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Twospot Flounder fish identification, Habitats, Fishing methods, fish characteristics
Twospot Flounder, Bothus robinsi, Two-spot flounder, is a left-eyed flatfish of family Bothidae, order Pleuronectiformes, occurs between 18 and 90 m depth in the Western Atlantic from North Carolina and Bermuda to Brazil, including the entire Gulf of Mexico, the Florida Keys, the Bahamas, and the Antilles.
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Twospot Flounder, Bothus robinsi, Two-spot flounder, is a left-eyed flatfish of family Bothidae, order Pleuronectiformes, occurs between 18 and 90 m depth in the Western Atlantic from North Carolina and Bermuda to Brazil, including the entire Gulf of Mexico, the Florida Keys, the Bahamas, and the Antilles.
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Description:
Twospot Flounder is a deep bodied fish with a very small mouth, widely separated eyes, and two horizontally arranged spots on caudal fin, located one anterior to the other. Mouth is downturned, with upper jaw extending posteriorly to or slightly beyond anterior margin of lower eye, Jaw teeth are small and sharp pointed and arranged in 2 rows. Males have a sharp-pointed spine on snout. Distance between eyes is about equal to eye width in adult females and about 2 times eye width in adult males, but less than eye width in juveniles. Eyes lack fleshy ridges.
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Gill rakers on first arch of ocular side are short and number 2 to 7 on upper limb and 5 to 9 on lower limb. Head length is 23-28% of a standard length, snout length is 4-6% of standard length, and eye diameter is 6-7%, upper jaw length is 5-8%, ocular-side pectoral fin length 21-32%, body depth 65-76% of body length. Pectoral fin rays on ocular side are longer than on blind-side. Uppermost pectoral fin rays on ocular side are elongated in mature males. Base of pelvic fin on ocular side extends to tip of urohyal. Anal fin originates anterior to pectoral fin base. Caudal fin is bluntly pointed. Scales are ctenoid on ocular side and cycloid on blind side. Lateral line is arched over pectoral fin on ocular side, and lateral line scales number 70 to 77. Pre-caudal vertebrae number 10, and caudal vertebrae number 26 to 28.
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Key characters
The twospot flounder has caudal fin spots located one anterior to the other, very small mouth and widely separated eyes.
10 Pre-caudal vertebrae
26 to 28 Caudal vertebrae
78 to 90 Dorsal fin rays
59 to 68 Anal fin rays
8 to 11 Pectoral fin rays on ocular side
70 to 77 lateral line scales
2 to 7 Gill rakers on upper limb of first arch of ocular side
5 to 9 Gill rakers on lower limb
Maximum length: 25cm; common size below 15 cm.
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Color on ocular side is light tan to brown, with many brown spotting and mottling, dark or light circles. Caudal fin has 2 horizontally arranged dark spots one above the other at the base along median rays and a dark spot on the lateral line.
Habitats:
Twospot flounder occurs in bays, lagoons and shallow coastal waters. Found on demersal, soft bottoms, sandy areas with coral rubble and seagrass patches near patch reefs. It inhabits depths up to 90 meters. Feeding takes place during daylight, and food consists of crustaceans, polychaete worms, mollusks, bryozoans, brachiopods, ophiuroids, chaetognaths, scaphopods, gastropods, bivalves, isopods, shrimps (carideans and penaeids), and crabs (majids, galatheids, and pagurids).
Spawning:
Twospot Flounder spawns year round with pick in July. Social organization is harem, with males defending a territory containing several females. Males have changing their secondary sexual characters such as increased body length, larger left pectoral fin, and greater interorbital distance. As a qualitative character, the rostral spine, which is part of the maxillary bone, is pronounced. The interorbital distance implies noticeable internal sexual differences, such as the broadening of the left frontal and lateral ethmoid bones, and a greater length of the oblique muscles of eyes, the optic nerves, and the left olfactory nerve.
Mating groups or harems consisted of one male and several females with each female occupying distinct area within the male's territory. Pairs are spawning daily at dusk. Both males and females retired into the sand at locations outside their daytime territory. The male positions himself under the female who was resting on the sandy bottom and followed by the pair slowly rising towards the surface. The male releases a cloud of sperm at the apex and descends while the female hangs and releases her eggs into the sperm cloud. This spawning activity continued with the male attempting to mate daily with each female within its harem in its territory.
Larvae flexion starts at length 6 to 7 mm. Transformation starts at length 16 to 21 mm. At the length 3 to 13mm first dorsal ray elongate and split into 2 pairs supported by large pterigiophore. By 5.5mm the first dorsal ray only split to halfway point with pigment spots only on unsplit portion. Most rays of dorsal and anal are formed. At 6 mm Pectoral fin forms. By 9 mm Dorsal ray much reduced in length. Small 2 teeth present on upper jaw at length 4.5 mm, at length 5 mm 3 small teeth on upper jaw and 1 on lower. By 9 mm length 5-6 teeth present on upper and lower jaws.
Pigmentation: In early larvae few pigment spots on elongate dorsal ray, caudal and posterior dorsal and anal fin folds. No pigment on larvae larger than 10 mm in length. At 4.5 mm 2 large ramified spots: 1 above and 1 below tip of tail. At 5.5 mm small melanophore is visible at tip of tail. Pigment is gone by 9 mm in length. Juveniles have 2 caudal spots in a horizontal line.
Fishing Methods:
It is occasionally caught by offshore anglers, very good meat.
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