The alewife herring is born in fresh native ponds, swims in a salt ocean with bigger fish for much of its young life, then comes home to spawn.
Dams and spillways like the one at Argyle Lake in Babylon Village have interrupted the natural order of things for more than a century, blocking the way for returning fish, leaving them vulnerable to predators and inhibiting their reproduction.
Now, with a fish ladder the Babylon Village Highway Department built and officials dedicated Thursday, the alewife is blocked no longer.
The ladder looks nothing like a ladder: more like an aluminum chute, 72 feet long and a foot wide, sunk into a trench leading from the lake down to the bottom of Argyle Falls just north of Montauk Highway -- a 10-foot drop.
Alewives will swim against the current, and gravity, up to the lake. "These fish are very capable swimmers," said Enrico Nardone, director of Seatuck Environmental Association, an Islip-based group that helped the village secure a $31,500 grant for the ladder from the National Association of Counties and the National Oceanic and Atmospheric Administration.
"They can handle a substantial current. They can handle small jumps of a couple inches," he said. "But they're not jumping six feet into the air," like salmon.
The humbler alewife, green-gray and up to 15 inches long, has seen its numbers dwindle in recent decades and is being considered for federal protection, officials said. But as a bait fish near the bottom of the maritime and inland estuary food chains, it is critical, Nardone said: "It helps drive this whole coastal ecosystem . . . I tell people, you may not care about this foot-long fish, but if you want to catch stripers, if you want to catch bass and bluefish, this is a piece of that whole puzzle."
Navigating by instinct and opportunism, alewives travel from the Atlantic 150 miles or more up the Hudson or a much shorter distance up Long Island tributaries such as the Peconic River, Massapequa Creek or Carmans River. About half a dozen fish ladders have been installed elsewhere on Long Island, mostly out east, Nardone said. Not all scientists agree that the ladders are effective in growing fish population.
Any alewife taking the Babylon Village fish ladder would have a much shorter swim. Construction of a second ladder at Southards Pond, which officials Thursdaysaid was being considered, would open up the way to Belmont Lake, a distance of about four miles from Great South Bay.
Just one problem so far: After the highway department's Skip Gardner, Scott Glenn and Andrew Alvarez spent close to a month building it, with long Sandy-related interruptions, they say they have not yet seen any alewives. "I've seen eels, snapping turtles and trout that I can confirm," Alvarez said.
Gardner said he was optimistic, though. "Probably once the word gets out, they'll all come up at once."