Nature's strategies: Fish that switch sex to thrive

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Science  02 Mar 2018:
Vol. 359, Issue 6379, pp. 975
DOI: 10.1126/science.359.6379.975

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About 450 species switch sexes over their lifetime to maximize their number of offspring. Now, fish like the sea bream are adapting their age-old strategy to a modern challenge that also disrupts the sex balance: overfishing. Fishers favor the biggest catch. Because one sex is usually bigger than the other, the bigger sex risks being fished out. But researchers have found that sea breams, which are common in warmer Atlantic Ocean coastal waters, are ready. Removing big males prompts earlier-than-usual sex changes in some females, so the sex balance is preserved. Still, it's more of a short-term strategy than a long-term solution, researchers say. The fish are switching sex at younger ages, making the newly minted males smaller. That trend translates into fewer offspring and a shrinking population. That resilience strategy keeps them reproducing for now—but the fish can't save themselves all on their own.