Adequate data on the Wadge Bank fishery relating to several groups of fish, including Carangids, taken in bottom trawls are available for study. Analysis of this data indicated that the variation in Carangid catches was related to the time of day. In this paper, the available Wadge Bank fishery data is analysed and discussed to show the diurnal changes in Carangid catches and the probable influence of light in affecting these changes

Munasinghe, N.L.R.

Aquatic Commons

!Bull. FISh. Res. Stn., Sri Lanka (Ceylon), Vol. 23, Nos. 1 & 2, pp. 9-18, June&: Dec., 1972 
Influence of Light on Diurnal Behaviour of Carangids 
in the W adge Bank Trawl Fishery 
By 
N. L. R. MUNASTNGHE* 
Introduction 
9 
Some species of fish, like the Carangids, which constitute a commercially important group 
are migratory and partly pelagic and partly demersal in habit. They are present in appreciable 
numbers in bottom trawl catches from the Wadge bank, mainly during May to October. Changes 
in the [and] hydrography of the environment due to monsoon activity occur during this season. 
These changes are generally believed to influence the migration, aggregation and dispersion 
of Carangids in the bank. 
Adequate data on the Wadge bank fishery relating to several groups offish, including Carangids, 
taken in bottom trawls are available for study. Analysis of this data indicated that the variation in 
Carangid catches was related to the time of day. In this paper, the available Wadge bank fishery 
data is analysed and discussed to show the diurnal changes in Carangid catches and the probable 
influence of light in affecting these changes. 
Data on Carangid Catches 
The data sheets for three calendar years, 1957 to 1959 when two trawlers were operated on the 
Wadge bank at maximum capacity have been examined in this study. The data sheets or trawlef 
returns contain amongst other details, the time and duration of a haul and the group composition or 
the catch in respect of each haul. The catch is separated into groups of one or more species and the 
quantity in each group recorded separately (Munasinghe 1969). The Carangids fall into two sections, 
(a) the "Paraw" (Carangids over 30 centimetres in length) and (b) the "Parati" (Carangids below 
30 centimetres in length). The Paraw are represented by a few species notably Carangoides chry-
sophrys (Cuvier), Caranx carangus (Bloch) and Gnathanodon speciosus (Forskal). The Parati notably 
sby the above three species and Carangpides ma/abaricus (Bloch). 
"' Fisheries Research Station, P. 0. Box 53J, Colombo &\Lanka (Ceylon.) 
10 DIURNAL BEHAVIOUR OF CARANGIDS 
TABLE I 
Variation with time of day in apparent Density and relative Abundance of large Carangids (Paraw) 
in bottom trawl catches from the Wadge Bank (1957-1959) 
Hours between which Hour before which Apparent Density Relative Abundance 
trawl was trawl was (CPUE-lbs./hr.) (%in Catch) of 
shot hauled for Carangids Large Carangids 
0000 
- 0545 23 2 
0100 
0100 
-
0600 28 3 
0200 
0200 
- 0700 2 0 
0300 
0300 
- 0800 34 8 
0400 
0400 
-
0900 99 5 
0500 
0500 
-
0930 307 16 
0600 
0600 
- 1100 183 8 
0700 
0700 
-
1200 339 17 
0800 
0800 
-
1300 213 10 
0900 
0900 
-
1345 377 15 
1000 
1000 
-
1500 251 18 
1100 
1100 
-
160lJ 260 14 
1200 
1200 
-
1700 173 8 
1300 
1300 
-
1800 445 12 
1400 
1400 
-
1900 184 13 
1500 
N, L, R. MUNASINGHE 
Hours 
was 
1500 
-
1600 
1600 
-
1700 
1700 
-
1800 
1800 
-
1900 
Variation with time of 
ill 
which 
Hours between which 
trawl was 
shot 
0000 
-
0100 
0100 
-
0200 
0200 
-
0300 
0300 
-
0400 
0400 
-
0500 
0500 
-
0600 
. 0600 
-
0700 
0700 
-
0800 
TABLE 1-contd. 
