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



363 



Significant deviation from the 'cube law' was ob- 

 served in mature females of C. lida due to gonad devel- 

 opment. Similar findings were observed by Dawson 

 (1962) in hogchokers Trinectes maculatus, and by Lux 

 (1969) in yellowtail flounder Limanda ferruginea. 



In male and female C. arel, and male, female, and 

 juvenile C. lida, the exponent values are >3, indicating 

 that the weight increase is more in relation to length. 

 But the exponent value for juveniles of C. arel is <3, 

 indicating that an increase in weight is less compared 

 with length. 



During the present investigation, specimens <83 

 mmTL in C. arel and <81mmTL in C. lida were not 

 available from the continental shelf off Porto Novo. 

 Arora (1951) reported such an absence of juveniles in 

 the commercial catches for California sand dab Citha- 

 richthys sordidus. Non-avaUability of juveniles in com- 

 mercial catches might be due to the gears operated or 

 due to their occurrence in deeper waters, since spawn- 

 ing of cjmoglossines in inshore waters has not been 

 reported (Seshappa and Bhimachar 1955). 



Reproductive biology 



Spawning periods of C. arel and C. lida were pro- 

 longed, lasting for 10 months. The present study agrees 

 with Qasim's (1973a) view that in Indian waters many 

 fish species may be prolonged breeders. Seshappa and 

 Bhimachar (1955) reported that the spawning season 

 in the Malabar sole Cynoglossus semifasciatus off the 

 west coast of India was prolonged (8 months). 



In C. arel and C. lida, ova in different maturity 

 stages taken from anterior, middle, and posterior re- 

 gions of both lobes of ovaries showed no variation in 

 their mean diameter. It is therefore concluded that the 

 development of ovarian eggs proceeds uniformly 

 throughout the ovary. Such a distribution of ova has 

 been reported for Indian halibut Psettodes erumei and 

 flounder Pseudorhombus arsius (Ramanathan and 

 Natarajan 1979). 



Male C. arel and C. lida attained maturity earlier 

 than females. Pitt (1966) observed that males of 

 American plaice Hippoglossoides platessoides were 

 obviously smaller than females at first maturity. 

 Results obtained by Lux and Nichy (1969) for yellowtail 

 flounder Limanda ferruginea (New England), by Wada 

 (1970b) for Limanda herzensteini (Japan), by Zouten- 

 dyk (1974a) for Agulhas sole Austroglossus pectoralis 

 (South Africa), and by Ramos (1982) for Solea solea 

 (Spain) were similar to the present findings. 



The GSI is used widely as an index of gonadal activ- 

 ity and as an index for spawning preparedness. In male 

 and female C. arel and in female C. lida, GSI did not 

 accurately reflect gonadal activity; the relation of 

 gonadal weight to body weight did not change with 



stage of gonadal development, de Vlaming et al. (1982) 

 stated that the GSI is widely and consistently used for 

 gonadal size and activity without verification of its 

 validity. According to de Vlaming et al. (1982), the GSI 

 is not always the best way of expressing gonadal ac- 

 tivity, and so this index should not be applied without 

 validation. Chrzan (1951) concluded that the ratio of 

 gonad weight to body weight, which normally char- 

 acterizes sexual maturity, could not be determined ex- 

 actly. According to Delahunty and de Vlaming (1980), 

 the exponential relationship between ovarian weight 

 and body weight did not change with the phase of 

 oocyte development. However, in male C. lida, higher 

 values of GSI indicated the occurrence of fully-mature 

 specimens during this period, and a sudden fall in GSI 

 value after September appeared to be due to spawn- 

 ing. Such a relationship between GSI and gonadal ac- 

 tivity was reported for Indian halibut Psettodes erumei 

 and flounder Pseudorhombus arsiv^ (Ramanathan and 

 Natarajan 1979). 



In male C. arel and male and female C. lida, a rise 

 in Kn value did not correspond with a rise in gonadal 

 activity. Webb (1973) observed no significant variation 

 in body condition, with onset of spawning, in sand 

 flounder Rhombosolea plebeia and yellow-bellied 

 flounder R. leporina off New Zealand. However, in 

 female C. arel, a rise in Kn value corresponded with 

 a rise in gonadal activity, and thus showed a positive 

 correlation. 



A linear relationship between fecundity and other 

 variables (total length, total weight, ovary length, and 

 ovary weight) was observed in C. arel and C. lida. The 

 result agrees with those of Hoda (1976). The correla- 

 tion coefficient between fecundity and total length, 

 total weight, ovary length, and ovary weight showed 

 a high positive degree of correlation in C. arel. In 

 C. lida, the correlation coefficient between fecundity 

 and ovary length and ovary weight showed a high 

 positive degree of correlation; whereas the correlation 

 coefficient between fecundity and total length and total 

 weight did not show significant correlations. Hence in 

 C. lida, fecundity was dependent only on ovary length 

 and ovary weight. 



In C. arel and C. lida, fecundity was better correlated 

 with total length and ovary length than with total 

 weight and ovary weight. According to Colman (1973), 

 in sand flounder Rhombosolea plebeia and yellow-bellied 

 flounder R. leporina off New Zealand, fecundity in- 

 creased at a rate greater than the cube of length, and 

 more than proportionately to weight; fecundity was 

 probably slightly less proportional to ovary weight. Col- 

 man (1973) suggested that this might be due to large 

 ovaries containing either great quantities of ovarian 

 fluid or connective tissue or a high proportion of 

 nondeveloping eggs. 



