Fish Sex Being Changed by Global Warming


perjerrey sex change

(Image Credits: Cousseau, B. and Perrotta, R.G. /, mrjerz)

Warmer water can change the sex and sex life of fish. Once scientists began studying the impact of global warming on everything from tourism to asthma, it was only a matter of time before they got around to sex. Now two biologists at Spain’s Higher Council for Scientific Research (CSIC) have done just that, at least when it comes to fish.

Take for example the Pejerrey Fish found in South America. In some fish species, sex is determined by temperature and with the Pejerrey or Silverside fish, a rise in water temperature can cause mostly all of the embryos to hatch as male fish.

Pejerrey Fish Caught in Argentina

(Image Credit: Johannrela)

In a study published in the July 30th edition of the scientific journal Public Library of Science, Natalia Ospina-Alvarez and Francesc Piferrer have gone a little further in explaining how that mechanism works. In laboratory tests, they have demonstrated that higher water temperatures result in more male fish.

“We found that in fish that do have temperature-dependent sex determination [TSD], a rise in water temperature of just 1.5 degrees Celsius can change the male-to-female ratio from 1:1 to 3:1,” says Piferrer, the study’s co-author. In especially sensitive fish, a greater increase can throw the balance even more out of whack. Ospina-Alvarez and Piferrer have found that in the South American pejerrey, for example, an increase of 4 degrees Celsius can result in a population that is 98% male.”

IPPC, International Panel on Climate Change Weighs In.

Now for the troubling part. The International Panel on Climate Change (IPCC) predicts that ocean-water temperatures are likely to rise by 1.5 degrees over the course of this century and they may even go up a few degrees more. “If climate change really does result in a rise of 4 degrees Celsius, which is the maximum the IPCC predicts, and if species can’t adapt in time or migrate, then in the most sensitive cases of temperature-dependent sex determination (TSDs), we’re looking at extinction,” says Piferrer. Note: 1 degree Celsius is equal to 1.8 degrees Fahrenheit, so 0 degrees Celsius to 4 degrees would be a net gain of 7.4 degrees Fahrenheit that the temperature will rise as noted by the IPCC. Maybe this will be a problem for the fish, maybe not.

TSD fish is Lower than Previously Believed

“At this stage, it is hard to tell what these results bode for already declining fish populations around the world. Of the estimated 33,000 piscatorial species, only 5,000 have had their sex-determination mechanism affirmed. But the study by the two CSIC scientists also suggests that the percentage of TSD fish is lower than previously believed. In tests of 59 species believed to be reproductively sensitive to temperature, only 40 proved to be true TSDs. ”


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