Octopus traps a threat to False Bay whales
SCIENCE / 5 September 2016, 10:10am
Marine conservationists and tour operators believe experimental octopus traps in False Bay are partly to blame for the increase in whale entanglements.
The octopus traps are attached to 22 longlines, connected with ropes and buoys.
At 10h55, Monday, 15th August, the SA Whale Disentanglement Network (SAWDN) volunteers were activated following eye-witness reports of a whale entangled in fishing rope and floatation buoys, approximately 400 meters off-shore of Glencairn (between Fish Hoek and Simonstown).The NSRI Simonstown sea rescue craft Spirit of Safmarine III and Spirit of Surfski II were launched accompanied by SAWDN volunteers and carrying the SAWDN specialised cutting equipment and the whale was located and found to be a 7.5 meter juvenile Humpback whale with wraps of rope entangled around the left and around the right flukes and around the caudal peduncle (at least three wraps around each) and a chain anchoring the whale to the sea floor effectively trapping the whale to the sea floor. pic NSRI. Credit: NSRI
Wilfred Chivell, who operates boat based whale watching trips and shark cage diving in Gansbaai, said it was unacceptable for traps to be put out during whale season.
“We can’t kill whales to help a fishing sector that isn’t even properly established.”
Chivell, who is also the founder of Dyer Island Conservation Trust, said crayfish traps were a problem for some time, but whales could swim with those attached whereas octopus traps could drown them.
He said whales are drawn to ropes, often to scratch against and they become entangled. He’d managed to stop people placing traps around Dyer Island.
Nan Rice, head of the Dolphin Action and Protection Group and a founder member of SA Whale Entanglement Network, said so far this year 34 whales had become entangled in rock lobster traps and about seven in octopus traps. Two others are believed to have died.
Rice said humpback whales were more often victims of entanglement than southern rights because their numbers were increasing and they breed every second year.
Rice said it was terribly costly to disentangle a whale. “We have donated around R200 000 to the SA Whale Entanglement Network and the NSRI uses a fortune in fuel.”
Chris Fallows, shark cage diving tour operator and photographer, said a year ago a simple whelk trap killed an adult female great white in Fish Hoek.
“The setting of dozens of traps in False Bay with long lengths of rope undeniably poses a risk of entanglement and especially when they are knowingly set in areas of highest white shark density such as at Seal island and off the inshore reefs of Strandfontein to Macassar.”
He said in New Zealand when a white shark was killed and left to decompose the whole population left areas where the sharks naturally occurred and moved into another area where they felt safe.
Fallows said if this happened in False Bay, it could have dire consequences to someone who made a living out of eco-tourism directly related to sharks.
“Most importantly, however, is the fact that has been shown by various scientists that these apex predators are in a serious decline and any threat to them needs to be seriously avoided or alternative options looked at.”
Palesa Mokomele, spokeswoman for Department of Agriculture, Forestry and Fisheries (DAFF), said they were working with fishers to improve gear and to ensure there was no or minimal by-catch.
“We regularly monitor the vessels’ catch, and have undertaken underwater dive inspections on octopus lines.” She said fishers agreed at a workshop to not undertake any fishing in the area where most whales occur during peak whale season.
Mokomele said the department, under the auspices of the New Fisheries Scientific Working Group, had been involved with the exploratory octopus fishery to assess the potential for a possible new commercial fishery in the future.
“Octopus is a species that is currently under-utilised and a sustainable fishery could offer future employment opportunities.” She said the five-year second phase to gather more data on the biology and sustainability of the octopus resource started in 2012.