Abstract
Fish diversity loss is threatened by the construction of dams as they prevent the regular natural dispersal among populations. Thus, conservation of key riverine habitats for fish reproduction may be essential for the recruitment of new native species of fish. The present study aimed to identify key habitats for fish spawning and early development in the Paranapanema River basin, as well as to determine the taxonomic composition, reproductive and life-history strategy, and to report spatial distribution of eggs, larvae and juveniles. The importance of lagoons, tributaries, and sub-tributaries was evaluated in the Paranapanema River basin between October 2012 and March 2013. Eggs and larvae samples were collected at dawn and dusk with conical plankton nets (0.5 mm mesh size), whereas juveniles were captured during the day with seine and sieve (0.5 cm mesh size). A total of 547 eggs, 904 larvae and 1 228 juveniles were captured. We observed that 2 larvae and 288 juveniles of non-migratory species, parental care, and equilibrium life-history strategy, predominated in lagoons and tributaries. On the other hand, 13 larvae and 60 juveniles of short migratory distance, no parental care, and periodic life-history strategy predominated in sub-tributaries. The highest densities of eggs were recorded in tributaries and sub-tributaries (Tukey’s test, P = 0.001 and P = 0.03, respectively), and the highest densities of larvae were recorded for lagoons and tributaries (P = 0.005 and P = 0.0001, respectively). Captures of eggs and larvae were higher at night; while the highest catches per unit effort of juveniles were recorded for tributaries and sub-tributaries. Fish species that adopt different life-history strategies can use diverse types of habitats during the early stages. Lagoons, tributaries and sub-tributaries of the Paranapanema River play different roles in the reproductive success of fish fauna in a heavily modified basin. The preservation of spawning and nursery areas trapped between reservoirs is necessary for Neotropical fish species recruitment and survival. Rev. Biol. Trop. 66(2): 605-621. Epub 2018 June 01.
Highlights
The life-history strategies of freshwater fish vary temporally and spatially according to abiotic environmental parameters, food availability, and predation pressure (Winemiller, 1989; 1995)
The highest densities of larvae Characiformes were in the lagoons and sub-tributaries, Siluriformes in the lagoons and tributaries, whereas Perciformes was most abundant in the lagoons
In sub-tributaries, larvae and juveniles of short distance migratory species predominated, with external fertilization and no parental care. Among these are rheophilics: Apareiodon spp., Leporinus spp., and Schizodon spp., as well as P. argentea, Oligosarcus paranensis Menezes & Géry, 1893, and Imparfinis borodini Mees & Cala, 1989, which were exclusive to this habitat and indicated that the use of such environments is very important for the development of these taxa
Summary
The life-history strategies of freshwater fish vary temporally and spatially according to abiotic environmental parameters, food availability, and predation pressure (Winemiller, 1989; 1995). The three downstream impoundments in the system are Rosana (17 m height of dam), Taquaruçu (23 m height), and Capivara (60 m height) dams, with capacity to generate 354, 525, and 619 MW, respectively Their reservoirs flooded areas of marginal lagoons and floodplain habitats. Migratory fish species spawn in tributaries and sub-tributaries located upstream in reservoirs, where higher abundance of eggs are found (Baumgartner et al, 2004; Makrakis et al, 2012; Suzuki et al, 2013; Da Silva et al, 2015). We tested the hypothesis that: (i) migratory fishes spawn in sub-tributaries, the larvae drift through tributaries and settle in lagoons for rearing to juveniles; (ii) non-migratory fishes spawn and rearing occurs in lagoons To test these predictions, the present study aimed to identify key habitats for spawning and the early development within the dammed Lower Paranapanema River basin. To determine the taxonomic composition of larvae and juvenile fish, and report spatial distribution of eggs, larvae, and juveniles among the three main habitats, lagoons, tributaries and subtributaries in the upper areas of the reservoirs
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