Food Habits and Feeding Intensity of Finlet Scad Atule Mate (Te1eostei) Off Gulf of Mannar, Southeast Coast of India
Indian Journal of Marine Sciences Vol. 28, September 1999, pp. 307-311
Food habits and feeding intensity of finlet scad Atule mate (Te1eostei) off Gulf of Mannar, southeast coast of India
S.David Kingston, V.K.Venkatararnani & K.Venkataramanujam Fisheries College and Research Institute, Tamil Nadu Veterinary and Animal Sciences University, Tuticorin - 628 008, Tamil Nadu,India
Received 8 September 1997; revised 16 March 1999
Atule mate exhibits two types of feeding patterns, the juveniles feeding mainly on crustaceans and the adults exclusively on fishes. Low intensity of feeding was observed in juveniles, males and females. Juveniles had high diet breadth (2.86) when compared to the males (1.86) and females (2.10). The overlap studies showed clustering of high overlaps in the younger and older length groups. The dendrogram of the diet at various length groups showed two principal clusters, one at 91-150 mm (TL) length group and another at 151-280 mm (TL) length group. As per the cluster analysis two types of food patterns are evident in this species.
Knowledge on the food and feeding habits is essential was noted. The stomach was designated as 'gorged' to have an idea on growth, distribution and general when it was distented with food, with its wall thin ecology of the fish. Changes in the food spectrum and transparrent. The stomach was considered as 'full' during different seasons help us to study the when it was filled with food, its wall being migratory patterns of the fish. It also helps in the comparatively thin and intact. Similarly they were selection of suitable species for aquaculture. Studies classified as '3/4 full', '112 full' and '1/4 full' on the food and feeding habits of carangid fishes in depending upon their relative fullness and the space l 4 the Gulf of Mannar region are limited . • In the occupied by the stomach in the body cavity. A present study, a detailed analysis on the food and stomach was designated and termed as 'trace' when its feeding intensity of one finlet scad,Atule content occupied less than one fourth of the capacity mate(Cuvier, I 833) has been attempted. Studies on of the full stomach. Shrunken stomachs containing these aspects have not been made so far in this mucus were considered as empty and were not species from the Gulf of Mannar region. This species evaluated. forms an important fishery along the coast of Gulf of The food items in the stomach were identified up mannar and has got good potential for aquaculture in to generic level depending on their digested state. The marine environment, as the matured specimens, eggs unidentifiable (partly digested) fishes in the gut were < and larvae are also available throughout the year. included in the category 'fish remains'. Adults were sexed and their stomach contents were analysed Materials and Methods separately. In the present study, specimens without The material for the present study were collected gonads (90-140 mm) were considered as juveniles. from the trawl fish landing centres (Vembar, The volume displacement method followed by Tuticorin and Tiruchendur) along the Gulf of Mannar McEachran et al.5 was used to quantify the gut (between lat.8S ;long.79° and lat.7S;long.77S). A contents. total of 530 specimens of Atule mate (230 males, 210 The diet breadth, an index which varies with the females and 90 juveniles) were examined for one year proportion of components in the stomach was (January 1992 to December 1992). All specimens ca\culated6 separately for juveniles, males and were measured accurately, their total length (TL) and females using the formula" B = I/Pij, where B = diet sex were noted. The stomach was preserved in 4% breadth and Pij = the proportion of resource in each formaldehyde for further study. category.Low breadth indicates clumping of the diet In order to ascertain the feeding intensity during components and high value indicates equidistributio'l various months, the degree of fullness of the stomach of various food components. 308 INDIAN 1. MAR. SCI., VOL. 28, SEPTEMBER 1999
