Canadian fishery closures provide a large-scale test of the impact of gillnet bycatch on seabird populations

Abstract

In 1992, the eastern Canadian gillnet fisheries for northern cod and Atlantic salmon were largely closed. These large-scale fishery closures resulted in the removal of tens of thousands of gillnets known to inflict high levels of seabird mortality. We used this unprecedented opportunity to test the effects of gillnet removal on seabird populations. Consistent with predictions, we show that the breeding populations of divers (auks, gannets; susceptible to gillnet bycatch) have increased from pre-closure levels, whereas the populations of scavenging surface-feeders (gulls; low vulnerability to gillnet bycatch but susceptible to removal of fisheries discards) have decreased. Using the most complete series of seabird census data for the species most vulnerable to bycatch, we demonstrate a positive population response of common murres to reduction in gillnet fishing within its foraging range. These findings support the widespread but seldom documented contention that fisheries bycatch negatively impacts populations of non-target large vertebrates.

Reducing bycatch in gillnets: A sensory ecology perspective

“…This rate of bycatch is thought to be unsustainable for some species, and there is evidence that in some localities gillnet bycatch has resulted in severe reductions in the numbers of breeding birds (Osterblom et al, 2002;Regular et al, 2013). Bycatch is also a well-established issue for other animals groups including sea turtles (Chelonioidea), pinnipeds, cetaceans and blue water fish (Tunas Thunnus spp.…”

“…It is recognised that there is an urgent need to reduce this bycatch, but at the same time, in order to obtain support and adoption by the fishing industry, it is desirable not to reduce the efficiency of gillnet fishing. Spatial and temporal closures of fisheries have a role to play in managing the impact of gillnets (Regular et al, 2013), but these may be difficult to establish and enforce. Thus, technological solutions to gillnet bycatch, of which there are currently few, are sought as important additions to the suite of prospective management measures.…”

Survival on the rocks: high bycatch in lobster gillnet fisheries threatens hawksbill turtles on rocky reefs along the Eastern Pacific coast of Central America

“…1). MPAs and area closures that eliminate gillnet fishing can produce positive population responses of both non-target and target species within demarcated borders (Regular et al, 2013) and across a spillover-induced density gradient outside the borders of the protected area (Gell & Roberts, 2003;Goñi et al, 2006;Forcada et al, 2009). This is particularly true for coral and rocky reef ecosystems in low-income regions, where ubiquitous use of destructive fishing gears, such as gillnets, can degrade habitat and capture high proportions of immature individuals of target species ultimately leading to reduced yields (Cinner, 2010), which is currently observed in lobster gillnet fisheries at Los Cóbanos and Punta Amapala (CENDEPESCA, 2012).…”

Comprehensive estimates of seabird–fishery interactions for the US Northeast and mid‐Atlantic

“…Estimated seabird-fishery interactions involving gillnets were an order of magnitude higher than any other gear type considered (Table 4b), representing~84% of the total estimate. trawls, longlines), with relatively little attention on population impacts as a result of insufficient data (Lewison et al, 2014;Regular, Montevecchi, Hedd, Robertson, & Wilhelm, 2013;Žydelis et al, 2013). trawls, longlines), with relatively little attention on population impacts as a result of insufficient data (Lewison et al, 2014;Regular, Montevecchi, Hedd, Robertson, & Wilhelm, 2013;Žydelis et al, 2013).…”