Call it “Ahi Fever,” “Yellow Fever” or “Money Fever!” Like spring fever, it’s an affliction caused by a strange virus that infects all boat fishermen starting in the early month of May.

Multiple symptoms: Argumentative, grumpy, daydreaming, restlessness, inability to think and work, an overwhelming feeling of anticipation, to procrastinate everything that’s important in life, anxiety for fishing. Just the mention of sashimi can trigger an attack.

There are actually many different races of “Allison” yellowfin tuna, which seem to migrate in overlapping circles across the Pacific. The various strains differ in the relative size of the eye, length of the fins and robustness of the body.

Yellowfin tuna, Thunnus albacares, were formerly regarded as a separate species, Thunnus allisoni, originating in the 1920s. Its earliest usage was found in The National Geographic, from the name of James A. Allison, U.S. entrepreneur and founder of an aquarium at Miami Beach, Florida.

Here are a few interesting facts:

After attaining maturity at around two years, female yellowfin can spawn repeatedly every day for long periods and will release millions of eggs per spawning. Actually, spawning occurs at night, usually between the early evening and the early morning hours. The eggs “hydrate,” or expand rapidly, by taking on water in the late afternoon prior to the evening spawning. The “hydrated” egg sacs swell noticeably, and may be around 8-12 inches long and over three inches in diameter. The eggs are approximately 1.0 millimeter in diameter and are fertilized in the open ocean where they float with the plankton until hatching.

Some spawning occurs all year long along the Equator, where surface water temperatures are always above 81 or 82 degrees Fahrenheit. An abundant food source and active feeding activity is coincident with daily spawning cycles. In Hawaiian waters, yellowfin concentrations close to the islands apparently increase at the onset of the spawning season in April and May with rising surface water temperatures. Yellowfin in Hawaiian waters also exhibit near daily spawning frequencies during the peak of the summer spawning season, with spawning ceasing around September and October. The active feeding required to fuel this reproductive activity increases their vulnerability to surface trolling gear, shallow set longline gear and ika shibi handlines. During the spawning season, all three fisheries are in direct interaction with each other for mature, reproductively active yellowfin.

The high spawning rates and tremendous egg production by the species is a great advantage to yellowfin stocks. Obviously, only a small fraction of the eggs survive to produce adult fish, while the rest are consumed by other fish or zooplankton. Their approximate longevity is around ten years.

Hawaiian yellowfin tuna appear to be mainly a product of localized spawning population, with a smaller immigration component coming in from south of Hawaii. These tuna tend to remain in Hawaiian waters throughout their lifetime with low exchange rates between Hawaii and other regions of the Pacific.

Unlike mahimahi, the sex of tuna cannot be reliably determined without actually cutting them open and looking inside.