To study the changes in the food pattern during the Among fishes, only bony fishes were recorded in growth of the species, the diet was analysed at the gut contents of A. mate. The juvenile bony fishes various length frequency levels. For this study, 10 include, c1upeids, leiognathids, sciaenids and mm size frequency was chosen. The diet overlap carangids. Among c1upeids Stolepho1"Us spp., Thryssa between different length frequencies was calculated spp. and Setipinna spp. were recorded. The group 7 based on the formula : ·'fish remains' include unidentified fishes and fish S = 100 [P-(Pxi-Pyi)] remains. Among crustaceans, shrimps, crabs and their where Pxi = proportion of ith category in 'x' length remains, exoskeleton were encountered. Broken group and shells of bivalves and gastropods constituted a minor Pyi = proportion of ith category in 'y' length group. share among molluscan remains. Algal remains were Cluster analysis was also used to study the also recorded in trace quantities in the gut of A. mare. similarity between the diets of various length groups. The Basic program of Ludwig & Reynolds8 was used Diet breadth a/juveniles and adults for this analysis. A dendrogram had been drawn to The percentage composition of food items and the depict the principal clusters. diet breadth of juveniles, males and females of A. mate (Table I) showed that crustacean remains Results and Discussion formed the main food item for juveniles (57.70%). Clupeid fishes dominated in the gut contents of males Food composition (73.52%) and females (66.81 %). The juveniles had . The food components, were grouped into 8 high diet breadth (2.86) whereas males had the least categories namely clupeids, fish remains, crustaceans, (1.86). The diet breadth of females was 2.10. Thus it leiognathids, sciaenids, molluscan remains, carangide was evident that the juveniles fed on a variety of food and algal remains in the order of abundance (Table items and its food spectrum narrowed down to a few I). varieties in adults. The monthly percentage Table I-Percentage composition of food items and diet breadth composition of various food items (Table 2) showed in 1uveniles, males and females of A. mate that clupeid fishes and fish remains were present in Food items 1uveniles (%) Males(%) Femalcs(%) the gut contents throughout the year. High percentage of c1upeids during September (67.63%) and October Clupeids 73 .52 66.81 (99.04%) showed that the fish fed largely on clupeids Fish remains 27.21 10.96 19.11 Crustacean 57.70 7.04 3. 12 during these months. The subsequent reduction of remains c1upeid diet during November (45,78%) and Leiognathids 9.84 3.37 5.62 December (31.25%) may be due to the monsoon Sciaenids 4.00 2.50 season during which time, the food intake might have Molluscan 5.25 0.66 0.71 remains been less owing to the reproductive activity of Carangids 0.32 0.62 A. mate. This is in confirmation with the more Algal remains 0. 13 1.51 occurrence of matured males and females during Diet breadth 2.86 1.86 2.10 these months. Generally the c1upeids showed a trend
Table 2-Seasonal Percentage composition of food items in A. mate
Food items 1an'92 Feb'92 Mar'92 Apr'92 May'92 1un'92 1ul'92 Aug'92 Sep'92 Oct'92 Nov'92 Dec'92
Clupeids 50.57 48.58 54.43 47.31 28.57 46.76 50.27 63 .52 67.63 99.04 45.7X 31.25 Fish remains 40.23 47.77 14. 18 17.54 60.71 20.86 29.89 11.37 15.20 O.l)() 14.46 45.83 Crustacean 2.83 14.68 21.29 21.58 14.40 2.95 0.45 38.55 20.84 remains Leiognathids 3.45 . 6.33 8.97 10.72 5.40 5.44 22.16 16.72 Scia\!nids 8.86 5.40 Molluscan 4.60 0.82 1.52 1.63 1.21 2.0S remains Carangids 3.26 Algal remains 1.15 DAVID KINGSTON et at.: FOOD AND FEEDING OF ATULE MATE 309
from January to October except during May The overlap of stomach contents between the (28.57%). Probably the fish would have consumed various length groups was calculated and given in more of c1upeids in this month and the same could Table 3. Out of 171 combinations, 84 (49.10%) have been partially digested, hence higher percentage showed high overlaps (>0.66) and 87 (50.90%) ... of fish remains registered in the month of May. In this showed low overlaps ( < 0.33). There was a clustering month fish remains were recorded to a maximum of of high overlaps in the earlier length groups and older 60.71%. Crustacean remains formed 38.55% during length groups. November and molluscan remains formed 4.60% The dendrogram of the diet during various length during January. groups (Fig.2) showed two principal clusters formed in the 91-150 mm length groups and 151-280 mm Food habits in relation to length group length groups. The two clusters formed clearly The diet pattern at various length groups (Fig.!) reflects two types of food patterns in A. mate. showed that there was a gradual shift in diet from the lower length group to the higher length group. The Feeding intensity critical change was observed in the 141-150 mm The intensity of feeding in males, females and length group. Crustacean remains dominated in the juveniles was given in Fig.3. In general, a low feeding gut contents of A. mate from 91 mm to 141 mm (TL) intensity was observed in this species. Such low and from 151 rnm to 280 mm, c1upeid contribution in feeding intensity has also been recorded in other the diet was more with a reduction of crustacean species of carangids like MegaLaspis cordyLa9 and lO remains (Fig. 1). ALectis indicus • In juveniles a high percentage of
