By Montana Grant

Posted: April 14, 2022

Big Fish do not just magically appear. They need to grow up to become Big Fish. Some fish, like Rainbow trout can grow quickly while others age more slowly. Telling the age of a fish usually involves a little Science class anatomy and magnification. 

We age trees by looking at the rings in a cross section. Counting the rings will add up its age. The distance between the rings will show which years had the best growing conditions.

Fish have rings to count too. You just need to know where to look. Generally, fish scales will tell a fishes age. Pull the scales off the top of a fish, near the front of the dorsal fin. You can use a magnifier to examine the rings. The thickest rings are called annulus. Each annulus represents one year. Other fish can be aged by counting rings on an Otolith, or inner ear bone. Fish without scales like catfish, can be aged by looking at their pectoral fin spine. Pull the spine and make a cross section, near its base. Now you can count the rings.

Older fish are certainly bigger but also contain more toxins. Lead, mercury, arsenic, and other toxins build up over their lifetime. Slow growing fish like walleyes and perch can contain a lot of toxins just as they become legal eating size. Smaller, fast growing fish like trout, are better eaten before they grow to trophy size. Old fish are like old elk, chewy and not prime eating.

Rainbow and Brown trout can live 5-7 years. Once they become large, finding enough food becomes harder. Stocked lunkers grew big by feasting on hatchery food. Once released, they begin to degrade within 3 months. Brook trout are slow growers while Rainbows can grow 6 inches in their first year.

Yellow perch can live up to 15 years, as do walleyes. They are keeper size around 8-9 years old. Females, in most fist species tend to be the largest and oldest.

Paddlefish can live over 60 years! To become 50 lbs., they have lived for around 20 years. Northern Pike needs to be around for 20-25 years to be around 40-45 inches long. Healthy fish growth depends upon the water quality and abundance of food in the ecosystem.

Pallid and Shovelnose Sturgeon can live up to 150 years old. The species has been on Earth for millions of years. A mature sturgeon, at 30-60 Inches, can be 85 lbs. and 25-30 years old. Sturgeon reproduces irregularly and are endangered.

One of the oldest sportfish is the Alaska Goldeneye Rockfish. At 3 ½ feet long and 40 lbs., the Goldeneye can be 150 years old. This is a real trophy, but I would maybe live and let live. 

Catching older fish may be harder, since they may have more experience. They could be easier to catch since they need more food to survive.

Getting old is no fun!

Montana Grant

New Podcast!