There is apparently great scope for improvement of the design and operational aspects of the gear particularly for the effective exploitation of seasonal fisheries like that of seer, tuna, barracuda etc. In order to evolve improved, yet cheap trolling gear regular investigations were undertaken by the Craft & Gear Wing of the Central Institute of Fisheries Technology, off Cochin for five fishing seasons and the results of these studies are incorporated in this paper

Deshpande, S.D.

Sivan, T.M.

Aquatic Commons

ON THE TROLL LINE INVESTIGATIONS Off COCHIN 
DURING FIVE FISHING SEASONS 
1. INVESTIGATIONS DURING 1960-61 AND 1961 .. 61 
SEASONS 
* S. D. DESHPANDB AND *T. M. SIVAN 
Central Institute of Fisheries Technology (Craft & Gear Wing), Cochin-5. 
INTRODUCTION 
Although trolling as a commercial 
method of fishing is of recent origin in 
this country, it can in no way be considered 
an innovation. Trolling lines were exten-
sively used for salmon fishery towards the 
turn of the previous century (Jordan 1880) 
The actual development however took 
place only after the replacement of sails 
by engines in fishing boats (Scofield 1956.) 
According to Chapman ( 1950), Bates 
(1950) Milne (1955) Scofield (op. cit.) and 
Koyma (1956) trolls are indigenous and 
effective gear for the capture of predatory 
and fast moving fishes of commercial impo-
rtance Jike seers, tuna, albacore, skipjack, 
salmon etc. 
Surveys of marine fishing gear along 
the Indian coasts have shown that troll 
Jines with baits such as coconut kernel, 
wooden plugs, coloured cotton rags, 
sisal or coir fibre are used by certain 
fishermen of Kerala, Madras and Andhra 
Pradesh as well as by those in Andaman, 
Laccadive and Minicoy Islands (Ayyangar 
1962; Hornel 1924). Hornell (op. cit.) 
has named them as 'whiffing lines'. He is 
further of the opinion that this way of 
fishing is not known to the Indian fisher-
men and the limited use of the gear is 
due to intercourse with Ceylon. 
There is apparently great scope foJ 
improvement of the design and operational 
aspects of the gear particularly for the 
effective exploitation of seasonal fisheries 
like that of seer, tunny, barracuda etc. In 
order to evolve improved, yet cheap 
trolling gear regular investigations were 
undertaken by the Craft & Gear Wing of 
the Central Institute of Fisheries Techno-
logy, off Cochin for five fishing seasons 
and the results of these studies are incor-
porated in this communication. 
MATERIALS AND METHODS 
Fishing vessel, Fishtech No. 1 (30 
fishing boat) was used to conduct the 
studies. The rigging of the outrigger 
bamboos for securing the troll lines is 
shown in text Fig. 1. 
* Present address: Central Instituta of Fisheries Technology Substation, Veraval. 
26 FISHERY TECHNOLOGY 
OUT RIGGAR POLES 
ii) Whale bone jigs, iii) Latex sponge 
rubber jiggs (Japanese type), iv) Rubber 
worm jigs (Norwegian) and v) Feather 
jigs with lead head (CIFT design). 
Text Fig. 3 shows the details of the 
jigs. Norwegian Mustad single hooks 
Nos. 3, 4 and 5, two of the same size 
welded together, were used as double 
hooks with each jig. 
Text. Fig. 1. Rigging of outer-rigger 
bam boo poles. 
The vessel towed 6 to 8 jigs each day 
from 7-00 A. M. to 4-00 P. M. Tows 
were made in different directions. The 
operations were concentrated in areas 
where signs such as jumping fish, bird 
dives and fish strikes were observed. The 
towing speed of the vessel ranged from 
4 to 7 knots. On observing a fish bite, the 
Design details of the gear are shown 
in Text Fig. 2. 
