Not Enough Male Gags?

Photo FWC

Gag grouper are protogynous hermaphrodites. All gags begin life as females and then some of them change into males when they mature.

A recent study suggests there might not be enough male gag grouper in Florida waters. According to the study, conducted by scientists with the University of Florida, Florida State University and the Florida Fish and Wildlife Conservation Commission, male abundance, fertilization success, and stock productivity are affected by where and when sex change occurs and how fishing pressure affects male recruitment and survivorship.

The study suggests that overall abundance of gag grouper is low and that current regulations do not protect the population of male gag grouper enough to allow recovery to historic levels.

According to the study, gag females formed pre-spawning aggregations before migrating to deep-water spawning sites, which overlapped with locations where males were sampled year-round. The observed male sex ratio in the marine protected area studied was 5 percent, compared to the expected 15 percent. It was 0 percent in less protected areas.

Sex change occurred occasionally in small fish and before, during, and after the spawning season. In addition, sex change was observed in pre-spawning female-only aggregations as well on the spawning grounds, indicating that male social cues are not requisite. The study proposes that shallow-water, pre-spawning aggregations are a key spatio-temporal bottleneck to gag productivity. They appear to be an important source of transitionals and are heavily fished, which may negatively impact male recruitment to the spawning grounds.

Read the full study at https://www.int-res.com/abstracts/meps/v639/p199-214.

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