The suitability of HDPE yarn and HDPE twine in place of nylon for gill nets has been studied. As regards total catch nylon gill net is found to be better than HDPE

nets. However, statistical analysis of the catch in respect of quality fishes shows that HDPE yarn nets are equally efficient as nylon nets

Boopendranath, M.R.

Kunjipalu, K.K.

Subramania Pillai, N.

Aquatic Commons

Studies on the Suitabil HDPE Materials for CUI ets 
N. SUBRAMANIA PILLAI*, M. R. BOOPENDRANATH* AND K. K. KUNJIPALU* 
Research Centre of Central Institute of Fisheries Technology, Veraval - 362 268 
The suitability of HDPE yarn and HDPE twine in place of nylon for gill nets has 
been studied. As regards total catch nylon gill net is found to be better than HDPE 
nets. However, statistical analysis of the catch in respect of quality fishes shows that 
HDPE yarn nets are equally efficient as nylon nets. 
Gill net fishing for hilsa, pomfrets etc. is 
one of the popular fishing activities in the 
Saurashtra region. Panicker et al. (1978) 
studied the selectivity of gill nets with 
reference to twine size, mesh size and ratio 
of take up for hilsa and pomfrets. Again 
Kunjipalu et al. (1984) studied the effecti-
veness of coloured webbing on the catch of 
hilsa and pomfrets. All these years nylon 
twine (polyamide) of different specifications 
has been exclusively used for the gill net 
fabrication. The HDPE materials, which 
was introduced to fishing industry during 
early 60's made very little impact on the 
gill net fishery till the end of 70's. The 
increased cost of polyamide materials makes 
the operation of the gill net fleet more 
and more expensive. This necessitated 
the need for introducing a cheaper material 
like HDPE in place of nylon for gill net 
fabrication in recent years. Pajot (1980) 
and Radhalakshmi et al. (1985) attempted 
to study the effectiveness of HDPE twine 
and tape twisted twines, for large meshed 
gill nets and mackerel gill nets respectively. 
The present investigation was initiated to 
study the suitability of HDPE yarn and 
thinner HDPE twine for gill nets. 
Materials au.d Metbods 
Nylon multifi.lament twine (210/2/3), 
HDPE yarn (single) and HDPE twine (multi-
ple yarn) were selected for experimental net 
(Table 1) as these materials were predominan-
tly used for fabrication of local gill nets. 
The variation in the diameter of the three 
materials has not been taken into considera-
* Present address: Central Institute of Fisheries Tech-
nology, Cochin - 682 029 
Vol. 26, 1989 
tion. The detailed specifications of the giH 
nets are given in Table 1. The properties 
of each material used for the above gill nets 
are given in Table 2. 
Experimental :fishing was carried out 
during 1985 and 1986 seasons from the 
departmental vessel. All the three types of 
nets namely, HDPE yarn, twine and the con-
trol nylon were operated as bottom drift 
on each day during day time at the depth 
range of 25 to 35 m off Veraval. The fish 
catch in number and weight in respect of 
each type of the net was recorded. 
Results and Discussion 
Th:i.rtythree viable observations were made 
for these studies. The details of catch in 
respect of each type of net are given in 
Table 3. The data were analysed statistically 
using the 't' test in two comparison, one 
between the HDPE yarn versus control 
nylon nets and another between HDPE 
twine versus the control nylon nets, in respect 
of quality :fishes and total catch separately 
in order to critically evaluate the new mate-
rial. The details of the analysis are given in 
Table 4. 
The catch rate as per Table 3 shows that 
the general performance of nylon gi.H net 
are found to be better than the other two 
materials. But the statistical analysis of 
the data in respect of the quality :fishes com-
prising hilsa, pomfret, seer, silver bar and 
razor edge shows that there is no significant 
difference in the performance between the 
nylon nets and HDPE yarn nets. In other 
words the HDPE yarn gill nets are equaHy 
efficient in the catching rate when compared 
2 N. SUBRAMANIA PILLAI, M.R. BOOPENDRANATH AND K. K. KUNJIPALU 
Table 1. Details of the gill nets 
Material 
Specification 
Mesh size 
Unit size 
Nylon 
216/2/3 
120 mm 
500 x 50 meshes 
