A note regarding conditioning simulation trials for data-poor management strategy evaluations

Abstract

A boat-based survey was conducted in the Tefé river and lake (Brazil) in December 2013, during the transitional water period. A combination ofstrip-width transects parallel to the river, lake-margins and confluences, and cross-channel line transects in the lake, were used to cover a totaldistance of 670 linear kilometres of the dolphins’ habitat. A total of 383 groups of Amazon river dolphin and 124 groups of tucuxi were observed.Group size, density and abundance estimates were obtained per species and habitat (tributary, lake-margin and confluence). Group sizes rangedfrom one to six individuals for the Amazon river dolphin and from one to eight individuals for the tucuxi. The abundance of river dolphins washigher for the Amazon river dolphin (911, CV = 0.15) than the tucuxi (511, CV = 0.26). Higher densities were found in the lake-margin and tributaryfor the Amazon river dolphin and in the confluences for the tucuxi. Lake-margins, confluences and tributaries are therefore proposed as criticalhabitats for the conservation of river dolphins in central Amazonia. The Tefé lake is identified as an area of concern due to a high number of humanstressors such as boat traffic, fishing and habitat degradation.