Studies on feeding and reproductive biology of Malabar tongue sole, Cynoglossus macrostomus (Norman, 1928) along the Ratnagiri coast of Maharashtra

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1 Indian Journal of Geo Marine Sciences Vol. 47 (06), June 2018, pp Studies on feeding and reproductive biology of Malabar tongue sole, Cynoglossus macrostomus (Norman, 1928) along the Ratnagiri coast of Maharashtra Bhalekar P.V. 1, Nirmale V.H., 1 Metar S.Y. 2 * Pawar R.A. 1 & Kende D.R. 1 1 College of Fisheries, Shirgaon, Ratnagiri , India 2 Marine Biological Research Station, Zadgaon, Ratnagiri , India * [E.Mail : santoshmetar@gmail.com] Received 16 August 2016 ; revised 09 December 2016 The length weight relationship showed isometric growth in Cynoglossus macrostomus. Except standard length other morphometric characters indicated low degree of correlation with total length. Qualitative and quantitative analysis of food revealed C. macrostomus to be a bottom feeder, feeding mainly on diatoms, algae and mysids. Analysis on sex ratio indicated equal ratio of male :females, in most months. C. macrostomus spawns during April-May and September - November. The fecundity ranged from 3280 to eggs with an average of eggs. Length at first maturity has been estimated to be 97 mm. [Keywords: Malabar tongue sole, Cynoglossus macrostomus, Feeding biology, GSI, Spawning] Introduction The total production of flatfishes in the country stood tonnes during the year With increase in targeted fishery for shrimps, this species is also being heavily fished 2 due to demersal in nature. In Maharashtra sole fishes are mainly landed by the trawlers with average catch of 3916 tonnes and a catch rate of 0.55kg/hr. Relative species abundance showed dominance of Cynoglossus arel (88.6%) followed by Cynoglossus macrostomus (11.4%) in the state 1. There is good market demand for Malabar sole in fresh condition in Malabar region and south Kerala. The fish is also dried and sold in markets. While decayed fish from multiday shrimp trawlers are being dried and sold as ingredient for poultry feed 2. C. macrostomus has a life span of about three years, with a maximum recorded length 169 mm. It attains first maturity at 97 mm length 3. The spawning season is reported to be during January to April and August to October along Kerala coast 2. Though the species is landed in significant quantity in Ratnagiri, no detailed study on the biology and fishery of this species has been reported from this region. The present work was initiated to study the biology of C. macrostomus from Ratnagiri waters. Material and Methods The present study was based on the total of 548 individuals ranging in the size range from 45 mm to 180 mm total length comprising of 318 males, 218 females and 12 indeterminants. Samples were collected from the Mirkarwada fish landing centre at weekly intervals during April 2014 to March 2015 mostly landed by trawlers. In the laboratory, the fish were cut open and the sex and the stage of maturity were noted. Gonads were excised out and weighed using analytical balance to the nearest g and preserved in 4 % neutral formalin for further study. Gut contents were analysed by following numerical method 4. Attempts were done to identify different organisms was done upto the lowest possible taxonomic level as identification of individual item was not always possible due to different degrees of digestion of food inside the stomachs. The number of each item was recorded and expressed as a percentage of the total number of food items in the sample studied. Gonado-somatic index (GSI) was estimated as per following equation 5. Gonad weight GSI Total body weight x100 Sex ratio was studied with respect to months and size groups of fish. Sex of individual fish was ascertained by examining the gonads after dissecting the fish samples. Data on sex ratio were analyzed by χ 2 (chi square) test to find out dominance of sex if

