Thursday, 28 July 2016

Increasing ocean acidity could impact fish spawning

By Matt McGrath
Environment correspondent
27 July 2016

A new study suggests that the increasing acidification of the oceans is likely to interfere with the ability of fish to reproduce.

Researchers found that elevated levels of CO2, which make the waters more acidic, saw significantly lower levels of spawning.

However, other mating behaviours of the same species were unaffected by the souring of the oceans.

The scientists say the changes are "subtle but ecologically important".

The study examined the complicated mating behaviours of ocellated wrasse, a common Mediterranean fish.

There are three different types of male who compete to father the offspring of this species.

Sneaky males
Dominant males build nests and provide defence, while satellite males aid the dominants in return for a share of the eggs. "Sneaker" males hover around the nests and try and take advantage when the dominants are distracted.

The researchers filmed and studied the complex interactions of these creatures in areas near underwater volcanic vents which seep CO2 into the water.

The higher levels of CO2 make the sea much more acidic in this area off the coast of southern Italy, equivalent to what is expected more widely around the world by the end of this century.

The scientists found that many mating behaviours were unaffected but that dominant male spawning with females was reduced by almost two thirds in areas of high CO2.

The researchers argue that the increased CO2 may be impacting the abilities of the dominant males to make rapid decisions.

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