A Cape Cod Notebook 7/15/08

ListenHerring Fry on the Pond

By Robert Finch

On a muggy morning in early July I go down to the shore of the pond landing and wade out into the shallow water where my boat is moored. It's a small, red, wooden punt that swings and rocks in the light westerly breeze like a tethered pony. The water is warm against my legs, so warm that it's like moving into a denser atmosphere rather than a different medium, a change of texture more than temperature.

The pond is not nearly as clear as it was a few weeks ago. Since then the upper layers have bloomed with microscopic algae. A blizzard of green flakes floats suspended beneath the surface. Each flake is made up of from three to five tiny, round, single-celled plants. Though the presence of algae clouds the water, it's from this humble and universal basis that the remarkable richness of plant and animal life in this pond springs.

Up through this light green algal snow, the bright red form of a velvet water mite paddles towards me. About the size and shape of an engorged dog tick, this brilliantly colored aquatic relative of spiders is an able swimmer and predator. When I lift it out of the water on my fingertip, however, it droops and melts into a shapeless tear of blood. I lower it back into the pond, where it regains its form and continues on its eight-legged way.

Swarming around the boat, just below the surface, are large, dark patches of tiny swimming creatures that look like hordes of aquatic insect larvae. But they are, in fact, masses of baby alewives or herring fry, recently hatched from eggs by the adults that migrated from the Bay up into this pond in spring. Though still less than an inch long, they already school together in wide circles like the adults, the basic herring rhythms already innate in their tiny bodies.

I've already seen other herring fry, only slightly larger and older than these, flipping down through the rushing waters of the herring run at the pond's outlet. They seem like cut blades of grass as they begin their precarious descent to an even more precarious saltwater world.

The spring ruin of adult alewives is a dramatic and colorful spectacle, yet to my mind these tiny fry seem to surpass their parents in sheer daring. (The fact that, from our point of view, they have no "choice" in the matter does not diminish the heroism of their undertaking.) They travel alone. No adult leads them or shows them where to go. Only a miniscule percentage of these herring fry will survive to mature and return here in three to five to spawn here in the pond where they were born.

Where do they go? Some tagged herring from this area have been found in the Chesapeake Bay region to the south, and as far afield as Norway - a staggering migration. Why do they go so far? And how do they navigate their return with such precision?

"We go," is all their delicate, silent forms say. They slip away before my approach, whirling off in miniature schools like underwater leaves blown along the shore.

myWGBH