Published March 28, 2022
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Environmental influences on the ichthyoplankton in hypersaline estuaries located in a Semiarid Northeastern Brazilian coast
Authors/Creators
- 1. Programa de Pós-Graduação em Ecologia e Conservação da Universidade Estadual da ParaÍba - UEPB, Avenida das Baraúnas, 351, Bairro Universitário, 58429-500 Campina Grande,PB,Brazil.(MLASB) luisaaraujosb@gmail.com, (CSSL) carollinnestefani@ hotmail.com, (ALMP) andrepessanhauepb@gmail.com (corresponding author).
Description
Badú, Maria Luísa A. S., Lima, Caroline S. Silva, Pessanha, André Luiz Machado (2022): Environmental influences on the ichthyoplankton in hypersaline estuaries located in a Semiarid Northeastern Brazilian coast. Neotropical Ichthyology (e210081) 20 (1): 1-21, DOI: 10.1590/1982-0224-2021-0081, URL: http://dx.doi.org/10.1590/1982-0224-2021-0081
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References
- In both estuaries, the highest salinities change gradually from lower to upper zone creating a complex environmental gradient, such that regulate the ichthyoplankton structure. Although it is not well known to ichthyoplankton abundance with variations linked to landscape characteristics, in our study spatial variations of larval fish stages were also related with channel width and distance of estuary mouth. Thus, a significant increase in abundance of earlier stages of development of fishes was recorded from the lower to the upper zone of these estuaries and may be related to spatial gradient, as has been reported for others estuaries by Barletta-Bergan et al. (2005), Costalago et al. (2018), and Ooi, Chong (2011). This was evident when a greater abundance was registered near the mouth zone, which decreased noticeably towards the upper zone of estuaries.
- The results of our study show that the abundance and composition of estuarine early life stages of marine fishes in both estuaries were represented by a larger number of marine estuarine-dependent species, suggesting continuous inputs of larvae and eggs in these systems. The increased density of larvae of the Carangidae and Clupeidae families in our results, which are typically estuarine-dependent species, supports this hypothesis. In agreement, Costalago et al. (2018) concluded that the importance of estuaries as fish nurseries may result from the availability of a wide range of habitats including seagrass meadows and mangrove forests, and higher water temperatures. Indeed, many of these larvae benefit from the hypersaline estuaries on the semiarid coast of Brazil, probably as a response to higher habitat quality, whose characteristics are favorable for their development and to maximize their fitness. For example, Sales et al. (2018) registered the presence of structured habitats along the salinity gradient in the Tubarao estuary, such as mangroves or seagrass beds, which necessarily supported this premise because provide abundant food resources and refuge against predators. This confirms the importance of these shallow habitats as nursery habitats for the early life history of marine coastal fishes (Lima et al., 2018; Sales et al., 2018; Silva et al., 2018).
- A similar conclusion may be drawn for species belonging to the solely estuarine guild (ES), indicating that these species developed adaptations and specialized their physiological systems for the hypersaline environment (euryhalinity - broad halotolerance and halohabitat distribution) (Ooi, Chong, 2011). Certain members of this group, such as A. brasiliensis and A. lineatus, are typically found in various estuaries along with the Brazilian coast (positive estuaries) (Barletta-Bergan et al. , 2002; Katsuragawa et al. , 2011; Oliveira, Pessanha, 2014), but exhibited a similar trend in these hypersaline environments (Sales et al., 2018).
- In tropical regions, the inter-seasonal variability of environmental factors influences the larval fish distribution and abundance in estuaries (Pritchett, Pyron, 2012; Eick, Thiel, 2014; Solari et al., 2015). Rainfall is often identified as an important factor in determining estuarine ichthyoplankton structure (Kantoussan et al. , 2012). Our results are in accordance with this hypothesis. Rainfall directly influences the reproduction of species and consequently the recruitment of ichthyoplankton in tropical estuaries (Barletta-Bergan et al., 2005). Strong rainfall-related patterns were also found with regard to abundance in this semi-arid environment despite the low rainfall (2.5-60 mm) in the region. This statement is supported by the results of the dbRDA. The main seasonal changes in the ichthyoplankton structure were due to variations in density of L. piquitinga, A. lineatus, A. brasiliensis, and C. latus, which probably reflects recruitment success in these systems.
- Similarly, the fluctuations that the larvae life stages tended to be correlated with changes in rainfall. Hence, abundant and numerically dominated larvae in flexion and post-flexion stages probably reflect the different times of recruitment of different species and could be associated with the changes in rainfall regimes. In the current study, the largest occurrences of C. cruentata, C. latus, O. palometa, and O. saurus in flexion stage coincided with the rainy season and seemed to confirm the greater occurrence of these species in the studied area. In addition, the presence of larvae can be indicative of recent adult spawning in the area as well as the transport and retention of eggs and larvae in estuaries (Katsuragawa, Matsuura, 1992). Representatives of the Carangidae family are thought to spawn in the neritic zone of the tropical northeastern Brazilian coast, but their larvae return to nursery grounds located in shallow waters (Souza, Junior, 2019). The most representative Carangid larvae were more abundant during the rainy period along the Brazilian coastal shelf area (Campos et al., 2010). Most of the groups found to reproduce in coastal areas near estuaries were Carangidae and Serranidae, which were also found in our study. Other studies conducted in tropical estuaries highlight the importance of these environments as places of dispersal and growth and consequently their importance for maintaining populations and fish stocks through recruitment processes (Lima, Barletta, 2016; Silva et al., 2018). These results, therefore, reinforce the importance of these hypersaline environments as nursery areas for fishes, especially for adults who live in the estuary and have coastal-marine origins.