V shaped all steel boards, with their inherent stability to tide over obstacles and mud, interchangeability of starboard and portside boards are found to be superior to conventional flat rectangular boards for bottom trawling. These are cheaper in construction, offer less resistance and give longer service. Comparative trials  with the two types of boards showed significant difference in tension between the boards but not in catch or horizontal opening

Boopendranath, M.R.

Krishna Iyer, H.

Kunjipalu, K.K.

Kuttappan, A.C.

Aquatic Commons

n parative Efficiency of 'V' Shaped and 
gul Otter oards Trawling off 
Veraval, North West Coast India 
K. K. KUNJIPALU, M. R: BOOPENDRANATH, A. C. KUTTAPPAN* and 
.H. KRISHNA IYER * 
Veraval Rr::search Centre of Central Institute of Fisheries Technology, Veraval ~· 362 265 
V shaped all steel boards, with their inherent stability to tide over obstacles and 
mud, interchangeability of starboard and portside boards, are found to be superior 
to conventional flat rectangular boards for bottom trawling. These are cheaper in 
construction, offer less resistance and give longer service. Comparative trials with the two 
types of boards showed significant difference in tension between the boards but not in 
catch or horizontal opening. 
Flat rectangular otter boards of wood 
and steel constructions are the exclusive 
type in use as the horizontal spreading device 
for commercial otter trawling along Saura-
shtra coast. The relative efficiency of differ-
ent types of otter boards like oval, horizontal, 
curved and flat rectangular have been stu-
died by Kuriyan et al. (1964), Mukundan 
et a!. (1967), Narayanappa (1968), Satya-
narayana & Mukundan (1963) and Desh-
pande et a!. (1970) at Cochin/Kaki-
nada/Veraval. The effectiveness of 'V' 
shaped otter boards were studied in Kaki-
nada by Satyanarayana et a!. (1978) 
and the performance is reported to 
be better than vertically and horizontally 
curved otter boards. 
'V' shaped boards of all~steel contruction 
are in extensive use for commercial ttawling 
elsewhere in the world since its introduction 
in Taiwan, Formosa in 1957 by Capt. Loo 
Chi Hu (Anon 1961). The main advantage 
of the design is that it allows the board to 
orientate itself to any position according 
to the force working upon it, thereby 
remaining inherently stable. The board will 
ride over obstacles and mud which would 
spell disaster to an all-flat board (Anon, 
1961). The authors have studied the com-
parative performance of 'V' shaped boards 
*Present address: Central Institute of Fisheries 
Technology, Cochin-682 029 
from a medium size trawler Fishtech viii 
(15.2 m OAL with 165 h. p. engine). 
Materials and Methods 
'V' shaped steel otter boards with an over 
all dimension of 1500 mm length and 890 mm 
breadth and 125 kg weight and flat rectan-
gular boards of wood and steel construction 
described by Kuriyan et a!; (1964) with 
1524 mm length and 762 mm breadth and 
100 kg weight were used for the studies 
(Table 1). Design details of 'V' shaped 
boards are given in Figs. 1 and 2 and Table 4. 
A 32 m large mesh demersal trawl descri-
bed by Kunjipalu et al. (1979) was used for 
the experiments. Double bridles of 5 m 
length were used in combination with the 
nets. The two types of otter boards were 
operated consecutively to give equal chances 
and a statistical rotation was maintained 
throughout the experiments. Fishing opera-
tions were conducted off Veraval during 
1979-1980. 
Twenty five observations were carried out 
