Length and weight relationship of Decapterus russelli (Ruppell, 1830) is worked out to be W = 0.00312 L³ which indicates the isometric growth of the fish. Study on food and feeding habits revealed that the species is carnivorous, pelagic, feeding primarily on small crustaceans and small fish species, viz. Acetes indicus, ostracods, Apogon sp., Leiognathus sp., sciaenids, Netnipterus japonicas, Myctophid sp., Trichiurus sp., Therapon sp., D.russelli and occasionally on prawns. It is a selective feeder on Aeetes indicus

George, J.P.

Gulati, D.K.

Jaiswar, A.K.

Swamy, R.P.

Aquatic Commons

journal of the Indian Fisheries Association 	 1 
23, 1993, 1.6 
A STUDY ON LENGTH-WEIGHT RELATIONSHIP, FOOD AND }FEEDING 
HABITS OF INDIAN SCAD, DECAPTERUS RUSSELL! (RUPPELL, 1830) 
ALONG THE NORTHWEST COAST OF IND 
A.K.JAISWAR, J.P. GEORGE, D. K. GULATI AND R. P. SWAMY 
Central Institute of Fisheries Education, 
Versova, Bombay 400 061. 
ABSTRACT 
Length and weight relationship of Decapterus russelli (Ruppell, 1830) is worked out to be 
W = 0.00312 L3•00 which Indicates the isometric growth of the fish. Study on food and feeding 
habits revealed that the species is carnivorous, pelagic, feeding primarily on small crustaceans 
and small fish species, viz. Acetes indicus, ostracods, Apogon sp., Leiognathus sp., sciaenids, 
Netnipterus japonicas, Myctophid sp., Trichiurus sp., Therapon sp., D.russelli and occasionally 
on prawns. It is a selective feeder on Aeetes indicus. 
INTRODUCTION 	 MATERIAL AND METHODS 
Decapterus russelli(Ruppe11,1830) (Family 
Carangidae) is a commercially important fish 
constituting on an average 2194 tons/year (30%) 
of the carangid landings NOR% was 7315 tons/ 
year in Maharashtra during 1984-88. It is caught 
throughout the year along the northwest coast of 
India by pelagic trawl, mostly in the depth range 
of 55-90 in and males are usually dominant in 
the catches. The fish probably migrates to deeper 
water after attaining penultimate stage of 
maturity (Bapat et al., 1982). During the period 
198488, Maharashtra and Gujarat contributed 
on an average 309,236 tons (28%) and 228,278 
tons (20.6%) against 1,105,668 tons total marine 
fish landings on the west coast of India. In the 
above fishery, carangids contributed nearly 5% 
in Maharashtra alone (Alagaraja et al., 1992). 
Inspite of this, there is no detailed report on the 
length-weight relationship and food and feeding 
habits of Decapterus russelli off the northwest 
coast of India except a brief study on food and 
feeding habits by Bapat et al., (1982) and brief 
information on its occurrence along the northwest 
coast of India (Rao, 1966) and along the 
Vizhinjam coast (Sreenivasan, 1979). Hence 
the present de tailed investigation was undertaken 
to study the length-weight relationship and 
feeding biology of this commercially important 
carangid. 
Specimens for the present study were 
collected twice a week at random from Ferry 
Wharf, Sassoon Dock and Versova landing centre 
in Bombay. In addition, specimens were also 
collected from the pelagic trawl catches of 
CIFE' s research corn-training vessel 
M.F.V .Saraswati, from the northwest coast of 
India (17°00' to 20°00' N and 69°00' E to 73 °00' 
E) from September, 1986 to AuguSt, 1988. A 
total of 1,831 fish specimens ranging from 8.0 
cm to 21.8 cm in total length and 4 to 950g in 
total weight were analysed. After recording the 
total length to the nearest mm, the corresponding 
weight of the fish was measured to the nearest 
gram on a monopan balance. The data on total 
length and weight were statistically treated by 
the least square method and putin its logarithmic 
form by using the general. formula log W 
log L (Le Cren, 1951). Analysis of covariance 
technique was carried out to test the significance 
of difference of growth in length and weight of 
the fish among males, females and juveniles. 
The fishes were dissected to determine the sex, 
stage of maturity and condition of stomachs in 
situ. Gonads and guts were carefully taken out 
and preserved in 4% neutral formalin for later 
studies. The intensity of feeding was determined 
by degrees of distension of stomachs as gorged, 
full, 3 /4 , 1 /2, 1 /4 , trace and empty. The volume of 
each item of gut contents was determined by 
2 
	 JAISWAR, GEORGE, GULATI AND SWAMY 
volume displacement method and further 
analysis was done by the method of Index of 
preponderance (Natrajan and Jhingran, 1961). 
The orientation of food items in the stomachs 
