Determination of Gillnet and Hook Selectivity for Caranx heberi Captured off Kanyakumari Coast of India | Chapter 12 | Advances in Applied Science and Technology Vol. 5
The larger carangids are most important
fishery in the coast of Kanyakumari, Tamil Nadu. They are caught by large
meshed gillnets and hooks in these region. However, there is no selectivity
studies conducted on this fishery especially in this coast. The selectivity
nature of every gear is important for managing the fishery as well as for
conservation of resources. Large meshed gillnets having mesh sizes of 13.5 cm,
14 cm, 14.5 cm and 15 cm and Hooks No.5,6,7 and 8 were chosen for determining
the selectivity and fishing
power of the
gears to capture
the larger carangid Caranx heberi of Kanyakumari coast of India. The
catch data were analysed using the software GILLNET (Generalized Including
Log-Linear N Estimation Technique) comprised of the methodology of SELECT
(Share Each Length Class Total)
by fitting various
uni-normal models viz.,
normal scale, normal
location, log-normal, gamma and
bi-normal model. Models were tested using various selectivity parameters like
Model Deviance, Dispersion Parameter and residual plots. Bi-normal model was
found appropriate for gillnet catch data while normal location for hook catch
data despite over dispersion was common in both the fits. The
mesh size of
13.5 cm and
hook No.5 and 6 were
found as optimum size for capturing larger carangid C. heberi.
Comparison of the selective effects of different gears is complex particularly
between selective gears. Further, the mean size of fish caught from one gear to
another gear varies due to various biological factors such as availability,
abundance, age, sex, and size, or environmental factors such as fishing ground,
depth, etc. Selection curves of gillnets and hooks of the present study are
assumed as bell shaped multi-normal and uni-normal in nature respectively. In
this study, hook selectivity data fit appropriately with uni-normal model
despite it is complex in nature in general. It is also opined that fit may
depend on models applied though it is normally influenced by biological behavior
and capturing methods. This study revealed that gillnet yielded obvious size selection range than hooks
in capturing larger carangid, C. heberi of the study area.
Author(s) Details
Dr. A. Balasubramanian
Professor and Head,
Department of Fisheries Resource Management, College of Fishery Science, Muthukur,
Nellore District, Andhra Pradesh, India.
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