Fish-food chef has a lot of hungry mouths [Archive] - Fly Fishing Forum

: Fish-food chef has a lot of hungry mouths

04-17-2002, 02:11 PM


Ann Gannam specializes in cooking up a mixture of ground herring, blood
meal, pulverized chicken feathers, wheat germ and fish guts.

It might sound revolting to people, but Gannam doesn't care. It's good for

Gannam, who has a doctorate in fish nutrition, tests and designs fish food
for hatcheries operated by the U.S. Fish and Wildlife Service. She works
out of a laboratory at the agency's Abernathy Fish Technology Center
near Longview, Wash.

Making food taste good to fish is important to Gannam, and she has a
variety of ways of doing that. For example, one population of steelhead at
the lab wouldn't touch the commercially prepared food until Gannam
flavored it with liquefied krill, a kind of ocean plankton. She also uses raw
chopped beef liver to coax finicky fish to eat.

More important, though, is making sure hatchery food is healthy. That's
crucial because most of the approximately 1 million salmon and steelhead
that return to spawn in the Columbia River Basin each year begin their
lives in one of the region's dozens of fish hatcheries, which produce more
than 100 million fish a year.

Historically, companies that manufacture fish food have focused on
making fish grow big quickly, Gannam says. But new theories about
raising fish have emerged. Gannam wants her food to yield hatchery fish
that look and act more like wild fish.

"We don't want big fat fish," Gannam says. "We want lean, mean fish that
behave like they're wild."

Salmon and steelhead are anadromous, beginning their lives in fresh
water, migrating to the ocean and returning to fresh water to spawn. The
eggs that wild salmon and steelhead lay in streams, rivers or lakes
develop into fry, and the fry into smolts (juveniles) that migrate downriver.
Depending on the species, smolts -- whether hatchery-born or wild -- live
in fresh water for months or as long as several years before heading to
sea. After spending most of their adult life feeding in the ocean, they
return to spawn in the stream or river where they hatched, and the cycle
repeats itself.

But some fish raised in hatcheries develop differently or behave strangely.
For example, some steelhead hatcheries produce a higher percentage of
jacks than normally found in the wild. Jacks are sexually immature males
that return from the ocean early.

Gannam thinks the jack count from those hatcheries may be high
because hatchery food is higher in digestible energy than the food that
fish eat in the wild.

Three years ago, working with Jack Tipping of the Washington Department
of Fish and Wildlife, Gannam fed a generation of hatchery steelhead a
low-calorie diet. Last year, they tried varying the amount of food the
steelhead were fed at the end of the summer, before they were released.
This year, they're raising steelhead in hatchery raceways with different
water temperatures.

Now the two researchers are waiting to see whether any of those
techniques reduce the number of jacks.

But Gannam doesn't just work to improve hatchery food. She also
troubleshoots when things go wrong.

Say you operate a hatchery and your fish are getting sick. Tests for
pathogens, viruses, parasites and water quality reveal nothing. It could be
the food. Different nutritional deficiencies cause different diseases. Some

A shortage of pantothenic acid causes "clubbed gills," with tissue forming
between gill endings, making it harder for the fish to breath.

A shortage of vitamin C impairs formation of collagen, or cartilage. That
can lead to curved spines, called scoliosis, or a condition known as
"broken back."

A shortage of folic acid can lead to anemia.

"Fish can't tell you what's wrong with them," Gannam says. "Their food
can provide clues."

Gannam and chemist Dick Anderson still talk about the time a hatchery
was producing fish with missing gill covers, which are held together by
collagen. They tested the food and found a vitamin C deficiency.

"If there is a problem with performance in a hatchery, and they can't find
another cause, they'll call us," Anderson says.

Gannam is looking for ways to stimulate fish immune systems to make
fish better able to ward off illness. She has experimented with adding
esoteric ingredients to fish food, including glucans from yeast or fungi cell
walls, and astaxanthin, an orange-red pigment found in crustaceans.

"Ann's a wizard, a magician," says Carl Burger, director of the Abernathy
center. "She's always coming up with new ideas to produce better-quality

Gannam and Jeff Poole, a technician, assemble fish food in a large room
near her laboratory that is dominated by a 20-foot-long steel machine
called a "cooker-extruder." Gannam mixes her concoctions in the room,
puts the mixture in a blue vat at one end of the machine and stands back.
The food is cooked with steam and emerges as pellets, which then go into
an oven for drying.

"It's pretty smelly when the steam is coming out," Gannam says. "But
when we have a success, it's great." You can reach Jonathan Brinckman
at 503-221-8190 or by e-mail at