Longlines mooted as cause of death of stranded Bryde’s whales

THE departments of Environmental Affairs (DEA) and Agriculture, Forestry and Fisheries (DAFF) have launched an inquiry into the recent deaths of three Bryde’s whales in Mossel Bay.

The departments said the situation would be monitored and measures put in place to address causes of death.

The local stranding network has collected samples from the two of the three recent strandings to shed light on the cause of death and inform possible management interventions.

“There is a perception that the experimental octopus fishery may have contributed to the deaths. However, this must still be confirmed. Other potential causes might include ship strikes, other type of fishing gear or of a natural nature.

“However, as the fishery make use of lines and buoys that have the potential to entangle whales, ongoing attention is being given to the fishery’s gear design to limit possible entanglements. Concerns around this fishery (including gear designs) were discussed at a stakeholder workshop co-ordinated by DAFF in June 2017,” the departments said.

The octopus fishing gear is designed to limit entanglement of large whales, and these designs have demonstrated success in reducing entanglement incidents in False Bay, said the departments. No entanglements have been reported in such gear since January 2018.

“The industry uses a longline fishing method. Weighted longlines lie flat on the seafloor to prevent bowing of ropes between traps. Anchor lines are made up of polypropylene rope, chain and an anchor and set up such that there is no slack in the buoy line.

“Entanglement probability is therefore reduced, both for bottom and pelagic interactions between the gear and large whales.” – Staff Writer