A block from home, the smell accosts you. You look around the dark street for the stray dog that's rolled in dead skunk then topped off the treatment with a wallow in fresh excrement. There is no dog. You reach the stairs, ascend to the porch, and the putrid scent intensifies. Check your feet -- nothing. Look around again for the dog -- nothing. But as you fiddle with key in lock, holding your breath, it seems you can feel that nonexistent dog, could swear he's trying to shoulder past you as you open the door and quickly enter, shutting it fast. Whew.

What the heck is that smell? Lately, especially at night, it envelops Eureka neighborhoods in ribbons of thick foulness. Maybe there's been a shift in wind patterns. Or maybe you're just being too sensitive. This is, after all, a working waterfront town where smelly things happen and the locals rejoice in it. It's like that pulp mill: Long-time residents like to boast that things smelled much worse back when Eureka had two pulp mills. Now there's just the one. Sure, its reduced-stinky plume wafts over parts of Eureka with regularity -- but how dare anyone complain about a job factory? Same goes for that fish smell, honey. Get used to it.

But no. Something is different. So you follow your nose one morning down to the waterfront.

Outside Pacific Choice Seafood's processing plant, a mushy waterfall of pale pink vomits from the maw of a big chute on the side of the building. Several giant bins contain heaping mounds of the stuff, which turns out to be shrimp shells. The smell wafts toward Old Town.

At the small boat basin, upwind at the moment, the air's clear. Terns circle, warble-shriek, and dive with loud plops into the bay then emerge and lift off, each with a tiny, shiny anchovy struggling in her beak. Marty Quant is patching a hole in a friend's sailboat. He's lived in the boat basin about eight years. The smells come and go, he says; crab season's pretty strong. "But I hadn't really noticed that strong smell coming out of there before," he says, nodding at Pacific Choice. "A couple of weeks ago it was particularly pungent."

Another permanent live-aboard, unlocking the door to the laundry facility, says she's definitely noticed the new smell.

"It's unbelievable," she says. "Even a little caustic. A lot of people here have said, 'Wow.'"

Two women amble along the main dock. "It's always horrid," says Judy Klapproth, who lives in town. "You know what I think? Nature abhors a vacuum. Now that the pulp mill doesn't smell as bad, they've [the fish plant] risen to meet the challenge."

Outside Englund Marine, next to Pacific Choice, three men are walking past the bins of shrimp shells. They say they know nothing. As they move away, one of them jokes, "Heh, heh, I smell an environmentalist."

So, it's inside the blue door on the side of the building and up and down stairs to Pacific Choice Plant Manager Kirk Younker's office. Where all is explained. The reek is related to a new organic fish fertilizer venture, in which Pacific Choice processes fish scraps -- which used to head to a landfill -- and trucks them to Gonzales, in the Salinas Valley, where they become either liquid or pellet fertilizer that another outfit, Converted Organics, then markets. The operation started up in April, and there have been some glitches.

"There's going to be a natural fish odor from a fish processing plant," says Younker. "But not that stench."

Several things have caused it. Summertime, for one.

"We've been running a lot of shrimp -- about a million pounds a month," he says, adding that the shells, which become the pellets, have piled up faster than they can be trucked away.

Plus, they've had problems with the pump in the tank that prepares other scraps for the liquid product. It keeps plugging up with bones and choking to a halt. That stops the fish goop from circulating, which then ferments -- stinking to high heaven.

"We fixed the bone problem," says Younker. "Now, we just need to keep the stuff moving. We're working on resolving it. Because I don't like it either."