Assessment of the impact of Light Emitting Diode (Led)- Fitted Gill Nets on Sea Turtle and Fish Catch in the Coastal Waters of Mankoadze, Ghana

Abstract

This study investigated the impact of light emitting diode (LED)-fitted gill nets on sea turtle and fish catch in the coastal waters of Mankoadze, Ghana. The study also assessed the artisanal fishery of the area and quantified the annual rate of sea turtle by-catch in the artisanal fishery. The methods used included interviews, analysis of fish landing data from Fisheries Commission and field data collection. The results indicated that set net was the most dominant fishing gear used in the coastal waters of Gomoa and Effutu, and comprised 35.6% of the total gears. Data from Fisheries Commission indicated that a total of 74 fish species belonging to 37 families were caught between 2001 and 2015 in the artisanal fishery. There was an increase in the number of artisanal fishermen and canoes in the study area by 13.0% and 27.5% respectively from 2001 to 2013, resulting in continuous decline in fish catches from 29,697.89 tonnes in 2001 to 7,213.66 tonnes in 2013. Catches of the common fish species (Sardinella spp., Engraulis encrasicolus and Euthynnus alletteratus) were highest during the months of July to October. The results also indicated that, irrespective of species, sea turtles were captured as by-catch in artisanal fishing gears at an average rate of 4 turtles per canoe per year. The leatherback (Dermochelys coriacea), green (Chelonia mydas) and the olive ridley (Lepidochelys olivacea) were the three main species captured. Deployment of LED lights on fishing nets resulted in a significantly lower (t=3.65, p<0.05) turtle by-catch in nets using the LED lights (4.6±1.2 turtle/100 m net/12 hrs) than in the nets without LED lights (6.5±2.1 turtle/100 m net/12 hrs), but did not significantly (t= 2.14, P>0.05) influence the fish catch. It was concluded from the study that LED light is an effective turtle by-catch reduction device. A recommendation for further studies on behavioural adaptation of sea turtles to LED light has been made.