Fisheries New Zealand yesterday said a Hector’s dolphin was reported caught in a fishing net off Otago Peninsula, marking the first report of a fishing-related Hector’s dolphin death in the area for more than a decade.
University of Otago marine science emeritus professor Steve Dawson, who is a nationally recognised expert on the species, said the reported death could represent the "tip of an iceberg" and the rules developed to protect the taonga cetacean were not fit for purpose.
Fisheries New Zealand fisheries management director Emma Taylor called the death "extremely disappointing" and said the incident had triggered discussions with industry representatives and local set net fishers about additional protections for Hector’s dolphins that could be required such as further area or seasonal closures, or gear restrictions.
"Potential measures including possible further spatial restrictions will be assessed and form advice to the minister.
"The first part of this involves discussions with industry and fishers to find out what changes they might do voluntarily."
The dolphin was caught in a commercial fishing set net on Sunday outside the Hector’s dolphin protection zone of 4 nautical miles, where fishing methods such as net setting were prohibited.
The fisher had been targeting school shark, a species commonly sold in fish and chip stores, she said.
A fisheries observer was aboard the vessel and its skipper reported the catch to Fisheries New Zealand as required.
The dolphin carcass was brought to shore for the Department of Conservation to send to Massey University for necropsy.
When available the results would include details of the sex and age of the dolphin.
The total South Island population was most recently estimated at up to 18,500 — of that population, the east coast population was believed to be about 9000 animals.
Ms Taylor said under the South Island Hector’s Dolphin Bycatch Reduction Plan, launched in November last year, Fisheries New Zealand estimated 23 commercial fishing-related deaths of Hector’s dolphins in all areas of the South Island every year.
Prof Dawson said while this was the first report of a fishing-related Hector’s dolphin death in the area since 2012, that did not mean there had not been other fatal entanglements.
Further, it was "a bit misleading" to say there were 9000 animals on the east coast of the South Island, because that population was split into several different, separate, sub-populations, which did not interbreed with one another.
The Otago population was small and the species had a very low reproductive rate.
"The loss of one [dolphin] even if it’s not female, is pretty serious; it absolutely is enough to send that local population into decline."
He said concerns had previously been raised about the protection zone extending to 4 nautical miles, because around Otago 4 nautical miles offshore it was still relatively shallow.
"Hector’s dolphins are far more interested in how deep the water is than how far offshore it is.
"And there are so few reliable sightings of Hector’s dolphins in waters deeper than 100m that that would be a really reliable way to demarcate an area that would be safe for them."
University of Otago marine science associate professor Will Rayment said a 2021 estimate for Hector’s dolphins off Otago was 41 from Taiaroa Head to Cornish Head, just north of Karitane.