2 1218 INDIAN J. MAR. SCI., VOL. 47, NO. 06, JUNE 2018 any. The maturity stages of C. macrostomus were classified as immature (I), maturing (II), mature (III), Ripe (IV) and spent (V). For the determination of fecundity freshly dissected ripe ovaries were used. Sub sample weighing 10 mg of mature ovary from anterior, middle and posterior region were weighed and numbers of mature ova in the subsamples were counted manually. Average count was taken for calculation and fecundity was determined 6. F x Average number of ova counted in the sample Where, F= Fecundity, TW= Total weight of the ovary, SW= Sub-sample weight Ova diameter of intra ovarian eggs was measured from small portion of ovaries taken from the anterior, middle and posterior region. The development of ova from one stage of maturity to another was studied using ocular micrometer. Using these ova diameter readings, frequency polygons were drawn. Length at first maturity was estimated using standard methodology described by King 7. Results and Discussion The details of qualitative and quantitative analysis of stomach contents of C. macrostomus during different months are presented in fig. 1. Gut content analysis indicated diatoms (27.3%), algae (30.4 %), bivalve remains (13%), crustacean appendages (5.3 %), gastropod remains (11.2%), polychaetes (4.5%), mysids (5.2%), copepods (2.6%) and fish eggs (0.5%) as the main food items of the species in order of preference. Present study shows that C. macrostomus is a bottom feeder. Feeding intensity was found to be higher in juvenile fishes and fed on all listed items but the preference for crustacean food was observed in larger individuals. C. macrostomus occurring along the coastal seas off Kerala is mainly adapted to bottom feeding habit and feeds on polychaetes, detritus, amphipods, copepods, small molluscs and foraminifera 9.Dominant food item of Malabar sole fish is reported to be polychaetes, amphipods and small lamellibranchs 10. The species is bottom feeder and it feeds actively on polychaetes, amphipods and molluscs which is showing differences in fishes from Ratnagiri. Hence, the occurrence of food items in gut content of the Malabar sole has been found to be closely related to the occurrence of the fauna in particular region 11. This feeding was also reported by other investigator 13. C. semifasciatus has also been reported to feed on polychaetes, amphipods, lamellibranches and other organisms 12. Monthly variations in the fullness of stomach in C. macrostomus are given in fig. 2. During the study period, % of the stomachs found to be full, % three quarter full, % half occupied, 5.57 % occupied upto a quarter and % were empty. The month of December recorded highest percentage of full stomachs (82.86%) followed by January (47.46%) and April (39.02 %). Month-wise data shows highest percentage of empty stomachs in November (28.81%) followed by February (22.5%).The present study has also indicated possible spawning during the month of November and occurrence of spent females in December as the feeding intensity is generally reduced during spawning due to breeding and spawning stress 8. Monthwise GSI values for females are given in fig. 3. GSI was found to be highest during September Fig. 1 Percentage composition of food items of Cynoglossus macrostomus during different months Fig. 2 Month-wise fullness of stomach in Cynoglossus macrostomus

3 BHALEKAR et al.: FEEDING AND REPRODUCTIVE BIOLOGY OF MALABAR TONGUE SOLE 1219 (4.904), October (2.798) and November (2.554) showing occurrence of more ripe individuals. The monthly average GSI values were reported to be higher in females during the months of September, October and November. Similarly higher GSI value was also noted during May indicating the occurrence of ripe females in all these months. It can be inferred from GSI values that spawning takes possibly twice in a year during pre-monsoon and post monsoon season along Ratnagiri coast. High GSI values in C. macrostomus from Kerala coast during September and a decline by October indicated spawning period 14. Further decrease in GSI also was seen during April-May which may be the result of the second spawning that might have taken place during February to April. The average sex ratio of the males