Browsing by Author "Winker, Henning"
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- Conservation successes and challenges for wide-ranging sharks and raysPacoureau, Nathan; Carlson, John K.; Kindsvater, Holly K.; Rigby, Cassandra L.; Winker, Henning; Simpfendorfer, Colin A.; Charvet, Patricia; Pollom, Riley A.; Barreto, Rodrigo; Sherman, C. Samantha; Talwar, Brendan S.; Skerritt, Daniel J.; Sumaila, U. Rashid; Matsushiba, Jay H.; VanderWright, Wade J.; Yan, Helen F.; Dulvy, Nicholas K. (PNAS, 2023-01-23)Overfishing is the most significant threat facing sharks and rays. Given the growth in consumption of seafood, combined with the compounding effects of habitat loss, climate change, and pollution, there is a need to identify recovery paths, particularly in poorly managed and poorly monitored fisheries. Here, we document conservation through fisheries management success for 11 coastal sharks in US waters by comparing population trends through a Bayesian state-space model before and after the implementation of the 1993 Fisheries Management Plan for Sharks. We took advantage of the spatial and temporal gradients in fishing exposure and fisheries management in the Western Atlantic to analyze the effect on the Red List status of all 26 wide-ranging coastal sharks and rays. We show that extinction risk was greater where fishing pressure was higher, but this was offset by the strength of management engagement (indicated by strength of National and Regional Plan of Action for sharks and rays). The regional Red List Index (which tracks changes in extinction risk through time) declined in all regions until the 1980s but then improved in the North and Central Atlantic such that the average extinction risk is currently half that in the Southwest. Many sharks and rays are wide ranging, and successful fisheries management in one country can be undone by poorly regulated or unregulated fishing elsewhere. Our study underscores that well-enforced, science-based management of carefully monitored fisheries can achieve conservation success, even for slow-growing species.
- Estimating IUCN Red List population reduction: JARA-A decision-support tool applied to pelagic sharksSherley, Richard B.; Winker, Henning; Rigby, Cassandra L.; Kyne, Peter M.; Pollom, Riley; Pacoureau, Nathan; Herman, Katelyn; Carlson, John K.; Yin, Jamie S.; Kindsvater, Holly K.; Dulvy, Nicholas K. (2019-11)The International Union for Conservation of Nature's (IUCN) Red List is the global standard for quantifying extinction risk but assessing population reduction (criterion A) of wide-ranging, long-lived marine taxa remains difficult and controversial. We show how Bayesian state-space models (BSSM), coupled with expert knowledge at IUCN Red List workshops, can combine regional abundance data into indices of global population change. To illustrate our approach, we provide examples of the process to assess four circumglobal sharks with differing temporal and spatial data-deficiency: Blue Shark (Prionace glauca), Shortfin Mako (Isurus oxyrinchus), Dusky Shark (Carcharhinus obscurus), and Great Hammerhead (Sphyrna mokarran). For each species, the BSSM provided global population change estimates over three generation lengths bounded by uncertainty levels in intuitive outputs, enabling informed decisions on the status of each species. Integrating similar analyses into future workshops would help conservation practitioners ensure robust, consistent, and transparent Red List assessments for other long-lived, wide-ranging species.