Bill Nyara: Fish offer great return on food they consume

Bill Nyara

For The New Era

Sometimes the things that you do every day without thinking can be the most interesting. Our summer high school employee reminded me of this when she asked about some of the little-known facts related to feeding and growing fish.

In the course of a year, South Santiam Hatchery grows about 81,000 pounds of fish by feeding about 90,000 pounds of fish food. This means that for every 10 pounds of feed they were fed, they gained more than 8 pounds. And you thought fast food was fattening! The cattle industry would love to see similar results for beef cattle. They typically get 1-2 pounds of growth for 10 pounds of feed.

The main ingredient in any fish food is protein. Most feed manufacturers are still using fish meal for the protein source in their feeds. Some large companies use herring and other ocean-caught forage fish while others use any fish byproduct they can obtain from canneries. A few manufacturers are using vegetable protein such as soy or cotton seed to reduce the cost of their feeds.

Regardless of the protein source, most feeds are about 50 percent protein. Fat makes up as much as 22 percent of the feed. Minerals, fiber, and moisture make up the remainder of most feeds. Vitamins A, C, D, E and others are added to the mix. The result is a high protein, high fat, vitamin rich diet that grows fish extremely well.

Most northwest hatcheries are now using what are called dry-extruded feeds. These feeds contain very little moisture and therefore can be stored for up to a year without refrigeration. These feeds have all but replaced the moist feeds used 10 years ago that required hatcheries to have large walk-in freezers to store feed.

Feeding of young fry takes place once the yolk sacs, attached to their bellies during the incubation process, are absorbed. Most hatcheries utilize starter tanks for early rearing because they improve food distribution and provide a cleaner environment with better water circulation compared to large raceway ponds.

Feed pellet sizes increase as the fish grow. Young fry are fed a very fine feed, similar to corn meal in texture. By the time smolts are released at 6 to 8 inches, they are eating pellets measuring over an eighth inch in diameter. Depending on the age of the fish and the desired growth rate, it can take anywhere from one to a dozen feedings throughout the day to give a pond of fish their daily ration.

Hatcheries usually schedule the growth of their fish stocks on a monthly basis. If you know how much gain in pounds that you need in each pond, you can easily calculate how many pounds of feed are needed in that month. The warmer the water, the better the fish eat.

Winter water temperatures in the low 40s makes feeding difficult compared to summer temperatures in the mid-50s. Some hatcheries are fortunate and have a spring-fed water supply where water temperatures maintain a constant temperature in the 50s. These hatcheries can grow fish faster or spread their fish growth out over a longer part of the year compared to a hatchery with a stream-fed water supply.

The real growth for salmon and steelhead, however, occurs once the smolts migrate to sea. While traveling around the Pacific Ocean, salmon really put on size, growing from 2 ounces each to as much as 20 pounds in just two years. A third year out at sea can add another 10 pounds in growth.

So there you have it ? a short course in fish feeding. It may seem to be the simplest job involved in raising salmon and steelhead but it’s also, without a doubt, the most important job we do.