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

Abstract

Abstract. Incidental hooking of Carcharias taurus is a threat to their populations' recovery on the east coast of Australia. Photo-identification techniques were used to investigate the frequency of hooking at 25 aggregation sites along the east coast of Australia between 2006 and 2008. Of the 673 sharks identified, 113 sharks were identified with signs of 119 incidences of hooking. For sharks with both their left and right flank photographed during a single survey day, up to 29% of females and 52% of males were identified with retained fishing gear or an attributed jaw injury. The largest number of sharks identified (222) were from a year-round aggregation of immature and mature sharks at Fish Rock, New South Wales, Australia. Forty-eight per cent of all sharks identified with retained fishing gear were first identified at this site. Fish Rock, a designated critical habitat for C. taurus, allows most forms of line fishing except fishing with bait or wire trace while anchored or moored. As interactions with fishing gear can result in debilitating disease, morbidity and death, the high incidence of hooked individual C. taurus is considered a key threatening process that is likely to reduce this shark population's ability to recover.

Distribution, site affinity and regional movements of the manta ray, Manta alfredi (Krefft, 1868), along the east coast of Australia

“…There is a possibility that rocky reefs and coral islands act as landmarks that are used by manta rays to orient themselves within their home range, and are also used during seasonal migrations. The observation of manta rays in moderately large numbers at prominent features may be analogous to the behaviour of grey nurse sharks, C. taurus, along the same coastline, in which sharks aggregate at and move between specific sites (Bansemer and Bennett 2010). It is also important to note that while the majority of our manta ray observations occurred at popular SCUBA-diving locations, as they are a major ecotourism drawcard, it does not preclude their occurrence at other non-dived sites.…”

Decadal trends in shark catches and effort from the New South Wales, Australia, Shark Meshing Program 1950 - 2010

“…Unfortunately, the lack of peaks in capture at any beaches, even for beaches such as Maroubra, which is within close proximity to a grey nurse shark Critical Habitat, precludes attempts to reduce capture of this Critically Endangered species. The small population size (Cardno Ecology Laboratory 2010), genetic isolation of the eastern-coast population of grey nurse sharks (Stow et al 2006;Ahonen et al 2009), plus ongoing captures in commercial (Macbeth et al 2009) and recreational (Bansemer and Bennett 2010) fishing gear all combine with ongoing catches in the NSW and Qld shark-meshing programs to contributing to the threatened nature of this population. Ongoing attempts to reduce negative human-induced effects should therefore continue to be a priority for this species.…”

Sex- and maturity-based differences in movement and migration patterns of grey nurse shark, Carcharias taurus, along the eastern coast of Australia

“…1) in July-August 2006and FebruaryMarch 2007, unless an absence of C. taurus was confirmed by local diver operators within the survey period. Each survey period was 27-48 days (weather dependent) (Bansemer and Bennett 2010). A PID survey comprised at least two 20-60-min dives conducted in a single day and aimed to photograph all C. taurus individuals at an aggregation site.…”

“…1. Individual sharks were identified by the unique spot-patterns on their flanks, with photographic matches of individuals used to describe a particular shark's movement patterns (Bansemer and Bennett 2008, 2010. Digital images of the flanks of sharks were obtained with cameras in underwater housings (video: DSRHC1000, Sony, Tokyo, Japan, and Invader Amphibico, Saint Laurent, Canada; still: DSC-100 and MPK-PHP, Sony, Tokyo, Japan; EOS400D, Canon, Tokyo, Japan; and SLR-DC, Ikelite, Indianapolis, USA).…”

“…Here, we utilise photo-identification (Bansemer and Bennett 2008, 2010 to determine the timing, magnitude and direction of movement of C. taurus. Heterogeneity of movement in relation to maturity, sex and pregnancy status was examined on the basis of observations of individually recognisable sharks at aggregation sites along the eastern seaboard of Australia.…”