Rajaguru: Biology of Cynoglossus arel and C lida from Indian waters 



329 



79' 



FATHd^t LINE 



10 FATHOM LINE 



^ 



11 30' N 



BAY OF BENGAL 



w- 



Figure 1 



Map showing 5- and 10-fathom lines off Porto Novo coast, India. 



of the study is reproductive biology. The objectives are 

 to (1) determine the spawning season, spawning 

 periodicity, age and size at first maturity, and (2) ex- 

 amine relationships between fecundity and total length, 

 total weight, ovary length and ovary weight. 



Materials and methods 



Samples of large-scaled tonguefish Cynoglossus arel 

 (Bloch and Schneider 1801) and shoulder-spot tongiie- 

 fish C. lida (Bleeker 1851) were collected twice week- 

 ly (a total of 96 collections) from commercial fish 

 catches landed in Porto Novo, southeast coast of India 

 (11°29'N, 79°46'E; Fig. 1), from October 1981 to Sep- 

 tember 1982. Fishing operations were confined to the 

 upper continental shelf, to a depth of 18-22 m, up to 

 4 km from the coast. 



A total of 1220 specimens of C. arel (627 males, 569 

 females, 24 juveniles) and 1382 specimens of C. lida 

 (718 males, 640 females, 24 juveniles) were collected 

 for stomach analyses. For the age and growth study, 

 a total of 1203 specimens of C. arel (634 males and 569 

 females), and 1374 specimens of C. lida (724 males and 

 650 females) were utilized; since juveniles were avail- 

 able only for 4 months, they were not included in the 

 age and growth study. Length-weight equations were 



computed using data of 1281 spe- 

 cimens of C. arel (655 males, 599 

 females, and 27 juveniles) and 

 1519 specimens of C. lida (768 

 males, 723 females, and 28 juve- 

 niles). A total of 1196 specimens 

 of C. arel (627 males and 569 

 females) and 1358 specimens of 

 C. lida (718 males and 640 fe- 

 males) were examined for the re- 

 productive biology studies. Some 

 specimens were used for all four 

 studies. Size range of the speci- 

 mens was as follows: C. arel 

 (males 95-360 mm TL, females 

 99-435 mm TL, juveniles 83-128 

 mmTL) and C. lida (males 97- 

 248mmTL, females 98-242 mm 

 TL, juveniles 81-125mmTL). 

 Total length (TL) of each fish was 

 measured to the nearest 1mm; 

 total weight (TW) was recorded 

 to the nearest O.lg. Sex, matur- 

 ity stages, TL, and TW were 

 noted in fresh-caught fish. Size 

 of monthly samples utilized for 

 various analyses is given in 

 Appendix. 



Feeding ecology 



Stomachs were removed and preserved in 5% formalin. 

 Some empty stomachs were shrunken and contained 

 mucus, while others were expanded but completely 

 empty; the latter type is believed to occur in fish which 

 have recently regurgitated (Daan 1973). Regurgitated 

 stomachs, as well as fish with food remains in their 

 mouths, were discarded. 



Gastrosomatic index (GI) and hepatosomatic index 

 (HI) were calculated to examine monthly variations in 

 feeding intensity and to correlate these variations with 

 breeding cycles, using the following formulae: 



Gastrosomatic index = 



Weight of gut (including contents) x 100 



Hepatosomatic index = 



Weight of fish 



Weight of liver x 100 

 Weight of fish 



For stomach analysis, the Index of Relative Impor- 

 tance (IRI) (Pinkas et al. 1971) was used. It incor- 

 porates percentage by number (N), volume (V), and 

 frequency of occurrence (F) in the formula 



