Sea lions haul out of the water onto trap platforms at Bonneville dam.

Sea lions haul out of the water onto trap platforms at Bonneville dam.

Nick Fisher/OPB

Two California sea lions died in a trap this week at the Columbia River’s Bonneville Dam after a door closed prematurely, confining  them for hours.

Oregon Department of Fish and Wildlife spokesman Rick Hargrave said a veterinarian has determined the two sea lions were likely crushed to death by a 1,500-pound Steller sea lion that was almost three times their size.

With the door closed, the smaller sea lions were unable to hop out of the way. The incident took place sometime between Tuesday evening and early Wednesday morning.

State biologists have a federal permit to regularly trap and kill sea lions deemed to be repeat offenders for habitually eating endangered salmon.

The two that died were not on the list of animals targeted to be removed and killed.

Sea lions hop on and off the trap platform frequently, using it as a place to haul out of the water.

The trap door should not close without a human triggering them by remote control. In this case, Hargrave says an electromagnetic lock failed.

A staff member discovered nine trapped animals about 3:45 a.m. on Wednesday.

So far this year, biologists have trapped 79 sea lions at Bonneville Dam. They have euthanized 14 of those animals.

The state has halted trapping operations and reported the accidental deaths to NOAA Fisheries.

Hargrave said his agency hopes to have the door on the trap repaired to resume trapping sea lions again next week.