Date of Award

Summer 1967

Document Type

Thesis

Degree Name

Master of Science

Department

Biology

Abstract

Paralichthys albigutta Jordan and Gilbert, the gulf flounder, which occurs over sand bottoms, and Paralichthys let:nostigma Jordan and Gilbert, the southern flounder,which occurs over mud bottoms , are southern species with ranges extending into the Gulf of Mexico.Paralichthys dentatus, the summer flounder, is tho northern species and is tolerant of several types of bottoms but is most frequently found over sand or hard bottoms. The ranges of the three species overlap in an area along the eastern coast of the United States from central North Carolina to near Jacksonville, Florida. The flounders are closely related and unless the pig­ment pattern is well developed identification "H' difficult. The difficulties are magnified where the ranges of the species overlap .

Pigment pattern does not develop until a size of about 40 mm is reached; smaller specimens frequently are problems in identification. Easier species identification of young flounders would be of economic advantage as two of the species are of considerable importance as food fishes. Life history studies of these flounders have been particularly difficult because of the confusion in identification.

The existence of three separate species was not fully acknowledged until Ginsburg separated them on the bases of gill raker, anal and dorsal ray counts or by a correlation of these. Hildebrand and Cable, using external characters, were unable to separate the fishes present at Beaufort, North Carolina into more than two species; and even though Norman did tentatively treat them as three species, he felt that P. albigutta was perhaps identical with P. lethostigma.

The present study was therefore undertaken to determine the changes that take place in the trunk skeletons of these species between the sizes of 10 mm and 60 mm, and to see if osteological characters could be used in species separation.As the study includes specimens from only a small portion of their range, the work also serves as a preliminary study to a more comprehensive one on races of each species throughout their ranges.

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