Among the many problems caused by global climate change is a general warming of the oceans. While this may sound pleasant to the average swimmer, it has already begun to have devastating effects on ocean ecosystems. For some species of fish, an increase of average water temperatures of even 1.5° Celsius can result in a 30% decrease in the number of female fish born in a given clutch. That reduction can severely hinder fish fertility, and render a given species less able to reproduce or adapt to changes in their ecosystem.

Scientists use the term “transgenerational plasticity” to refer to a species’ ability to adapt to changes in their ecosystem, such as increased water temperatures. In the case of some reef fish, that plasticity can allow them to adapt to changes in water temperatures, but it takes time.


Scientists at the University of Technology, Sydney, studied several generations of the Spiny Chromis coral reef fish species. What they found was that, following an increase in the average water temperature, the number of females being born dropped in the first generation but, when those younger fish were allowed to grow and then breed, the population balanced out after two generations.

Over several generations, the fish managed to rebalance their population in water that was 1.5° warmer, but in water which was 3° warmer, even after two generations the female population was not high enough. The researchers aren’t sure what allows the fish to adapt in this way, but it seems that there is either a cap to how much warmer the water can be before Spiny Chromis cannot adapt, or that it will take even more generations to adapt to warmer water.

Future research will hopefully be able to determine how fish adapt, and if they can adapt at all to even higher temperatures. It is likely that, given enough time, new species could arise that could survive in warmer water, but in the meantime, most species of fish are in danger if we can’t, or won’t, limit climate change.