On land, every spring bears the face of flowers. Right now in March, the first subtle bloom of redbud and red maple flowers in the tree tops a month ago has exploded in a riot of azaleas, wisteria and dogwoods where I live.
But the seasons of the sea, as marine biologists and fishermen all know, are as strongly marked as those on land. Right now in March, the season’s first horseshoe crabs are returning to the breeding beaches they will visit every full and new moon all summer. Manatees are returning to coastal sea grass beds, emerging from the year round warmth of coastal spring fed rivers that sheltered them all winter.
Come the full moon in April everything else will explode back into life again as well. Pink shrimp that spent the winter buried in the sandy sea floor will emerge by the millions and swarm across the bottom in what shrimpers call the spring hopper run. Fish that moved offshore into deeper warmer water move back into the shallows even as the white pelicans are flying north overhead.
It all reverses in the fall. With the first few cold fronts, the water chills, gets stirred up and choppy. It’s a signal to all the juvenile crabs and fish and shrimp that grew up in the warm shallow food rich inshore waters of summer that it will soon be too cold for survival. Just like birds headed south for the winter, they head offshore to deeper water, water that will stay relatively warm through the brief chill of a Gulf Coast winter.
Fall is run season for mullet — the year’s crop of fish form schools and run along shore, their bodies ripe with eggs and sperm, to spawn in deep open water. In a few places fishermen still wait along the shore to catch them as they did 100 years ago. The mullet that complete the migration will spawn their microscopic offspring that will ride the currents back into the bays and marshes a few months later in early spring. Rare Keep’s ridley sea turtles disappear from their crab rich grass bed feeding grounds in the fall. Some will move south, some will bury in the mud, hibernating like pond turtles till the water warms up again. Off Cape Cod, other ridleys are traveling south for hundreds of miles, maybe as far as Cape Hatteras to escape the lethal freezing temperatures of a north Atlantic winter, a real winter.
In the surf zones of northern Gulf Coast barrier islands from Dog Island in Florida west to the Mississippi, mother electric rays who came inshore to birth their young in August and September leave in November, headed back to offshore sand bars in thirty feet of water. The newborn brown spotted babies will stay on, feeding on tiny worms and burrowing sea anemones until January cold forces them to remain buried and inactive until spring time.
When a fall cold front swept through one year, the November sky looked like a blue porcelain dish above our heads. My Florida State University students and I walked along the shore, all of us bundled up against the cold north wind that was blowing with bared fangs across the water. The full moon tide had fallen hard and fast that morning, pushed by both gravity and the wind and the mud flats were dry for a quarter of a mile off the beach. Dry and covered with shrimp, hundreds of shrimp, big shrimp stranded as the water rushed off the flat. Unlike the pink shrimp of spring, these were closely related white shrimp trekking to the open ocean from the muddy shallow nearly fresh water in river mouths where they had spent the summer growing from microscopic babies into big edible seafood shrimp, 6 inches long.
Their opalescent white bodies and green and black tail fans gleamed in the bright sun. Caught by the weather, by the unusually fast fall of the wind driven tide as they moved along the shore toward the open ocean, these shrimp would not complete their fall migration from the marshes at the head of the bay out to the sea.
Their misfortune was our gain. Scientific theory and learned discussion of marine animal migration was on total hold as the students switched from ecology to applied biology, specifically to fisheries biology, more specifically to harvesting the marine resource at our feet. Lunches were emptied out of coolers as somebody drove to the nearest store to buy ice. Marine biology was all very well but this was dinner, this was real.