Half a century of global decline in oceanic sharks and rays

Abstract

Overfishing is the primary cause of marine defaunation, yet individual species' declines and rising extinction risk are difficult to measure, particularly for the largest predators found in the high seas 1-3 . We calculate two well-established indicators to track progress towards Aichi Biodiversity Targets and Sustainable Development Goals 4,5 : the Living Planet Index (a measure of changes in abundance aggregating 57 abundance time-series for 18 oceanic shark and ray species), and the Red List Index (a measure of change in extinction risk calculated for all 31 oceanic species). We find that, since 1970, the global abundance of oceanic sharks and rays has declined by 71% due to an 18-fold increase in Relative Fishing Pressure. This depletion elevated global extinction risk to the point where three-quarters of this functionally important assemblage are threatened with extinction. Strict prohibitions and precautionary science-based catch limits are urgently needed to avert population collapse 6,7 , avoid disruption of ecological function, and promote species recovery 8,9 .Over the United Nations 'Decade of Biodiversity' from 2011-2020, governments committed to improve human well-being and food security by safeguarding ecosystem services and halting biodiversity loss 10 . The Sustainable Development Goals, adopted by all United Nations Member States, and the 20 Aichi Biodiversity Targets of the Convention on Biological Diversity, provide a framework to track progress towards the 2020 deadline 4,5,10 . Seafood sustainability is an integral part of these commitments, and wild capture fisheries are essential nutritional and economic resources for millions of people globally 11,12 . Yet beneath the ocean surface, it is difficult to assess changes in the state of biodiversity and ecosystem structure, function, and services 13 .

Temporal niche partitioning as a novel mechanism promoting co-existence of sympatric predators in marine systems

“…Regardless of the relative contribution of morphological versus behavioural mechanisms in driving patterns of diel activity, this study has demonstrated the importance of diel temporal variability as a niche partitioning axis in a marine predator guild for the first time. Recent and historical work suggests that healthy marine ecosystems are almost always characterized by abundant and diverse predator populations, although such healthy or pristine systems are unfortunately becoming increasingly rare [70,71]. Considering that many species of sharks tend to share space with other species as both juveniles and adults, and often display an overlap in prey and hierarchical predation that would incite interference competition, diel temporal niche partitioning may be an important factor in allowing multiple shark species to coexist in a variety of ecosystems.…”

Evolving Perspectives of Stewardship in the Seafood Industry

“…Much of this manuscript has tended toward the optimistic: introducing the possibilities and promise inherent to an industry showing initial signs of moving beyond short-term operational priorities to exploring the dimensions of stewardship. But a bitter reality of swift degradation of the biosphere cannot be ignored (Halpern et al, 2008;Crespo et al, 2019;Duarte et al, 2020;Pacoureau et al, 2021). The urgency of slowing and reversing current trajectories is omnipresent, as illustrated by a growing proportion of overfished stocks, a 70% loss of global shark and ray populations in 50 years, the rapid spread of antimicrobial resistance, and a dozen more grim statistics (Wernli et al, 2017;FAO, 2020;Lau et al, 2020;Pacoureau et al, 2021).…”

“…But a bitter reality of swift degradation of the biosphere cannot be ignored (Halpern et al, 2008;Crespo et al, 2019;Duarte et al, 2020;Pacoureau et al, 2021). The urgency of slowing and reversing current trajectories is omnipresent, as illustrated by a growing proportion of overfished stocks, a 70% loss of global shark and ray populations in 50 years, the rapid spread of antimicrobial resistance, and a dozen more grim statistics (Wernli et al, 2017;FAO, 2020;Lau et al, 2020;Pacoureau et al, 2021). The future of the ocean and humanity's relationship with it may rest on efforts to translate stewardship from an aspirational notion to a pillar of standard operating procedure anchored in supportive public policy.…”

The Eastern Tropical Pacific Marine Corridor (CMAR): The Emergence of a Voluntary Regional Cooperation Mechanism for the Conservation and Sustainable Use of Marine Biodiversity Within a Fragmented Regional Ocean Governance Landscape

“…Available at http://cmarpacifico.org/web-cmar/quienes-somos/que-es-el-cmar/. (Pacoureau et al, 2021) and a main reason for the decline of many migratory marine species in the ETPO (Peñaherrera-Palma et al, 2018, p. 71, 112). As well as intense fishing pressure from national vessels (WildAid, 2010, p. 2;The Economist, 2020;Hearn et al, 2021, p. 8), the high seas areas in this region have been subject to increased fishing effort in recent years by foreign flagged fleets, often loitering adjacent to or entering a marine protected area (Alava and Paladines, 2017;Collyns, 2020), a trend which is predicted to worsen in the future.…”