A Review of Trawl Selectivity Studies carried out along Indian Coast

Abstract

Though trawling contributes significantly to landings
in India, issues like bycatch which comprises
of juveniles of commercially important species and
impacts to the sea bottom are often implicated.
There has been a significant increase in the capacity,
both in terms of number and in terms of the size
of trawlers during the last decade in India. Technical
measures like closed season and gear modification
are proposed in the Marine Fisheries Regulation
Acts of different states. A large number of Bycatch
Reduction Devices (BRDs) have been field tested
along the Indian waters which have proven to be
effective for exclusion of juveniles. Among the
different BRDs, square mesh codends are the most
popular, due to its conceptual simplicity and ease
of modifications of the existing codends. A large
number of studies related to the selection parameters
for trawlnets of different mesh sizes, are
reported from India. This study attempts to review
the results of these studies with respect to methods
used for deriving the selection parameters. It is
observed that variation exists in the methodology
adopted for deriving selection parameters among
the reports. None of the studies have analyzed the
operational factors that affect selectivity of the gear
and similarly the survival of the escapees from the
BRDs is not quantified. Though preliminary in
nature, the selectivity estimates available now are
good enough for coming out with proposals
regarding the optimum mesh required for individual
species. Inclusion of factors affecting selection
into the studies, biological parameters of the
targeted species and modeling approaches will help
in refining the results already available and a development and adoption of a standard protocol for trawl selectivity studies will help significantly.