Extinction risk and overfishing: reconciling conservation and fisheries perspectives on the status of marine fishes

Abstract

Anthropogenic disturbances are ubiquitous in the ocean, but their impacts on marine species are hotly debated. We evaluated marine fish statuses using conservation (Red List threatened or not) and fisheries (above or below reference points) metrics, compared their alignment, and diagnosed why discrepancies arise. Whereas only 13.5% of Red Listed marine fishes (n = 2952) are threatened, 40% and 21% of populations with stock assessments (n = 166) currently are below their more conservative and riskier reference points, respectively. Conservation and fisheries metrics aligned well (70.5% to 80.7%), despite their mathematical disconnect. Red Listings were not biased towards exaggerating threat status, and egregious errors, where populations were categorized at opposite extremes of fisheries and conservation metrics, were rare. Our analyses suggest conservation and fisheries scientists will agree on the statuses of exploited marine fishes in most cases, leaving only the question of appropriate management responses for populations of mutual concern still unresolved.

Figure 1. Total number of marine fish species on the IUCN Red List each year by category.

Red List categories are Data Deficient (DD), Least Concern (LC), Near Threatened (NT), or one of the three threatened categories, Vulnerable (VU), Endangered (EN), Critically Endangered (CR). Inset is expanded view of the species listed in threatened categories: VU, EN, or CR.

Figure 2. Proportion (%) of assessed marine fish populations that currently meet (A–C), or have ever met (D–F), fisheries or conservation criteria for concern.

(A) Current adult biomass of European populations (n = 42) as a proportion of their B_pa and B_lim reference points, and (D) the minimum adult biomass ever experienced by those same populations as a proportion of their reference points. Colors correspond to fisheries threat level: above upper ICES reference point B_pa (green), between upper and lower ICES reference points (yellow), and below B_lim (red); (B) Current adult biomass of all other assessed populations (n = 124) as a proportion of their B_msy reference point, and (E) the minimum adult biomass ever experienced by those same populations as a proportion of their B_msy reference point. Colors correspond to increasing threat, from not overfished (green) through to overfished (orange and red). (C) Estimated percent change in adult biomass for each population (n = 166) from the most recent year back over the longer of ten years or three generations, and the corresponding IUCN Red List category: CR (red), EN (orange), VU (yellow), or not threatened (green), under Criterion A1. (F) Estimated greatest percent decline in adult biomass for the same populations (n = 166) over the longer of ten years or three generations, and the corresponding IUCN Red List category, as above.

Figure 3. Time series of adult biomass illustrating cases of alignment and misalignment.

Populations are organized by management region: US (left column), non-US (middle column), or Europe (right column), and illustrate cases where the current fisheries reference points and estimated IUCN Red List status (Criterion A1) align (positive hits (top row) or negative hits (2nd row)), where the Red List would miss listing an overfished population as threatened (3rd row), or would list a population that is not considered overfished as threatened, producing a false alarm (bottom row): (A) Georges Bank Atlantic cod (Gadus morhua), (B) Atlantic bluefin tuna (Thunnus thynnus), (C) Irish Sea Atlantic cod (G. morhua), (D) U.S. northern Pacific Coast petrale sole (Eopsetta jordani), (E) Central western Pacific yellowfin tuna (Thunnus albacares), (F) Iceland cod (G. morhua), (G) Southern New England-Mid Atlantic yellowtail flounder (Limanda ferruginea), (H) Western Pacific Ocean striped marlin (Kajikia audax), (I) North Sea and eastern Channel whiting (Merlangius merlangus), (J) Bering Sea and Aleutian Islands Greenland turbot (Reinhardtius hippoglossoides), (K) Indian Ocean bigeye tuna (T. obesus), and (L) Faroe Plateau Atlantic cod (G. morhua). Note (L) is only a false alarm from the perspective of its lower fisheries reference point. Colored circles correspond to IUCN Red List categories: Critically Endangered (red), Endangered (orange), Vulnerable (yellow), or not threatened (green); associated estimated decline is located in the upper left of each plot. Colored dotted lines correspond to fisheries reference points: B_msy or B_pa (green), 0.5B_msy (yellow), 0.2B_msy or B_lim (red).