Scuba divers at Narooma have noticed healthy numbers of endangered grey nurse sharks at Montague Island in recent weeks.
Among them is local diver Matthew Tworkowski, who so far this year has documented and identified 41 separate grey nurse sharks – 29 females and 12 males.
“These sharks are a beautiful, peaceful creature and need all the help they can get to survive in the future,” Mr Tworkowski said.
The sharks have unique markings which act as a fingerprint equivalent for identification. Each of the sharks was identified based on images of their right side only, but he and his fellow divers have also documented 26 females and 10 males from the left side.
There understood to be only 1000 to 1500 grey nurse sharks remaining on the East Coast of Australia, making them one of the most critically endangered species in the country, according to the Environment Protection and Biodiversity Conservation Act of 1999.
They were the first shark in the world to be afforded protective status in 1984 after they were nearly hunted to extinction by spearfishing and fishing, he said.
Grey nurse sharks are thought to live between 30 and 40 years, grow to around 3.2 meters and are relatively slow to mature. Female sharks mature between 2.2 and 2.6 m at 9 to 10 years, while males mature between 1.9 and 2.2m at 6 to 7 years of age. The females gestate for 9 to 12 months and give birth to one or two pups, which at birth pups are around 1m in length, every two or three years.
“Because of this slow reproduction rate, grey nurse shark numbers are struggling to recover, which makes sanctuary/habitat protection zones critical,” Mr Tworkowski said. “The national recovery plan has identified 19 known aggregation sites which are considered key for the survival of the East Coast population, Montague Island is the most southern of these sites.”
Local divers say the majority of grey nurse sharks have been identified on the northeast end of the island in the grey nurse habitat protection zone, they have also photographed them on the northwest corner between Pebbly Beach and the seal colony, the west side at Yakka Bay and Pinnacles and also at Aughinish Rock, south of Montague Island.
Injuries sustained from accidental, incidental or illegal capture both commercially and recreationally and mortality related to shark control activites are understood to be the primary threats to the sharks survival on the East Coast.
“We have identified 10 separate individuals with either fishing hooks with wire traces or hooks with mono/braid, the wire traces get wrapped around teeth and gills and almost certainly kill the shark in time,” Mr Tworkowski said. “Swallowed hooks and tackle cause internal injuries and puncture the stomach lining which effects feeding and digestion, stress, liver malfunction and in many cases kills the shark.”
See first three photos in the gallery above that feature sharks trailing fishing gear at Montague Island as photographed by Mr Tworkowski.
The local divers will continue to closely monitor the sharks over the following months as the grey nurse habitat protection zone only runs from November 1 to April 30. They hope to determine how much longer they remain at Montague Island and whether there are grounds to extend the duration of the zone and the period that anglers are only allowed to use artificial lures.
“Generally the sharks are here for six months and head north when water temperatures drop,” Mr Tworkowski said. “I suspect with warmer water temperatures now common place the sharks will be around longer and at greater risk of harm from fishing practices. Last year we still were having sightings up until June.”