Jigs of the following types were used 
for the investigations. i) Feather jigs, 
DESIGN OF TROLLING L~E 
To out rlooor polo 
SprJnQ l'*dlo.sa''lono or 2~wldth okl ~or tubo 
Moln uno !rnm. dlo. hord twlotad cottorl or nylon 
· ' 26 to30Fothomt 
No 4 
ooublo noolo: 
Swivel (heavy duty bran) 
Snood wire 
0·9mm.dlo 4 '1ono 
Flshhood 
,• Woloht S2·5grms 
Flo 2 
Text Fig. 2. De3ign details of Trolling line gear. 
VoL VI No. 1 1959 27 
• U:AOHEAD F£AT~EA JIGS C.i.F,T,DE.SIGNS 
f::\. ~ 
A 
NORWEGIAN RU89ER WORM 6Alr 
. -. 
e 
A&e :·FeW>or )IO wlm>eooheoo 
F ;.. Foather Jig, 
H:- Ruf>bqr worm bait. 
Text Fig. 3. Different jigs used for the experiments. 
speed of the boat was reduced and the 
concerned line hauled in. The hooked 
fish was removed and the vessel regained 
the required speed. The line was released 
again and operations continued. 
In order to enumerate the different 
factors affecting the landings of the gear 
particulars such as varieties, quantities of 
fish caught, time of hooking, temperature 
and turbidity of the water, length of each 
line, speed of tow, effectiveness of different 
lures and stabilisers and stomach contents 
of fish caught were recorded regularly 
during the operations. 
RESULTS 
Sixtythree fishing trips were made 
during the period from October 1960 to 
May 1961. The total trolling time was 
28 
325.75 hours using 6 to 8 lines each day. 
The catches landed were 1.056 fishes 
having a total weight of 1427 kgs. 
(Table I). 
The fishing season during 1960-61 
commenced in the month of October. The 
majority of the catches were landed during 
the months of November and December. 
The catches per day for these two months 
were 31.1 and 17.1 fishes respectively. 
From January 1961 onwards landings 
were considerably reduced. 
During the 1961~62 season, fiftysix 
trips were made for the period extending 
from October 1961 to February 1962. The 
total time trolled was 314.5 hours using 
4 to 7 lines per day. 601 fishes weighing 
2,905.4 kgs. were landed. (Table II). 
FISHERY TECHNOLOGY 
-< 0 
t"' 
< 
...... 
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0 
,_;.. 
-\0 
0'\ 
\0 
N 
\0 
TABLE I RESULTS OF TROLLING OPERATIONS CONDUCTED DURING 1960-61. 
MONTH AND YEAR 
Particulars 
October November December January February March 
1960 1960 1960 1961 1961 1961 
Total No. of trips made 11 18 13 8 6 4 
Total troiling duration 55 94.5 75 27 24.25 23 
(hours) 
Average number of lines 6.2 6.2 8 8 8 7.5 
used per day 
CATCH Seer No 122 248 209 15 17 33 
Wt (Kg) 94.5 236 374 117 51.8 74.5 
Tunny No 22 346 10 0 5 5 
Wt (Kg) 22.7 351 13 0 13.1 7.3 
Others No 5 2 4 0 0 3 
Wt (Kg) 4 10 18 0 0 17.7 
Total catch No 149 596 223 15 22 41 
Wt (Kg) 121.2 597 405 117 67 99.5 
Catch/day No 13.5 33.1 17.1 1.9 3.7 10.3 
Wt (Kg) 11.02 33.2 31.2 14.6 11.2 24.9 
Max. catch/day No 46 106 88 4 10 20 
Wt (Kg) 58.2 96.4 100.5 13.2 25 45.4 
Total 
May 
1961 
3 63 
17 315.75 
6.5 6.2 to 8 
7 651 
14.3 962.1 
3 391 
6.4 413.5 
0 14 
0 49.7 
10 1056 
20.7 1427.4 
3.3 16.7 
7.0 22.66 
7 
14.3 
V;) 
0 
"'''l 
-
til 
::r: 
t!l 
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....:: 
>-i 
t!l () 
::r: 
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0 
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0 
0 
....:: 
TABLE H RESULTS TROLLTNG OPERATIONS CONDUCTED DURING 1961-62. 
