Mapping patterns of shark finning and shark mortality through satellite-derived fishing effort data

About

There are approximately 1,041 known chondrichthyan species - the class of animals that includes sharks, rays, skates and chimaeras - living in the world oceans, and about 30% of these species are currently considered to be threatened with extinction, according to IUCN Red List of Threatened Species. Sharks are often killed for their valuable fins (“shark finning”) when they are caught as bycatch, but they may also be specifically targeted for their meat, fins, and oil. An estimated global mortality rate of 100 million sharks per year has been deemed unsustainable and has led to large population declines over the last 50 years. As a result, shark finning has been banned in many jurisdictions since the 2000s, however the practice reportedly continues in many areas.

Building upon a previous effort in 2013, we estimated the extent and geographic distribution of shark finning by using global satellite data to map out patterns of shark finning and shark mortality by fleet, Regional Fisheries Management Area (RFMO), and fishing nation to identify hotspots of shark mortality worldwide.

Approach

We combined estimates on the prevalence of shark catch, bycatch, and shark finning from our partners at Dalhousie University with satellite-derived fishing effort data for >100,000 fishing vessels tracked by Global Fishing Watch via analysis of Automatic Identification System Data and other sources. We layered this information with shark finning regulations, management effectiveness, and conservation status to map patterns of shark finning and shark mortality by fleet, management area, and fishing nation at a 1x1 degree square scale. We also conducted in-depth interviews with shark fishery experts to better contextualize current trends in shark finning and fishing practices.

Key findings

In collaboration with Dalhousie University and The Nature Conservancy, our team evaluated the effectiveness of shark regulation fishing and finning bans regulations in protecting shark populations. This first-of-its-kind study published in Science mapped spatial patterns of shark fishing mortality from 150 countries over the course of seven years. We found that total shark fishing mortality increased from 76 million to 80 million sharks per year even though protective legislation to reduce finning increased more than 10-fold during the same time. More than 30% of this catch was for species currently threatened with extinction. Mortality increased by 4% in coastal waters but decreased by 7% in pelagic fisheries, especially across the Atlantic and Western Pacific. By linking fishing mortality data to the global regulatory landscape, we show that widespread legislation designed to prevent shark finning did not reduce mortality but that regional shark fishing or retention bans had some success. These findings suggest that area-based conservation measures and species-specific fisheries management measures to address overcapacity and disincentivize retention regulations managed by regional fisheries management organizations may be more effective in protecting sharks.

Partners

This project is a collaboration led by Dr. Boris Worm at Dalhousie University.