Global Spatial Risk Assessment of Sharks Under the Footprint of Fisheries

Effective ocean management and conservation of highly migratory species depends on resolving overlap between animal movements and distributions and fishing effort. Yet, this information is lacking at a global scale. Here we show, using a big-data approach combining satellite-tracked movements of pelagic sharks and global fishing fleets, that 24% of the mean monthly space used by sharks falls under the footprint of pelagic longline fisheries. Space use hotspots of commercially valuable sharks and of internationally protected species had the highest overlap with longlines (up to 76% and 64%, respectively) and were also associated with significant increases in fishing effort. We conclude that pelagic sharks have limited spatial refuge from current levels of high-seas fishing effort. Results demonstrate an urgent need for conservation and management measures at high-seas shark hotspots and highlight the potential of simultaneous satellite surveillance of megafauna and fishers as a tool for near-real time, dynamic management

Challenges in Monitoring and Managing Large Marine Fishes: Lessons from the Galápagos Archipelago

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Spatial patterns of distribution and relative abundance of coastal shark species in the Galapagos Marine Reserve

A better understanding of the patterns of distribution and abundance of sharks and their potential biological and environmental drivers is essential to develop and evaluate spatial management plans for conservation and fisheries. Benthic and pelagic baited remote underwater stereo-video systems (stereo-BRUVs) were used to describe spatial and temporal patterns in coastal shark assemblages in the Galapagos Marine Reserve (GMR). From 629 stereo-BRUV deployments, 877 sharks from 10 species were recorded. Shark assemblages displayed high spatial variation, likely in response to the diversity of habitats occurring in the GMR. The relative importance of environmental and biological drivers differed among shark species according to their mobility. Some species were widespread across the Galapagos Archipelago (GA) but oc - curred primarily only as either juveniles (Carcharhinus galapagensis) or adults (C. limbatus and Triaenodon obesus), while others were more spatially restricted and associated with geographical features (Sphyrna lewini and Galeocerdo cuvier) or specific habitats (Triakidae spp. and Hetero - dontus quoyi). The highest diversity of sharks was found in the Centre South bioregion of the GA, in areas with heterogeneous habitat and high overall fish diversity (islets and Floreana Island), while the greatest total abundance of sharks was recorded at the northern oceanic islands of Darwin and Wolf. Overall, the GMR harbours a unique coastal shark community that varies in composition across the GA. It is dominated by large semipelagic species but is also characterised by the presence of less mobile benthic species that are not found near other oceanic islands in the Eastern Tropical Pacific region

Reply to: Shark mortality cannot be assessed by fishery overlap alone

Abstract not availableNuno Queiroz ... Simon D. Goldsworthy ... et al

Global spatial risk assessment of sharks under the footprint of fisheries

Effective ocean management and the conservation of highly migratory species depend on resolving the overlap between animal movements and distributions, and fishing effort. However, this information is lacking at a global scale. Here we show, using a big-data approach that combines satellite-tracked movements of pelagic sharks and global fishing fleets, that 24% of the mean monthly space used by sharks falls under the footprint of pelagic longline fisheries. Space-use hotspots of commercially valuable sharks and of internationally protected species had the highest overlap with longlines (up to 76% and 64%, respectively), and were also associated with significant increases in fishing effort. We conclude that pelagic sharks have limited spatial refuge from current levels of fishing effort in marine areas beyond national jurisdictions (the high seas). Our results demonstrate an urgent need for conservation and management measures at high-seas hotspots of shark space use, and highlight the potential of simultaneous satellite surveillance of megafauna and fishers as a tool for near-real-time, dynamic management.Nuno Queiroz, Nicolas E. Humphries, Ana Couto, Marisa Vedor ... Simon D. Goldsworthy ... Paul J. Rogers ... et al

Patterns of residency and diel occurrence of acoustic-tagged tiger sharks.

<p>Left panels refer to Bachas-Salinas and right panels to Cerro-Ballena. The top panel (a, b) shows residency index (RI, the total number of days a shark was detected divided by the number of days that the shark was monitored by the receivers) for the total monitored time (Total) and per season (Non-nesting and Nesting); the middle panel (c, d) shows Fast Fourier Transformations (FFT) of the number of hourly detections, with peaks indicating periods of dominant cycles; and the lower panel (e, f) shows daily detections of tiger sharks; the circle represents a period of 24 hours and the length of each wedge indicates the number of detections within each hour.</p

Collective activity space (95% PVC) and core range (50% PVC) areas (pooled across individual satellite-tagged tiger sharks) within the Galapagos Marine Reserve.

<p>Collective activity space (95% PVC) and core range (50% PVC) areas (pooled across individual satellite-tagged tiger sharks) within the Galapagos Marine Reserve.</p

12-hourly estimated positions provided by SSM by shark size.

<p>Colours indicate three size classes of tiger sharks (large = red, medium = orange, small = white). Black dashed lines indicate the 5 and 10 km buffer areas around the study sites (I-S = Isabela-South, C-B = Cerro Ballena, B-S = Bachas-Salinas) and sea turtle nesting beaches (white sea turtle icon). Local bathymetry is displayed by 100 m isobaths (blue dashed lines). Right panels show zoomed areas of the study sites of I-S (upper) and B-S (lower).</p

Relative abundance of tiger sharks at the three study sites.

<p>Number of individual tiger sharks per hour by sex recorded by the stereo-BRUVs in the nesting or the non-nesting season for turtles. The number of camera deployments at each site is reported in parentheses. The average TL ± SE (cm) of the sharks recorded at each site is given at the top of each bar.</p