Forest & Bird says an endangered New Zealand sea lion has been killed in a squid fishing net, the second since the squid fishing season began five weeks ago.
"The two deaths are especially alarming because they were both females. They are likely to have a dependent pup on shore and be pregnant so three lives are lost each time," said Forest & Bird marine conservation advocate Katrina Goddard.
"Sea lions can be trapped in the large squid fishing nets, and it is difficult for some to escape from the nets through sea lion exclusion devices (SLEDs). The ongoing concerns with SLEDS means we don't know how many sea lion deaths go unnoticed."
Ms Goddard said the squid fishing industry could switch to more sustainable fishing methods.
"If the companies want to continue fishing in the same sub-Antarctic waters where the sea lions feed, a better method is jigging - which uses hooks," she said.