THE EQUATORIAL EFFECT; IMPACT OF EL NINO UNCLEAR.

Byline: Brett Pauly Daily News Staff Writer

The 1997-98 El Nino will be heralded by future generations of anglers as the saltwater marvel that showcased exotic species off the West Coast.

A potential state record for yellowtail harvest. Skipjack and yellowfin tuna at the northernmost Channel Islands. Dorado in Oregon. Marlin in Washington. Even yellowtail off Alaska's Kodiak Island.

Yet largely overshadowed by the foreign-fish fanfare is the impact on local species that the Southern California sport-fishing fleet so completely depends on in normal years. It happens to be a big question mark; nobody knows for certain the fate of the regional fishery.

``When the yellowfin and the yellowtail all go home to Baja California and we turn to our buddies (the Southland fishes), what are we going to find?'' said Milton Love, a UC Santa Barbara marine biologist. ``For most species, El Nino is probably not a good thing.''

Especially hard hit may be squid, anchovies, rockfish and, to a lesser extent, halibut.

Cal State Northridge marine biologist Larry Allen takes a different viewpoint on the irregularly occurring flow of unusually warm Pacific water from South America.

``Pretty much all nearshore species seem to do better in warm-water years,'' he said.

White seabass, calico bass, sand bass, spotted bay bass and possibly halibut might actually benefit from the tepid temperatures.

Talk about confusing. Even the scientists are frustrated they must issue terms as inconclusive as ``probably'' and ``may'' and ``might.'' Indeed, the jury is still out on El Nino, a name meaning ``Christ child'' that Peruvian fishermen gave the occurrence two centuries ago after they noticed a heating of the ocean at Christmastime.

``In a way, there is no predicting; all you can do is go from past experiences,'' Love said. ``The problem is that all we can go from are three small El Ninos (1987-88, 1989-90 and 1992-93) and one humongous one in 1982-83. In 1957-58 (during another whopper of an El Nino), nobody was studying it.''

In other words, the data is the proverbial drop in the bucket.

Fortunately, this El Nino, which on average has elevated area waters 5 degrees above normal for this time of year (from the high 60s to the mid-70s), will serve as a living laboratory for students of the sea. More about the natural phenomenon will be learned by science than from all previous warm-water years combined.

Here are some generalizations biologists feel fairly certain of:

The dictionary notes that El Nino ``prevents upwelling of nutrient-rich cold deep water causing a decline in the regional fish population.''

Coldwater species, like rockfishes, are particularly stressed because equatorial waters contain less plankton, specifically krill, which is the main source of their diet and dramatically impedes the entire food chain, Love said. Reproduction is also impaired, and what larvae are produced tend to starve. Consequently, next year's crop of rockfish, an extremely territorial group that regional anglers target more than any other species, may be hurt. Those rockfish that do migrate, like bocaccio, will get out of harm's way.

Squid and anchovies, staples for many fishes (squid is a primary forage for white seabass and halibut, for example), simply cannot handle the heat and swim north or for deeper, cooler waters - where some predators are less likely to follow. (Despite their fragile appearance, anchovies are quite mobile; fish tagged outside Los Angeles have been found off Monterey, Love said.) Classic baitfish, their departure causes terrible grief among bait haulers and anglers. The resilient sardine, on the other hand, sticks around.

California halibut may move north to escape the heat. But, by the same theory, the local numbers may not be greatly diminished; fish migrating from Malibu to Morro Bay might simply be replaced by fish moving from Mexico to Malibu. White seabass tend to swim up the coast, too, and catches of both species between Point Conception and San Francisco could be excellent for the next year or two.

Calico bass, an intensely popular topwater game fish, are generally happy in temperatures up to 73 degrees. With pockets reaching 78 off Dana Point and 80 off San Clemente, the kelp bass will retreat to cooler depths of 80 feet or greater, meaning anglers must change technique and make deeper presentations.

Virtually all young sheephead are swept into the region with the warm waters. Likewise, young black sea bass do extremely well in El Nino years, either drifting in from Baja California or adapting to the radical temperature change.

Good news: ``Warm-water years produce the nearshore fisheries of the future,'' Allen said. The larval development of white seabass, calico bass, sand bass, spotted bay bass and halibut, all of which reside within 10 miles of shore, are greatly enhanced. Their metabolisms increase, meaning they eat more plankton and grow faster and healthier. They also get out of the water column quicker and are less likely to become a meal. Inshore waters still receive significant upwellings, due to currents and tidal movements, so finding sources of food isn't as much a problem, Allen said.

Bad news: The elevated-metabolism theory only holds true to a certain degree, Allen added. If coastal waters get too warm, which can happen, the plankton will die off, leaving the larvae to starve or to more readily become prey.

With so many anglers going gaga over the exotics (this year's state sport-fishing harvest of more than 350,000 yellowtail is second only to the catch of 450,000 in 1959, the third year of a long El Nino), it has taken a tremendous amount of fishing pressure off domestic species, according to Steve Crooke, a senior marine biologist for the Department of Fish and Game. ``It will look like the catches have declined among sand bass, barracuda and, to some extent, kelp bass. But the effort simply was diverted to yellowtail,'' he said. ``That's numbers in the bank for next year.''

Kelp weakens after waters exceed 71 degrees and eventually dies, Love said. The plants fall victim to crustaceans and fishes that devour them faster than they can grow, are ripped from their roots in the first big storm or simply cook on the vine. The loss of canopies takes structure and productivity away from calico bass and other game fish. It's not detrimental to adult fishes; they adapt and start hanging around deeper reefs. Anglers take heed: They're tougher to target because they're no longer found in the regular spots. Calico larvae gravitate to kelp, but it's unclear if their development will be hampered by the loss of structure and shelter.

Just when you think you've heard the last of El Nino, you probably haven't.

``Even when an El Nino is gone from the Central Pacific, it's impact is a year later in Southern California,'' Allen said. ``That's when water temperatures here usually peak.''

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Photo: (1-6--color) THE LONG ARM OF EL NINO

Overlooked in all the chatter about the impending El Nino is its impact on the local fishery. While predicting the outcome is far from a precise science - research on the warm-water phenomenon is minimal, at best - marine biologists note that some area species may benefit, some may be hurt and some may not be effected either way.

(1--color) Good: Most young sheephead flow into the region with the southern waters, then stay on and grow to maturity.

(2--color) Good: Calico bass and other inshore species grow faster and healthier in elevated temperatures.

(3--color) Bad: Rockfish really take it on the chin, starving in the plankton-poor flows and having trouble reproducing.

(4--color) Bad: Kelp shrivels and growth is impaired; structure is lost to fish and anglers must cast elsewhere to target game.

(5--color) Indifferent: Halibut swim north to escape heat, but numbers don't dwindle; fish from Mexico move in to take their place.

(6--color) Indifferent: While anchovies and squid swim for cooler havens, the hardy sardine couldn't care less about El Nino.

Gregg Miller / Daily News