Effects of recreational and commercial fishing on blue sharks (Prionace glauca) in Atlantic Canada, with inferences on the North Atlantic population

Abstract

The nominal catch of blue sharks (Prionace glauca) reported for the Canadian Atlantic grossly underestimates the annual catch mortality of about 1000 tonnes (t), making blue sharks the most frequently caught large shark in Canadian waters. Although blue sharks accounted for 99% of all sharks landed at recreational shark fishing tournaments, tournament catches accounted for only 3% of total fishing mortality. Standardized catch rate indices suggested a decline in blue shark abundance of about 5%–6%·year–1 since 1995. An increased mortality rate in recent years was suggested by a decline in the median size of blue sharks in the commercial catch. Two independent calculations suggest that North Atlantic catches exceeded 100 000 t, with catch mortalities ranging between 26 000 and 37 000 t. Because tagging studies indicated that blue sharks are highly migratory with a single population in the North Atlantic, the Canadian contribution to overall population mortality accounts for only 2% of the total. The fact that blue shark populations are relatively productive and resilient may help explain their persistence in the face of high international catch mortality and a decline in relative abundance.

Risk perceptions and conservation ethics among recreational anglers targeting threatened sharks in the subtropical Atlantic

“…Commercial exploitation is a larger contributor to their overall extinction risk compared to recreational fishing (Worm et al 2013). Although it is generally accepted that shark fishing mortality is much higher in commercial fisheries than in the recreational sector (Pine et al 2008) and that fishing mortality in general is more detrimental to shark populations than other anthropogenic impacts, sharks have been highly prized in recreational fisheries globally since the mid-20th century, and is a growing source of significant mortality (Pepperell 1992, Campana et al 2006). In the USA alone, more large sharks were killed by recreational anglers than commercial fishers in 2013 (Lowther & Liddel 2014, Shiffman 2014.…”

Retained fishing gear and associated injuries in the east Australian grey nurse sharks (Carcharias taurus): implications for population recovery

“…Many shark species that are targeted commercially, caught and harvested as bycatch, or captured incidentally and released by recreational or commercial fishers are at risk of over-exploitation and possible extinction (Baum et al 2005;Campana et al 2006;Myers et al 2007). Significant population declines of the grey nurse shark, Carcharias taurus (Rafinesque 1810), throughout most of its range has resulted in it being listed as Vulnerable on the World Conservation Union's Red List of threatened species (IUCN 2009) and Critically Endangered on the Australian east coast (Bansemer and Bennett 2008).…”

Transboundary movements, unmonitored fishing mortality, and ineffective international fisheries management pose risks for pelagic sharks in the Northwest Atlantic

“…(c) CPUE (North Atlantic) -The mean recent pelagic longline CPUE of blue sharks across several nations fishing for sharks in the North Atlantic was 18.4 sharks·1000 hooks -1 , corresponding to 430 kg·1000 hooks -1 (Campana et al 2006). North Atlantic pelagic longline effort was the value used in Campana et al (2009).…”