Available online at http://www.urpjournals.com International Journal of Research in Fisheries and Aquaculture Universal Research Publications. All rights reserved ISSN 2277-7729 Original Article Food and habits in Leiognathus berbis (Valenciennes) from Turicorin, Southeast coast of India. D.Nagarajan Dept.of Zoology, Kamaraj College, Thoothukudi 628003, Tamilnadu Received 07 July 2014; accepted 25 July 2014 Abstract Food and habit of silverbelly Leiognathus berbis (Valenciennes) collected from trawl catches at Thoothukudi Fishing Harbour was analysed for two years. Phytoplankton, Zooplanktons and microinvertebrates constituted the major food of the fish and females were found to be more active feeders than males. Active in males were observed in February and that for females in November. Active was observed in size groups from 81-90 to 111-120 mm in males and 81-90 to 131-140 mm in females. The maturing and matured females fed more actively than the immature and gravid females. Copepods constituted the major food items and were observed in all the months. No remarkable variation in size related selection of food items was observed. The other minor constituents of the diet were foraminiferans, diatom, nematodes, polychaetes, coelenterates, amphipods, lucifer, fish scales, zoea, mysis and dinoflagellates. Also, no sexual variation in selection and preference of food was observed in the present study. 2014 Universal Research Publications. All rights reserved Key words: Leiognathus berbis, Feeding conditions, Food items. 1. Introduction The silverbelly, Leiognathus berbis is one of the genus of polyfishes native to the Indian Ocean and the Western Pacific ocean. Palk Bay and Gulf of Mannar regions yield very high catches and it also constitutes one of the major portions of the bycatch in prawn fishery. Food is an important factor in the biology of fishes to the extent of governing their growth, fecundity and migratory movements. The horizontal and vertical movement of fish stock is greatly influenced by the variations in seasonal and diurnal abundance of the favorite food organism in the region. Hence the knowledge on the relationship between the fishes and food organisms is considered essential for the prediction and exploitation of fish stocks and to further understand the different aspects of biology of fishes such as growth, behaviour, migration etc. Being a commercially important fish, it needs special attention. Since no detailed information is available on the food and habit of L.berbis, this study is carried out on L.berbis from Tuticorin coast in Gulf of Mannar. 2. Material and Methods Samples were collected once in a week from trawl catches at Thoothukudi Fishing Harbour during 1993-1995. The stomach contents of 770 males and 850 females of L.berbis ranging in size from 80 136 mm and weight from 7.0 to 36.2 g were examined. For each specimen the total length, sex, maturity stage and weight were noted in fresh condition. Gut was removed and preserved in 5% formalin for further studies. The stomach contents were analyzed by points method (Swynnerton and Worthington [10]; Hynes [4]). The intensity of in each fish was determined by eye examination based on the distension of the stomach and the amount of food contained in the stomach. The various stomach conditions are gorged, full, ¾ full, ½ full, ¼ full, little and empty in which gorged & full are considered as indication of active, ¾ full & ½ full as indication of moderate and the rest of the conditions i.e., ¼ full, little empty as poor. Latter, the gut of each fish was emptied into a petridish and examined under binocular microscope. Gut contents were identified up to generic level. If the food items were in the advanced state of digestion, they are treated as semidigested matter. The stomach contents were placed in various groups food items and each food item was allotted points according to its volume in the stomach. In this way one large organism counted as much as several small ones. All the points for each food items were added up and converted into percentages of the total number of points allotted for all items in different month and size groups as the case may be. The two years data were pooled and the results were 126
