (dashed lines) for the fitted GAM by year and month from 1992 to 2013. Neonates (A and B) and juveniles/adults (C and D). Y-axis = fitted function with estimated degrees of freedom in parentheses.</p
Bycatch is one of the main causes of mortality of marine megafauna over the world. In the coastal... more Bycatch is one of the main causes of mortality of marine megafauna over the world. In the coastal waters of southern Brazil, bycatch in gillnet fisheries affects threatened species that use this region as a breeding and feeding area. The identification of hotspot areas of bycatch is necessary to design and prioritize efficient spatial-temporal closures that protect the largest possible number of threatened species of marine megafauna. In this context, the use of a multispecies approach is an important step towards planning effective fisheries management measures. This study has two main objectives: 1) to identify hotspot areas of bycatch in gillnet fisheries for the most threatened marine megafauna species on the continental shelf of Rio Grande do Sul (RS); 2) compare single species and multispecies mapping methods for the identification of these areas. To meet these objectives, data collected by onboard observers during fishing trips in the coastal commercial RS-based gillnet fleet...
<p>Estimated smooth function (solid line) with 95% confidence interval (dashed lines) for t... more <p>Estimated smooth function (solid line) with 95% confidence interval (dashed lines) for the fitted GAM by year (A) and month (B) from 1992 to 2013. Y-axis = fitted function with estimated degrees of freedom in parentheses.</p
Franciscana dolphin Pontoporia blainvillei bycatch has been high for near six decades in western ... more Franciscana dolphin Pontoporia blainvillei bycatch has been high for near six decades in western South Atlantic, with large regional variation. In 2012, the Brazilian Government‐regulated gillnet fisheries in south and southeast Brazil by reducing fishing effort and establishing no‐fishing zones. However, there is evidence that the magnitude of franciscana bycatch remains high and unsustainable. The aims of this study were to identify hotspot areas of franciscana bycatch associated with two main gillnet fisheries and to propose no‐fishing zones combined with limited total allowable fishing effort (i.e. total net length per season) in order to meet management objectives in southern Brazil. A hierarchical Bayesian model using integrated nested Laplace approximation (INLA) was employed based on 1427 reported settings from 1999 to 2003 and 2006 to 2009. Hotspot zones were detected and are proposed as no‐fishing zone during the white croaker Micropogonias furnieri and striped weakfish Cynoscion guatucupa gillnet fishing seasons. Their extents represent 6% (1466.8 km2) and 19% (4493.7 km2) of the fishing ground (23 204.1 km2) during croaker and weakfish fishing seasons respectively. The total allowable fishing effort estimated outside the no‐fishing zones were estimated at 541 km (95% credible interval (CrI) [339; 940]) during croaker and 688 km (CrI [312; 2,166]) during weakfish fishing seasons, one order of magnitude lower than the current total fishing effort. The drastic reduction of total fishing effort estimated in this study is largely due to weak protection measures since the gillnet fisheries became the major conservation concern for franciscana by the end of 1970s in southern Brazil. Although the implementation of the proposed exclusion zones and limiting fishing effort will strongly impact the status quo, they were based on the best scientific evidence and on a clearly defined management goal to reduce the risk of the franciscana population’s collapse in southern Brazil.
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