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“Nowadays these mammals and salmon have more sublethal threats than they used to,” Mastick says, including warming seas, pollution, and shipping noise.

"In a seven-day test, we'll get three to four rounds of reproduction with daily hatching, so we can look for both lethal effects and sublethal effects such as reproductive and growth impacts that have an effect on population survival."

While salmon won’t venture into water warmer than 70 degrees, any water above 59 degrees is considered “sublethal,” stressing the fish and making them susceptible for disease and developmental issues.

The right whale consortium said sublethal injuries to whales from collisions and fishing gear are also a major concern for the remaining population.

Documenting often-invisible, sublethal effects in wild animals that are definitively linked to plastic itself has remained elusive.