Hour before which Apparent Density IR,.J,:,tivf' A 
trawl was (CPUE-Ibs./hr.) for (% ·~~:~~% hauled Carangids Large ~Car 
2000 385 15 
2100 71 5 
2200 66 4 
2300 15 3 
TABLE II 
"'l'.l''u""• Density and Relative abundance of small Caralllgids 
catches from the Wadge Balik (1957-1959) 
Hour before which I Apparent Density Relative Abundance 
trawl was (CPUE-Ib./hr.) for (% in Catch) of 
hauled small Carangids small Carangids 
0545 75 10 
0600 108 12 
0700 78 8 
0800 266 20 
0900 305 22 
0945 183 19 
1100 553 22 
1200 413 23 
ll 
DIURNAL BEHAVIOUR OF CARANGIDS 
TABLE II-contd. 
Hours between which Hour before which Apparent Density Relative Abundance 
trawl was trawl was (CPUE-lbs./hr.) for (%in Catch) of 
shot hauled small Carangids small Carangids 
0800 
- 1300 375 20 
0900 
0900 
- 1345 725 28 
1000 
1000 
- 1500 435 18 
1100 
1100 
- 1600 572 23 
1200 
1200 
- 1700 362 23 
1300 
1300 
- 1800 890 29 
1400 
1400 
- 1900 343 19 
1500 
1500 
- 2000 482 24 
1600 
1600 
- 2100 239 16 
1700 
1700 
- 2200 196 11 
1800 
1800 I 
- 2300 90 13 
1900 
1900 
- 0100 206 12 
2000 
2100 
- 0200 30 5 
2200 
N, L. R. MUNASINGHE 
of the data on 
Fishing goes on continuously throughout the day and night a break at 
intervals for hauling and shooting the trawl. The duration of a haul lasts between 2 to 4 hours. 
size of the catch in consecutive hauls varied in magrutude during the course of a day. This was true 
for all days of a month and all months of an year. The variation was more marked in all three years 
when Carangids were present. 
As a follow through of this observation, a closer study of the data seemed necessary in order to 
establish whether a correlation did exist between magnitude of catch and time of day. The data for 
all three years, therefore, was condensed into a catch size, time of day relationship. The catch per 
unit effort (lbs. per hour) which is an index to apparent density and percentage in the catch an index 
to relative abundance has been analysed in relation to time of day by dividing the day into several 
well defined constituent periods. 
A period of day for this purpose has its upper limit as the time of shooting the first trawl within 
this period and its lower limit as the time at which a trawl shot within this period was last to be hauled. 
The results have been tabulated separately for large and small Carangids in Tables I and II respectively· 
The processed data for each group is represented diagramatically in figs. 1 and 2. Table III shows the 
frequency of occurrence of each hour of the day within the periods with densities over 100 lbs./hr. 
and abundance over 8% for large Carangids. Similarly Table IV is for densities over 300 lbs./hr. 
and abundance of over 18% for small Carangids. 
500 
0: <100 
l: 
.... 
,; 
<!J 
..J 300 
,._, 
::0 
0. 
u 
200· 
•00 
l 
I 
I 
, .. t::::::,:::::::,::·.: ::1:::: ... ::: ........ -~:~ :::::: :::ttJ 
....... · ~~r::~t:~=k. 
~0000 0•00 0;>00 0~00 0<>'~00 Q~OO ()600 0"00 0600 0900 tooo t100 1~0 130Q to$00 1500 1000 17()0 1QOO 1900 2000 i'iOO .2200 ;1.500 )400 
Ttlldl Of {).Ia~> 
tiii•OM~IJ,~."l @.d..af<> <i!<J'"<!tlu;( ..,og,wu~JI@ "11001:11 ,o,:T!iPe;OOM Sv~Sf(T <!i16t11f MIDr.rll!l$.1 
50 
45 
<!0 
..J 
35 ~ 
0 
... 
50~ 
25 "-' 
<.::> 
<:1 
20 ~ 
w 
15 ii 
"' 10 Q. 
Fig fipparen~ Density and Relative Abundance in Relation to time of 
Bottom Trawl Catches from the Wadge Bank. 
for Carangids in 
The apparent density and relative abundance of this group in the fishing grounds appear to be 
very low during the periods before sunrise. From sunrise onwards up to sunset both density and 
abundance increase more or less proportionately and decrease rapidly during the periods of darkness. 
peaks in density and abundance are between afternoon and sunset (Fig. 1). Variation in both 
density and abundance for this group during the periods of daylight is not very marked. However 
the periods of high density and great abundance appear to be between 1000 hours and 1500 
(Table III). 
