Indian J. Fish., 37 (1): 63 - 66 (1990)

BIOLOGY OF PSETTODES ERUMEI (SCHNEIDER, 1801) AND ARSIUS (HAMILTON, 1822) FROM THE NORTHERN ARABIAN SEA

SYED MAKHDOOM HUSSAIN Centre of Excellence in Marine Biology, University of Karachi - 32, Pakistan

ABSTRACT The (Pleuronectiformes) are represented by four families and 28 spedes along Sind and Makran coasts (northern Arabian Sea). Psetlodes erumei and Pseudorhombus arsius contribute major portion of the flatfishes caught from these coasts. The two spedes are distributed in coastal waters, shelf area and off shore waters. P. arsius migrates into aedcs and estuaries. The analysis of length and weight relation­ ship showed isometric growth in both spedes. Studies on food contents revealed higher percentage of invertebrate in juvenile fishes and as fishes grow they change over to fish as major food. Dial difference in feeding habit is also noted in two spedes. Spawning seems to occur fromMarc h to May, before onset of monsoon in P. erumei and after monsoon, September - November in P. arsius.

Fish assessment surveys made on F. R. definite studies on ecology and biology of the V. Dr. Fridtjof Nansen (Anon., 1977, 1978) two species from the northern Arabian Sea. showed significant catches from north- Study material was collected onboard em Arabian Sea. Generally the inshore F. R. V. Dr. Fridtjof Nansen (January - June, bottom trawling yielded much heavier flat­ 1977), R. V. Thakeeq, Marine Fisheries Karachi fish catches than off shore. The shelf area Pakistan (August, 1978), occasionally hired bottom trawling also yielded large number of commercial trawlers (March, 1976, and Sep­ soldds, cynoglossids, bothids and psettods. tember- December, 1978 and 1979) and vari­ Psettodes erumei and Pseudorhombus arsius, ous landings at Karachi, Korangi and Makran are the two abundant commercial flatfishes fish harbours. Freshly caught specimen were caught from the northern Arabian Sea. only used for stomach content studies. Four stages of maturity are recognized as: Stage I: Except for a few studies on Immature stage, sex cannot be discriminated. (CJureshi, 1955; Hussain and Alikhan, 1980, Stage II: sex can be separated but gonads not 1981a, b) nothing is known about population, developed. Stage III: Maturing gonads and reproduction and feeding habits of these Stage IV:Ripe and running gonads. commercially exploited species. The objec­ tives of this study are to provide basic The two spedes Psettodes erumei and information on length-weight relatior^hip, Pseudorhombus arsius differ from each other in feeding habit and reproduction of the two flat their anatomical structures. P.erumei has fishes. It is hoped that the data presented perch like appearance, with spines in the fins here will serve as a frame work for more and typical carnivore teeth. P. arsius lacks NOTE such structures, they are soft rayed fishes W= 00280 L2-486 more close to other flatfish. Both the species 2.00^ were well adjusted in almost the same envi­ r= 0-9318 ronment as observed in the present studies. 1-80 Psettodes erumei 160 This species is almost uniformly dis­ 140 tributed in coastal waters, shelf areas and also in offshore waters upto 100 m depth. Higher d) 1-20 catches are reported from coastal waters not exceeding 50 m depth from Somiani Bay, ^ 100 Gawadar and off Karachi. Coastal catches .5> .80 yielded fishes of 39 - 45 cm in total length and catches from off shore waters ranged from 55 ^ .60 to 64 cm in total length. Juveniles (<25 cm total length) are often caught from the nurs­ .40 ery grounds in the shelf area and estuaries. .20 The length-frequency data shows -T 1 1 1 1 1 1 higher percentage of fishes with length 25 30 35 40 45 50 55 60 groups upto 35 cm. Length groups 41 - 50 cm and 55 - 64cm are the commercially exploited Length, cm. stock. The length-weight relationship curve Fic. 1. Length-weight relationship curve of Psettodes (Fig.l), shows isometric growth with signifi­ erumei. cant r value. Calculated relationship for 224 various sizes are found in the ovaries. The fishes is : batch of mature eggs counted in five fishes W = 0.0028 L^*^ ranged from 16 to 24 thousand (mean 22 thousand). Fishes caught during day hours con­ tained mostly digested food and fish remains Pseudorhombus arsius while some had empty stomachs. Night P. arsius is mostly caught in coastal catches mostly revealed full stomachs with waters all along Sind and Makran coasts, undigested food items in the stomachs. from depths not exceeding 30 m. It is also Analyses of stomachs show that younger caught at the mouth of estuaries and creeks. fishes take inverterbrates {Sqjia and crab) as The juveniles are more often caught from es­ their major food, but as the fish grows the tuaries and creeks. Juveniles of P. arsius are invertebrates are gradually replaced by small often confused with other similar species P. fish mostly Enguralis sp. and Clupea sp. (Table javanicus and P. annulatus. The length- fre­ 1). quency data shows a higher percentage of This Sf)ecies attains maturity at 35 cm fishes with 30 - 34 and 35 - 39 cm length total length and ripe gonads are often seen groups. The length-weight relationship cal­ during March - May. Maturation of gonads culated for 558 fishes shows significant r seen\s to start in February and March - May value (0.9318). Figure 2 is drawn from the are the spawning months. Batches of eggs in equation

64 NOTE

TABLE 1. Percentage occurrence of food items in the stomach of Psettodes erumei

Length N Sepia Qab Fish Engraulids Clupea Empty groups sp. sp. remains Sp. stomach (Cm)