and females was found to be 1:1.20. Chi-square test indicated significant difference during September, October, November and February (P 0.05) (fig. 4). Except September females dominated the catch of the remaining months. Male: female sex ratio in C. macrostomus from Kerala coast 14 was found to be 1.3:1 during and 1.2:1 during The sex ratio between male and female was reported to be 1:5.2 in C. macrostomus from Calicut coast 15. Maturity stages were examined in 298 ovaries (Fig. 5). The maturity stage I (Immature) was observed in the month of January, February, August and December. Stage II (Maturing) was observed in the month of April, September, May and November. Stage III (Mature) occurred in all months of study. However, it was dominant during October, September, May and March. Stage IV (Ripe) was also observed in all months of study. Maximum ova in Stage IV were noted in October, May, September and November. While maximum ova in Stage V (Spent) were seen in December and January. Availability of gravid and spent females in the fishery during most of the months indicates that the spawning season is protracted with two peaks in April - May and September - November. Spawning takes place during November with occurrence of more mature individuals and subsequent observation of spent females in December also confirms the finding. Similar scenario probably occurs during May and June. But samples from the June month are lacking due to monsoon ban on fishing. Possibility of pre and post monsoon spawning season is also substantiated by GSI studies. The occurrence of mature and spent individuals is an indication of the spawning season 16. According to Jayaprakash 14 there are two broods in C. macrostomus in a year, one during the post monsoon and the second spawning during the pre monsoon period. Manojkumar 15 reported that availability of mature and spent fishes during most of the months pointed to the prolonged spawning season in C. macrostomus with two peaks in Feb- May and Sept-October from Malabar Coast. Findings in present study more or less confirm to the above results. The spawning season of the Malabar sole from Malabar Coast starts by September - Fig. 3 Monthly GSI trend in Females of Cynoglossus macrostomus Fig. 4 Monthly variation of Sex ratio in Cynoglossus macrostomus Fig. 5 Monthly variation in maturity stages in female of Cynoglossus macrostomus

4 1220 INDIAN J. MAR. SCI., VOL. 47, NO. 06, JUNE 2018 October and ceases by June 12. C. macrolepidotus reportedly spawns during August to October in Porto Novo Waters 17. The Malabar Sole has prolonged spawning period extending from October to May off Mangalore and Calicut 13. Further peak spawning is noted during October - December. While C. dubius spawns during October - December and C. macrolepidatus January - February and August occurring Rameshwaram coast. Two spawning seasons of C. macrostomusone during January - April and another from August - October have been reported from Cochin waters also 2. The fecundity of C. macrostomusranged from 3280 to eggs with an average of eggs (Table 1). Knowledge of the total number of eggs produced by a fish during a year is important in determining the spawning potential of fish. Fecundity of C. macrostomus is reported to be 5021 and eggs for 76 mm and 156 mm size group respectively off Kerala 14. It has been reported to be eggs in size group of 155 mm from Calicut coast 10. Fecundity of C. arel lies between 6023 and eggs 19 and C. macrolepidotus is and for sizes of 334 mm and 205 mm respectively from Port Novo coast 17. However in the present study the fecundity of Table 1 Number of mature ova in individuals of Cynoglossus macrostomus Sr. No. Total Length(mm) Weight of fish(g) Weight of Ovary (g) Total No. of mature Ova in Ovary Malabar sole appears to be low possibly indicating the presence of low productive stock. In the present study, the typical ovaries belonged to the five stages of maturity (Fig. 6). In stage I, the size of ova ranged from 0.01 mm to mm with modal value of mm. The size of ova in stage II of maturity measured from to mm. Stage III showed ova in range of to with modal value of mm. In stage IV the ova measured from 0.2 mm to mm. The size of ova in stage V measured from 0.02 to 0.15 mm with a mode at The group of ova of size mm in stage I move to size mm in stage III. The mode mm in Fig. 6 Stage wise ova diameter trend