800 
"00 
li 
'::1: 
... 
~ 500. 
..! 
400 
300 
::?:00 
I 
........... <II ....... "~ ..... "'\. .. 
100 ~ •• , ................ . 
I . I 
DIURNAL BEHAVIOUR OF CARANGIDS 
~ ~ 6 ., .. • .. • • <I. • .. ..... 
flo D 0 <t <0 0 .. 0 ~ q <> 0 ~ ~" 
... 
<1: 
1-
0 
[40 1-
:!: 
w 
f$0 ~ 
z 
w 
u 
Ill: 
f20 ~ 
~10 
-----------------~-------TIME: OF DAY NtGH11" 
• • • ~ ~. • li'ERC~TCJSE «W 
,ltl 'f@,.-&1!., 
Fig. 2 Apparent Density and Relative Abundance in Relation to tim~ of day for small Carangids 
in Bottom Trawl Catches from' the Wadge Bank 
As in the case of large Carangids the density and abundance are low in the periods before 
sunrise. There is a rapid increase in both density and abundance from the period of sunrise up to 
sunset. A rapid decrease is observed during the periods of darkness. The peak in density and 
abundance is between afternoon and suset (Fig. 2). In this group variation in density is more marked 
than the variation in abundance. However, the periods of high density and abundance appear to be 
between 0900 hours and 1500 hours (Table IV). 
For both groups the rise and fall in both density and abundance are irregular. However, 
a definitive trend is apparent from both figs. 1 and 2. The trend in density and abundance for both 
groups is similar with a peak between afternoon and sunset, and the dis-similarity is only in the degrees 
of density and abundance which are higher for the small Carangids. 
"" l 
.... 
"" 
"" ... 00 
~ 
__, 
~ ?eriod of Day 
TABLE ID 
Fr!lQ!lii''ncy Distribillti!ll:i of each ho111!" in periods of day wit!! Densities above 1!01} :nul 
Al:mu,iance a !Jove 8% foR' Large Caraagi!ls 
Hours of Day within each period of day 
0500-0930 
--
--~---""1 0500 I 0600 I 0700 I 0800 \ 0900 I 0930 1--=--l---=-1---=-l---=- ---=-!---=-1---=-:-=-· - ' -
•• ' -- I 0600 I o:oo I 0800 I 09:0 1000 11100 ----=----1--=-1--=----=-- --=--1--=--j--=--0600-1100 .. 
----
0700-1200 
-
0800-1300 
----
0900-1345 
--
1000-1500 
--
. .
1 
-- .
1 
- I 0100 I 0800 I 09v0 1000 11100 L!.OO 1 - - -- I --. I -- -·----------~--l--1-----.-----l--l--l----·--·--
.. , - , , , 0200 I 0900 11000 11100 ! 1200 11300 1-~1-=--- -=---i-=---i--=--
. ·1--=--1--=--1--=--1-~1 09CO I JOOO 1100 11200 1300 1345 ~. I - - - . - . -
--------· -~--=-~--=--~---=--~--=--~--=--~1000 I 1100 I 1200 I 1300 I 1400 I bOv 
HOD-1600 .. : -- ; -- ; -- ; -- ; -- ; -- ; 1100 I 1200 I Boo I 14oo I 1soo I I6oo . -
-------------·-------------\----·------·-----·---·---·-----·-----·------·------·-----·-----·------·------·------·------·-----
1200-1700 
--
-- I -- I -- I - I - I - I -- I 1200 I 1300 I 1400 I 1500 I 1600 I 1700 ' -- ' --
----------1--------I-_, __ , __ , __ , __ , __ , __ , __ , __ , __ , __ , __ 
1300-1800 
-----
1400-1900 .. 
