Variações entre contagens de Arapaima gigas (Schinz) (Osteoglossomorpha, Osteoglossidae) feitas por pescadores individualmente em Mamirauá, Brasil

Abstract

Censusing of pirarucu (Arapaima gigas) is being increasingly used in conservation initiatives throughout the Amazon, and is done essentially by counting the individuals at the moment they come out of the water to breathe air. This ‘counting method’ was developed recently based on analyses of counts of pirarucu made by groups of knowledgeable and skillful fishers. But fishers vary with respect to their knowledge and skills, and the accuracy of their counts of pirarucu. In this study, we evaluated the accuracy of the counts of pirarucu made by 34 individual fishers; we compared their censuses of pirarucu in four lakes with captures of all pirarucu in the same lakes. We found that not all fishers censused the pirarucu populations accurately. Seventy-five percent of the fishers under- or over-estimated the abundance of pirarucu in the lakes up to thirty percent. The individual tendencies of the fishers were minimized when their counts were considered in groups, which is the main way fishers census pirarucu populations. The groups of fishers under- or overestimated the abundance of pirarucu in the lakes by about ten percent. These results highlight the need to pay attention to the individual ability of fishers to census pirarucu populations in the many management and conservation schemes that currently are censusing pirarucu populations.