was recorded to assess the active or passive type 
of predatory habit. Unrecognisable jelly like 
matrix or digested food were separately recorded 
as a constituent of the gut contents only and not 
as a food item. 
RESULTS 
The length-weight relationship of 
Decapterus russelli was worked out to be 
W = 0.003120 L3 '0° (Table 1). The length 
weight relation worked out separately for male, 
female and juveniles were W = 0.006165 L3 ' 14 , 
W = 0.007585 L3 '07 and W = 0.0213796 L 2 ' 64 
respectively. Analysis of covariance revealed a 
significant difference in the growth of male, 
female and juveniles in terms of weight in 
relation to length. 
Table 1 Values of coefficient of regression 
and coefficient of correlation. 
Sex 	 Coefficient of Coefficient of 
regression 	 corelation 
(b) 	 (r) 
Male 	 3.14 	 0.92195 
Female 	 3.07 	 0.91104 
Indeterminate 	 2.64 	 0.95917 
Pooled 	 3.00 	 0.97979 
Composition of food 
Table 2 depicts the Index of preponderance 
and composition .of various food items in the 
guts of Decapterus russelli. Crustaceans and 
fishes were the major food items. 
Crustaceans : Acetes indicus, ostracods and 
prawns contributed 56.3% by volume of the gut 
contents. Among crustaceans, Acetes indicus 
alone contributed 81.33%, ostracods 13% and 
prawns 5.7%. 
Fishes : Altogether nine species of fishes 
were encountered in the guts and contributed 
10.47% of total volume of food consumed (Table 
3). These were Nemipterus japonicus, 
Leiognathus sp., Apogon sp., sciaenids, 
Muraenesox sp., Therapon jarbua, Trichiurus 
sp., and Decapterus russelli itself. 
Food compositions in different months 
Monthwise percentage composition of 
different food items observed in the gut contents 
of Decapterus russelli has been shown in Table 
3 which indicates that there were considerable 
variations in the percentage composition of 
different food items, during different months of 
the year of the investigation. 
Acetes indicus was present in the guts 
throughout the year, except in December, 
occupying the maximum volume (100%) in 
August and minimum volume (3.44%) in 
February. It occupied more than 50% by volume 
in September (73.99%), May (58.77%) and in 
April (51.65%) and in other months it ranged 
between 40% to 3.44% (Fig.2). Percentage 
composition of ostracod was as high as 92.8% in 
the month of February and the lowest at 3.88% 
in March. In November and January it constituted 
20% and 29.9% of the gut contents respectively, 
but absent in othermonths. Prawns were devoured 
by the fish only in the months of October 
(14.84%), June (15.02%) and July (1.37%). 
Table 2 m Index of preponderance of various food items of the guts of Decapterus russelli 
Food item V 0 V 1 01 V 1 01 V 1 0 1 	 100 x Rank 
*V 0 
Acetes indicus 170.6 264 45.72 52.90 2418.58 76.28 I 
Digested matter 48.77 137 13.08 27.45 359.05 11.32 II 
Fishes 114.55 54 30.70 10.82 332.17 10.47 III 
Ostracod 27.15 40 7.28 8.02 58.38 1.84 IV 
Prawn 12.00 4 3.21 0.80 2.57 0.08 V 
LENGTH-WEIGHT RELATIONSHIP AND FEEDING HABITS OF DECAPTERUS RUSSFLIJ 
	 3 
Table 3 : Monthly percentage indices of different food items of Decapterus russelli 
during September, 1986 to August, 1988. 
Food item Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June 	 July Aug. 
Acetes indicus 73.99 39.90 16.75 32.00 3.44 5.18 51.65 58.87 24.22.-40.00 100 
Ostracod - 20.00 24.82 93.81 3.88 
Apogon sp. - 11.62 - 19.53 56.88 
Leiognathus sp. 5.81 - - 5.25 - 15.63 	 - 
Sciaenids 8.08 39.25 10.36 - 24.06 - 
Njaponicus - 5.25 
D.russelli - 30.34 - - 
Trichiurus sp. - 0.82 - - 13.12 - 
Myctophids - - 46.63 6.2 0.93 
Therapon sp. - - 12.4 
Eel - - 10.5 
Prawn - 14.84 15.62 	 1.87 
Digested matter 8.58 6.01 24.00 100 8.97 2.75 33.94 29.75 16.97 25.00 	 0.40 
Nine species of fishes were encountered in 
the guts of these specimens. Except in December, 
February and August at least one species of fish 
was observed. Percentage composition of fishes 
was observed to be highest in July (57.8%), 
followed by March (56.99%), and lowest in the 
month of April (18.6%). In other months it 
ranged between 39.25% and 24.06%. Digested 
unrecognisible gelatinous matrix occupied the 
gut contents throughout the year except in August 
and occupied 100% of the contents in December 
and minimum 0.4% only in July. 
Food composition in relation to size 
There was no major difference in me rood 
constituents although composition among 
different size groups varied. It was observed that 
