BOSTON (AP) _ Former government tea taster Tony LaTerza has put his educated nose to work distinguishing merely smelly fish from the really rotten.

LaTerza works for the U.S. Food and Drug Administration smelling fish from foreign trawlers to check for decomposition. He also occasionally whiffs other products.

He doesn't just sniff for a single telltale stench. LaTerza says he can pinpoint a fish's stage of decay and distinguish between types of decomposition the way a wine taster tells a Bordeaux from a Burgundy.

There is the smell of rancidness, for example, from rotting fat in tuna and turbot, and ammonia from decomposing shrimp. Not to mention the smell of general putrefaction.

''But usually, when a fish is decomposed, you can probably smell it as soon as you come into the room,'' he said.

LaTerza, who would not give his age or his salary, is a 26-year veteran of the FDA who turned to so-called ''organoleptic examinations'' when he found policing the docks as an inspector not to his liking.

His first assignment was tea tasting. A 19th century act of Congress outlaws inferior tea imports, so every winter a board of tea experts convenes in New York to sip and set standards for the year.

To impose those standards, LaTerza tested tea coming into Boston much as a vintner tastes wine: by slurping it, to get the full bouquet. He particularly disliked Lapsang souchong, he recalled.

He said he switched to fish because he seemed to have a knack for it. Boston is one of 10 ports around the nation with FDA fish smellers.

A small man with an unremarkable-looking nose, LaTerza said his skill is a natural talent fine-tuned by years of training.

''I'm always the first one to come running out of a room and yell 'Something's burning 3/8''' he said.

LaTerza estimates that he smells at least 20,000 pounds of fish a year. About 15 percent fails to pass the inspection.

Occasionally the work gets to him. ''I have to leave for 15 minutes to acclimate myself again, get a breath of fresh air,'' he said.

LaTerza's rejections are rarely challenged. Foreign fishermen apparently accept his judgments and the FDA prefers to use his nose rather than sophisticated lab equipment because he's quicker.

Periodically he is called upon to sniff other foods and drugs, usually because of a consumer complaint. He also trains would-be smellers in the fine art of fish, but demands that they refrain from wearing cologne or aftershave.

''I don't like perfume anyway, but what bothers me most are subways,'' he said.