Estimating IUCN Red List population reduction: JARA—A decision‐support tool applied to pelagic sharks

Abstract

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 datadeficiency: 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. K E Y W O R D SBayesian state-space model, biodiversity conservation, demography, elasmobranch, extinction risk, population decline, threatened speciesThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Overfishing drives over one-third of all sharks and rays toward a global extinction crisis

“…In addition, a concerted effort to compile time series of relative abundances, combined with decision-support Bayesian state-space methods has improved population reduction estimates. [31][32][33][34] These approaches were applied to 111 (9.3%) assessments. Prior to this development, the calculation of population reduction of relatively data-rich species was controversial (1) because of the challenge of choosing among multiple, potentially contradictory time series, and (2) because the focal species was a target or significant incidental catch of commercial fisheries.…”

“…Prior to this development, the calculation of population reduction of relatively data-rich species was controversial (1) because of the challenge of choosing among multiple, potentially contradictory time series, and (2) because the focal species was a target or significant incidental catch of commercial fisheries. 33 Further, new space-for-time approaches were applied to extensive baited remote underwater video abundance estimates for nine wide-ranging coral reef species 35…”

Long‐term catch trends and risk assessment of the Critically Endangered white‐spotted wedgefish (Rhynchobatus djiddensis) from South Africa

“…Based on the distribution of the posterior probability, the estimated population trend is assigned a probability of satisfying each of the Criterion A categories adopted by the IUCN Red List procedure: Least Concern, Near Threatened, Vulnerable, Endangered or Critically Endangered (Mace et al, 2008; IUCN, 2012). In this way, JARA allows for a quantitative approach to categorizing the threat of extinction that accounts for both the process error and uncertainty which are inherent in estimated population trends (Sherley et al, 2019; Winker, Pacoureau & Sherley, 2019). Here, we applied the JARA approach to the R. djiddensis standardized CPUE estimates and their associated standard errors, calculated from shore angling competition data from South Africa for the period 1977–2017.…”

“…The objectives of this study were to: (i) investigate the size composition and seasonality of catches taken by the competitive shore angling fishery on the east coast of South Africa from 1977 to 2017; (ii) investigate the size composition, sex ratio and seasonality of the shark net catches on the KZN coast from 1981 to 2017; (iii) investigate the catch per unit effort (CPUE) trends for both the competitive shore angling fishery and the KZN shark nets; and finally, (iv) incorporate the shore angling standardized CPUE model estimates into a Bayesian state‐space framework ‘JARA’ (Just Another Red‐List Assessment), with the aim of conducting a national population assessment for R. djiddensis as per the IUCN guidelines (Sherley et al, 2019).…”

Monitoring elasmobranch assemblages in a data-poor country from the Eastern Tropical Pacific using baited remote underwater video stations

“…Using bait increases the probability of detecting predators in the environment, since the resulting bait plume can trigger bait-search behaviors in nearby species 24,25 . Therefore, this technique has the potential to provide relatively fast baseline data on sharks and rays, an ecologically and economically important group for which basic information on distribution and population trends is often lacking 4,26 .…”