Spatiotemporal variations in density and biomass of rocky reef fish in a biogeographic climatic transition zone: trends over 9 years, inside and outside the only nearshore no‐take marine‐protected area on the southern Brazilian coast

Abstract

Biogeographical transition zones are important areas to investigate evolutionary ecological questions, but long‐term population monitoring is needed to better understand ecological processes that govern population variations in such edge environments. The southernmost Brazilian rocky reefs are the southern limit of distribution for 96% of the tropical ichthyofauna of the western Atlantic. The Arvoredo Marine Biological Reserve is the only nearshore no‐take marine‐protected area (MPA) located in this transition zone. The main aim was to investigate how the populations of rocky reef fish species vary in density and biomass in space and over time, inside and outside the Arvoredo MPA. This study presents results based on a 9 year (2008–2017) underwater visual census monitoring study to evaluate the density and biomass of key fish species. Variations in density and biomass were detected for most species. Factors and mechanisms that may have influenced spatial variation are habitat structural complexity and protection from fisheries. Temporal variations, otherwise, may have been influenced by species proximity to their distributional limit, in synergy with density‐dependent mechanisms and stochastic winter temperature oscillations. The MPAs harbour higher density and biomass for most species. Nonetheless, a prominent temporal decline in the recruitment of Epinephelus marginatus calls into question the continuous effectiveness of the MPA.

Habitat use of five sympatric predatory reef fishes at a remote island in the south‐western Atlantic

“…Our work presents remarkable similarities of habitat use patterns for serranids to those reported by previous works conducted on nearshore and coastal environments (Anderson et al ., 2019; Gibran, 2007). Species spatial distribution and habitat use in both isolated and coastal environments seems to be influenced by the reef's topographic complexity and density‐dependent mechanisms ( e.g ., inter and intraspecific competition, predation) (Almany, 2004a, 2004b; Anderson et al ., 2019, 2020; Gibran, 2007).…”

“…Standard 40m 2 (20 × 2 m) strip belt transects [underwater visual censuses (UVCs)] were used to estimate the Serranidae density (Anderson et al ., 2019, 2020). A total of 120 transects were performed ( i.e ., 4800 m 2 ), 20 ( i.e ., 800 m 2 ) in each of the six sites.…”

“…The northern and western sites (Ponta Norte, Farilhões, Racha and Eme) are rocky reefs covered mostly by macroalgae, sponges and corals (Figure 1). Standard 40m 2 (20 Â 2 m) strip belt transects [underwater visual censuses (UVCs)] were used to estimate the Serranidae density (Anderson et al, 2019(Anderson et al, , 2020. A total of 120 transects were performed (i.e., 4800 m 2 ), 20 (i.e., 800 m 2 ) in each of the six sites.…”

A safe haven for potential reproductive aggregations of the critically endangered Brazilian guitarfish (Pseudobatos horkelii)

“…Photographs were taken during routine reef fish surveys on Rancho Norte (Arvoredo Island no-take portion). Since 2008, a monitoring programme has been conducted in AR MPA to evaluate the effectiveness of the MPA (Anderson et al, 2020). Sampling expeditions are conducted annually, in the morning, during the Austral summer (from December to March) (see Anderson et al, 2020).…”