discussed for one year. 3. RESULTS 3.1. Feeding intensity in relation to months: In males the fish with little stomach were dominant (27.2 %) followed by the fish with ¼ full stomachs (25.2 %) and empty stomached fishes (20.2 %) (Table 1). In Females, fish with ¼ full stomach were dominant (27.3 %) followed by fish with little stomachs (26.2%) and empty stomachs (18.4 %) (Table 2).In all the months, irrespective of sex, the poor stomachs were dominant with an average of 72.5 % in males and 71.8 % in females followed by moderate stomachs of 23.7 % in males and 21.3 % in females and active stomachs of 3.8 % in males and 6.8 % in females. The active of male was nil during April, May, September and December whereas, in females the active stomach were recorded in all the months indicating that the female fed more actively than the male (Fig. 1 and 2). 3.2. Feeding intensity in relation to size of fish: It was observed that the middle order size groups of males from 81-90 to 111-120 mm fed better than the small and larger size groups. In females, there is no definite trend in in different size groups (Table 3 & 4).The intensity of male increased from 81-90 mm to reach a peak in 101-110 mm, then declined to nil in 120-130 mm and moderate intensity increased from 71-80 mm to reach a peak in 111-120 mm, then declined to nil in 131-140. It appears that the middle order size group males were more active feeders than the small and older size groups as already pointed out. In females, the active and moderate conditions increased with increasing size groups with mild fluctuations (Table 5). 3.3. Feeding intensity in relation to maturity of ovary: The maturing and matured females fed more actively than the immature and gravid females (Figure 3). 3.4. Monthwise variation in food items: The diet of males constituted semidigested matter (28.9%), copepod (24.5%), crustacean remains (8.3%), foraminiferans (6.2%), diatom (5.6%), nematodes (5.5%), polychaetes (5.4%), coelenterates (4.5%), amphipods (3.3%), lucifer (2.9%), fish scales (2.7%) and miscellaneous such as zoea, mysis and dinoflagellates (2.1%) (Fig.4). In females, the food items comprised of semidigested matter (29.8%), copepod (23.1%), crustacean remains (14.2), foraminiferans (5.8%), nematodes (5.1%), diatom (3.2%), polychaetes (2.1%), coelenterates (1.9%), amphipods (2.9%), lucifer (3.8%), fish scales (6.3%) and miscellaneous such as zoea, mysis and dinoflagellates (1.9%) (Fig.5). Copepod occurs in all the months in the diet of both sexes and dominated over the other items followed by crustacean remains. Crustacean remain was available more during October-December and January in males whereas in females it occurred in March April and October-February. The peak occurrence of foraminiferan was during March in males and August in females. Throughout the year except the fish scale in females the remaining food items constituted only below 6% in both sexes. There was no marked difference in the preference of food items between sexes except that the females preferred more crustacean and fish which could be inferred from the occurrence of more crustacean remains and fish scales in the diet of female (Figure 6 & 7). 