Size selective harvesting

https://phys.org/news/2022-01-size-fishing-chance-big-fish.html

Related:

Our letter to the California Fish and Game Commission RE: Sheephead in 2018:

A contradiction in conservation.

First, Commissioners, did you know all sheephead are born female? Most morph into male in response to social cues - usually removal of a dominant male. They live in harem-like groups - one alpha male overseeing a group of females. At night, when they sleep, sheephead conceal themselves in a cocoon of mucous to avoid detection by predators. 

Purple sea urchins are a threat to kelp forests. The Commission just recently adopted emergency regulations increasing the bag limit for purple sea urchins due to an overabundance. The sheephead is a critical predator of the purple sea urchin, however, sheephead do not begin eating sea urchins until they about 12”.  That happens to be the minimum size limit set forth in the California Fishing Regulations. 

Clearly, this keystone predator of the kelp forest must be allowed to grow larger before it’s allowed to be taken. Clearly.

Excerpt from: California Sheephead Populations Dwindling : Researchers Claim Fishing Disrupted Species’ Intricate Gender-Change Process

https://www.independent.com/news/2009/may/13/california-sheephead-populations-dwindling/

The natural process is such that when an alpha male dies, the largest and most capable female in the area will switch her sex to take his place. But the sudden absence of a dominant male caused by sport fishing will still signal a female to switch sex, even if she’s too young and too small to effectively patrol the territory that her male predecessor did. “Fishing will take a large male out of the system, and all of a sudden there’s no male around,” Hamilton said. “That will stimulate a female to change sex into a male, so in places like Catalina where fishing is removing a lot of the big males, you’re seeing a lot of really small, tiny males, a lot of dwarf males which you didn’t see historically.”

The result, then, of sport fishing in the Channel Islands is an overabundance of tiny, underdeveloped males and a shortage of egg-producing females. Premature sex-change also causes a deficiency of older, bigger females, which are capable of producing a greater number of eggs.

“Essentially, you see that these fish aren’t spending as many years producing eggs as a female, because they’re changing sex at a smaller size and a younger age,” Hamilton said.”

California sheephead need to be allowed to get older and larger so they can 1) consume the largest quantities of purple urchin, and 2) to be more productive as females - producing more offspring, and 3) for the populations to maintain a more natural and healthier balance of male to females.