Month and year 
Particu Iars October November December January February 
1961 1961 1961 1962 1962 
Total no. of trips made 5 21 15 4 11 
Total trolling duration (hours) 8.15 109.45 89.45 19.30 86.45 
Average number of lines used per day 4 5 to 6 6 6 6 to 7 
CATCH Seer No 18 409 100 11 18 
Wt (Kg) 88.7 1,980 472 45 85.5 
Tunny No 1 4 25 5 1 
Wt (Kg) 1.4 7.3 148 9 3.0 
Others No 1 4 0 3 1 
Wt (Kg) 4.5 44.5 0 7.5 9.0 
Total catch No 20 417 125 19 20 
Wt (Kg) 94.6 2,031. 8 620 61.5 97.5 
Catch/day 1'-T 0 4 19.9 8.3 4.8 1.8 
Wt (Kg) 18.9 97.0 41.3 15.4 8.9 
Max. catch/day No 13 75 23 19 12 
Wt (Kg) 47.7 411.4 112.3 61.5 51.5 
Total 
56 
314 
4 to 7 
556 
2,671.2 
36 
168.7 
9 
65.5 
601 
2,905.4 
38.8 
181.5 
The fishing season commenced in the 
month of October. The bulk of the 
catches were in the month of November 
and showed average per day of 19.9 fishes 
weighing 97 kgs. From December onwards 
the catches dwindled. 
DiscussiON 
Varieties of fish hooked: Table III 
shows the analysed data of the composition 
of the catches. 
It would be evident from Table III 
that the varieties which dominate troll line 
catches are seer and tunny. Tunny catches 
were relatively poor in 1961-62 season 
when compared to the year preceeding. 
Size of fish caught: The monthly 
average of the body weight of seer hooked 
in the 1960-61 and 1961-62 seasons is 
given in Table IV. 
It would be clear from Table IV that 
during the months of October-November 
1960 only small seers were hooked. As the 
months passed the sizes of seer in the 
landings also increased. 
During 1961-62 season seers of re-
latively bigger sizes were landed. Tunnies 
were also bigger porticularly those landed 
in the month of December. 
Trolling speed: Observations on the 
effective trolling speed for enticing seer 
and tunny indicated that a speed between 
4 and 6 knots was resonably effective. 
Length of main line: Table V shows 
the length of the main line for each 
TABLE III COMPOSITION OF CATCHES 
Name of fish Number percentage Weight Kg. Percentage 
1960-1961 
Seer (Cybium sp) 651 61.7 962.1 67.5 
Tunny (Euthynnus sp) 391 37.1 413.5 29.0 
Others 14 1.2 49.7 3.5 
1961-1962 
Seer 556 92.5 2,671.2 92.0 
Tunny 36 6.0 168.1 5.8 
Others 9 1.5 65.5 2.2 
TABLE IV MONTHLY AVERAGES OF BODY WEIGHTS OF FISH 
Season Name of fish Monthly averages of body weight of fish in kgms 
Oct. Nov. Dec. Jan. Feb. March May 
1960-61 Seer 0.77 0.95 1.79 1.81 3.05 2.26 2.05 
Tunny 1.03 1.01 1.'30 2.63 1.46 2.13 
1961-62 Seer 4.93 4.84 4.72 4.90 4.76 
Tunny 1.40 1.82 5.82 1.80 3.00 
VoL VI No. 1 1969 31 
operation and the corresponping catch 
recorded. 
TABLE V CATCH IN REI ATION TO LENGTH 
OF MAIN LINE. 
