Comprehensive Spatial Distribution of Tropical Fish Assemblages from Multifrequency Acoustics and Video Fulfils the Island Mass Effect Framework
|Author(s)||Salvetat Julie1, Bez Nicolas2, Habasque Jeremie2, Lebourges-Dhaussy Anne2, Lopez Cristiano1, Roudaut Gildas2, Simier Monique2, Travassos Paulo1, Vargas Gary1, Bertrand Arnaud2|
|Affiliation(s)||1 : Federal Rural University of Pernambuco, Brasil
2 : Institut de Recherche pour le Développement, France
|Source||Preprint (Research Square Platform LLC), 2021-01 , N. Version 1 , P. 32p.|
|Note||This is a preprint ; it has not been peer reviewed by a journal|
|Keyword(s)||marine tropical ecosystem, mesophotic reefs, marine protected area, biomass estimation, geostatistics, marine spatial planning, fish assemblages|
Tropical marine ecosystems are highly biodiverse and provide resources for small-scale fisheries and tourism. However, precise information on fish spatial distribution is lacking, which limits our ability to reconcile exploitation and conservation. We combined acoustics to video observations to provide a comprehensive description of fish distribution in a typical tropical environment, the Fernando de Noronha Archipelago (FNA) off Northeast Brazil. We identified and classified all acoustic echoes into ten fish assemblage and two triggerfish species. This opened up the possibility to relate the spatial different spatial patterns to a series of environmental factors and the level of protection. We provide the first biomass estimation of the black triggerfish Melichthys niger, a key tropical player. By comparing the effects of euphotic and mesophotic reefs we show that more than the depth, the most important feature is the topography with the shelf break as the most important hotspot. We also complete the portrait of the island mass effect revealing a clear asymmetry. While primary productivity is higher downstream, fish concentrate upstream. The comprehensive fish distribution provided by our approach is directly usable to implement scientific-grounded Marine Spatial Planning.