Group items tagged

Human activities in the oceans increase the extinction risk of marine megafauna. Interventions require an understanding of movement patterns and the spatiotemporal overlap with threats. We analysed the movement patterns of 33 white sharks (Carcharodon carcharias) satellite-tagged in South Africa between 2012 and 2014 to investigate the influence of size, sex and season on movement patterns and the spatial and temporal overlap with longline and gillnet fisheries and marine protected areas (MPAs). We used a hidden Markov model to identify 'resident' and 'transient' movement states and investigate the effect of covariates on the transition probabilities between states. A model with sex, total length and season had the most support. Tagged sharks were more likely to be in a resident state near the coast and a transient state away from the coast, while the probability of finding a shark in the transient state increased with size. White sharks moved across vast areas of the southwest Indian Ocean, emphasising the need for a regional management plan. White sharks overlapped with longline and gillnet fisheries within 25% of South Africa's Exclusive Economic Zone and spent 15% of their time exposed to these fisheries during the study period. The demersal shark longline fishery had the highest relative spatial and temporal overlap, followed by the pelagic longline fishery and the KwaZulu-Natal (KZN) shark nets and drumlines. However, the KZN shark nets and drumlines reported the highest white shark catches, emphasising the need to combine shark movement and fishing effort with reliable catch records to assess risks to shark populations accurately. White shark exposure to shark nets and drumlines, by movement state, sex and maturity status, corresponded with the catch composition of the fishery, providing support for a meaningful exposure risk estimate. White sharks spent significantly more time in MPAs than expected by chance, likely due to increased prey abundance

Human activities in the oceans increase the extinction risk of marine megafauna. Interventions require an understanding of movement patterns and the spatiotemporal overlap with threats. We analysed the movement patterns of 33 white sharks (Carcharodon carcharias) satellite-tagged in South Africa between 2012 and 2014 to investigate the influence of size, sex and season on movement patterns and the spatial and temporal overlap with longline and gillnet fisheries and marine protected areas (MPAs). We used a hidden Markov model to identify 'resident' and 'transient' movement states and investigate the effect of covariates on the transition probabilities between states. A model with sex, total length and season had the most support. Tagged sharks were more likely to be in a resident state near the coast and a transient state away from the coast, while the probability of finding a shark in the transient state increased with size. White sharks moved across vast areas of the southwest Indian Ocean, emphasising the need for a regional management plan. White sharks overlapped with longline and gillnet fisheries within 25% of South Africa's Exclusive Economic Zone and spent 15% of their time exposed to these fisheries during the study period. The demersal shark longline fishery had the highest relative spatial and temporal overlap, followed by the pelagic longline fishery and the KwaZulu-Natal (KZN) shark nets and drumlines. However, the KZN shark nets and drumlines reported the highest white shark catches, emphasising the need to combine shark movement and fishing effort with reliable catch records to assess risks to shark populations accurately. White shark exposure to shark nets and drumlines, by movement state, sex and maturity status, corresponded with the catch composition of the fishery, providing support for a meaningful exposure risk estimate. White sharks spent significantly more time in MPAs than expected by chance, likely due to increased prey abundance

A veteran WA diver has discovered a remote haven for great white sharks, including babies, that could indicate a nearby nursery off WA's south coast.

A veteran WA diver has discovered a remote haven for great white sharks, including babies, that could indicate a nearby nursery off WA's south coast.

Great white shark killed Australian diver: officials.

Australian surfer in bloody shark attack.

Fisheries cleared to catch, kill sharks.

'Screams' could chase away other marine life.

Western Australia applies to extend shark cull for three years.

Ne pas se jeter dans la gueule du requin.

Hunt on for killer shark in Australia.

Australia: Bryn Martin Feared Shark Attack Victim.

Un nageur australien disparaît, probablement victime d'un grand requin blanc.

Australia's 'Rogue' Man-Eating Sharks Actually Chasing Whales.

GOING ROGUE: Has this shark killed three people in two months?

Sharks of more than three metres to be caught, shot and dumped into sea.

West Australian shark attack: authorities seek to kill great white after Jay MUSCAT death.

West Australian shark attack: authorities seek to kill great white after Jay MUSCAT death.

WA shark cull: Colin BARNETT defends catch-and-kill policy for 'serious threat'.

WA shark cull: Colin BARNETT defends catch-and-kill policy for 'serious threat'.

WA shark cull: 'imminent threat' criteria scrapped in favour of 'serious threat'.

WA shark cull: 'imminent threat' criteria scrapped in favour of 'serious threat'.

Western Australia may have to justify great white shark catch rates.

Western Australia may have to justify great white shark catch rates.

A SEVEN-year-long research project has revealed most tagged white sharks off WA tend to cruise up and down the coast while only some of them venture c...

A SEVEN-year-long research project has revealed most tagged white sharks off WA tend to cruise up and down the coast while only some of them venture c...