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Ancient rockfish caught in Alaska: Why nobody threw it back

July 03, 2013|By Deborah Netburn | This post has been updated, as indicated below.

Ten miles off the coast of southern Alaska, an insurance adjuster from Seattle caught a neon orange rockfish that is probably more than 100 years old.

The fish, a type of rockfish called a shortraker, was caught in 900 feet of water, weighed in at 39.08 pounds and is just under 41 inches long. It is the largest rockfish to have been caught by a recreational fisherman in this part of the world and it might be the oldest as well.

[Updated, 10:53 a.m. July 3: For those wondering why the fisherman Henry Liebman did not throw the ancient fish back into the sea immediately after catching it, the answer is that the fish was almost certainly dead by the time he reeled it in.

"When a rockfish caught in 900 feet of water is brought to the surface it usually dies," said Julie Speegle, a spokeswoman for NOAA's Alaska region, in an interview with the L.A. Times.

Rockfish have a gas filled organ called a swim bladder that helps them control their buoancy. When they are brought up to the surface, the gas in the bladder expands and can cause it to burst which can kill the fish.]

Scientists with the Alaska Department of Fish and Game will determine the age of the fish later this week by slicing through its head and removing two small ear bones called otoliths that float in a cavity beneath the fish's brain.

PHOTOS: Weird sea creatures

The otoliths have rings like a tree, and scientists can get a pretty good estimate of how old the fish is by counting these rings.

So far, the oldest shortraker on record is more than 150 years old.

Shortrakers live along the ocean floor at depths that range from 84 feet to 4,000 feet. They snack on crabs, shrimp and the occasional small squid.

These long-lived fish don't become sexually mature until they are about 10 years old and often live to more than 50 years old.

"Their life strategy is to have babies year after year after year," said Kristen Green, a ground fish biologist with the Alaska Department of Fish and Game. "They might have some years where their larvae do really well, and some years where they don't do well, but if they are reproducing for 50 years or more, they will definitely have some good years in there."

While the fish pictured above is the largest shortraker to be caught by a sport fisherman off the coast of Alaska, it is not the largest shortraker to have ever been found. That record is held by a 62-pound giant caught by a commercial fishing net in the Bering Sea in 2007, which you can see if you click through the photo gallery above. Scientists say that fish is 95 to 115 years old. (And yes, they used the otolith method to determine its age.)

The mean size of shortraker fish in the inner waters of southeastern Alaska is just over 26 inches and 10.9 lbs, but Green said it is likely that commercial fisherman catch shortrakers over 40 pounds every day in their nets.

"There is always a feeling that it is sad when something this old is taken from the sea, but this is a drop in the bucket compared to what the commercial fisheries take," Green said. "He just happened to be fishing at a really deep depth. Most recreational fisherman don't fish that deep."

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