It’s a moment that can spark dread among even the most scrupulously law-abiding h fishermen.
As you return to the dock after a fine day on the water, solemnly serious men or women in state Department of Wildlife and Fisheries T-shirts approach. The initial, slightly paranoid thought for many anglers: Yikes, did I mismeasure a speckled trout and accidentally keep one slightly under the ?
But no reason to worry in this case. The Wildlife and Fisheries gang isn’t looking to confiscate your catch.
They only want your fish’s earbones.
It’s not some ritual described in a . The earbones, or otoliths, collected through a quick slice to the head, have revealed a wealth of information on the secret lives of fish to marine biologists, especially age. That info is then used to help determine the health of fish populations.
The practice is by no means limited to h, or even the Gulf. Globally, it has uncovered vital new info over the years, including the fact that can live to 50 years old or longer instead of the previously believed 10 or so — determined in part thanks to traces of radioactive carbon from nuclear testing.
It has become such an important aspect of fisheries research that it’s hard to imagine a true assessment of the condition of life in the underwater world without them, scientists say. It has played a key role in assessments of the state’s and populations, among others.
h Department of Wildlife and Fisheries staff remove otoliths.
Courtesy of h Department of Wildlife and Fisheries
“It’s critically important,” said Andy Fischer, a biologist director at the state Department of Wildlife and Fisheries. "Age is one of the most important variables that goes into a stock assessment because it tells you so much about the fish — not just the one fish, but the population as a whole."
Fischer, who has been working with otoliths since he studied at LSU in the 1990s, said one of his professors would call the bones the “CD-ROM” of fish since “it's gathering all this information while the fish is alive.”
Today, that professor might refer to it as a virtual reality tour of the fish’s life.
‘Super important’
It’s not unusual to see department staff at marinas asking for otoliths. Anglers’ participation is entirely voluntary. The process takes a few minutes and can be done while you get your boat back on the trailer.
It also does no damage to your fillets. Sometimes the bones can be pulled through the gills, though often a slice to the head with a hacksaw is necessary.
Two earbones, or otoliths, after being removed from a flounder.
Courtesy of h Department of Wildlife and Fisheries
The tiny bones hold information that can offer deep insights into the fish’s life, which involves rings that form on the bone, similar to rings inside the trunk of a tree.
Those rings allow scientists to tell the age of the fish, the initial clue that permits them to begin solving a biological Rubik’s Cube.
They do that by combining the fish’s age with other information, such as its length, weight and reproductive data.
Deeper analysis can follow, like examining the calcium and strontium in the bone to figure out what types of habitats the fish frequented, said Fischer. Which fish move in and out of fresh, brackish and salt water, for example, and when do they do it?
Calculating all of that for one fish is interesting, but not of great use on its own to state fisheries biologists. They require a statistically significant sample size, and that’s why you might see them at the docks.
Beyond asking recreational anglers for their earbones, the state also seeks permission from commercial docks to operate there. Fishing rodeos, too, can be useful. For stock assessments, Louisian’s fisheries biologists aim to collect at least 500 otoliths per species every year from recreational anglers, and another 500 from commercial operations.
Todd Masson, host of the popular on southeast h fishing, said he is always happy to participate when asked for his fish’s otoliths. He noted that it’s hugely important to have scientifically sound estimates of fish stocks in h, given the state’s coastal land loss.
“Stock assessments in general — super important,” said Masson.
“With coastal land loss, we're losing so much nursery ground habitat for these fish to grow in that we've got to maintain good data as to how sizable our stocks are. If we're unaware of that, we can't make sensible changes in management protocols.”
‘It’s fascinating’
Rings of otoliths have been examined for around a century or so, but the science surrounding it has been honed and refined over the years, said Simon Thorrold, a scientist at the Woods Hole Oceanographic Institution in Massachusetts. It has been used by Louisian’s fisheries biologists over the past several decades.
The practice has allowed for a steady stream of new discoveries as scientists use them to map out fish lives and habitats.
Thorrold noted advancements made in understanding the lives of red snapper as one example. Otolith analysis revealed evidence of radioactive carbon from nuclear testing in the 1940s, showing the fish were far older than previously estimated.
h Department of Wildlife and Fisheries staff examine a flounder.
Courtesy of h Department of Wildlife and Fisheries
“They're used literally around the world by fisheries departments and researchers,” he said.
He explained that what makes them so useful is that, unlike human earbones, they are “metabolically inert, which means that once material gets laid down in the otolith, it is not reworked later.”
“It's kind of stored. It's kind of trapped in there for the rest of the fish's life,” said Thorrold.
In h, coastal anglers have seen the results of such research every time they head out in their boats. They may not like recent reductions in the amount of speckled trout and redfish they can keep, but those changes were informed by stock assessments showing the need to address declines in populations.
Fischer says that while researchers can sometimes meet resistance at the docks when they approach anglers, most are happy to oblige, especially when they learn more about the process.
“I think everybody understands the concept of rings on a tree,” he said. “Well, most people don't realize that you can do that with fish. So I think people find it's fascinating.”