5 BHALEKAR et al.: FEEDING AND REPRODUCTIVE BIOLOGY OF MALABAR TONGUE SOLE 1221 Fig. 7 Size at First maturity stage II is also seen progressing very fast. Both these groups appear to merge in stage IV. In stage V most of these ova are shed thereby suggesting the fish has spawned. Ova diameter studies in the present work suggests that fish spawns once during spawning season. However, the findings contradict the conclusion from GSI and maturity studies wherein it is stated that C. macrostomus spawns twice in protracted spawning season. This may be attributed lack of ova diameter studies data during monsoon. The size at first maturity of C. macrostomus is estimated to be 97 mm during present study (Fig. 7). The same is reported to be 120 mm and 97 mm from Calicut coast 10 and Kerala coast 3 and 102 mm from Malabar coast 15, while mm from Cochin waters 2. Length at first maturity in C. macrolepidotus is reported at 191 mm from Porto Novo coast 17. Size at first maturity of C. macrostomus has also been reported by different authors to vary between 97 mm and 120 mm. Acknowledgement Authors are grateful to the authorities of Dr.B.S. Konkan Krishi Vidyapeeth, Dapoli, Dist. Ratnagiri (Maharashtra) for providing facilities to carry out this work. References 1 CMFRI, Annual Report , Central Marine Fisheries Research Institute, Cochin, 2013, pp Nair, R.J., Flatfish fishery off Cochin and some aspects of the biology and stock of Malabar Sole Cynoglossusmacrostomus (Norman), Indian J.Fish., 54(1)(2007) Jayaprakash, A. A. and Inasu N. D., Age and growth of Malabar sole Cynoglossusmacrostomus Norman off Kerala coast, J. Mar. Biol. Ass. India, 40 (1&2)(1998) Biswas, S.P., Manual of methods in fish biology, (South Asian Publishers Pvt. Ltd., New Delhi) 1993, pp Bal, D.V. and Rao, K.V., Marine fisheries, (Tata Mcgraw- Hill, New Delhi) 1984, pp Sinha R.K., Some aspects of biology of freshwater catfish Clariasbatrachus(Linn.1758) of the Bombay region, M. Sc. (Zool.) Thesis, Deemed university C.I.F.E. Bombay, India, King, M., Fisheries biology, assessment and management, (Fishing news Books,Osney Mead, Oxford OX2 0EL, England) 1995, pp Kore, B. A. and Joshi M. C., Food of the squid, Loligoduvauceli, Proc. Indian Acad. Sci., 813(1)(1975) Jayaprakash, A.A., Food and feeding habits of Malabar sole Cynoglossusmacrostomus (Norman), J. Mar. Biol. Ass. India, 42(1&2)(2000) Khan, M.F. and Nandakumaran K., Population dynamics of Malabar sole Cynoglossusmacrostomus, Norman along Calicut coast, Indian J. Fish., 40(4)(1993) Rao K.V.N., The flatfish sovenier, 20th Anniversary of CMFRI, Cochin, Seshappa, G. and Bhimachar B. S., Studies on fishery and biology of the Malabar sole CynoglossussemifassiatusDay, J. Mar. Biol. Ass. India, 40(1&2)(1955) Vivekanandan, E, Rajkumar U., Nair R. J., Gandhi V., Flatfishes. in: Status of exploited marine fishery resource of India, edited by Joseph, M. M. And Jayaprakash, A.A., (CMFRI-Kochi, India) 2003, pp Jayaprakash, A.A., On the breeding biology of Malabar sole Cynoglossusmacrostomus Norman off Kerala, J. Mar.Biol. Ass. India, 44 (1&2)(1999) Manojkumar, P.P., Fishery, biology and stock assessement of Cynoglossusmacrostomus(Norman) off Malabar coast, Indian J. Fish, 53(4)(2006) Pradhan, M. J., Observations on the maturity and spawning of Psettodeserumei (Schneider), IndianJ. Fish., 9(2)(1964) Ramanathan, N., Vijaya P., Ramaiyan V. and Natrajan R., On the biology of large scaled tongue sole C. macrolepidotus (Bleeker), IndianJ. Fish., 24 (1&2)(1977) Devadoss P., Pillai K.M., Natarajan P., and Muniyandi, K., Observation on some aspects of biology and fishery of Psettodeserumei (Bloch) at Porto Novo, Indian J. fish.,24(1&2)(1977) Datta and Das M., Fecundity of Cynoglossusarel (Schneider). Mahasagar, Bull. of the Nat. Insti. ofoceano., 16(4)(1983)