smaller fishes prefered smaller food items like 
ostracods and Acetes indicus than fish. The 
fishes above 15.0 cm prefered fish as food over 
Acetes and others. 
Compostion of food in relation to maturity 
stages 
Acetes indicus was encountered at all stages 
of maturity of fish. The immature fishes were 
found to feed mainly on small crustaceans like 
ostracods and Acetes sp. Maturing and mature 
fishes fed primarily on fishes. Some of the ripe 
fishes were also noticed to feed on fishes but  
otherwise empty stomachs were encountered; 
spent fishes were observed with full stomachs 
except in a few cases. 
Feeding intensity in relation to months 
Percentage occurrence of stomachs in 
different degrees of fullness in Decapterus 
russelli during 1986-88 is depicted in Table 4. It 
is clear from the table that there were wide 
variations in the feeding intensity in different 
months of the year. It was highest in September 
followed by JUly and lowest in December, 
followed by January and May. Feeding intensity 
was moderate in October, November, February, 
June and August. 
Feeding intensity in relation to size, sex and 
maturity stages 
Percentage occurrence of stomachs in 
different degrees of fullness in different size 
groups is shown in Table 5. It is clear from the 
Table that there were wide variations in the 
feeding intensity of different sizes of the species. 
Larger fishes (15.1 - 25.0 cm) had very high 
feeding intensity whereas smaller fishes between 
5.0 - 10.0 cm had very poor feeding intensity. 
Fishes between 10.1 - 15.0 cm fed moderately. 
There was no significant difference in the 
4 
Table 4 e 
JAISWAR, GEORGE, GULATI AND SWAMY 
Percentage of stomachs in different degrees of fullness in Decapterus 
russelli during September 1986 to August, 1988. 
Month Gorged Full 3/4 1/2 1/4 Trace Empty 
September 30.43 8.70 4.35 2.17 2.17 41.3 . 10.87 
October 11.54 19.23 17.31 13.46 14.63 21.65 
November 7.32 12.20 41.46 14.63 1.32 17.07 
December 3.03 15.15 51.52 30.30 
January 4.61 1.54 12.31 21.54 23.08 36.92 
February 5.55 27.78 11.11 22.22 27.78 5.55 
March 6.67 3.33 6.67 10.00 30.00 43.33 
April 11.90 21.43 21.43 16.67 7.14 21.43 
May 8.82 2.94 11.76 76.47 
June 8.00 4.00 4.00 16.00 12.00 24.00 32.00 
July 16.67 16.67 4.17 29.17 4.17 16.67 12.50 
August 9.38 28.12 9.38 53.13 
feeding intensity between the sexes. 
Immature fishes were found to have very 
poor feeding intensity. Maturing and mature 
fishes had high feeding intensity. Nearly 29% of 
the ripe fishes had vary high feeding intensity 
whereas the remaining had very poor feeding 
and had more than 40% clearly empty stomachs. 
Empty stomachs 
Table 4 indicates varying percentage of 
empty stomachs during the different months of 
the study. It was highest in May (76.47) and 
lowest in February (5.55%). Table 5 also reveals 
varying percentage of empty stomachs in 
different size groups encountered during the 
investigation. 70% empty stomachs in size groups 
5.0 - 10.0 cm, 18.3% in the size groups of 10.1 
- 15.0 cm, 31.36% in size groups of 15.1- 20.0 
cm and 40% in size group 20.1 - 25.0 cm fishes  
were observed whereas theoretically there should 
not be empty stomach except in those which are 
everted. 
DISCUSSION 
The present study on length and weight 
relationship revealed that D. russelli has isometric 
growth charactersitic,' b' value (3.00) indicating 
that growth of fish by weight was proportional 
to the cube of its length. The compared characters 
were highly correlated toeach other as coefficient 
of corelation `r' (0.9797) was very near to 1. It 
is very clear from the curvilinear relationship of 
length and weight that growth of fish by weight 
was faster than its length. 
The present study on food and feeding 
habits of Decapterus russelli revealed that the 
species is a carnivore, predating on small 
crustaceans and small fish. It is not herbivorous, 
Table 5 a Percentage of stotnachs in different degrees offullness in dtfferent size groups ofD.russelli 
during September 1986 to August,' 1988. 
Size group 
(cm) 
Gorged Full 3/4 1/2 1/4 Trace Empty 
50- 100 20.00 10.00 70.00 
101 - 150 2.80 9.85 1.40 7.00 15.49 45.07 18.30 
151 - 200 12.11 13.04 0.93 15.53 .  10.25 16.77 31.36 
201 - 250 20.00 20.00 20.00 40.00 
100 
90 . 
70 
• 6 0- 
50 
▪ 40 - en) 
4, 30- 
r 
oil 
20 .  
cL 1 " 
J 	 F 	 AMJJ 	 A 
MONITh S 
LENGTH-WEIGHT RELATIONSHIP AND FEEDING HABITS OF DECAPTERUS RUSSELL' 
110 
100 
90 
80 
70 
50 
co 40 
1.1.1 
30 
20 
10 
0 
10 	 15 
	 20 
	
