Ichthyofauna in an ecological station in the Pantanal of Brazil: the hydrological cycle affecting species composition

Study Extent

The Taiamã Ecological Station (TES) is located in the Pantanal of Mato Grosso (between W 57o 24' and W 45° 40'; and S 16° 48' and S 16° 58'; fig. 1), 165 km t from the municipality of Cáceres. The TES covers an area of 11,550 ha, comprising the islands of Taiamã and Sararé, and limited by a bifurcation of the Paraguay River (Ikeda-Castrillon et al., 2011). The annual average temperature is 26oC, with highest temperatures in the rainy season (October to December) according to Neves et al. (2011). The flood pulse directly influences the area, promoting marked changes in the availability of aquatic habitats. The Pantanal is made up of several phyto physiognomies, such as wet fields, and permanent and temporary bays (Carvalho, 1986; Junk and Da Silva, 2000). The uniform geographical relief denotes a lentic water flow, with periodic flooding due to the flood pulse, which regulates the ecological process in this region (Fernandes et al., 2010). The annual droughts and floods lead to variations in the abundance of certain species (Da Silva et al., 2001; Junk et al. 2014).

Sampling

We conducted three field excursions, in September 2014, February 2015, and May 2015. These three periods comprise the seasonal hydric periods of low waters (drought), decreasing waters (ebbing), and high waters (flooding). The study was approved by the Instituto Chico Mendes para a conservação da Biodiversidade–SISBIO num 46263-1).

Quality Control

Fish were identified following Britski et al. (2007) and manuscripts of species description. Specimens were then conserved in 70 % alcohol (and deposited in the Laboratory of Ichthyology of the Northern Pantanal – LIPAN, linked to the Research Centre in Limnology, Biodiversity and Ethnobiology of the Pantanal – CELBE/UNEMAT. Abundance, richness (Taxa S), diversity (Shaanon's index, H’) and equitability (Pielou, J’) were calculated for each season with PAST 3.0 free software (Hammer et al., 2001).

Method steps

1. Fish samples were collected at three different points surrounding the TES. Fish capture were captured using a square metallic structure (1 m width x 2 m length x 1 m depth) with a 3 mm nylon net that was passed underneath the macrophyte beds three times. Netting of several mesh sizes and a dragging net (5 mm internode, 25 m length and 4 m high) were also passed once in the limnetic region of the water body. After the samples were collected, the fish were anesthetized with Eugenol (Keene et al., 1998; Fernandes et al., 2017) and fixed in formalin (concentration of 10 %) until identification.

1. Actinopterygii
   rank: class
2. Characiformes
   rank: order
3. Acestrorhynchidae
   rank: family
4. Anostomidae
   rank: family
5. Characidae
   rank: family
6. Curimatidae
   rank: family
7. Erythrinidae
   rank: family
8. Hemiodontidae
   rank: family
9. Iguanodectidae
   rank: family
10. Lebiasinidae
    rank: family
11. Parodontidae
    rank: family
12. Serrasalmidae
    rank: family
13. Triportheidae
    rank: family
14. Cichliformes
    rank: order
15. Cichlidae
    rank: family
16. Cyprinodontiformes
    rank: order
17. Rivulidae
    rank: family
18. Gymnotiformes
    rank: order
19. Gymnotidae
    rank: family
20. Hypopomidae
    rank: family
21. Rhamphichthyidae
    rank: family
22. Sternopygidae
    rank: family
23. Siluriformes
    rank: order
24. Doradidae
    rank: family
25. Heptapteridae
    rank: family
26. Loricariidae
    rank: family
27. Pimelodidae
    rank: family

The Taiamã Ecological Station (TES) is located in the Pantanal of Mato Grosso (between W 57o 24' and W 45° 40'; and S 16° 48' and S 16° 58'; fig. 1), 165 km t from the municipality of Cáceres. The TES covers an area of 11,550 ha, comprising the islands of Taiamã and Sararé, and limited by a bifurcation of the Paraguay River