This is just an exerpt of the article based on this study . It's a long read but very informative .
Based on his research, Foster recommended anglers carefully remove even deeply imbedded hooks. If the hook can not be removed, then it seems better to leave about 18 inches of line attached. Perhaps, someday, these findings will reach C&R anglers, the biologists who are researching C&R and publish C&R guidelines, and TV anglers who teach by their example.
Hooks in or out