Recent Trends of Small Meshed Gillnet Fishery in the West Coast of Sri Lanka
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Date
2013
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Uva Wellassa University of Sri Lanka
Abstract
Marine fish is the main animal protein source of Sri Lankan nation. With the increasing of the
population, the demand for marine fish has been increased. The coastal subsector is the major
contributor to the total marine fish production in Sri Lanka and small pelagic fish resources
contributes in the coastal catch in a higher proportion. At present, coastal fishery resources of
Sri Lanka have to be properly managed as in the case for most other marine fisheries in tropical
developing countries. The fishing pressure on the coastal fish has increased and small pelagic
fish in the coastal waters are subjected to high fishing pressure (Haputhantri, 2004). The
increased fishing pressure on small pelagic resources has adversely impacted on the sustainable
utilization of the resources. Therefore, for the sustainability of small pelagic precautionary
measures should be addressed. The small pelagic are mostly harvested by small mesh gillnets.
The present study aims to investigate the west coast small mesh gillnet fishery by using
commercial gillnet fishery data in order to provide a platform for sustainable utilization of the
resources.
Methodology
Catch and Effort data and information with regard to small mesh gillnet fishery operations such
as spatial data (fishery districts, ports etc.), temporal data (year, month etc.) and operational data
(fishing depth, true fishing time etc.) which were collected by NARA Marine Biological
Resources Division from the west coast (Chilaw, Negombo and Kalutara fisheries districts) for
the period 2000 – 2011 was used for present study. Also, information was obtained by
interviewing the enumerators of small pelagic fishery data collection programme of NARA. The
data used for this audit was confined to the Fibre Reinforced Plastic (FRP) boats since small
pelagic fish are mostly captured in the west coast by FRP boats. Data were analyzed using
Microsoft Office Excel and Minitab 14 Statistical Software.
Results and Discussion
Three types of coastal vessels (i.e. non mechanized traditional crafts, mechanized traditional
crafts and Fibre Reinforced Plastic boats referred as FRP boats) are operated in the west coast
gillnet fishery. Traditional non-mechanized crafts are usually operating in shallow coastal
waters within the 5 m to 25 m depth range whereas FRP boats are frequently operating within
15 to 60m depth range. The engine power of a FRP boat may vary between 10 to 30 hp, but
most frequently used range is 15 and 25 hp. The total number of FRP boats in the west coast
has considerably increased replacing traditional boats which possessing better facilities (high
holding capacity, ability to access in the deeper waters etc.) when compared with traditional
crafts.
According to the study, around 60% of total fishing effort on coastal pelagic resources in the
study area in terms of number of boat days is provided by small meshed gillnets along. In
addition, around 28% of total fishing effort is provided by small meshed gillnet and hand line
gear combination. A wide range of mesh sizes are being used in the commercial gillnet fishery
but, small meshed gillnets with mesh sizes between 1″ (25.4 mm) to 2″ (50.8 mm) are widely
used by FRP boats in the west coast targeting small pelagic. Gillnets with mesh sizes ranging
from 9/10″ (22.86 mm) to 1½″ (38.1 mm) are frequently used for catching clupeids including
Ambligaster sirm, Sardinella longiseps, Sardinella albella, etc. Smaller mesh sizes bellow 9/10″
(22.86 mm) are normally used in the west coast for catching Stolephorus spp.
One fishing trip per day normally takes place in the west coast. The duration of one fishing trip
varies between 3 to 8 hours and the duration for which gillnet in operation is normally 0.5 to 3
hours. There is a slight increment in the true fishing time (the time which gillnets are actually
operated) for the period considered under this study. Accordingly, it seems that fishermen tend
to stay more time at the sea for searching and capturing fish.
In the west coast, FRP boats are operated in a wide depth range, where it may vary between 5 to
90m. Depth of fishing has been varied between 14 to 32m during the period of 1983 to 1984
(Karunasinghe and Fonseka, 1985). Further, the depth of fishing has been varied between 6 to
70m during the period of 1995 to 1997 (Karunasinghe et al., 2000). According to the present
study, the fishing depth range has become much wider and boats trend to go and fish in deeper
waters. Moreover, an increasing trend in the average depth of fishing in the west coast was
observed for 2000-2011 period.
Number of gillnet pieces used per gillnet operation was 9 to 24 during the period 1995-
1997(Karunasinghe et al., 2000). However, this has considerably increased now upto3 to 42
gillnet pieces of gillnets per fishing operation per FRP boat. A clear increasing trend in the
gillnet usage was observed for 2000-2011 period. In general the best fishing season in the west
coast is at the latter part of the south west monsoon and higher catches are obtained in August
and September &The period of January to March is considered as the lean fishing season
according to the fishery data collected by NARA.
The major target fish group in small pelagic fishery in the west coast is clupeids. In general, this
group includes Ambligaster sirm and Sardinella spp. Ambligaster sirm is the dominant species
in the catch over the considered period of time and it provides around 46% of the total catch in
the west coast. The contribution of each sardine species individually is relatively lower
(i.e.Sardinellagibbosa-11%, Sardinella longiseps- 9%, Sardinella albella - 6% and Sardinella
sindensis- 0.0008%) However, as a group these species are very important since they contribute
around 26%in the total catch.
Since there is a considerable variation in the number of net pieces used in the study area CPUE
was computed in two ways: CPUE in terms of catch in kilogram per boat per day basis and
CPUE in terms of catch in kilogram per net piece per day basis. The annual CPUE in terms of
kilogram per net piece per day has varied on a range of 2 to 3.5 kg/net piece/day and a clear
declining trend in the CPUE in terms of kilogram per net piece per day was observed. CPUE in
terms of kilogram per boat per day seemed to have fluctuated from 2000 to 2011 in arrange of
40-70 kg/boat/day. Since there is a reduction in the CPUE in terms of kilogram per net piece per
day, fishermen tend to use more net pieces to increase their catch per boat.
Description
Keywords
Animal Sciences, fish Industry, Fishery, Fish Marketing