Algae :: Lelognathids
Molluscan remains Carangids
Fish remains Clupeids Crustacean remains Sciaenids
w C> ~ I- Z W 50 u 0::: a.W
LENGTH ·
Fig. I-Histogram showing the diet components of A.mate at various length groups 310 INDIAN J. MAR. SCI., VOL. 28, SEPTEMBER 1999
'trace' (56.52) and 'empty' (34.78) stomachs were The presence of" more fish food in the stomach recorded and 'gorged', 'full' and '3/4 full' stomachs reveals that this fish is piscivurous in nature and the were absent. In males and females, 'trace' and 'empty' presence of more clupeids confirms that this species stomachs were more. The more occurrence of 'trace' is mainly a pelagic feeder. Similar feeding nature has and 'empty' stomachs also confirm the piscivorous also been reported in other carangid fi shes like feeding nature of the fish food which has more Decapterus dayi3 and Megalaspis cordylct" . ll calorific value as explained by Longhurst • The change in the food pattern in the higher length According to him, species having fish as their groups as observed presently has also been observed important food item, the intake will be less owing to in other carangids like D. dayP and M. cordylt/ . the high calorific value of the diet. According to Sreenivasan9 such change can be related Table 3-Diet overlap between various length groups in A. mate (Underlined numbers indicate high overlaps) Length Length 101 III 121 131 141 151 161 171 181 191 201 211 221 23 1 24 1 25 1 261 271 91 -100 0.75 0.76 0.78 0.89 0.88 0.41 0.20 0.39 0.27 0.42 0.23 0.25 0.28 0.2 i 0.10 0.1 i 0.32 0.25 101-110 0.99 0.97 0.86 0.80 0.31 0.07 0.16 0.17 0.17 0.03 0.10 0.05 0.07 0.04 0.00 0.08 0.00 111-120 0.98 0.87 0.81 0.32 0.08 0.17 0.18 0.18 0.04 0. 11 0.06 0.08 0.05 0.01 0.0<) D.O I 121-130 0.89 0.83 0.34 0.10 0.19 0.20 0.20 0.06 0.13 0.08 0.10 0.07 0.03 0. 11 0.03 131 -140 0.93 0.41 0.20 0.30 0.27 0.31 0.17 0.24 0.19 0.21 0.10 0. 11 0.22 0. 14 141-150 0.41 0.25 0.29 0.27 0.30 0.17 0.23 0.20 0.21 0.10 0. 11 0.22 0.13 151-160 0.64 0.85 0.86 0.77 0.72 0.74 0.74 0.76 0.69 Q.69 0.77 0.69 161-170 0.67 0.64 0.69 0.63 0.67 '0.69 0.68 0.57 0.58 0.68 0. 60 171-180 0.87 0.89 0.84 0.79 0.89 0.82 0.71 0.72 0.92 0. 84 181-190 0.77 0.86 0.74 0.85 0.80 0.83 0.83 0.83 0.77 191-200 0.73 0.80 0.78 0.76 0.63 0.61 0.82 0.76 201-210 0.72 0.93 0.80 0. 86 0.88 0.88 0.97 211-220 0.74 0. 89 0.69 0. 65 0.77 0.69 221-230 0.83 0.80 0.81 0.94 0.90 231 -240 0.77 0.74 0.85 0.77 241-250 0.88 0.75 0.73 251-260 0.76 0.78 261-270 0.89 1'1 J J
0·5 100
0 Emp ty > I- 0 Trace Vi :z: UJ ~ J;: Full I Z :; 50 • !z Full 0 .2 z 0 1;: Full o ... UJ Full UJ •• 0·1 lJ.. •• 0 Gorged ••00 0 0 ••• • ...... DO •• FEM MAL JUV Length groups
Fig.2-Dendrogram showing the percentage di ssimilarity of gut Fig.3-Figure showing the intensi ty of feeding in Juven il es, maies contents at various length groups in A. mate and females in A. mate DA VID KINGSTON e/ al.: FOOD AND FEEDING OF A TULE MATE 311
to the area of filtration formed by the gill apparatu~ as References demonstrated by Magnuson & Hettz 12 . I Chacko P I, Proc Indian Acad Sci, 29 (1949) 83. The dominance of crustacean remains in the lower 2 Kuthalingarn M D K, J Madras Ulliv. 29 (1959) 79. 3 Sreenivasan P V, Indian J Fish, 21 (1979) 76. length groups shows that the juveniles resort to 4 Venkatararnani V K & Natarajan P. Matsya. 14 (1988) 53. bottom feeding nature and the presence of more 5 McEachran J D, Noesch D F & Musick J A. Mar Bioi. 35 pelagic fishes in the adults show that they confine to (1976) 301. pelagic region. Thus the animal experiences a change 6 Levins R, Evolution in changing environments, (Princeton Univ. Press, USA) 1968, pp. 120. in habitat as it grows. Moreover the presence of 7 SchoenerTW, Ecology, 51 (1970)408. carangid fishes in the diet shows that this species is 8 Ludwig J A & Reynolds J F, Statistical ecology, a primer 011 cannibalistic in feeding habit at times. me/hod and computing, (Wiley Interscience.New York) 1988, The fusiform body of this species helps to prey pp.329. ' upon fast moving organisms both in juveniles as well 9 Sreenivasan P V ,Indian J Fish, 21 (1974) 76. 10 Venkatararnani V K, Sundararaj V &. Gopalakrishnan p, 1. as in adults. However the high diet breadth in the Aquatic Organisms, 2 (1989) 80. juveniles shows that their food spectrum is high when II Longhurst A R, J Animal Ecol, 26 ( 1957) 369. compared to the adults. This is in confirmation with 12 Magnuson J J & Hettz J G, Fish Bull. 69 (1971) 361. 13 14 the views expressed by Eggleston and Rao & Rao 13 Eggleston D, J Mar Bioi Ass India, 14 (1972) 357. in nemipterid fishes. 14 Rao D M & Rao K, J Mar Bioi Ass India. 33 (1991) 335.
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