• Published:May 11, 2018
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Are we killing all of the superspawners?

A study just published in the journal Science shows that in most cases, the larger the female fish, the more eggs it will produce. The eggs laid by a big female are also larger than eggs laid by smaller fish, and richer in fat, so they have a higher success rate of proliferation.
This study could change the mindset of fishery managers, especially in cases where small fish are released because they are under sized and big fish are taken legally.

For decades, marine fisheries managers encouraged the release of juvenile fish for the simple reason that if we released more baby fish there was a better chance these fish would reach spawning age. Many fisheries protect fish up to the point where they can spawn two or more times before they grow to a size that they can be harvested legally. This new study throws a bit of a wrench into that mindset.

While researchers have known that fish fertility generally increases with size, there has been much debate about the importance of protecting larger female fish to support the overall fish stock. Bigger fish, it turns out, produce not just a few more eggs, but a lot more, becoming what the scientific community is calling “superspawners.”

One of the more commercially important species looked at was the codfish, which has seen its population dwindle to very low number numbers over the last five decades in the North Atlantic. According to the study, a 66-pound codfish will out produce a fish half its size by nearly 30X. To put that in other words, it would take more than 100 pounds of small codfish to lay the same number of eggs as one large codfish.

The biggest difference in the study came from the vermillion snapper, where the big mamas dropped 400 times more eggs that their little sisters. That’s a pretty massive difference.

Researchers at Monash University in Melbourne, Australia, authored the study, working with colleagues from the Smithsonian Tropical Research Institute in Panama. They studied 342 species of fish across various segments. They discovered that in 95 percent of the species studied, the bigger, older females that hit superspawner status contributed more eggs and more offspring to the overall fish population.


One the biggest questions this brings up is whether or not fishery managers should try to protect more juvenile fish so they can grow to become a superspawner, or should they protect those large females? The answer is somewhere in the middle.

Superspawners are rare. How many marlin over 1,000 pounds have you caught? How many striped bass over 50 pounds have you caught? How many yellowfin over 300 pounds have you caught? I think you get my point.

Catching a true superspawner does not happen every day for a recreational angler, or even a commercial fishing operation, so yes, we should try to protect the ones that are out there, within reason. But, it’s a lot more important to protect the entire population of spawning fish, regardless of whether it’s a lot of small fish or a lesser amount of big ones.

This study is proving what many fishery folks have known for years, but now they have the scientific data to prove what they’ve seen in the field. How all of this may change fishery management is up to debate. Many fish are already managed with slot limits, allowing the smallest fish to swim free, as well as the larger ones. In the Southeast, redfish and snook have been managed this way for years, and it’s helped the stocks rebound to much healthier levels.

For fish that are more sought after commercially, think tuna, swordfish, halibut and cod, it may be much more difficult. Migratory fish move into and out of international waters and regulations change depending on where they are caught. It is a very complicated puzzle. However, with more data comes more power. Enforcing regulations is yet another giant can of worms, but for now, think of the superspawners next time you pull in a beast.