Title: The development and effects of the gillnet mesh size regulation on Lake Victoria, Uganda. Case of the Nile perch fishery.

Prior to the introduction of Nile perch various selectivity studies have been undertaken to establish the minimum mesh size regulation of gillnets ranging from 5 inches to the currently emphasized 7 inches as per the 2009 council of ministers’ directives. However, few studies on the minimum mesh regulations have been carried out to show how the fishery has developed in relation to the regulation. Therefore, the study employed various statistical tests in SAS to relate development and effect of gillnet mesh size effect on the landed catch by fishers based on craft using engines (motorized) and paddles. Using Catch assessment studies, the data were sorted according to craft using gillnets resulting in 10800 samples for motorized craft and 8021 cases for paddled craft over a period of 8 years adjusted to a linear scale to represent a period from 2005 to 2015. Study findings indicated the growing use of motorized craft over the past decade with 90% of their nets above the minimum mesh size 5 with a concentration on mesh size 6 since 2005, and a growing increase in the use of 5.5 inches since 2010. Their estimated catches, however, indicated declines; from 30kg of Nile perch per boat sampled in 2005 to 19 kg in 2015 and a corresponding decline in CPUE from 3 kg per hour to less than 2 kg per hour in 2015. This in turn has led to an ever-increasing price premium with the large sized fishes earning 4 times the price per kilogram compared to the small sized fishes. This was not the case with the paddled craft who were considered uncommon in the fishery. However, there was a steadily growing composition of meshes below the minimum from 31% in 2005 to 69% in 2015. This paper therefore, provides a baseline on understanding how imposing minimum size regulations affects harvesting patterns in the fishery and fisher’s behaviour as they exclusively target large sized species. Therefore, management decisions on future selectivity studies should consider societal and economic implications that might trigger situations such as size selective fishing.