Ichthyoplankton community structure on the shelf break off northeastern Brazil

Abstract

Oceanographic features influence the early stages of fish to a high degree. We investigated the influence of continental shelf-slope gradient on the ichthyoplankton composition and distribution off Northeastern Brazil. Two oceanographic campaigns were performed during July-August 2010 and 2012. The samplings were performed along three transects composed by three stations, covering the continental shelf and slope areas. Abiotic data were obtained by an ADCP and a CTD. The ichthyoplankton was sampled through diurnal and nocturnal hauls using a 500-µm bongo net from 200 m to the surface. A total of 1634 larvae and 4023 eggs, representing 91 genera and 76 species, were collected. Higher concentrations of fish eggs were found on the continental shelf, probably because of the North Brazil Undercurrent flux. Higher concentrations of larvae were found at night and could be associated with net avoidance or natural variation. Neritic, oceanic and transition groups of species association were determined. Larvae of neritic, demersal and pelagic fishes prevailed on the continental shelf, while larvae of oceanic, mesopelagic and bathypelagic fishes on the continental slope. Melanostomiidae, Scorpaena sp., Lestidium atlanticum, Lampadena sp. and Diaphus sp. were identified as indicators of the continental slope.

Mesoscale spatial variability of ichthyoplankton in the Southwest Atlantic during the autumn–winter period

“…Myctophidae family was the most abundant in this study, a result expected as it usually appears in striking dominance elsewhere on SE Brazilian coastal and oceanic waters (Macedo‐Soares et al, 2014; Santana et al, 2020) as well as other regions of Atlantic and South Pacific (Osorio‐Zúñiga et al, 2018; Rodríguez et al, 1999). The prevalence of Myctophidae larvae can be attributed to the extensive number of species within the family (Moser & Ahlstrom, 1974) and their broad distribution in oceanic regions influenced by the warm and saline Brazil Current (BC) (Namiki et al, 2017).…”

“…Therefore, a detailed examination of species-specific responses is essential to understand the complex relationships between fish larvae density and environmental factors. The db-RDA ordination, for example, highlighted certain genera that thrive in warmer temperatures, while others prefer cooler conditions.Myctophidae family was the most abundant in this study, a result expected as it usually appears in striking dominance elsewhere on SE Brazilian coastal and oceanic waters(Macedo-Soares et al, 2014;Santana et al, 2020) as well as other regions of Atlantic and South Pacific (Osorio…”

“…Conversely, Sparisoma represents a genus of reef fish. Its dispersive larval stage plays an important role in oceanic fish larvae assemblages (Bonecker et al, 2012; Santana et al, 2020). In the shelf and oceanic waters off NE Brazil, the occurrence and density of these larvae have been associated with warmer and saltier conditions (Souza et al, 2010), corroborating the results of this study.…”

“…These rates are affected by environmental processes such as continental runoff, eddies, and shelf‐break upwellings (Cushing, 1975; Parrish et al, 1981; Rodriguez, 2019). These processes frequently occur across continental margin zones (Franco et al, 2006; Sabatés & Olivar, 1996; Santana et al, 2020), determining gradients of temperature, salinity, phytoplankton biomass (chlorophyll a ), nutrients, and dissolved oxygen in surface waters.…”

Planktonic cnidarian responses to contrasting thermohaline and circulation seasonal scenarios in a tropical western boundary current system

“…Most samples were then dominated by cnidarian species that typically dominate in the open ocean, such as the siphonophores C. appendiculata, D. bojani, B. bassensis and A. tetragona. In the western tropical South Atlantic, the dominance of such oceanic communities over the continental shelf is not exclusive in cnidarians and has been observed for other zooplanktonic groups such as copepods, chaetognaths, thaliaceans and fish larvae (Neumann-Leitao et al, 2008;Neumann-Leitão et al, 1999;Santana et al, 2020;Schwamborn et al, 1999). Meanwhile, the coastal community (group A), with a high abundance of M. kochii and L. tetraphylla and an absence or reduced abundance of the siphonophores mentioned above, was restricted to a particular area over the Pernambuco Plateau.…”