Scavenger communities and fisheries waste: North Sea discards support 3 million seabirds, 2 million fewer than in 1990

Abstract

Understanding fishery impacts is imperative for understanding marine ecology and conservation. The global marine fishing industry currently dumps ~10 million tonnes (10%) of their annual catch (Zeller, Cashion, Palomares, & Pauly, 2018), yet discarding is probably one of the least studied component of fishery impacts. Discarding peaked at 18.9 million tonnes in 1989, but has since almost halved (Zeller et al., 2018), and changes in policy, such as discard bans in the European Union (EU Landing Obligation), Norway, Chile and New Zealand, are likely to reduce discarding further (Real et al., 2018). Although bans are desirable for stock management, they may have unforeseen knock-on effects for the mammals, seabirds, fishes and crustaceans that scavenge on discharged biomass (Bicknell, Oro,

Sexual Mismatch Between Vessel-Associated Foraging and Discard Consumption in a Marine Top Predator

“…Discards are an important food source for many seabirds around the world (i.e., 52% of seabird species exploit discards to different degrees) in the form of undersized fish, offal or non-commercial species (Furness, 2003;Oro et al, 2013). For example, in the North Sea, fisheries discards support around three million seabirds (Sherley et al, 2020), enabling access to prey species otherwise beyond the diving ability of many species (Furness et al, 1988;Navarro et al, 2009). Changes in discard availability affect several ecological processes and trophic levels, and thus can have effects that propagate through the whole ecosystem (Votier et al, 2004;Oro et al, 2013).…”

First records of Gray-hooded Gull, Chroicocephalus cirrocephalus (Vieillot, 1818) (Charadriiformes, Laridae), in the state of Espírito Santo, Brazil

“…Based on an increasing number of records for Grayhooded Gull in the last decades, including breeding evidence in northern Rio de Janeiro, noted that this species has expanded its range along the Brazilian coast. This range expansion could be associated with ongoing habitat degradation and availability of anthropogenic food resources (Camphuysen and Garthe 2000;Sherley et al 2019). In Argentina, population growth and range expansion of Kelp Gull, Larus dominicanus Lichtenstein, 1823, was observed on the coast of northern Patagonia and was possibly linked to anthropogenic food resources (Lisnizer et al 2011).…”

Observation of marine mammal and bird interactions focused around a commercial fishing vessel in central Baffin Bay, Nunavut

“…Fisheries can provide food resources that would normally not be available to predators through discards, including bycatch and offal, and via depredation of fishing gear, such as long lines (Read 2008). For marine birds, fisheries discards are well documented as supplementary food, influencing foraging behaviour, diet and distribution across fisheries and oceans (Tasker et al 2000;Renner et al 2013;Sommerfeld et al 2016;Sherley et al 2020). In many instances, these discards provide a resource (e.g., occurring at great depths or benthic species) that would otherwise be inaccessible to predators limited by diving capabilities (Schreer and Kovacs 1997).…”