A study published in Scientific Reports by Professor Stefano Mariani and Dr Ilaria Coscia at the University of Salford notes that the direction of the sex change in the over 400 species of sex-changing fish has implications for population numbers, with smaller populations for fish that change from female-to-male (termed protogynous) when compared with male-to-female (protandrous). This has serious implications for the fishing industry as these population numbers could be a factor in selection of fish taken from the sea.
The research team measured offspring production based on the number of eggs and sperm produced every year, over a lifetime, based on their growth rate, and then used the diversity of genes transferred to the next generation as a proxy for reproductive success. Both, protogynous and protandrous fishes produced more offspring having changed sex, indicating that this as a successful evolutionary strategy, but population numbers were smaller for protogynous species, therefore marking them as less resilient.
The study plans to focus on the effects of overfishing these species next, as many of them are commercially important, sought by fishermen and appreciated by consumers.