3.5. Variation in food items in relation to size of fish: Copepods are the dominant food items and preferred by all size groups in both the sexes. Occurrence of crustacean remains and fish scales increased with increasing size of the fish in both sexes with mild fluctuations. Large size group males preferred coelenterates and lucifer better whereas females preferred nematode. The remaining food items showed no trend with the size groups of both sexes (Figure 8 & 9). DISCUSSION The analysis of different conditions of stomach in both sexes of revealed that the ¼ full, little and empty stomached fishes were more than gorged, full, ¾ full and ½ full stomachs in all the months which indicated poor habit of this species. The active was recorded during July, October, November and February with the peak in February in males whereas in females it was during October and November with the peak in November. There was no seasonal variation in among both the sexes of this species under this study and in general active was more during June to December. Jayabalan and Ramamoorthi [5] reported that in G.minuta active is evident during May, September, January and April. In the present study active, moderate and poor intensity has no relation to growth and maturity stages. The moderate was recorded during October and November with the peak in October in males whereas in females it was during March and June with the peak in March. In the moderate condition also the seasonal variation was lacking among both sexes and in general moderate was more during January to April. The females fed better than the males. Jayabalan and Ramamoorthi [5] have also reported that the occurrence of poor condition throughout the year in Portonovo waters. In the present study also poor fed stomachs were observed throughout the year at higher percentage. The middle size groups from 81-90 to 111-120 mm in males and females from 81-90 to 131-140 mm fed actively than young and older groups. In this study L.berbis are poor feeders without any seasonal as well as lengthwise variation. In all the size groups the percentage of poor was dominant followed by moderate and active. The present study shows that Phytoplanktons, zooplanktons and microinvertebrates are formed the main dietary composition. In the present study the major food items of are copepod, crustacean remains and foraminiferans. The major food items occur in all the months or most part of the year. Several authors have reported a variety of food organisms from the gut of various silverbellies species from various places. Chacko [2] have reported that L.bindus, L.equulus, L.daura, L.ruconius, L.brevirostris, L.insidiator are plankton feeders from Pamban waters. Preference of polychaete and crustacean remains by Leiognathyus ruconius have been reported from Bombay waters Bapat and Bal [1]. Kuthalingam (1958) have reported that S.insidiator feeds on all the form of planktons. Srinivasa [9] reported that L. bindus and S. ruconius off 127
1993 1995 1993 1995 1993 95 Table 1. Monthwise percent occurrence of different stomach conditions among L.berbis (male) 1993 1995. Year Month No.of fish Full ¾ Full ½ Full ¼ Full Little Empty Mar 68 5.9 11.8 14.7 29.4 26.5 11.7 Apr 61 0.0 0.0 14.8 27.9 41.0 16.3 May 67 0.0 3.0 14.9 19.4 32.8 29.9 Jun 58 1.7 0.0 17.2 29.3 22.4 29.4 Jul 56 7.1 5.4 21.4 19.6 26.8 19.7 Aug 66 4.6 3.0 21.2 15.2 30.3 25.7 Sep 68 0.0 11.8 13.2 26.5 25.0 23.5 Oct 74 6.8 6.8 27.0 24.3 17.6 17.6 Nov 72 8.3 8.3 25.0 22.2 20.8 15.3 Dec 51 0.0 3.9 17.6 25.5 31.4 21.6 Jan 62 1.6 8.1 17.7 25.8 30.6 16.2 Feb 67 9.0 9.0 9.0 37.3 20.9 14.9 % 3.7 5.9 17.8 25.2 27.2 20.2 Table 2. Monthwise percent occurrence of different stomach conditions among L.berbis (Female) during 1993 1995. Year Month No.of fish Full ¾ Full ½ Full ¼ Full Little Empty Mar 73 6.9 16.4 16.4 27.4 11.0 22.0 Apr 76 2.6 7.9 15.8 35.5 18.4 19.8 May 66 3.0 3.0 16.7 25.8 30.3 21.1 Jun 63 7.9 14.3 12.7 25.4 25.4 14.3 Jul 59 6.8 8.5 6.8 18.6 42.4 17.0 Aug 56 5.4 1.8 14.3 23.2 32.1 23.3 Sep 81 4.9 2.5 18.5 25.9 22.2 26.0 Oct 71 11.3 11.3 11.3 26.8 16.9 22.4 Nov 69 20.3 13.0 4.4 21.7 26.1 14.6 Dec 69 4.4 8.7 15.9 29.0 23.2 18.9 Jan 83 6.0 6.0 14.5 30.1 34.9 8.5 Feb 84 2.4 2.4 13.1 38.1 31.0 13.0 % 6.8 8.0 13.4 27.3 26.2 18.4 Fig. 1. Monthwise active, moderate and poor conditions in percentage among L.berbis (Male) during 1993-1995. Fig. 2. Monthwise active, moderate and poor conditions in percentage among L.berbis (Female) during 1993-1995. 