Ecologia trófica e migração vertical de Diaphus brachycephalus na Região Norte do Brasil

Abstract

Lanternfish (Myctophidae) are among the most abundant vertebrates in the world, they connect the oceanic vertical layers and represent an important trophic link between zooplankton and large consumers. However, despite its importance, there is still a lack of studies and information regarding some aspects of its ecology. Therefore, this study investigated the trophic ecology and vertical migration of the species Diaphus brachycephalus in the Northern Region of Brazil, as well as characterizing the composition and the most important items in the diet, evaluating the breadth of the trophic niche and evaluating the dietary difference concerning depth and period of day. To investigate trophodynamics, the specimens' stomachs and contents were analyzed. To define migration patterns, the vertical distribution of the species was observed during periods of day and night. Of the 83 stomachs analyzed, all of them contained prey in their contents. In total, 20 types of food items were found. The diet was mainly composed of crustaceans and molluscs. The breadth of the trophic niche showed that D. brachycephalus has a generalist diet. The multidimensional analysis (nMDS) result showed that the factors, period of day and depth did not influence feeding patterns. Vertical distribution patterns showed that during the day, the species predominated in upper mesopelagic waters, with a small part of the population also present in lower mesopelagic regions. At night, its distribution peaked in superficial epipelagic regions, with part of the population also present in upper and lower mesopelagic regions. The study showed that crustaceans were the most abundant and important group for D. brachycephalus. The species was classified as an asynchronous migrant, as only part of its population migrated at night. It was also classified in Group II as a vertical migrant with an upper mesopelagic distribution.