------l-· 
1500-2000 
- , - , -- , -- I -- - -- - \ 1300 I 1400 I tsoo I 1600 I 1100 I 1soo , -- -
- ' - ' -- ' I I I 1400 I 1500 I 1600 I 1700 I 1800 I 1900 
-- , -- , -- , -- I - -- -- -- I -- I -- I t5oo I 1600 I 1100 I 1soo I 19oo I 2000 
, _____ , _____ , ______ , ______ , _____ , _____ , ____ , ____ , ____ , _____ , ______ , _____ , ______ , ______ , ______ l _____ _ 
Total Frequency 2 3 4 5 6 6 6 6 6 6 5 4 3 2 
~ 
I:"' 
~ 
~ 
~ 
~ 
..... 
V; 
TABLE l[V 
FreqlffiefltY Distriibll.l!tion of each l.cm.llli' in of with Densities above 300 and 
Ab11ndance 2bove 18% for small Carangids 
Period of Day Hours of Day within each Period of Day 
0400-0900 . . o4oo osoo 0600 0100 osoo 0900 - - - - - I - - - - - -
------------------·----------------
0500-0945 . . - 0500 0600 0700 0800 0900 0945 - - - - - - - - ~ -
--------------------------------
0600-1100 . . - - 0600 0700 0800 0900 1000 1100 - -- - - - - - - -
------- --- --- --- --- --- --- ------ --- --- --- ---~ --
0700-1200 . . - - - 0700 0800 0900 1000 1100 1200 - - - - - - - -
--------------------------__ I ___ ----------------
0800-1300 . . - - - - 0800 I 0900 1000 . 1100 1200 1300 - - - - - - -
-----------------------------~ --
0900-1345 . . - - - - - 0900 1000 UOG 1200 1300 1345 - - - - - -
--------------------------------------
1000-1500 . . - - - - - - 1000 1100 1200 1300 1400 1500 - - - - -
--------,--------------------------
1100-1600 . . - - - - I - - - 1100 . 1200 1300 1400 1500 1600 - - - -
. I 
---------1----------------------------------------
1200-1700 . ·I - - - - - - I - - 1200 1300 1400 1500 1600 11700 - - -
-----------------------------------------
1300-1800 . ·' - - - - - - - - - 1300 1400 1500 1600 1700 1800 - -
-------------~ ------. -------------~ 
1400-1900 . . - - - - - - - - - - 1400 1500 1600 1700 1800 1 1900 -
1500-2000 .. ---~--- -_- -_- -_- -_- -_- -_- -_- -_- -_- -1-50_0_ -1-6-00- -1-7-00- -1-8-00-~-1-9-00- -2-0-JO-
----------------------------------------------
Total Frequency . . 1 2 3 4 5 6 6 6 6 6 6 6 5 4 3 2 1 
----------~---
s 
~ 
~ 
F' 
1::0 
tii 
~ 
~ 
g 
~ 
z 
~ 
"'"' 
N. L. R. MUNASINGHE 17 
Discussion 
Carangids both and small become increasingly vulnerable to by a bottom 
trawl from dawn to dusk, in other words during daylight hours. As :figs. 1 and 2 show they are more 
or less unavailable for capture at the sea bottom during the periods of darkness. rapid in 
both apparent density and relative abundance soon after sunset seems to indicate a movement out of 
range of a bottom trawl. These fish though partially pelagic, Shabotinets (1969) are mainly bottom 
feeders. An examination of stomach contents showed that their food generally consisted of bottom 
dwelling forms such as crabs, shrimps, and bivalve molluscs (Fernando 1968). Generally, after sunset, 
when the light intensity falls below critical limits for feeding activity, the fish move away from the 
bottom as shown by the relatively low densities indicated in the Tables. As the apparent density and 
relative abundance tend to increase from dawn to dusk, it maybe assumed that there is a movement 
of these fish from the surface to the bottom for feeding. This diurnal rhythm or up and down movement 
is for feeding at depths of a preferred light intensity. In a recent review of herring biology, Parrish 
and Saville (1965), state that it is generally accepted that the diurnal behaviour pattern results from 
the fish following a preferred light intensity. In the Carangids, therefore, greatest activity is generally 
between dawn and dusk. The~e fish remain at or near the bottom of the fishing grounds, which is 
their feeding gronnd making themselves vulnerable to capture by the bottom trawl. The peak in 
vulnerability for Carangids appears to be before sunset, suggestive of greater activity while feeding 
together with the pressing action of the light (Balls 1950) which under normal conditions is more 
intense at this time of day forcing them nearer the sea bottom. This explanation could account for 
the peaks in density and 2.bundance bef~Dre sunset. 
