Fish assemblages on the southeastern Brazilian Bight, sampled by midwater trawl during spring and summer seasons: species composition, abundance, and environmental drivers

Abstract

Abstract-We provide an overall description of the species composition and abundance of pelagic fish assemblages sampled with midwater trawls at depths <100 m in the southeastern Brazilian Bight (SBB, south-southeastern Brazil) during the spring-summer period from 1995 through 2010. We also investigated the effect of 1) 3 water masses, the South Atlantic Central Water (SACW), Coastal Water (CW), and Mixed Water (M), and 2) a set of environmental and spatial variables on the SBB pelagic fish assemblages. The aggregations comprising 43 species, were dominated by highly abundant mid-trophic-level schooling species. The Argentine anchoita (Engraulis anchoita), rough scad (Trachurus lathami), Atlantic cutlassfish (Trichiurus lepturus), and Brazilian sardinella (Sardinella brasiliensis) were the dominant species by biomass. They were distributed widely over the SBB and occurred in all years. Results from multivariate analyses indicate that SACW and the combination of CW and M affected the SBB pelagic assemblage structure and that each contained a specific species grouping, whose abundance changed in relation to depth within the water column and to distance from shore of both SACW and CW+M. This pattern is consistent with the hydrographically complex structure of the SBB in spring and summer.

On the trophic role of pelagic fishes and fishery landings shifts in the South Brazil Bight

“…in the ECOSAR II teams' sampling networks suggests that the consumption of teleost fish by S. brasiliensis occurred after capture and not in their natural habitat. This justification can also be associated with the data found by Contente and Rossi-Wongtschowski (2016) that show the presence of Bregmaceros atlanticus in ECOSAR cruises with a total frequency of occurrence of 2.2. Thus, it may have been captured simultaneously with S. brasiliensis.…”

“…In order to collect specimens, 26 hauls were conducted during the survey using a midwater trawl from which 24 caught pelagic fish. The survey was carried out on pre-established stations during the day and night, at a mean speed of 10 knots (Contente and Rossi-Wongtschowski, 2016). Particular details on the grid sampling, methods of acoustic data, and procedures of fishing operations were described in Soares et al (2005), Madureira and Rossi-Wongtschowski et al (2005), and Contente and Rossi-Wongtschowski (2016).…”

“…To describe and investigate the abundance of fish aggregations in this study at SBB, data on total biomass, the total frequency of abundance, and the total frequency of occurrence presented by Contente and Rossi-Wongtschowski (2016) on biomass related to ECOSAR III (1995) to VII (2010) were compiled. Such data were adapted for the ECOSAR II species, except for D. punctatus and A. lyolepis, whose data were not measured.…”

Dietary metabarcoding of keystone sardine species reveals the importance of their ichthyoplankton prey in food webs of the Southern Brazilian Bight fisheries

“…The species exhibits a well‐defined reproductive season, with distinct periods of gonadal maturation and spawning, and its reproductive cycle overlaps with that of S. brasiliensis , indicating potential interspecies interactions and competition for resources during these periods (Petermann & Schwingel, 2016). During the spring–summer period from 1995 to 2010, data from midwater trawls in the SBB showed that O. oglinum was one of the most abundant species and strongly associated in the combination of the Coastal Water and areas of mixing between Coastal Water and South Atlantic Central Water, alongside two other clupeiform species, S. brasiliensis and Harengula clupeola (Cuvier, 1829) Contente & Rossi‐Wongtschowski, 2016.…”

“…The species exhibits a well-defined reproductive season, with distinct periods of gonadal maturation and spawning, and its reproductive cycle overlaps with that of S. brasiliensis, indicating potential interspecies interactions and competition for resources during these periods (Petermann & Schwingel, 2016). During the spring-summer period from 1995 to 2010, data from midwater trawls in the SBB showed that O. oglinum was one of the most abundant species and strongly associated in the combination of the Coastal Water and areas of mixing between Coastal Water and South Atlantic Central Water, alongside two other clupeiform species, S. brasiliensis and Harengula clupeola (Cuvier, 1829) Contente & Rossi-Wongtschowski, 2016. The Brazilian fishing industry experienced significant growth in the 1960s, primarily focusing on highly productive pelagic and demersal resources (Paiva, 1997). However, overfishing and the subsequent decline in fish stocks have led to a notable decrease in productivity, resulting in the necessity of implementing conservation policies (Dias-Neto, 2010;Freire et al, 2015).…”