Abstract:
Fisheries in Lake Victoria have been threatened by declining fish stocks and
diversity, environmental degradation due to increased input of pollutants,
industrial and municipal waste, overfishing and use of unapproved fishing
methods, infestation by aquatic weeds especially water hyacinth, de-oxygenation
and a reduction in the quantity and quality of water. Remote sensing and GIS
are essential tools in detection of fishing grounds which is important in providing fish sustainability for human beings and allows fishing grounds detection at minimal cost and optimizes effort. This research tends to identify the
most favorable both environmentally and ecologically satisfactory factors
which favor fish breeding and growth. The main aim of the study was to
identify habitat variables that promote fish breeding and growth to maturity
including the extraction of environmental variables from Landsat 8 images
for the study period and using suitability index derived from fishery data. The
study concentrated on establishing suitability ratings in different parts of
Lake Victoria using lake surface temperature and chlorophyll-a levels. The
study was conducted for months; January, May and December 2019 on Lake
Victoria (limited by the availability of recent data). The factors were analysed
and the favorable regions mapped satisfying the conditions for fish breeding.
The output obtained illustrated the availability of suitable and habitable zones
within the lake using satellite imagery and the suitability index. The fish catch
data and satellite derived variables were used to determine habitat suitability
indices for fish during January, May and December 2019. More than 90% of
the total catch was found to come from the areas with sea surface temperature
of 23.0˚C - 28.3˚C and chlorophyll-a concentration between 0.72 - 1.31
mg/m3
. The catch data was used to validate the images. This study indicated the capability of High Satellite Resolution Imageries (HSI) as a tool to map
the potential fishing grounds of fish species in Lake Victoria. The variables
were affected by climatic change factors like rainfall and temperature of the
lake basin and other human activities around the lake and also the species
ecosystem like competition or predation
