JAUNTS : Hatchery Welcomes Visitors to Join in the Feeding Frenzy : About 1 million rainbow trout spend their formative months at the Fillmore facility, open daily to the public.

It’s feeding time at the Fillmore Fish Hatchery, and the fish are jumping--thousands of them, wiggling fin to fin, in huge troughs of water that splash and bubble with all the ruckus.

The fish, rainbow trout, even get excited before the food arrives. They can sense the vibration of the feeding cart as it approaches, spewing high-protein animal and plant meal out of a long mechanical arm into the water.

While Fillmore is still reeling from damage caused by the Jan. 17 earthquake, the constant feeding frenzy at the fish hatchery goes on as usual. The hatchery wasn’t damaged in the quake, but it shut down for two days while the operation was on auxiliary power.

“We lost a few fish,” said Terry West, assistant manager of the hatchery. About 600 in all--either from sloshing out of the troughs or from lack of oxygen when the air-flow system was jostled.

But when you deal with 1 million fish, the loss is not considered much. That’s the number of rainbow trout the hatchery raises each year for planting in Southern California lakes and streams.

You can see the rearing in progress. The hatchery, operated by the California Department of Fish and Game, is open to the public. Although there are no guided tours, the hatchery is open for viewing from 7 a.m. to 3:30 p.m. daily, and there is no charge.

The fish arrive at the hatchery in the form of fertile eggs for the final stages of incubation, which lasts three to five days. That part of the process is too delicate to be open to the public.

When the tiny fish are ready to start feeding, they are put into “raceways” composed of a series of rearing ponds. Each is a rectangular concrete trough measuring 100 feet long, 10 feet wide and 32 inches deep.

As they grow, they graduate to nine other such troughs, each one housing gradually larger fish. The biggest tend to nibble on the smallest, so they can’t be raised together.

“They’re very cannibalistic,” West said.

They do love to eat--and eat often. The larger ones feed four to six times a day and the smaller ones 12 times a day. Almost any time you visit the hatchery, you’ll see some feeding activity. Also, visitors can pay 5 cents for a handful of feed to toss into the water and watch the frenzy. (Don’t bring food from home because it gums up their delicate digestive systems.)

Signs warn visitors not to put their hands in the water or try to grab the fish. The most outrageous case of fish nabbing occurred there during the 1970s. As West tells it, four guys wearing overalls were caught pulling fish out by dropping lines down their pants’ legs.

Until Fish and Game workers installed netting over the rearing ponds eight years ago, the 52-year-old hatchery was continually pilfered by other culprits: egrets and herons that snatched about 30% of the fish. The birds still hang out within view of the hatchery, but workers now feed them the 25 to 30 fish that normally die each day.

For the survivors, their stay at the hatchery lasts almost a year. When they have fattened up to about half a pound--ranging from 7 to 12 inches long--they are ready for planting, according to West.

In Ventura County, they could end up in Lake Casitas, Lake Piru or Rose Lake or in a number of streams, including Matilija, Reyes, Santa Paula and upper Sespe creeks and the north fork of the Ventura River. Fish and Game officials say now is the busiest season for planting fish, although it extends from September through June.

“Without the hatcheries in California, we would not have the sport of fishing as we know it today,” West said. There simply wouldn’t be enough fish.

The trout hatchery is one of 11 operated throughout the state by the Department of Fish and Game.

Even without tours, the hatchery draws 3,000 to 7,000 visitors a month, depending on the time of year. For some, it’s almost therapy, according to West. “I’ve heard people mention that water calms the nerves. It’s very soothing for what ails them.”

Details

* WHAT: Fillmore Fish Hatchery.

* WHERE: Off California 126, about one mile east of Fillmore. Watch for the turnoff to the south of the highway.

* WHEN: Viewing hours are 7 a.m. to 3:30 p.m. seven days a week.

* FYI: There is no charge, but fish food can be purchased for 5 cents. For information, call (310) 590-5132. Call (310) 590-5020 to hear a recording about the fish-planting schedule.