No. 57–Southern Flounder

We now close our series on game fish found in local estuarine waters with an eye to the southern flounder. I was going to, out-of-hand; proclaim this fish as arguably the favorite for the table of those in the series. Instead I have conducted a very nonscientific survey of Estuarium board members and others as to their favorite. The results may be seen at the end of this piece.

While several species of flounder inhabit local waters, most are small in both size and overall numbers. The three most commonly caught by anglers are the gulf (Paralichthys albigutta), summer (Paralichthys dentatus) and southern flounder (Paralichthys lethostigma) with the southern being the most common of these.

A hint to differentiating a southern flounder from the other two may be found in the Latin species name “lethostigma” which translates as “forgotten spots”. The gulf flounder may be identified by its three spots; one above and one below the lateral line just ahead of mid body and one closer to the tail. The summer flounder sports five spots near the tail in a pattern of two above and two below the lateral line with the fifth on the lateral line. The southern flounder, as the Latin implies, has no spots.

No permanent markings, however, does not mean southern flounder are visually bland. They possess the remarkable ability, which I have observed at the Estuarium, of being able to change body surface coloration and pattern to match their substrate. I’ve seen them rise pale like a blank page from a sand bottom and, by utilizing pigments within cromatophores cells in the skin, become virtually invisible immediately upon settling on a broken shell bottom.

The gulf flounder is the smallest of the three growing to 15 inches and 2 pounds. Summer flounder generally average in the 2 to 5 pound range but may reach 20 pounds. Southern flounder may grow to 36 inches and weigh more than 20 pounds. It should be noted that as with the other fish species in this series, it is the females that live the longest and grow the largest.

The two most obvious elements of anatomy that distinguish members of the flounder family from other fishes are the facts that what appear to be the top and bottom of the fish are actually its sides and both eyes are on the same side of the head. While they begin their live with a vertical orientation as other fish, that all begins change in their fourth larval stage.

Southern flounder spawn off shore in late fall and early winter. Randomly fertilized eggs become buoyant and float to the surface where they hatch in 48 hours. Newly hatched larvae at 1/10 of an inch are nourished by their yolk sack. The mouth and digestive system develop through the second and third stages with the eye on the right side of the head beginning to migrate in the fourth stage. During these stages they are suspended in the water column and feed on zooplankton as ocean currents slowly transport them into estuaries. Both eyes are located on the left side of the body, which has become pigmented, by the end of stage five and the now half inch long juvenile southern flounders drop from the water column to begin their lives as bottom dwellers from January through March.

The juveniles congregate in the smaller creeks away from the main channels where they feed on grass and mysid shrimp at first and expand their menu to include small fish as they grow. Most will have moved from the smaller nursery creeks to the larger estuarine branches by mid summer and will reach a length of 10 inches (males) and 12 inches (females) by the end of their first year.

The difference in growth rate between males and females after the first year is dramatic. At four years females average nearly a third longer at more than 19 inches and more than 2 pounds heavier at 3.35 pounds. There is also a wide disparity in life spans with few males living beyond 3 years and many females reaching 7 years.

The bag limit for southern flounder is 20 per person per day (40 per boat) with a minimum length of 14 inches. There is no maximum size limit.

The results of the favorite fish to eat are as follows; the gets- no- respect black drum zero, sheepshead 1, cobia 2, spotted sea trout 3, red drum 5, and flounder 18. My instincts were correct.