STURGEON ARE AWASH IN MYSTERY.

Byline: Brett Pauly Daily News Staff Writer

Ichthyologists are fascinated by the sturgeon's long life span, impressive size and late maturity, but overall this creature, which has existed in its present form for millions of years, is largely misunderstood.

``There is a lot of information that is not known about the fish,'' said Dave Kohlhorst, senior biologist with the Department of Fish and Game at the Bay Delta Division in Stockton. ``For instance, we don't know all the factors that control abundance or survival of young sturgeon. We're not at all sure about where they spawn in the Sacramento River or their spawning habitat requirements in general.''

``No natural science is a real exact science,'' said Kohlhorst, a specialist in sturgeon and striped bass. The statement has never been more true than when applied to the sturgeon.

Here's a rundown of what is known about the animal:

It is nicknamed diamondback for the five rows of bony plates, or scutes along its back. They probably offer some protection from predators for younger animals, but since adults have few natural enemies it's unclear why they are needed.

Females don't spawn until age 15 to 25 but have an extraordinarily high fecundity rate. A white sturgeon at age 15 may produce 100,000 eggs. An older fish (they reach 7 feet at 30 years, 8 feet at about 40) may produce 1.5 million to 2 million eggs.

There are stories about 100-year-old sturgeons. The oldest the DFG has aged is 47 years, which weighed 405 pounds and was caught on the Sacramento River upstream of Sacramento. The sturgeon's life span is nothing short of remarkable considering that some fish, like delta smelt, live only one year and many salmon live just three or four seasons before they spawn and die.

The state record for a sturgeon caught sportfishing is 468 pounds, boated in Carquinez Strait, south of Vallejo, in the late 1980s. Kohlhorst has heard tales and seen old pictures of sturgeon that were claimed to weigh 1,800 pounds. The biggest found in the Sacramento River system is thought to have weighed 1,300 pounds, caught in the vicinity of Sacramento around the turn of the century.

Rather than having a bony skeleton, the sturgeon is cartilaginous like the shark but doesn't share the same family tree.

It is a bottom-feeder that uses barbels - worm-like sensory organs on the bottom of its protruded snouts that function like our senses of taste and smell - to locate clams, shrimp, marine worms and fish eggs, especially herring eggs. Contrary to popular belief, it is not a scavenger, preferring live prey to carrion.

The western portion of North America is home to two species, the green and the white sturgeon, which spawn primarily in the Sacramento and San Joaquin river systems, the Columbia River and the Fraser River in British Columbia.

White sturgeon, a mild-flavored white-meat fish commonly broiled, grilled, fried, smoked and added to stews, may spawn as far along the Sacramento River as Hamilton City, some 200 miles upstream. Green sturgeon, which are less abundant and not often targeted by anglers because of their reputation for poor eating, swim 245 to 290 miles to spawn between Red Bluff and Redding.

The white variety spends most of its life in estuaries and rivers, whereas the green sturgeon, considered by some a candidate for threatened-species status, is predominantly found in the ocean.

Tackle Box How to catch sturgeon by boat on the Sacramento River:

Rod: Six-foot, medium to heavy action, one-piece bait rod.

Reel: Conventional, 4/o bottom-fishing unit with level wind and lots of capacity for seriously heavy line.

Line: At least 150 yards of 50- to 135-pound-test monofilament or Dacron line.

Terminal tackle: Slip an 8-ounce sliding sinker on the line above a 150-pound-test snap swivel. From there use about three feet of 60- to 90-pound-test steel leader. Like sharks, sturgeons love to roll up on the line toward the end of a fight; their rows of sharp scutes have been known to cut lesser leader. Many anglers use 7/o to 9/o octopus hooks or c-shaped hooks, sometimes in a tandem setup with hook points facing opposite directions.

The bait of choice is ghost shrimp; mud shrimp and crawdads are popular, too. Sandwich two shrimp on the hook and wrap them generously with polyester sewing line to dissuade bait robbers - striped bass, Sacramento squawfish, western suckers and small steelhead trout. For extra insurance against pilferers, some anglers prefer to first enfold the shrimp in cheesecloth, panty hose or sport wrap - thin, foamy material used underneath athletic tape. Don't overwrap the point of the hook.

The coup de grace for diamondback-savvy fishers is Sturgeon Cocktail (Pro-Cure) or similar-scented attractors. Some marinate square-inch pieces of dish sponge in the putrid brew and attach a section above the baited hook.

Angling rules: The season is open year-round in most counties. However, there are periodic closures and nighttime fishing restrictions when herring and striped bass are spawning; be sure to consult the California Sport Fishing Regulations. The limit is one fish per day, with a minimum size limit of 46 inches and a maximum of 72 inches, designed to reduce the overall harvest rate and protect the larger, more fecund females.

CAPTION(S):

Photo, Box

Photo: Sturgeon bait is prepared using wrapped ghost s hrimp and a scent-coated sponge.

Brett Pauly / Daily News

Box: TACKLE BOX (see text)