Every year fisheries discard >10 million tonnes of fish. This provides a bounty for scavengers,
yet the ecological impact of discarding is understudied. Seabirds are the best-studied discard
scavengers and fisheries have shaped their movement ecology, demography and community
structure. However, we know little about the number of ...
Every year fisheries discard >10 million tonnes of fish. This provides a bounty for scavengers,
yet the ecological impact of discarding is understudied. Seabirds are the best-studied discard
scavengers and fisheries have shaped their movement ecology, demography and community
structure. However, we know little about the number of scavenging seabirds that discards
support, how this varies over time or might change as stocks and policy change. Here we use
a Bayesian bioenergetics model to estimate the number of scavenging birds potentially
supported by discards in the North Sea (one of the highest discard-producing regions) in 1990,
around the peak of production, and again after discard declines in 2010. We estimate that
North Sea discards declined by 48% from 509,840 tonnes in 1990 to 267,549 tonnes in 2010.
This waste had the potential to support 5.66 (95% credible intervals: 3.33–9.74) million
seabirds in the 1990s, declining by 39% to 3.45 (1.98–5.78) million birds by 2010. Our study
reveals the potential for fishery discards to support very large scavenging seabird communities
but also shows how this has declined over recent decades. Discard bans, like the European
Union’s Landing Obligation, may reduce inflated scavenger communities, but come against a
backdrop of gradual declines potentially buffering deleterious impacts. More work is required
to reduce uncertainty and to generate global estimates, but our study highlights the magnitude
of scavenger communities potentially supported by discards and thus the importance of
understanding the wider ecological consequences of dumping fisheries waste