.in the depth range of 27-47 m with a scope 
ratio of 1:5 at a trawling speed of 2.5 knots 
per hour keeping the engine r.p.m. at 1250. 
The horizontal spread between the boards 
was estimated by the method of Benyami 
(1959) and Deshpande (1960) and the ten-
sion on the warp was measured by using a 
mechanical tension meter described by 
Satyanarayana & Nair (1965). 
FISHERY TECHNOLOGY 
STUDIES ON OTTER BOARDS 
T7 
Fig. 1. Design details of 1500 x 890 'v' shaped 
otter board (measurements in mm) 
Results and Discussion 
Total catch of 1594 kg and 1921.5 kg were 
obtained respectively in nets with rectangular 
flat and V shaped boards. The operational 
details are given in Table 2 and details of 
catch in Table 3. To ascertain significance 
if any for the type of otter boards on the 
catch, horizontal opening and towing ten-
sion, the data were analysed based on ana-
lysis of variance by converting to logarit-
hmic values. The 'F' values for (1, 24) degrees 
Vol. 21, 1984 
114 
Item No.7. 
H] G.t.Pipe ~~edfl. 12 I ?S I --..._ t • Top late f> 4 [[[]i 
f--200--j 
~ 
12 
Fig. 2. Details of parts (measurements in mm) 
of freedom for horizontal opening, total 
catch, catch of cephalopods, ribbon fish and 
miscellaneous fishes were 1.0, 3.59, 3.05, 
2.64 and 1.71 respectively indicating no signi-
ficant difference with respect to type of boards. 
Except for horizontal opening, the between 
days variation, was significant in the above 
data. With an 'F' value of 9.5, warp ten-
. sion developed by the two boards showed 
significance at 1% level. 
The lower warp tension in spite of increase 
in surface area (9.4%) and weight (25%) 
115 K. K. KUNJIPALU, M. R. BOOPENDRANATH, A. C. KUTTAPPAN AND 
H. KRISHNA IYER 
Table 1. Specifications of otter boards 
Type of otter boards Material Length Breadth Area Weight in 
rnm rnm rnl air, kg 
'V' shaped Steel 1500 890 1.270 125.0 
Rectangular flat Wood and 1524 762 1.161 100.0 
steel 
Table 2. Details of fishing operations 
Type of otter board Trawl Depth Warp No. of Towing Towing Average Warp 
net of length hauls time speed hori- tension 
opera- m h knots zontal kg 
tion spread 
m between 
otter 
boards 
m 
'V' shaped 32m 27-47 135-255 25 25.0 2.5 17.85 591.92 
large 
mesh 
trawl 
Rectangular flat 
" " " " " " 
17.86 609.16 
Table 3. Details of catch 
Type 0f otter board Catch per unit effort (catch in kg/h) 
Quality Ribbon Cephalo- Miscellan- Total 
fish fish pods eous fish catch 
'V' shaped 7.22 33.88 3.54 32.22 76.86 
Rectangular flat 6.50 25.20 2.48 29.58 63.76 
FISHERY TECHNOLOGY 
STUDIES ON OTTER BOARDS 
Table 4. Details of 'V' shaped otter boards 
Description Size 
mm 
Top plate 5 thick 
G.I. pipe beeding 15 diameter 
Centre strip 75 X 12 
Bottom plate 10 thick 
Shoe rod 50 diameter 
Bridle attachment 20 diameter 
Bracket 25 diameter 
Clamps 100 X 12 
Towing plate 75 X 20 
G. I. pipe braces 15 diameter 
of V shaped boards indicates hydro-
dynamic efficiency of V shaped boards. 
This is advantageous for the better utiliza-
tion of the vessel's engine power as it enables 
a higher trawling speed without additional 
increase in engine out-put. The lack of 
corresponding increase in horizontal spread 
commensurate with large surface area indi-
cates the lesser spreading force developed 
by V shaped boards. A better bottom 
(ground) contact with least flying effect is 
essential for stability and efficiency of otter 
boards in bottom trawling. Flat rectan-
gular otter boards required constant ground 
contact and hence make it unsuitable for 
uneven and rocky grounds. If it fails to 
