Abstract:
The fishing grounds of the multiday longline fisheries of Sri Lanka are identified from
the remote sensed satellite data measurements. The fisheries catch rates of longlines
relevant to the major commercially targeted fish species (Thunnus albacares, Xiphius
gladius and Thunnus obesus) in the Indian Ocean was calculated by the Generalized
Additive Model (GAM) and the Empirical Cumulative Distribution Function (ECDF)
model. The optimum oceanographic conditions of the sea surfaces including the
Temperature (SST), Chlorophyll (SSC), Salinity (SSS), Height (SSH), Eddy Kinetic
Energy (EKE) and the Mixed Layer Depth (MLD) relevant to the target fish species were
analyzed to ascertain the relationship between the catch rates and spatiotemporal
distribution of Potential Fishing Zones (PFZ). The Catch Per Unit Effort (CPUE) varied
in the South–West and North- East monsoon seasons. Four main regions; Bay of Bengal,
Exclusive Economic Zone (EEZ) of Sri Lanka, Eastern and western margins of the
Maldives island EEZ, and the East-Central Arabian Sea in the Indian Ocean were
observed as highly aggregated PFZ. The best fitting models in the GAM analysis
indicates that all the oceanographic parameters influence in different proportions for the
abundance of the fish species. It can be concluded that SST is the primary driving force
of the fish distribution in the ocean. The SSC and SSS indicate that the fluctuating
sensitivities considerably impacts on the fish distribution. Results suggest that the
optimum oceanographic conditions derived for the fish species can be useful for tracking
and predicting the potential fishing grounds in the Indian Ocean. However, the reliability
of model results strictly depends on the fisheries catch data recordings that can cause
errors related to the catch rates and the prediction of fishing grounds.
