Bryde’s whale mortalities in Mossel Bay
The Department of Environmental Affairs (DEA) and Department of Agriculture, Forestry and Fisheries (DAFF) are aware of recent mortalities of three Bryde’s whales in Mossel Bay. Both Departments would like to ensure members of the public that they share the concerns and a full investigation on the death of these whales will be undertaken, the situation will be monitored and measures will be put in place to address identified causes.
There is currently a perception that the Experimental Octopus Fishery may have contributed to the deaths, however this must still be confirmed. Other potential causes of death might include ship strikes, other type of fishing gear or of natural nature. However, as the octopus fishery make use of lines and buoys that have the potential to entangle whales, ongoing attention is being given to the octopus fishery’s gear design to limit possible whale entanglements. Concerns around this fishery (including gear designs) were discussed at a Stakeholder workshop coordinated by DAFF in June 2017.
The octopus fishing gear is designed to limit entanglement of large whales. These designs have demonstrated success in reducing entanglement incidents in False Bay. No entanglement was reported in octopus fishing gear since January 2018.
The industry uses a long-line fishing method. Weighted longlines lie flat on the sea floor 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. Interference with this design, e.g. cutting of buoy lines, become an entanglement hazard due to the resulting slack or lost gear, a problem known as Ghost Fishing. These interferences drastically increase the risk of entanglement.
DAFF will, with the assistance of DEA and all role players continue to monitor this experimental fishery closely. Mitigation measures will be implemented as the need arises. Measures already put in place by DAFF include:
Permit holder is expected to form part of a local disentanglement team
Permit holder shall report all entanglement incidents to authorities
Report to DAFF each time a vessel leaves the harbour for fishing operations
Industry Updates to the DAFF’s New Fisheries Working Group
GPS locations of all the fishing gear
The experimental nature of this industry means stakeholder engagements are ongoing and all concerned parties should approach DAFF for further industry specific queries and DEA can be contacted if any whale are observed that are entangled, including in fishing gear.
In February 2018, the DEA coordinated whale and dolphin National Stranding Network convened in Cape Town. Invited guests were Academia, NGO’s, Provincial Environmental Departments, Municipalities, Museums, State Vet, Private Vets and Environmental Agencies. The Network discussed and agreed on improving interventions and scientific data collection protocols during stranding events, towards understanding amongst others, the cause of death.
The Mossel Bay local stranding network has therefore responded to the three incidents by collecting samples from the two of the three recent strandings. Consultations with local and international experts are ongoing regarding these incidents. These results will help to identify the possible causes of death for the whales stranded at Mossel Bay and will help to inform management interventions, where necessary.
Bryde’s whales have two different forms; one that occurs offshore and the other one inshore. The latest assessment of the species by the Endangered Wildlife Trust (EWT), classified the inshore form as Vulnerable and the offshore form as Data Deficient. The total population size remains unknown but a study of the inshore form off Plettenberg Bay on the South Coast of South Africa estimated between 125 and 195 individuals.
This indicates that the number of whales are low and the mortality of one individual is therefore one too many.
Source: Government of South Africa