Comprehensive spatial distribution of tropical fish assemblages from multifrequency acoustics and video fulfils the island mass effect framework

Abstract

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 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 spatial dissymmetry regarding fish distribution. Indeed, 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.

Feeding behavior of yellowfin tuna around two insular regions of the western Atlantic Ocean

“…In fisheries management, understanding how migratory species use and move between habitats in time and space and what life processes (i.e., foraging, reproduction) are performed in which environments is of utmost importance (Logan et al, 2020). This is relevant especially as global anthropogenic impacts advance, with ocean warming expected to strongly affect species distribution, trophic interactions, and the balance of food webs (Salvetat et al, 2022). Ecological knowledge of energy flow and trophic interactions is pertinent for conservation, including the integrated assessment of different marine resources with multifaceted approaches to subsidize the development of ecosystem‐based management policies (Coletto et al, 2021; Niella et al, 2017).…”

“…In this area, oceanographic processes transform oligotrophic waters into highly productive environments around oceanic islands (Lima et al, 2016). They favor the enrichment of primary production in insular habitats, attracting marine life that finds an opportune place to develop in these environments (Salvetat et al, 2022; Silva et al, 2019). This is the case of Fernando de Noronha (FNA) and Saint Peter and Saint Paul (SPSPA) archipelagos, which represent high fishing interest due to local aggregations of yellowfin tuna.…”

Spatial Distribution of Major Fish Species Catches and Their Relationship with Environmental Factors in the Beibu Gulf, South China Sea

“…A continuous increase in temperature leads to the narrowing of marine biodiversity, alterations in the community structure, and shifts in fish distribution in the polar regions [4]. In recent years, the improved efficiency of social and industrial fishing has diminished the availability of sustainable fish stocks, therefore accelerating the degradation of the marine ecosystem and causing irreparable dangers of ecological transition [5][6][7]. In addition, changes in fish resources can affect the stability and sustainability of ecosystems, disrupting the biodiversity and ecological balance [8].…”