New research shows that millions of scavenging seabirds survive on fish discarded by North Sea fishing vessels, new research shows. University of Exeter’s scientists calculates that 267,000 tonnes of fish were thrown away in the North Sea in 2010 — sufficient to feed 3.45 million birds. This discard number is down from almost 510,000 tonnes — sufficient for an estimated 5.66 million birds—in 1990.
Dumping in the North Sea — one of the places in the world with the maximum levels of this — is thought to have climaxed around 1990. The study inspected eight species, including herring gulls and northern gannets, and the figures are based on birds that depend on to some extent on discarded fish (grounded on observations of how much discarded fish different bird species eat).
“Commercial fishing has a variety of impacts on marine life, but the effect of discards is one of the least considered and least recognized,” said chief author Dr. Richard Sherley, of the Environment and Sustainability Institute on Exeter’s Penryn Campus in Cornwall. “Our research emphasizes the sheer number of scavenging birds possibly supported by discards and thus the importance of knowing the wider ecological consequences of dumping fisheries waste.
“With discards decreasing over the period we studied, the number of birds able to depend on this has also dropped.”
The researchers approximate that the largest declines were in black‐legged kittiwakes (1.3 million), northern fulmars (1.4 million), and herring gulls (630,000). These drops also coincide with the population declines at some North Sea colonies in each of these types. However, the reasons for these declines are not completely clear, and may not necessarily be supported by changes in discards, though variations in herring gull numbers at some sites have been associated with diminishing discards.
Dr. Sherley said fish are thrown away for a variety of reasons.
“Fishers trying to trap one species may catch another (called bycatch), and some fish may be partially processed on fishing boats, with the subsequent remains thrown overboard,” he said. “Changes including the EU’s ‘landing obligation’ – which says any fish caught should be brought to shore—have decreased the amount of discard. “There have also been enhancements in fishery management, more targeted fishing—assisted by technology to avoid bycatch—and attempts to land and use any fish that are caught, even if they’re not among the types that humans generally eat.”
The study, backed by the University of Kiel (Germany), deliberated the following seabird species: northern gannet, northern fulmar, common gull, great skua, lesser black‐backed gull, great black‐backed gull, herring gull, and black‐legged kittiwake. The University of Exeter academics included masters student Hannah Ladd‐Jones and undergraduate Olivia Stevenson.
The research, published in the journal Fish and Fisheries, is titled: “Scavenger communities and fisheries waste: North Sea discards support 3 million seabirds, 2 million fewer than in 1990.”