Cascading ecological effects of eliminating fishery discards

Abstract

Discarding by fisheries is perceived as contrary to responsible harvesting. Legislation seeking to end the practice is being introduced in many jurisdictions. However, discarded fish are food for a range of scavenging species; so, ending discarding may have ecological consequences. Here we investigate the sensitivity of ecological effects to discarding policies using an ecosystem model of the North Sea—a region where 30–40% of trawled fish catch is currently discarded. We show that landing the entire catch while fishing as usual has conservation penalties for seabirds, marine mammals and seabed fauna, and no benefit to fish stocks. However, combining landing obligations with changes in fishing practices to limit the capture of unwanted fish results in trophic cascades that can benefit birds, mammals and most fish stocks. Our results highlight the importance of considering the broader ecosystem consequences of fishery management policy, since species interactions may dissipate or negate intended benefits.

Exploring the effects of discarding using the Atlantis ecosystem model for Icelandic waters

“…Another study on the effect of landing discards and improving selectivity in the North Sea using an ecosystem model showed that landing discards had negative impacts on seabirds and mammals (Heath et al 2014), a finding which is consistent with those of the present study. Heat et al (2014) did, however, observe that seabirds and mammals could benefit from improved selectivity (depending on fishing pressure), which was not the case for the seabirds in the present study, though some of the mammals (e.g.…”

“…It also had little effect on the landings and profit, as the biomass of the discarded fish is low, even though their numbers are high. Another study on the effect of discards in the North Sea showed that landing discards had no effect on the stock size of fish groups (Heath et al 2014).…”

“…This change in predation mortality would, however, be overlooked by single-species models, which would predict higher yield with increased mesh size (Pope 1991). With ecosystem models the effect of the landing obligation and improved selectivity can be explored for the whole ecosystem (Heath et al 2014). Environmental factors also influence growth and survival of species but are usually excluded from multi-species model (Hollowed et al 2000).…”

Suitability of artisanal fishery discards as feed for juvenile tub gurnard (Chelidonichthys lucerna L.) reared in sea bottom cages in the mid Adriatic Sea

“…The adopted feeding plan was favorable because it largely reflected the feeding habits of gurnard in the local environment. Many studies have shown that fishery discards, which are not targeted by the http://epublishing.ekt.gr | e-Publisher: EKT | Downloaded at 10/05/2018 11:11:11 | fishery, may affect the biodiversity of the marine ecosystem (Johnsen & Eliasen, 2011;Heath et al, 2014;Sardà et al, 2015). When the current study was granted, the new EU CFP had not yet come into force; however, this study confirms that local fish species that are excluded by the market contain high amounts of protein and n-3-rich fatty acids.…”

The Common Fisheries Policy: A Difficult Compromise Between Relative Stability and the Discard Ban

“…58 Food subsidies to wildlife as a result of human activity have an important effect on terrestrial and aquatic ecosystems, and intentional discarding at sea is recognized as one of the major global subsidies. Heath et al (2014). 59 Wilson and Jacobsen (2009), p. 6.…”