25 
LENGT H (C 
Fig. 1 Length weight relationship of Decapterus russelli along the north west coast of India. 
Fig. 2 Monthly percentage indices of Acetes indices a food item in the total food of D.•usselli 
along the north west coast of India. 
6 
	
JAISWAR, GEORGE, GULATI AND SWAMY' 
nor does it feed on benthic organisms. It has a 
Very narrow spectrum of diet, subsisting mainly 
on small crustaceans like Acetes and small fish 
species. These findings are in conformity with 
those Of Sreenivasan (1979) who, however, also 
observed varieties of plankton and cephalopods 
in its diet at Vizhinj am which were conspicuously 
absent in the specimens examined in the present 
study. According to Hardy (1924) and De Silva, 
(1973) this type of difference in feeding habits 
may occur in the same species collected from 
different habitats at different times and at 
different stages of growth. Among crustaceans, 
Acetes sp. was encountered in almost all the 
months with a domination in most of the months 
and it was the sole food item in August (fig .2). 
But fishes were found to be the dominant food 
item in Vizhinjam (Sreenivasan, 1979). In the 
present case Acetes was the preferred food item 
as evidenced by the presence of this organism in 
all the months even though other food items also 
could have been abundant in that environment. 
As it is seen that this fish fed on nine species of 
fishes, it can be inferred that it. is not very 
selective in case of feeding on fish ; any fish 
easily available in the surrounding environment 
suited to its mouth size serves its purpose of diet. 
It can be a voracious feeder, as it continues 
feeding even when more than 33% ofgut (March) 
is full with digested matter. Some of the spent 
fishes were encountered with empty stomachs. 
It is possible that they were caught very soon 
after spawning and could not feed. due to 
spawning stress whereas others were well fed. 
Feeding intensity was highest in September 
followed by July and lowest in December and 
January. This coincides with availability of 
suitably sized Acetes and fishes as it is observed 
that 73% Acetes was encountered in September 
and 40% Acetes and 57.81% fishes were 
encountered in the months of July. Very high 
feeding intensity was observed in mature (15.1 
- 20.0 cm length) specimens, which seem to be 
the preparation for the breeding. This fish is also 
cannibalistic in nature. 
ACKNOWLEDGEMENTS 
The authors are greatful to Prof. Y. 
Sreekrishna, Ex-Director, CIFE for facilities 
provided to conduct the research work and to 
Dr.S.D.Tripathi, Director CIFE, Bombay for 
permission to publish this paper. We are highly 
indebted to Dr. M. Devaraj, for his valuable 
suggestions. The authors are also grateful to Shri 
P. Acharya and Shri K. Venkateshvaran, 
Scientists, for critically going through the 
manuscript. 
REFERENCES 
Alagaraja, K. Balan, K., Karia, K.S., 
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C'...J., 1992. Marine fish production of 
maritime states of the west coast of India. 
Bull. Cent. Mar. Fish. Res. Inst. 1992, 45: 
38-45. 
Bapat, S.V., and Deshmukh, V.M. 1982. 
Fishery resources of exclusive economic 
zone of north west coast of India. CMFRI , 
Bulletin No. 33. 60-62. 
De Silva, S.S. 1973. Food and feeding habits of 
herring Clupea harengus and the sprat 
C.sprattus in inshore waters of the west 
coast of Scotland. Mar. Biol., 20: 282-290. 
Hardy, A.C. 1924. The herring in relation to its 
marine environment Part-I. The food and 
feeding habits of herring with special 
reference to east coast of England. Fish. 
invest. London Ser. 2 (7) : 1-53. 
Le Cren, C.D. 1951. Length-weightrelationship 
and seasonal cycle in gonad weight & 
condition in perch (Perca 
J.Animal Ecol., 20 : 201-219. 
Natarajan, A.V. and Jhingran, V.G. 1961. 
Index of preponderance a method of grading 
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fishes. Indian J. Fish., 8 (1) : 54-59. 
Rao, S. K. 1966. The occurrence of Decapterus 
dayi Wakia in the Arabian sea off Bombay 
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A study on length-weight relationship, food and feeding habits of Indian scad, Decapterus russelli (Ruppel, 1830) along the northwest coast of India

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A study on length-weight relationship, food and feeding habits of Indian scad, Decapterus russelli (Ruppel, 1830) along the northwest coast of India

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