Naturalist Fact: Flounder

There are two species of flounder that are commonly found in the tidal creeks and off the shore of Little St. Simons Island, the summer flounder and southern flounder. Both are members of the left-eyed flounder family Paralichthyidae. Summer flounder can be distinguished from the southern flounder by the presence of 5 to 14 eye-like spots called ocelli. Like most members of the left-eye flounders, they can change the color and pattern of their dark side to match the surrounding bottom, and are also capable of rapidly burrowing into muddy or sandy bottoms. Flounder lay buried with only their head exposed to ambush prey which includes many species of fish, squid, shrimp, and crabs. A small body cavity and the absence of an air bladder aid the fish in maintaining its position on the bottom. While primarily considered a bottom fish, they are rapid swimmers over short distances and can become very aggressive, feeding actively at middepths, even chasing prey to the surface. Flounder have a fascinating life history as well. After hatching, the larval fish swim in an upright position and the eyes are located on opposite sides of the head. As the young fish grows, the right eye begins to “migrate” to the left side of the head. When body length of about one-half inch has been attained, the eye migration is complete and the fish assumes its left-side-up position for life. Flounder migrate inshore and offshore seasonally in response to changes in water temperature. During winter and early spring, they are found offshore along the outer edge of the continental shelf where spawning occurs, but in late spring and early summer, they move inshore and concentrate in shallow coastal waters and estuaries. Flounder are considered to be a very important species along the Atlantic coast as it is important to both the commercial fishing industry and very popular for recreational fishing.

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Naturalist Fact: Blue Crab

Blue crabs (Callinectes sapidus) are a delicious resident of our island’s waters. They are members of the Order Decapoda, in which all members have ten legs. The blue crab has two legs modified as pinchers that aid in defense and feeding, six walking/climbing legs, and two legs that have adapted into a paddle shape that allow it to swim. These paddles are an excellent aid in mobility, as other species of crabs are restricted to the bottom or structures on which they can climb. Their common name comes from the bright blue color exhibited on the mature crab’s pinchers and legs, and their Latin name literally means “savory beautiful swimmer.”

Blue crabs are most abundant in our saltmarshes and tidal creeks in the late spring and summer months, and can be caught in traps, or simply by tying some bait to the end of a string, lowering it into the water, and waiting for the tug of a hungry crab. Blue crabs are omnivores, feeding on a variety of things including fish, oysters, snails, other crustaceans, and plant material. They will also scavenge the carcasses of dead marine life. Chicken is a popular bait when fishing for crabs.

As crabs grow, they periodically shed their exoskeleton, or molt. They separate from their shell and scoot out backwards, leaving the intact shell behind. Sometimes crabs will consume their molts for the calcium. The crab’s body expands (grows) while its shell is soft, and then will harden into a new exoskeleton. This process usually takes a few days. While they are in the state of “soft-shell,” the crab is very vulnerable and will take cover until their new shell has hardened.

Female blue crabs will only mate once during their lifetime and this happens after what is called the terminal molt. After the female sheds her shell for the last time and is still in the soft-shell stage, a male will mate with her and then guard her until she her new shell hardens. Later, the female will develop a spongy egg mass under the apron on her abdomen, which she will carry with her until the larvae hatch. Since females can only mate once, it is a common practice to release any females that are caught.

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