Run, herring, run!

Or, rather, swim, herring, swim, to your natal stream. River herring — harbingers of spring — should be back soon, if they are not already.

River herring are actually two different species, the alewife and the blueback herring. They are grouped together because of the great difficulty in telling them apart. They are virtual twins, except that the peritoneum (tissue lining of the body cavity) is gray or silver with small dark spots in the alewife, and dark brown or black in the blueback. Only an ichthyologist (fish scientist) or very detailed observer can tell the difference.

These anadromous fish are seasonal residents that are born in freshwater habitats, live most of their life in the open ocean, and then return to the freshwater stream of their birth. Their cue for when it’s time to return comes from the temperature of the fresh water, which needs to be 51 degrees for the blueback herring and 57 degrees for the alewife in order to lure them back.

They swim in schools and were once so abundant along much of the East Coast that they were called “glut herring.”

River herring are no longer as plentiful as they once were. Their decline has been due to overfishing, damming of spawning rivers, and pollution. There are a few still active herring runs on the Vineyard. Head of the Lagoon and Tashmoo, Aquinnah, and Mattakesett at Katama boast a past or present fishery.

Now these tasty little fish are almost exclusively for other animals’ meals. Osprey are back in our skies, and on their menu is river herring. The very name of the herring gull, of course, leaves no doubt what’s on its mind and in its stomach. Larger fish, including bluefish and striped bass, will soon return and partake in the herring feast too. Even seals and river otter wouldn’t refuse such a protein-packed morsel. But there will be no river herring for you, at least not this year.

The Massachusetts Division of Marine Fisheries has instituted a moratorium on the harvesting, possession or sale of river herring in the commonwealth. A three-year moratorium (through 2008) is in place after significant declines of these small fish.

Even without human predation, survival is tough enough for these feisty fish. Infant (or would it be “finfant”) mortality is high. Only about 1 per cent of the up to 100,000 eggs produced by the female river herring will make it to adulthood and go out to sea. Their predators don’t eat them salted, smoked, or pickled, but they are a delicacy nevertheless. Adulthood is no easier: 32 to 90 per cent die annually.

With the weather warming, daylight lasting into the evening, and all of the wild signs, I know that spring has come. Still, I have not yet seen or heard of the arrival of schools of river herring. If they aren’t here yet, just consider this article a read herring.

Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown.