Identification of Potential Fishing Zones Using Remote Sensing and Gis Techniques Along the Kilifi Coastline

Abstract

Marine fishing is a major economic activity along the Kenyan coast which supports the livelihoods of vulnerable and marginalized communities and provides a source of food. Increased fishing pressure in the near shore waters has led to reduced fish catches and a decrease in the average size of fish. The fishers lack accurate information on identification of fishing grounds and rely on traditional methods, resulting in increased operational costs, time and effort. This study seeks to identify Potential Fishing Zones (PFZs) in Kilifi Territorial and EEZ Waters using Remote Sensing (RS) and GIS techniques. The objective is attained through identification, acquisition and analysis of satellite derived parameters that influence the distribution of marine fisheries e.g. Sea Surface Temperature (SST) and Chlorophyll-a (Chla) Concentration, from the MODIS-Aqua satellite. Total fish catch data is also incorporated in the study. PFZs were identified through detection of oceanic frontal features from the satellite imagery using the Single Image Edge Detection (SIED) algorithm and validated using Catch Per Unit Effort (CPUE) values from georeferenced longline fishing data. Maximum CPUE values of 0.1726 in April, 0.1815 in May, 0.1518 in June, 0.1667 in July and 0.2560 in August were observed in the identified PFZs and surrounding areas. These values were above average against mean CPUE values of 0.1142, 0.1153, 0.1349, 0.1390 and 0.1234 for the respective months. More PFZ areas were identified in the EEZ waters compared to near shore waters. Favourable oceanographic conditions were also extracted from the high CPUE value areas for future research. The study has demonstrated a cost-effective alternative method for the identification of potential fishing grounds / zones that can assist fishers reduce fishing search times, cost and effort while increasing catch quantities. This approach can be applied on near real time satellite derived data for distribution of PFZs to fishermen for informed decision making. Exploration of the rich EEZ waters needs consideration to ease fishing pressure on near shore waters.