100 100 P E R C E N T 80 60 40 20 0 Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb - Active - Moderate - Poor P E R C E N T 80 60 40 20 0 Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb - Active - Moderate - Poor M O N T H S M O N T H S Table 3. Lengthwise percent occurrence of different stomach conditions among L.berbis (male) during 1993 1995. Year Length (mm) No.of fish Full ¾ Full ½ Full ¼ Full Little Empty 76-80 24 0.0 0.0 4.2 37.5 45.8 12.5 81-85 58 0.0 0.0 5.2 31.0 34.5 29.3 86-90 121 2.5 1.7 10.7 17.4 28.9 38.8 91-95 182 5.5 9.9 17.0 18.1 29.7 19.8 96-100 131 2.3 6.1 18.3 22.1 28.2 22.9 101-105 81 3.7 7.4 21.0 44.4 12.4 11.1 106-110 72 9.7 4.2 30.6 18.1 25.0 12.5 111-115 65 6.2 15.4 21.5 30.8 21.5 4.6 116-120 17 0.0 0.0 58.8 29.4 11.8 0.0 121-125 5 0.0 0.0 60.0 0.0 40.0 0.0 126-130 4 0.0 0.0 0.0 25.0 75.0 0.0 131-135 6 0.0 0.0 0.0 100.0 0.0 0.0 136-140 4 0.0 0.0 0.0 75.0 25.0 0.0 128
1993 1995 Table 4. Lengthwise percent occurrence of different stomach conditions among L.berbis (female) 1993 1995. Year Length (mm) No.of fish Full ¾ Full ½ Full ¼ Full Little Empty 76-80 13.0 0.0 7.7 0.0 7.7 30.8 53.9 81-85 37.0 0.0 5.4 16.2 16.2 35.1 27.0 86-90 63.0 3.2 6.4 9.5 28.6 41.3 11.1 91-95 133.0 0.0 4.5 10.5 36.1 18.1 30.8 96-100 170.0 1.2 0.0 18.2 30.6 31.2 18.8 101-105 127.0 5.5 14.2 15.0 22.8 24.4 18.1 106-110 107.0 16.8 8.4 15.9 17.8 21.5 19.6 111-115 92.0 6.5 9.8 9.8 38.0 32.6 3.3 116-120 41.0 24.4 24.4 14.6 19.5 9.8 7.3 121-125 41.0 2.4 12.2 7.3 36.6 29.3 12.2 126-130 10.0 40.0 0.0 10.0 20.0 0.0 30.0 131-135 7.0 28.6 28.6 0.0 42.9 0.0 0.0 136-140 9.0 55.6 11.1 33.3 0.0 0.0 0.0 Table 5. Lengthwise active, moderate and poor conditions in percentage among Leiognathus berbis (Male and Female) during1993 1995. MALE FEMALE LENGTH (mm) moderate active moderate active poor poor 71-80 0.0 4.2 95.8 0.0 7.7 92.3 81-90 1.2 8.8 90.0 1.6 18.8 79.7 9-100 3.9 25.7 70.4 0.6 16.6 82.8 101-110 6.7 31.6 61.7 11.2 26.7 62.1 111-120 3.1 47.9 49.1 15.5 29.3 55.3 12-130 0.0 30.0 70.0 21.2 14.8 64.0 131-140 0.0 0.0 100.0 42.1 36.5 21.4 Total 14.9 148.1 537.0 92.1 150.4 457.6 Average 2.1 21.2 76.7 13.2 21.5 65.4 Fig.3. Distribution of different conditions of stomach at varying stages of maturation of ovary among L.berbis during 1993-1995. PERCENT 70 60 50 40 30 20 10 0 I II III IV V VI VII - Empty - Little - 1/4 Full - 1/2 Full - 3/4 Full - Full MATURITY STAGES 129
Waltair mainly prefer copopod, foraminifera, polychaete and Alima. Mangalik [7] have reported that L. splendens feeds mainly on copepods and benthic organisms. Honey sebastin and Inasu [3] have reported that L. brevirostris mainly on Planktonic crustaceans, diatom, nematodes, polycheates and foraminiferans from Kerala coasts. Nagarajan [8] reported that copepods constituted the major food items in Leiognathus dussumieri from Thoothukudi waters. 5. Conclusion In the present study, the major food items are copepod, crustacean remains and foraminiferans. The major food items occur in all the months or most part of the year. There is no remarkable relation in the selection of food items with the size group. However, large size fishes preferred coelenterate, lucifer and nematode. The downward protracted mouthparts and the present qualitative study indicate that L.berbis are bottom zooplankton feeders. Mucus and semidigested material were invariably present in the stomach contents, almost in all the months, throughout this investigation. This may be mainly due to the very small size of the food items and rapid digestion and poor preservation in the fishing vessels. The scales were observed in the stomachs in most of the months. But the total absence of any other solid parts of fish tends to suggest that the scales might be accidental ingestion. REFERENCES 1. Bapat, S.V. and D.V.Bal 1952. The food of some young fishes from Bombay. Proc.Indian.Acad.Sci., 35B:78-92. 2. Chacko, P.I. 1944.The silverbellies of Pamban. Proc.31 st Ind.Sci.Cong: 86. 3. Honey Sebastian and Inasu, N.D (2011). Observation on the diet of the silverbelly Leiognathus brevirostris (valenciennes, 1935) from Kerala coast. J. Mar. Biol. 130
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