OLD OAK TRAIL by Joe Reynolds AH Environmental Commission Member

published Atlantic Highlands Herald 7 July 2005

A VISIT WITH FIDDLER CRABS IN RARITAN BAY

The sun dangles high and large in the warm, muggy air of summer. An unending southwest wind blows across the marsh bringing with it hazy, hot conditions. I am located near the Church Street Bridge in Port Monmouth overlooking Comptons Creek.

It is dead low tide. I start to move down from the upland to the muddy edges of Comptons Creek where the marsh grass is waist high. The mud-covered brackish portion of a creek is perfect habitat to find Fiddler Crabs in the Bayshore Region.

Fiddler Crabs are one of the most abundant and vital animals in the bay. Nonetheless, they are largely overlooked and disregarded by residents today as not being of great consequence in our bay ecosystem.

One reason for this error is perhaps due to their size. Fiddler crabs are small. They are only up to an inch in length, which makes them one of the smallest crabs in the Bayshore Region and easy to ignore. Fiddler Crabs also only active during low tide between spring and mid-autumn, which confines the time they can be seen.

Yet, Fiddler Crabs are a crucial link in an estuarine food chain. They help to transfer the sun’s energy in use by marsh plants to animals that live in the bay. At low tide Fiddler Crabs wander over mudflats in pursuit of algae or decaying vegetation. Unlike other crabs, which use their claws to grab live food, the Fiddlers' claws pick up mud, which they scrape with their mouths for plant matter or detritus. Fiddler Crabs, the herbivores, in return are a valuable food source for carnivores in the bay, such as blue-claw crabs, egrets, herons, glossy ibises, and small mammals such as raccoons.

(An adult male Fiddler Crab showing off his large characteristic claw)

As I get closer to the mudflats, I notice there is a flurry of activity from some very miniature critters. These are the Fiddler Crabs and the muddy embankment of Comptons Creek is teeming with these little critters as they forge for food.

Male Fiddler Crabs are easy to identify. They are the only crab that has a single enlarged claw, usually pale in color. The males wave or saw back and forth this claw in a "fiddling" motion to attract females and to ward off other male competitors. Female Fiddler Crabs on the other hand do not have a large claw, so they are best identified based on their nearness to a male.

In addition to their distinctive claws, Fiddler Crabs are well-known for their fascinating way of creating elaborate burrows in the mud for mating, protection from predators during feeding, and hibernating during winter. The burrows can be up to three feet deep. At night or during high tide, Fiddler Crabs retreat into their elongated mud burrows and carefully plug the entrance with muck to make them water-tight. Fiddler Crabs in the winter remain protected deep in their enclosed burrows below the frost line.

(A male Fiddler Crab digging a burrow that can be up to 3 feet deep in the mud)

By digging burrows in marsh mud this way, Fiddler Crabs help to preserve a healthy saltwater wetland ecosystem by contributing to the aeration of soil around wetland grasses. This helps to accelerate the turnover in soils of important nutrients, which supports the growth of these valuable grasses.

Fiddler Crabs are a good indicator species to declare how healthily a creek might be since they will generally only be found in creeks where there are plenty of lush and green marsh grasses to provide food. The abundance of vegetation along the edge of a creek suggests a relatively healthy waterway with good habitat for a diversity of critters.

Although Comptons Creek is a good place to observe Fiddler Crabs, there are several other sites in the Bayshore Region. Two others that come to mind at the moment include Chingorara Creek at Broadway on the border of Keyport and Union Beach, and in Cheesequake State Park along Cheesequake Creek.

Unfortunately, Fiddler Crabs cannot be found in all of our creeks in the Bayshore Region. Due to human disturbance over the decades from impulsive development in the Raritan Bay watershed, especially from excessive erosion and runoff, there has been an overload of dirt and soil in our creeks. This runoff has buried many of the little Fiddler Crabs and suffocated them in their burrows.

I hope there will always be enough good habitat in the Raritan Bay-Sandy Hook Bay watershed region for people to take pleasure in the seasonal sight of Fiddler Crabs. We should all wish for people to forever recognize the fundamental value of Fiddler Crabs, and that proper actions, such as the creation of sizeable stream or riparian buffers to control erosion, are made to guarantee their future.

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