74 11.6 13.9 19 52.3 15.8 37-46 54 - - - 74.07 14.8 18.5 >46 58 - - - 74.13 3.4 22.4

TABLE 2. Percentage occurrence of food items in the stomach of Pseudorhombus arsius Length N Squilla Sepia Crab Fish Sdea Engraulids Cynoglossus Empty groups sp. sp. sp. rem. Sp. stomach (Cm)

24-27 83 65 14 14.4 29-32 123 28.4 60.9 10.57 33-36 167 13.7 25.1 55 5.98 >36 171 4.56 14.6 18.7 36.8 25.14

1.40 W = .000020 L^™» 1.30 W=0.000020 l2-a89 r> 0.889 No significant changes have been noted 1.20 in the degree of fullness of stomach of P. 1.10 arsius during day and night. The juveniles 00 use invertebrates, (Squilla sp.. Sepia sp. and crabs) as major food items, and as they grow .90 to adult, gradually shift to small fishes, Solea 80- sp. and Enguralis sp. as major food item, some .70- what identical to P. erumei. Large size P. dl .60 arsius are more selective and seem to prefer small flatfishes (Solea and Cynoglossus) (Table f -^ 1) ^ .30 Female P. arsius attains maturity at 33- .20- 35 cm total length. Mature fishes have three prominent ocelli on the . Observa­ .10 tions also reveal that males attain maturity —I ! 1 1 1 1 1 1 1 1 little earlier at 29 - 30 cm total length. Mature 27 25 28 3 34 37 40 43 46 49 females have bulging triangular shaped Length, cm. ovaries lying on either side of the body. Mature males have milky white testes in FIG. 2. Length-weight relationship of Pseudorhombus ar- apfjearance. Soon after the southwest mon-

65 NOTE soon the male and female gonads undergo period while P. arsius spawns after the mon­ development and become ripe by September. soon period. Fecundity is higher in P. erumei The spawning seems to prolong till Novem­ (mean 22,0(X)) compared to P. arsius (mean ber. The gonads, as in P. erumei have 9,500). Different batches of eggs occurring in different batches of eggs in ovaries. The ovaries of teleosts (Atison, 1939; DeMartin, counts of mature eggs in 8 females ranged 1978; Golberg, 1980; Hussain and Ali-Khan, from 8,000 -12,000 (mean 9,500). 1983) are found in the two species. Occurrence of such eggs can be regarded as Commercially, P. erumei is preferred a basis for suggesting multiple batch of because of the large size( >60 cm) in total spawning in a single season. length and attains a weight of 2 kg. P. arsius is a comparatively smaller fish, less fatty, not I am thankful to Norwegian Agency of exceeding 45 cm in total length and rarely Development, Norway for giving me an acquiring 2 kg of weight. opportunity to work on F. R. V. Dr. Fridtjof Nansen. My thanks are also due to Director, Many species of fish change diet as Centre of Excellence in Marine Biology, Uni­ they grow (Ross, 1987; MacPherson, 1981). A versity of Karachi for providing me the similar pattern has been observed in the facilities to undertake this study. present two species. Their juveniles have almost similar forage pattern. The adults of REFERENCES the two species show feeding differences as P. ANON. 1977. Final report. Survey results of R. V. Dr. erumei feed on pelagic fishes and P. arsius on Fridtjof Nansen. FAO. pp. 1-26 (Mimeo). ANON. demersal fishes such as sole and Cynoglossus 1978. Survey results of R. V. Dr. fridtjof Nansen. thereby eliminating chances of interspecific Fish Assessment Survey, Pakistan waters, Janu­ ary -June, pp. 1 - 12 (Mimeo). BRAY R. N., AND competition for food. Day and night differ­ A. W. EBELING 1975. ¥ish. Bull. U. S., 73: 815 - ences in feeding patterns have also been 829. ATKINSON, C. E. 1939. Copeia. 1939 : 23 - 30. observed in the two species. Such differ­ DBMARTINI, E. E. 1978. Enophrys bison. Environ. ences, also found in other teleostean fishes Bid. Fish., 3:331 - 336. GOLDBERG, S. R. 1980. Butt. Mar. Sci., 30:131 -135. HUSSAN, S. M. AND J. Au- (Keast and Webb, 1966; Schoener, 1974; Bray KHAN 1980. Proc. Ist. Pakistan Congr. Zool. B., 365 and Ebeling, 1975) Perhaps may be due to the - 377. HUSSAIN, S. M. AND J. AU-KHAN 1981 a. ecological demand of the co-occurring spe­ Biologia, 27.1. 19-32. HUSSAIN, S. M. AND J. ALI- cies exploiting similar resources for keeping KHAN 1981b. Indian ]. Fish., 28 (1 & 2): 128 -142. HUSSAIN, S. M. AND J. ALI-KHAN 1987. Deep Sea the interspecific comf)etition low. Research, 34 (7): 1293 - 1299. KEAST, A., AND D. WEBB 1966. /. Fish. Res. Board Can., 23; 1845 - P. erumei attains maturity at 35 cm total 1874. MACPHERSON, E. 1981. Mar. Ecol. Prog. Ser., length and P. arsius matures at 29 - 30 cm in 4 :183 - 193. QURESHI. M. R. 1955. Government Press of Pakistan. 1- 80, 113 figs. Ross, S. T. total length. Spawning time of two species 1987. Fish. Butt., U. S., 76 : 225 - 234. SCHOENER, differs; P. erumei spawns before the monsoon T. W. 1974. Sciencxs (Wash., D. C), 185 : 27 - 39.

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