Occurrence, age and growth of two morphological types of sand seatrout (Cynoscion arenarius ) larvae in the winter and early spring coastal waters off west Louisiana

Two distinct morphological types of sand seatrout, Cynoscion arenarius , larvae were collected in west Louisiana coastal waters in the winter and early spring of 1981-1982. The two larval morphs were separable by three pigment differences: the presence or absence of a melanophore on the dorsal midline (hypomere 16-17); the number of melanophores on the preanal finfold; and, the size of larvae at the initiation of lateral pigment formation. Based on data obtained from growth analyses, both morphs were assumed to deposit daily growth increments in their saccular otoliths; the data were used to generate a linear growth equation for each by using analysis of covariance. Morph A grew significantly faster (0.20 mm/d) than morph B (0.14 mm/d). The two morphs were separated in horizontal space and little overlap occurred in their distribution.