Abundance and distribution of flying fishes (Exocoetidae) and flying squids (Ommastrephidae) in the Eastern Atlantic Ocean based on a large-scale visual survey

Flying fishes (Teleostei: Exocoetidae) and flying squids (Cephalopoda: Ommastrephidae) are key components of tropical and subtropical epipelagic ecosystems, but information about their ecology, abundance and global distribution is still scant. Here we present some notes on the occurrence of flying fishes and flying squids in the Eastern Atlantic Ocean along a large-scale visual transect between 31°S and 53° N. The density of airborne specimens startled by the passage of the ship was used as a proxy of their abundance. The number of flying individuals was estimated using visual census, and individual densities were computed according to a fixed-width strip transect protocol. During the survey, 119 vessel-based transects were performed during March and April 2017, for a total surveyed length of 1540.8 km. Flying squids were observed only in a narrow latitudinal band between 17.5° and 26.1° S. Flying fish abundance, on the other hand, varied significantly along the ship's route. Maximum densitities occurred between 3° and 15° S. Flying fish abundance markedly decreased around the equator and then increased again towards 8-10° N. No flying fishes were seen north of 19° N, with the only exception of 4 individuals sighted near the Strait of Gibraltar (35-36° N). No attempt was made to identify fishes or squids down to the genus or species level; however, the observed variations in size class distribution suggest a certain degree of habitat segregation between different species or life stages. Sea surface temperature was the best descriptive variable explaining the distribution of flying fishes in the area surveyed. Further work is needed to better understand the environmental factors governing the distribution of these important, but seldom surveyed, organisms.