On the use of the finetti ternary diagrams to show the species composition of free and fad associated tuna schools in the Atlantic and Indian oceans

Abstract

This paper shows the difficulty to visually to illustrate the variability of the species composition of sampled sets landed by purse seiners in the Indian and Atlantic Oceans. When large numbers of sets have been sampled during the last 30 years, it is still quite difficult to visualize the heterogeneity of their species compositions. This paper proposes to use the ternary plots proposed by De Finetti to solve this problem. These ternary plots have been drawn as examples on the Free and FAD schools sets sampled in the Indian and Atlantic oceans during the 2002-2008 period. These ternary plots have been drawn as examples using 3 different plotting methods, but other alternate improved methods could also be envisaged following the discussion of this working document