The 7” inch mesh size harvest Nile perch fish with size range more than the slot size in place i.e 50 to 80cm therefore there is need to revise the slot sizes based on the selectivity of the mesh sizes.
Gillnets are nets made of multifilament nylon strings of varying thickness and mesh size. The gear has been in existence since the ancient times whereby fishermen used cedar canoes and natural fiber nets with stones attached to the bottom to act as sinkers and planks to act as floaters this aided the net to hang straight in water. Gillnets were first introduced into the Kenyan waters in 1905. According to the 2016 Lake Victoria frame survey, the total number of gillnets has increased by 2.1% from 188,984 in 2014 to 192,987. 76,731 of these were undersized (< 5” or 127mm) while 116,256 were legal (> or equal to 5” or 127mm) in contrast to 75,205 undersized and 113,779 legal gillnets in 2014. Monofilaments have also greatly increased from 1,432 in 2014 to 20,842. Gillnets are known as an efficient gear in catching broadly distributed fish and multiple species because they can also be deployed to capture fish in the upper reaches, mid or in lower reaches, making them crucial in fishing operations. Current fisheries management measures are geared towards biodiversity conservation and maintenance of a healthy ecosystem. Therefore it is crucial to understand the selectivity parameters for sustainable and effective management of fisheries. Gillnet selectivity studies are vital for assessing the effects of fishing on recruitments, and ensuring juveniles are protected sufficiently to grow to sexual maturity to reproduce to replace lost populations. To protect small and juvenile fish, the mesh size of commercial gillnets must be strictly regulated. The gillnet selectivity of most freshwater fish is poorly known. The aim of this study was to assess the selectivity of gill nets on fish catches in Lakes Victoria and consequently inform fisheries management. The study was conducted in 9 across Lake Victoria Kenya and the gillnet selectivity models produced from the findings showed that gillnets were best selective from mesh size 7” for Nile perch and 5” for Nile tilapia. The 7” inch mesh size will harvest fish with size range more than the slot size regulation of 50 – 80cm total length. Therefore, there is need to revise the current slot sizes. Illegal use of mesh sizes still threatens the two fisheries and there is still a need for enforcement on the recommended mesh size from this study. READ MORE