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At 64 years old, record rockfish was younger than first thought

Posted: July 8, 2013 - 10:14pm  |  Updated: July 9, 2013 - 12:10am
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Lab supervisor Kara Hilwig examines a sample of the rockfish at the Alaska Department of Fish & Game Age Determination Unit in Juneau.   JENNIFER CANFIELD | JUNEAU EMPIRE
JENNIFER CANFIELD | JUNEAU EMPIRE
Lab supervisor Kara Hilwig examines a sample of the rockfish at the Alaska Department of Fish & Game Age Determination Unit in Juneau.

An oversized shortraker rockfish — a fish that some believed could be more than 200 years old — isn’t.

The fish was caught in Sitka waters by Seattle resident Henry Liebman and weighed 39.08 pounds, breaking a previous record set with a 38.69-pound shortraker caught in 2000.

Fish and Game Sitka Area Manager Troy Tidingco confirmed Liebman’s catch and told the Sitka Sentinel that the fish could break an age record. Tidingco calculated that Liebman’s 41-inch fish might be about 200 years old, considering a 32-inch shortraker that was found to be 175 years old, the Sitka Sentinel reported.

The story of Sitka’s now-famed rockfish was first picked up by the Associated Press. Before long, news outlets such as the Christian Science Monitor, CBS, NBC, Fox and USA Today had it reposted on their websites. Comments on the story ranged from outrage that Liebman didn’t release the fish and instead had plans to mount it for a showpiece to outright disbelief and wonder that there existed a fish that had lived through the War of 1812, the Civil War, Women’s Suffrage and the attack on Pearl Harbor.

After further inspection, Fish and Game biologists now estimate the fish’s age at 64 years. Other than providing fodder for local and national news media, what’s it matter how old a fish is?

“When you start talking age estimates, it’s not trivial,” said Kara Hilwig, a lab supervisor at Fish and Game’s Age Determination Unit in Juneau. “It’s really an interesting science when you start looking at all the number crunching going on here.”

Fish and Game has age data on rockfish dating back to the 80s. Scientists like Hilwig use that information to create harvest models.

“More and more, these age-structured models are becoming the way to better manage fisheries, as opposed to looking at fish length,” Hilwig said. “One of the key components you get from the age data is what kind of mortality do these species have out in the ocean so that you can factor that with how much mortality you’re willing to impose on the species through fishing.”

Hilwig said the confusion and excitement about the Sitka shortraker was caused by equating size with age.

“The tough part with rockfish is that a fish that is 40 inches could be 35 (years old) or 135 (years old),” Hilwig said. “They’re just like people. They grow to be a certain size and then they just don’t grow anymore.”

So how did the lab determine how old the Sitka fish was? Fish have a bone structure in their inner ear called an otolith.

“We take those out, crack them in half, put them over an alcohol flame until they’re a nice toasty brown and then we put them under a microscope,” Hilwig explained. “Then it’s just like reading a tree’s rings.”

Maintaining a healthy rockfish population is the focus of much of the lab’s age data analysis, Hilwig said. Because it’s not unusual to catch a rockfish that’s been alive since before statehood, Fish and Game has developed a technique for release — in case you’ve reached your bag limit. It’s not guaranteed that the fish will survive the pressure change, but it’s better than leaving the fish out on the beach. The technique involves a homemade release device that weighs the rockfish back down to its deep underwater dwelling where it at least has a chance of survival.

“If you think about it, the deep sea environment is quite stable,” Hilwig said. “You can just see these rockfish setting up shop and getting quite old.”

If only fish could talk.

• Contact reporter Jennifer Canfield at 523-2279 or at jennifer.n.canfield@juneauempire.com.

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