BIOLOGY OF 2 COOCCURRING TONGUEFISHES, CYNOGLOSSUS-AREL AND C-LIDA (PLEURONECTIFORMES, CYNOGLOSSIDAE), FROM INDIAN WATERS

Feeding ecology, age and growth, length-weight relationships, and reproductive biology of two species of tonguefishes, Cynoglossus arel and C. lida, from Porto Novo, southeast coast of India, were studied during October 1981-September 1982. These tonguefishes are benthophagus; adults feed primarily on polychaetes, while juveniles more often consume smaller prey such as hyperiid amphipods and copepods. A negative correlation between spawning activity and gastrosomatic index/hepatosomatic index was noted for C. arel. In C. lida, a higher percentage of empty stomachs was observed in males than in females. Age and growth of these tonguefishes were determined by three methods, viz, (1) Petersen method, (2) probability plot, and (3) von Bertalanffy's equation. Rate of growth from the time of hatching through the first year is higher than that of older year-classes. Both species reach commercial size during their 2d and 3d year, and have a life-span of 3-4 years. Value of L infinity (theoretical maximum attainable length) is 570 mm for male and 615 mm for female C. arel, and 335 mm for male and 340 mm for female C. lida. Analyses of the length-weight relationship showed a significant difference in length-weight slopes of male and female C. arel. Due to gonad development, mature female C. lida deviated significantly from the 'cube law.' Cynoglossus arel and C. lida have prolonged spawning periods of 10 months, with a spawning peak in January and September, respectively. Individuals spawn only once during each season. Both sexes of both species attain first sexual maturity during the 2d year. In male C. lida, higher values of the gonadosomatic index (GSI) in September indicate the occurrence of fully-mature specimens during this period. A rise in Kn values (relative condition factor) corresponds with a rise in gonadal activity in female C. arel. The correlation coefficient shows that fecundity in C. arel is correlated with total length, total weight, ovary length, and ovary weight, whereas in C. lida it is correlated only with ovary length and ovary weight.