Environmental influences on the ichthyoplankton in hypersaline estuaries located in a Semiarid Northeastern Brazilian coast

Abstract

Hypersaline estuaries are commonly found in the Semiarid Northeast Brazilian coast. However, the utilization of these estuaries by early life stages of fishes is less well documented. This study aimed to evaluate the effects of environmental factors on the ichthyoplankton, and to describe their spatial and temporal variation in two estuaries (Tubarão and Casqueira). The sampling were diurnally in four excursions carried out during two dry-season months (November and December 2017) and two rainy-season months (May and July 2018). A total of 423 larvae representing 30 species (14 families) and 2,762 eggs (five families) were collected. Although the community structures were similar in both estuaries, there was strong seasonal variation, with higher abundances observed during the dry season. Low rainfall was the primary environmental driver affecting ichthyoplankton in both estuaries. Other environmental factors, such as depth, water temperature, and channel width, were also predictor variables for the distribution of eggs and larvae. The ichthyoplankton was dominated by marine estuarine-dependent species in both estuaries, accounting for 76% of individuals. The presence of the early life stages of typically marine species suggests that hypersaline environments provide important nursery areas and play an essential role for some coastal fish species.

Ichthyoplankton and plastic waste drift in a river in the Amazon Basin, Brazil

“…The highest ichthyoplankton densities during the drought phase may have been strongly influenced by the occurrence of rainfall since, during November 2021 (drought phase), there was precipitation before the rainy season. As rainfall is considered a key environmental factor for the gene flow of species, it directly influences the abundance of fish eggs and larvae (Ferreira et al, 2016;Teixeira et al, 2019;Sanches et al, 2020;Badú et al, 2022). Furthermore, temporal variability of ichthyoplankton drift is related to functional characteristics and life history of each species (Nagel et al, 2021;Gogola et al, 2022).…”

Analysis of a hypersaline drought-prone estuary reveals low density and diversity of fish eggs and larvae

“…Although the fish assemblage from this low-inflow estuary is composed of taxa commonly found in tropical estuarine systems (Bonecker et al, 2009;Marcolin et al, 2010;Lima et al, 2015), the number of species recorded here is considerably low, which is expected in hypersaline coastal environments (Rosa et al, 2016; Chermahini ). The lack of freshwater species due to high salinity levels and the occurrence of only marine and estuarine species is a pattern found in other hypersaline aquatic environments (Rosa et al, 2016;Badú et al, 2022), and points to an oversimplification of the fish assemblage under the influence of hypersalinity and severe drought. In addition, the mangrove fish community was composed of salinity-tolerant species.…”

“…On the Brazilian semiarid coast, short estuaries are already experiencing hypersalinity due to local impacts (e.g., multiple dams) and ongoing climate change, which makes them useful models for understanding this phenomenon (Schettini et al, 2017;Soares et al, 2021). However, few studies have analyzed these extreme mangroves and their ichthyoplankton communities (Badú et al, 2022). Using a semiarid estuary in an extreme drought year as a model, we analyzed the intra-annual distribution and density of fish eggs and larvae.…”