Forest and Bird is calling for fishing boats to be fitted with cameras following the death of at least four Hector's dolphins.
"Those tragic deaths show there is a major problem in our fisheries, and raises serious questions over the industry's dismal record of killing threatened native species," Forest and Bird ocean advocate Karen Baird said today in a statement.
"Without observers or cameras on most of these boats, we have no idea how many dolphins are killed every year, and no ability to protect them."
At least four Hector's dolphins were caught in two separate incidents involving commercial fishers trawl fishing off the east coast of the South Island this summer.
In one incident, one dolphin was caught, while three were caught in another incident.
Fisheries New Zealand's manager of inshore fisheries, Steve Hailey, said in a statement that it was good fishers were reporting the incidents quickly.
"Any captures of these dolphins is extremely disappointing," he said. "Hector's dolphins are nationally endangered taonga and we're interested to find out as much as we can about these captures so we can work with the industry to avoid them occurring.
"Prompt reporting by fishers ensures the best opportunity to gather details about these incidents, and in this case the commercial fishers reported the captures immediately, which enabled recovery of three dolphins for necropsy."
He said the Department of Conservation will include information on the captures to its Hector's and Māui Dolphin Incident Database, which records the date, location and cause of the mortalities when known. The incidents are published on DOC's website every quarter.
DOC manager of marine species and threats Ian Angus said in a statement that the information will help inform the agency's approach towards the protection of the dolphins from human-related activities.
"We also encourage the public to report beachcast dolphins as soon as possible. The earlier we can examine them, the better information we have to build a picture of the risks posed to these marine mammals."
The Hector's and Māui dolphin Threat Management Plan is currently under review by DOC and Fisheries New Zealand, with a public consultation planned for 2019.
Hector's dolphins are listed as nationally endangered, with an estimated population of 15,000 remaining.