The time at which both and abundance of Carangids increase and decrease appear to 
coincide very closely with the times at which light intensities are likely to increase and decrease. 
highest intensities will be between 0900 hours and 1500 hours. This intensity will decrease propor~ 
tionately from surface to bottom. The lowest intensity will be at the sea bottom. The fish will 
remain at a depth in which the intensity is at an optimum for their comfort and feeding 
The data analysed in this paper have been obtained from the Wadge Bank within a depth range of 10-30 
fathoms (Mueasinghe 1969) and it has now been shown that densities and abundance vary with the 
time of Chestnoy (1970) refers to the influence of hydro-optical conditions in availability of 
fish for capture. In other words, the visual acuity of the fish is conditioned by the light intensity 
prevailing at that depth of water. From the above evidence it may be assumed that light intensity 
plays au important role in diurnal changes in Carangid catches taken bottom trawls 
in the Wadge Bank. 
Carangid catches in bottom trawls operated in the Wadge Bank have shown variation 
the course of a day. This variation is governed by the apparent density and relative abundance of 
these fish within a limited time and space. The results show a diurnal rhythm in behaviour of these 
fishes indicating a descent to the bottom commencing at dawn and an ascent to the surface at sunset. 
Both density and abundance increase from sunrise to sunset with a peak between afternoon and 
sunset. This is explained as due to greater activity while feeding at depths with a preferred light 
intensity with the result that these fishes remain nearer the bottom, and consequently, are more 
vulnerable to capture by a bottom trawl. A strildng feature of the diurnal rhythm in behaviour is 
that it coincdes very closely with the times at which light intensity generally increases and decreases 
underlying the importance of this factor in the behaviour of Carangids in the Wadge ~ank. 
18 DIURNAL BEllA VI OUR OF CARANGIDS 
1"'"'"'"''"'''"'+ of Fisheries, for the many 
useful discussions on the of this paper. 
REFERENCES 
BALLS, R., 1950. Environmental Changes in Herring Behaviour. Jour. de Conseil, VoL 17, No. 1, p. 247. 
BEAMISH, E. F. H., 1966. Vertical Migration by Demersal Fish in the North Atlantic. Jour. Fish. Res. Bd., Canada, 
Vol. 23, No. 1. 
CLARK, F. N., 1939. Measures of Abundancy of Sardine. Cal. Div. Fish and Game. Fish Bull., No. 53. 
CHESTNOY, V. N., 1970. The Adaptive Variations in the Catchability of Trawls on the Wadge Bank. Bull. Fish. Res. 
Stn., Ceylon Vol. 21, No. 1, pp. 39-47. 
HIGH, W. L. & LUTZ, L. D., 1966. Underwater Observations on fish in an off bottom trawl. Jour. Fish. Res. Bd., 
Canada, Vol. 23, No. 1, pp. 153-154. 
' MoRGANS, J. F. C., 1962. Ecological Aspects of Demersal Tropical Fishes off East Africa. Nature, Vol. 193, No· 
4810, p. 86. 
MUNASINGHE, N. L. R., 1969. Seasonal Variation in the Distribution and Availability of Carangids in the Wadge 
Bank. Bull. Fish. Res. Stn., Ceylon, Vol. 20, No.2, pp. 191-200. 
RicHARDSON, E. I. D., 1952. Some Reactions of Pelagic Fish to Light as Recorded by Echo Sounding. Fishery Inve'!t;-
gation Series II, Vol. XVlli, No. 1. Ministry of Agriculture, Fish and Food, London. 
SHABOTINETS, E. I., 1966. Fishes of Wadge Bank (Southern Hindustan). Rybnoe Khoz.raistvo, No. 11, pp. 6-7. 
Azcherniro, Moskva. 
WOODHEAD, P. M, J., 1969, The Behaviour of Fish in Relation to Light in the Sea. Oceanogr. l'vlar. Bio!. 
Ann. Rev. 1., 337-403. 


Influence of light on diurnal behaviour of Carangids in the Wadge Bank trawl fishery

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Influence of light on diurnal behaviour of Carangids in the Wadge Bank trawl fishery

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