“200-year-old fish” is actually only 64

not old fish

Age Reading Shortraker

120y shortraker annotated

The three-and-a-half foot shortraker rockfish caught by Seattle-resident Henry Liebman last month was believed to be 200 years old. The Department of Fish and Game lab in Juneau has proven otherwise. (Photo courtesy of James Poulson/Daily Sitka Sentinel)

Kevin McNeel and Jodi Neil age read the otolith of the shortraker rockfish caught near Sitka under a dissecting scope at the Alaska Department of Fish and Game’s Age Determination Unit. (Photo courtesy of Kara Hilwig/ADF&G)

Under a dissecting scope: a view of the age reading surface of the otolith belonging to a 120-year-old shortraker rockfish . The otolith is broken in half, then toasted over an ethanol flame to see the growth increments. The broken surface is used for age estimations. Annuli, like rings of a tree, can be seen here as fine horizontal lines. An age reader from the ADF&G Age Determination Unit added some tick marks to denote the approximate counts of annuli. This fish was caught by a sport fisherman June 18, 2013 near Behm Canal and was 29.6 lbs, 39” long. (Photo courtesy of Kevin McNeel/ADF&G)

The rockfish caught near Sitka last month was not 200 years old, but a different fish caught near Ketchikan was over 100 years old.

The Department of Fish and Game lab in Juneau received two otoliths from two different fish. An otolith is a bone found within a fish’s ear that contains annuli, similar to rings on a tree. Scientist use otoliths to determine the age of fish

The shortraker caught off Kruzof Island near Sitka last month was suspected to be 200 years old, which is five years shy of the record age for a rockfish.

Kara Hilwig is the lab supervisor for the age determination unit. She says the 41-inch, 39-pound rockfish was not that old.

“This particular specimen was interesting in that it represents what we typically see as what we call a ‘fast growth specimen,’ so even though it was really long, it was quite young, so it grew very, very rapidly. We aged that fish to be 64,” Hilwig says.

The circumference of the otolith from the hexagenarian Sitka shortraker was the size of a quarter, but it wasn’t thick. Hilwig compares that otolith to the one found inside another shortraker caught in West Behm Canal near Ketchikan last month.

“It was a smaller circumference on the otolith but it was really thick and heavy. It sounded like a glass marble when you dropped it on the table, whereas the otolith of the fish that came out of Sitka sounded more like a paper clip.”

The otolith from the Ketchikan shortraker revealed the rockfish to be 120 years old.

That fish was 39 inches and nearly 30 pounds – two inches shorter and ten pounds lighter than the Sitka fish half its age.

Learn more about rockfish and how to release one at depth.

Comments

comments