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International Journal of Marine Science 2015, Vol.5, No.7, 1-4
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4
are usually transparent and have low production and
it’s obvious that light colors are less visible in this
waters. This condition is taken place for dark color in
trophic and deep waters.
Mesh size is an important issue in gillnet efficiency. A
specific mesh size catch specific length group more
than the others (Hosseini, 2003). Determining an
appropriate and efficient mesh size to catching various
species in water reservoirs seems to be impossible.
Gillnet has high diversity and by-catch (Gerami et al.,
2014). Local fishermen believe that nets with smaller
meshes have the best efficiency in catching. Result
showed that economic diversity index of 10 cm (STR)
mesh has the best condition in relation to Simpson
diversity index versus the two other mesh size in this
study. When mesh size changed from 5.1 to 15.2 cm
(STR), catching valueless species is reduced and
selectivity is optimized (Jester, 1977). Hosseini (2003)
reported that among 4 experimental mesh sizes (237,
215, 197 and 170 mm STR), net with 237 mm (STR)
mesh size has more better efficiency of catching
Yellowfin tuna (
Thunnus albacares
) in Sistan and
Balouchestan waters. In addition, Faife (2003) stated
that the mean lengths of cod increased with mesh size
of gillnet (6, 7, 8 and 9cm STR). Figure 4 also showed
that 10 cm (STR) mesh size has the highest diversity
and catch composition rather than the other meshes.
Results show that catch with green net with 10 cm
(STR) mesh size in Khouzestan waters is more
economic than blue, white, 3.75 and 6 cm (STR) mesh
sizes nets. It’s important to note that frequency of
various species in this study was ignored and
catchability of fishing gears for all species was
assumed equal. In addition, the process of catch such
as wedging, snagging, and entangling was not
considered in this study. Future researches can
evaluate behavior of various species against different
colors of net in experimental condition.
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