get ground contact the conventional flat 
boards spell dangers like falling flat and 
flying in water which causes instability, 
over spreading of the net mouth and fouling 
of the gear. Moreover in soft muddy 
grounds the conventional rectangular flat 
boards have a tendency to dig into the mud 
(Brett, 1962, Anon, 1974). In contrast, 
slighty smaller ground contact is sufficient 
for 'V' shaped boards to maintain equilibrium 
as the design features make it inherently 
stable. The 'V' section is said to prevent the 
door digging into soft mud and manoeuvring 
is improved. Besides, 'V' shaped boards are 
Vol. 21, 1984 
116 
Length Number Material Wt. 
mm kg 
1500x410 1 M.S. 22 
2500 1 G.I. 5 
1500 1 M.S. 10 
1500 X 380 1 , 46 
1750 1 , 26 
Ring 1 
" 
2 
2450 1 
"· 
8 
200 3 
" 
3 
175 1 
" 
1 
500 2 G.I. 2 
Totalweight per board 125 kg 
efficient in rough and uneven grounds as 
they are able to ride over obstacles and mud 
(Brett, 1962, Anon, 1974). The fishing 
grounds in the inshore waters on the Saura-
shtra coast are rocky and muddy inters-
persed with shell and pebbles. Hence V 
shaped boards are more suitable for trawling 
along the Saurashtra coast. They are more 
suitable for fish trawling in combination with 
demersal trawl for off bottom and demersal 
fishes as the grounds are well known for 
demersal fishes rather than for prawns. 
By effecting slight changes in the present 
design it is possible to have interchangeable 
boards as tried elsewhere (Brett, 1962, Anon, 
1974). This is an added advantage as the 
same board can be used either at starboard 
side or portside by changing the towing 
brackets to avoid uneven wear of the keel 
(Anon, 1974). 
The V shaped all-steel boards are relati-
vely cheaper when compared with the wood 
and steel combination boards and are known 
to give long overall life. 
The authors express their thanks to Dr. C.C. Pan-
duranga Rao, Director C.I.F.T. for permission to 
publish this paper. Thanks are also due to Shri M.S. 
Fernando, Skipper and his crew for the co-
operation rendered during the fishing operations. 
117 K. K. KUNJIPALU, M. R. BOOPENDRANATH, A. C. KUTTAPPAN AND 
H. KRISHNA IYER 
References 
Anon (1961) Wld Fishg. 10 (4), 77 
Anon (1974) Otter Boards, Design and 
Pe1jormance, FAO Fishing Manuals, 
FAO,Rome 
Benyami, M. (1959) Modern Fishing Gear 
of the World (Kristjonsson, H. Ed)p. 213, 
Fishing News (Books) Ltd., London 
Brett, D. (1962) Wld Fishg. 11 (5), 43 
Deshpande, S. D. (1960) . .Indian J. 'Fish. 
7, 458 
Deshpande, S. D., Sivan, T. M. & Rama 
Rao, S.V.S. (1970) Fish. Techno!. 7, 
38 
Kuriyan, G. K., Satyanarayana, A.V.V. & 
Nair, R. S. (1964) Proc. Indo Pacif. 
Fish. Coun. 11 (2), 204 
Kunjipalu, K. K., Kuttappan, A. C. & 
George Mathai, P. (1979) Fish. Tech-
no!. 16, 19 
Mukundan, M., Satyanarayana, A.V.V. & 
Krishna Iyer, H., (1967) Fish. Tech-
no!. 4, 53 
Narayanappa, G. (1968) Fish. Techno!. 5, 15 
Satyanarayana, A. V. V., & Mukundan, M. 
(1963) Indian. J. Fish., 10, 11 
Satyanarayana, A. V. V., Narayanappa, 
G. & Chandrapal, G. D. (1978) Fish. 
Teclmol. 15, 13 
Satyanarayana, A. V. V. & Nair, R. S. (1965) 
Res. Ind. 10, 229 
FISHERY TECHNOLOGY 


On the comparative efficiency of "V" shaped and rectangular flat otter boards for trawling off Veraval, north west coast of India

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On the comparative efficiency of "V" shaped and rectangular flat otter boards for trawling off Veraval, north west coast of India

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