Length of main line 
met.rAs fms 
9.1 
18.3 
27.4 
36.5 
45.7 
54.8 
5 
10 
15 
20 
25 
30 
No of fish caught 
47 
198 
220 
196 
32 
15 
It would be clear from the above 
table that maximum catches were recorded 
when the length of the line was between 
18.3 m and 36.5 m. Lines with length 
exceeding the above range proved to be 
less effective. 
Effect of depressor: Metal stabilizers 
are commonly used by the trolling vessels 
in California particularly in a rough sea. 
The device has been subsequently used 
as a measure to ensure sinking of· the Jure 
below the water surface. Such depressors 
or diving boards have a hydrofoil shape 
and are usually constructed with a light 
wood. (Isouli and Kawakami 1951). The 
Japanese wooden stabilizers (Text Fig. 4) 
were tried in the course of the present 
study. 
Table VI shows the analysed data 
recorded. 
TABLE VI 
With 
depressor 
Without 
depressor 
No of operations 
Total no of lines used 
Trolling time 
No of seer caught 
No of tunny caught 
Others 
Total catch 
32 
29 29 
84 100 
149.2 hrs 149.2 hrs, 
184 184 
201 164 
2 6 
387 354 
STABILISERS 
Text Fig. 4. Details of Japanese wooden 
Stabilisers. 
The lines rigged with depressor landed 
more catch of particularly tunny. 
Efficiency of different lures: Tables 
VII (a) and (b) show efficiencies of the 
different lures experimented with. 
It would be seen from Table VII (a) 
that whale bone jig is extremely effective 
for both tunny and seer. Cuttle fish jigs 
also landed seer in good numbers but the 
jig was damaged very easily. The octopus 
jig and rubber worm baits were less 
effective compared to others. 
White and green coloured feather jigs 
and jigs with combination of red and 
white feathers landed the maximum catch. 
Red and yellow coloured feather jigs were 
next in order of efficiency. Crimson and 
blue coloured jigs were inferior. 
Data presented in Table VII (b) 
would show that colour of feather had 
apparently no effect on the catches of 
tunny. 
FISHERY TECHNOLOGY 
< 0 
t"' 
< 
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~ 
-
...... 
\0 
0\ 
\0 
t;.J 
t;.J 
Type of jig 
Feather jig 
TOTAL 
Whale bone jig 
Cuttlefish 
Octopus 
Rubber worm baits 
TOTAL 
TABLE VII a 
Colour of jig 
White 
Red 
Red & White 
Green 
Yellow 
Blue 
Crimson 
White 
Pink & White 
-rink & White 
Green 
Red 
Yellow 
Blue 
NOTE: 
COMPARATIVE SEER CATCHES LANDED BY DIFFERENT TYPES OF JIGS. 
Total no of days Total no of days Total no Ratio Average no of 
operated fish hooked fish hooked bja fish hooked per day 
(a) (b) (c) c/a 
29 20 83 0 69 3.03 
36 22 83 0.61 2.31 
10 6 48 0.60 4.80 
31 22 77 0. 71 2.49 
30 18 63 0.60 2.10 
21 9 31 0.43 1.47 
13 6 24 0.46 1.85 
170 103 414 0.61 2.43 
14 12 118 0.86 8.43 
3 2 1l 0.67 3.67 
3 3 3 1.00 1.00 
11 3 7 0.27 0.64 
8 1 2 0.13 0.25 
9 3 4 0.33 0.45 
11 1 1 0.09 0.09 
39 8 14 0.21 0.36 
Days on which Seer was not hooked are not includedin the Table. 
w 
~ 
'"Ij 
-Ul ::r: 
trl 
:;::::1 
...:: 
..., 
trl (") 
::r: 
z 
0 
r 
0 
Cl 
...:: 
Type of jig 
Feather jig 
TOTAL 
Whale bone jig 
Rubber worm bait 
jig 
TALE VII b COMPARATIVE TUNNY CATCHES LANDED BY DIFFERENT TYPES OF JIGS. 