0.50 
HDPE yarn 
Single yarn 
120 mm 
500 x 50 meshes 
0.50 
HDPE twine 
1 x 3 multiple yarn 
120 mm 
500 x 50 meshes 
0.50 Hanging coefficient 
Head rope } 
Foot rope 6 mm dia HDPE rope 
Floats 
Sinkers 
Foam plast 150 x 20 mm size 5 to 6/uni~ 
Cement sinker of 500 g each 4 to 5/umt 
Average area of net 
operated per fishing day 
(rn2) 1602 
Table 2. Properties of the materials used 
for the gill net fabrication 
bia, mm 
'Nt/m, g 
Runnage m/kg 
Strength kg 
Stretch% 
HDPE HDPE 
yarn twine 
0.270 
0.059 
17,000 
L6 
36.00 
0.410 
0.110 
9,090 
2.10 
50.00 
Nylon 
0.620 
0.155 
6,450 
8.75 
26.60 
to control nylon nets. But in the case of 
HDPE twines there is significant difference 
with the nylon net at a probability of 0.05, 
l;ience found to be unsuitable. The analy-
~is of the total catch including miscellaneous 
P.shes shows that there is significant difference 
in the catching rate between nylon and HDPE 
yarn nets and nylon and HDPE twine at a 
1645 1428 
probability of 0.05 and 0.01 respectively. 
But generally the catch of miscellaneous 
fishes in gill nets is not given much importance 
due to its lesser value whereas the catch of 
high cost quality fish is taken into account 
to evaluate its efficiency. Accordingly the 
:findings indicate that HDPE yarn is a suitable 
substitute for the costly nylon. 
EventhoughTable 3 shows a high preference 
of hilsa catch in nylon net and pomfret 
catch in HDPE yarn net, it has no rele-
vance statistically. While considering the 
cost of the two materials, the HDPE yarn 
costs 35 % less than nylon and hence the use 
of this material for gill nets fabrication will 
substantially reduce the total investment 
for a gill net fleet and thereby makes fishing 
more profitable. Considering all these 
factors the authors are of the opinion that 
Table 3. Total catch of each variety of fish in each type of net calculated on the basis for l 000 m 2 
area for each type of net 
Fish caught Nylon HDPE HDPE 
net yarn net twine net 
kg kg kg 
A. Quality fish 
Hilsa spp; 10.721 1.972 2.464 
Pomfret. ( Pampus spp., 
Parastromateus spp.) 4.876 14.991 4.015 
Seer ( Scomberomorus spp.) 2.874 l.050 1.332 
Silver bar ( Chirocentrus dorab) 2.587 2.813 2.494 
Razor edge (Pellona spp.) 2.641 2.136 1.357 
Total 23.6)9 22.962 11.662 
B. Other :fishes 30.741 21.918 14.248 
Grand Total 54.440 44.880 25.910 
FISHERY TECHNOLOGY 
SUITABILITY OF HDPE MATERIALS FOR GILL NETS 3 
Table 4. Details of statistical analysis 
Nylon 
A. HDPE yarn with nylon 
as control 
Total catch 0.3870 
Quality fish 0.1887 
B. HDPE twine with nylon 
as control 
Total catch 0.3870 
Quality fish 0 i887 
* Significant at the probability of 0.05 
*** Significant at the probability of O.Ol 
HDPE yarns can be successfully introduced 
in the gill net fishing industry. 
The authors are thankful to Shri M.R. Nair, 
Director, Central Institute of Fisheries Technology, 
Cochin for permission to publish this paper and to 
Shri P.A. Panicker, Scientist S-3, CIFT for critically 
going through the manuscript and suggesting neces-
sary modifications. Thanks are also due to S/Shri 
J. B. Paradua and K.V. Dholia, Technical Assistants 
for their active participation during the field trials. 
References 
Kunjipalu, K. K., Boopendranath, M. R., 
Kuttappan, A. C., Subramania Pillai, N., 
Gopalakrishnan, K. & Kesavan Nair, 
A. K. (1984) Fish. Technol. 21, 51 
Vol. 26, 1989 
Mean log-transferred value 
HDPE Difference Calculated 
yarn/twine t 
0.2828 0.1042 2.0865* 
0.1499 0.0388 0.8435 
0.2455 0.1415 3.7703*** 
0 114 0 0 73 2.1930'~ 
Pajot, G. (1980) Development of Small 
Scale Fisheries BOBP/WP/S 
Panicker, P.A., Sivan, T. M., Mhalathkar 
H. N. & George Mathai, P. (1978) 
Fish. Technol. 15, 61 
Radhalakshmi, K. & Gopalan Nayar, S. 
(1985) in Harvest and Post-harvest 
Technology of Fish. (Ravindran, K., 
Unnikrishnan Nair, N., Perigreen, P.A., 
Madhavan, P., Gopalakrishna PiHai, 
A. G., Panicker, P. A. & Mary Thomas, 
Eds.) Society of Fisheries Technologists 
(India), Cochin 


Studies on the suitability of HDPE material for gill nets

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Studies on the suitability of HDPE material for gill nets

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