Trawling effort distribution and influence of vessel monitoring system (VMS) in Malindi-Ungwana Bay: Implications for resource management and marine spatial planning in Kenya

Abstract

Bottom trawling is a common fishing method for harvesting demersal marine resources such as prawns and ground fish species. However, bottom trawling is known to have negative impacts on marine ecosystems and several measures have been suggested to sustainably manage the fishing method including, mapping trawling pressure and restricting its use away from fragile marine ecosystems. In this study, we map spatio-temporal distribution of trawling effort using 8900 trawls obtained from logbook statistical data and consequently evaluate the effectiveness of a Vessel Monitoring System (VMS) and a Prawn Fisheries Management Plan (PFMP) in the Malindi-Ungwana Bay, Kenya. The PFMP and VMS aimed at restricting prawn trawling to areas beyond 3 nm from shoreline since 2010 in order to reduce conflict with artisanal fishers. Results show spatio-temporal adjustments in the distribution of fishing effort and catch rates of prawns following regulatory changes in the bay. Encroachment in no-trawl areas occurred gradually between 2011 and 2017 with some years (2013, 2016) depicting over 50% of fishing effort in the no-trawl areas. Trawling within the restricted zone produced higher catch per unit effort (CPUE) of prawns compared to fishing outside the zone. Introduction of VMS in 2017 led to a significant reduction of fishing effort in no-trawl area of about 80% by 2018. The change in fleet behaviour in the bay after introduction of the VMS, provides important insights on how marine spatial planning and technology could be applied to enhance compliance with fishing area regulations, reduce resource use conflicts and promote sustainable fisheries.