No. 11–Transition Time

Circadian clocks within countless salt marsh creatures are ticking in autumnal time. The pace of estuarine life is winding down as the daylight hours shorten and night air cools the waters. For some it is a time of harvest, for others a time of feasting, for still others it is the beginning of renewal while others are spent and drifting to their preordained end.

The most visible of the seasonal changes is the browning on the marshes. The ubiquitous perennial spartina grass is the fuel that drives the biological engine of the estuary. The annual death and decay of the hearty cord grass is the primary source of detritus which is at the center of the estuarine food web. Next to the water it is arguably the single most important element within the ecosystem.

The offshore migration of white shrimp is now climbing to its peak. That is if there aren’t abnormally heavy storm related rains between this writing and its reaching print. The threat of tropical storms and hurricanes is always in the mix during fall transition time. With normal rainfall over the period, white shrimp continue their annual off shore migration from August through December or until estuarine water temperatures drop into the mid to low sixties. That can all be turned on its head by eight to ten inches of rain in a short period.

The reason the fall shrimp season is so long, under normal conditions, is related to the length of the spring spawn which produced the current generation. First spawned are first into the estuary and first out after a summer of growth. Last in are last out. There are still young small shrimp growing in the creeks even as older ones are moving down river and off shore. Shrimp are particularly sensitive to salinity swings and torrential rains creating a drastic drop in estuarine salinity would flush even the smallest shrimp into the ocean, ready or not, thus putting an end to the fall recreational harvest.

Oysters are now in season bringing an air of conviviality as the succulent shellfish steam over the coals in back yards and in social settings throughout the lowcountry. Both local and out of state oysters may be consumed at these gatherings depending on the preference of the host. Oysters from the gulf states are singles (individual oysters from sub tidal waters) and preferred by some for general uniformity of size and relative ease of opening. Restaurants tend to prefer gulf oysters for the same reasons. Local oysters are prized for their arguably better taste but require a bit more skill and dexterity in the handling.

The vast majority of local oysters consumed are intertidal cluster oysters. The cluster effect is the result of the way this branch of the species reproduces. The post larval spat oyster requires a hard surface on which to cement itself and begin to grow. A large three or four year old oyster may have smaller cousins in a range of sizes from subsequent spawns attached to it.

It’s not unlikely that you’ll find a few singles in the mix at a roast of local oysters as clusters do break up in harvesting and handling. They’re easy to differentiate from gulf oysters, however, by their shape. Gulf oysters are more rounded with thicker shells sometimes resembling a baseball catcher’s mitt. Cluster oysters tend to become more elongated as they mature. Possibly an evolutionary adaptation brought on by crowded living conditions.

Soon the waters will begin to clear as the plankton load diminishes in concert with estuarine metabolisms. Strands of the food web are packed away for the winter as those who are able move to deep holes in the sounds or to offshore waters. When the frost is on the periwinkle, except for the raucous rail, it is quiet time in the marsh.