Colour of jig Total no of days Total no of days Total no Ratio Average no of 
operated fish hooked fish hooked b/a fish hooked per day 
(a) (b) (c) cja 
White 20 14 61 0.70 3.05 
Red 19 12 54 0.63 2.84 
Red & White 2 1 6 0.50 3.00 
Green 18 12 66 0.67 3.66 
Yellow 18 11 69 0.61 3.83 
Blue 20 9 52.5 0.45 2.63 
Crimson 14 7 56 0.50 4.00 
111 66 364.5 0.50 3.29 
White 5 3 8.5 0.60 1.70 
Green 
Red 2 0 0 0 0 
Yellow 
Blue 
NOTE: Days on which tunny was not hooked are not included in the Table. 
Time of hooking: The no. of fish 
caught in every hour was recorded and 
graphically represented in Text Fig. 5. 
0 200 
~ 
01110' 
0 
%160 
:X: 
1.1'1 
u:: 140 
1!. 
0120 
6 
ZIOO 
..J 
~80 
0 
... 40 
40 
.... ~~TUNNY 
---sEER 
~TOTAl. SEER FOR TWO SEASON$, 
Oil 10 II (Nd~N) 13 14 15 16 HRSI, 
TIME HOOKED 
Text Fig. 5. Graph showing the variation 
of catch in different hours. 
As per the figure there is progressive 
increase till 11 A. M. reaching the peak 
between 10 A. M. and 11 A. M. 
Observation on the stomach content: 
The gut contents of 41 seer and 30 tunny 
were observed and qualitative analysis was 
also made. It is interesting to note that 
about 49% of the seer and 30% of tunny 
had empty stomachs. It is also recorded 
that tunny and seer are generally fed on 
pelagic fishes such as sardines, whitebaits, 
mackerel, and cuttle fish. 
Table VIII shows that seer and tunny 
catches are more when the surface water 
temperature is 29° and 30°C. Observations 
VoL VI No. 1 1969 
TABLE VIII CATCH IN RELATION TO WATER 
TEMPERATURES 
~-----.. ---·---
Temperature No. of No. ->f Other Total 
oc seer tunny fish 
27 10 10 
28 66 30 2 98 
29 157 75 2 234 
30 139 86 2 227 
31 10 12 
-~-.=--~----~=~-.. 
on certain other materiological factors 
show that seer was caught more on sunny 
days than cloudy days and when the turbi~ 
dity of the water ranged from 1 to 9 
fathoms. 
REFERENCES 
Ayyangar, S. R. 1922 Madras Fish Bull 
15: 63~66. 
Bates, D. H. 1950 U. S. Fish & Wild 
Life Service Fishery Leaflet JS: 1-32. 
Chapman, W. M. 1946 California Fish 
& Game 32, 4: 165-70. 
Hornell, J. 1937 "Fishing Methods of 
Madras Pre~idency." 
XXVIII, 1: 40. 
Tsouti, N. and Kawakami, T. 1957 Me~ 
moirs of the College of Agri Kyoto 
University. 76: 1-8. 
Koyama, T. 1959 Modern Fishing gear 
of the world: 567-70. Fishing News 
Books London. 
Milne, D. J. 1955 Progress report of the 
Paciflc coast stations, 103. 
Scofield W. L. 1956 Fish Bulletin No. 
103. State of California Dept. of Fish 
and Game. 
Welsch, J. P. 1950 Territorry of Hawaii 
Spl. Bull. 2. 
Wigutoff, N. B. 1950 U. S. Dept: of 
Interior, Fish & Wild Life Service 
Fishery Lea{Jet 387; 1-8. 
35 


On the troll line investigations off Cochin during five fishing seasons. Pt. 1. Investigations during 1960-61 and 1961-62 seasons

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On the troll line investigations off Cochin during five fishing seasons. Pt. 1. Investigations during 1960-61 and 1961-62 seasons

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