bycatch

Reader's Digest 10月号の記事 'The Healthy Wellness from thehealthy.com' からの引用です。
Source sustainable seafood
"The most environmentally friendly seafood choices would likely be those that are wild-caught with a line-and-pole method--meaning only one fish is caught at a time,"　Hunnes says. "Industrial fishing methods are abhorrent when it comes to sustainability, as they pull up all types of bycatch."
What's bycatch? Hunnes explains that these are "unintended species that end up dead when they're thrown back into the ocean."

"bycatch" の意味は文中にありますが、一応辞書の説明も見ます。

・Vocabulary.com: unwanted marine creatures that are caught in the nets while fishing for another species: The tricky part with this fishing method is that there is often considerable bycatch—unintended species, also trapped inside the pouch, who perish in the harvesting process.