Abstract. -Feeding ecology, age 

 and growth, length-weight relation- 

 ships, and reproductive biology of 

 two species of tonguefishes, Cyno- 

 glossus arel and C. lida, from Porto 

 Novo, southeast coast of India, were 

 studied during October 1981-Sep- 

 tember 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 spawn- 

 ing activity and gastrosomatic index/ 

 hepatosomatic index was noted for 

 C. arel. In C. lida, a higher percent- 

 age of empty stomachs was observed 

 in males than in females. 



Age and growth of these tongue- 

 fishes were determined by three 

 methods, viz, (1) Petersen method, 

 (2) probability plot, and (3) von Ber- 

 talanffy'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„ (theoret- 

 ical 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 rela- 

 tionship showed a significant differ- 

 ence 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, respective- 

 ly. Individuals spawn only once dur- 

 ing 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 speci- 

 mens during this period. A rise in Kn 

 values (relative condition factor) 

 corresponds with a rise in gonadal 

 activity in female C. arel. The cor- 

 relation coefficient shows that fecun- 

 dity 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. 



Manuscript accepted 4 March 1992. 

 Fishery Bulletin, U.S. 90:328-367 (1992). 



Biology of two co-occurring 

 tonguefisFies, Cynoglossus arel 

 and C lida (Pleuronectiformes: 

 Cynoglossidae), from Indian waters 



Arjuna Rajaguru 



Systematics Laboratory. National Marine Fisheries Service. NOAA 

 National Museum of Natural History, Washington, DC 20560 



Out of 77 species of flatfishes occur- 

 ring along the east and west coasts 

 of India (Rajaguru 1987), only one 

 species, viz, the Malabar sole Cyno- 

 glossus macrostomus, constitutes an 

 important fishery along the Malabar 

 coast (west coast of India) (Bal and 

 Rao 1984). The Indian halibut Pset- 

 todes erumei, because of its larger 

 size and delicious flesh, fetches a high 

 value in fish markets (Pradhan 1969); 

 however, it does not comprise a high 

 value fishery. Other species of flat- 

 fishes which contribute to fisheries 

 along the Indian coasts are: Cyno- 

 glossus viacrolepidotus, C. arel, C. 

 dubius, C. lida, C. puncticeps, C. 

 bilineatus, C. lingua, Paraplagusia 

 spp., Solea spp., and Pseudorhombus 

 spp. (Seshappa 1973, Ramanathan 

 1977, Rajaguru 1987). However, 

 none of these species comprises a 

 single-species fishery. Separate sta- 

 tistics are not reported for these 

 species; all flatfish species are joint- 

 ly reported as 'soles' (CMFRI 1969, 

 Fischer and Bianchi 1984). Average 

 landings of flatfishes along the Indian 

 coast is about 2% of the total marine 

 fish catches (Ramanathan 1977, Ra- 

 jaguru 1987). Most of these flatfish 

 species became prominent in the 

 landings only after the introduction 

 of trawlers (Devadoss and Pillai 

 1973). These species, except the 

 malabar sole Cynoglossus macrosto- 

 mus, are generally not the target 

 species, but are taken incidentally in 

 the penaeid shrimp fishery. Along 

 the Porto Novo Coast, of the 47 flat- 



fish species (Rajaguru 1987), only 

 Psettodes erumei, Pseudorhomims ar- 

 sius, Cynoglossus arel, and C. lida 

 occur throughout the year. The latter 

 two species are taken in a fishery 

 throughout the year, even during 

 the northeast monsoon period, when 

 other marine fish are generally 

 absent. 



The biology of these two tongue- 

 fishes is poorly known, except for 

 work on age and growth of 138 C. 

 lida from the west coast of India 

 (Seshappa 1978). The present study 

 examines various aspects of biol- 

 ogy, including feeding ecology, age, 

 growth, length-weight relationships, 

 and reproductive biology of C. arel 

 and C. lida in Porto Novo coastal 

 waters. 



Objectives of the study on the feed- 

 ing ecology of these two species of 

 tonguefishes are to determine (a) the 

 diet of juveniles and adults, (b) dif- 

 ferences in diet between seasons, and 

 (c) relationships between feeding 

 morphology, digestive morphology, 

 and diet. An age and growth study 

 was also undertaken to (a) evaluate 

 differences in growth patterns be- 

 tween males and females, (b) deter- 

 mine age of recruitment to the Porto 

 Novo fishery, and (c) determine lon- 

 gevity of these two tonguefishes. The 

 objective of the studies on length- 

 weight relationships is to determine 

 if there is a significant deviation from 

 the cube law of length-weight rela- 

 tionship related to ontogeny and go- 

 nadal development. The final aspect 



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