Ichthyological Overview and Remarks on Freshwater Fishes from Capim River, Lower Amazon Basin, Brazil

Júlio Cesar Garavello,Alexandre Kannebley De Oliveira

doi:10.4236/oje.2014.413068

Abstract

The Capim River drainage should be considered small and thin by comparison with large Amazonian rivers. It rises by confluence of the Surubiú and Ararandeua rivers near 400 m high and their headwaters would be comfortably included in the Dry Emerged Lowland (terra firme) forest area of Sternberg’s Amazonian concept. Because of this reason the freshwater fish fauna of Capim River is comprised mainly by Amazonian fish families found in tributaries also with origin in terra firme areas. The ichthyofauna from the main channel of the poorly sampled Capim River, in the stretch between its confluence with Tauarí River and its mouth at Guamá River, is herein reported by way of rapid assessment. Also broad comparisons were made among freshwater fishes of the Capim with that from Tocantins and Guamá rivers. Two rapid access research surveys of collecting ichthyological material were performed in dry and humid periods of the year 1998 comprising the regional hydrologic cycle. The ichthyological diversity showed by the 461 studied specimens includes 79 species probably derived from Guamá and Tocantins rivers. These species are distributed between two situations: 1) downstream Capim River, at confluence with Guamá River, where is under tidal waters influence and periodically flooded, and 2) upriver Capim that is less humid and with water rapids, independent from sea hydrologic influence. This fish fauna includes local species common at high areas of the Amazonian Dry Emerged Lowland that are in part shared with that from Tocantins River. In view of these observations, we assume that the Capim River freshwater ichthyofauna may reflect diverse origin from the simple transfer of populations from Guamá River, but originate through a more complex process including the past ichthyofauna of the earlier drainages of terra firme forest and their reorganization.

Highlights

To comprehend the geologic structure and distribution of the ichthyofauna from the Capim-Guamá river system is important to understand that the Amazonian basin is characterized as a disordered sedimentary drainage
The drainage is situated at a region of open fields of Pará State, outside from forested areas of Amazon basin
The delta of Capim River included an ample area where the primary production was very high, following Barthem and Goulding [6]; it furnished enough nutrients to form an area of creation for the large catfishes and other estuarine freshwater fishes

Summary

Introduction

To comprehend the geologic structure and distribution of the ichthyofauna from the Capim-Guamá river system is important to understand that the Amazonian basin is characterized as a disordered sedimentary drainage. According to Silva and Rosseti [2], part of the geological structure of this large hydrographic basin is surely generated in geologic Holocene times, which conditions all the Holocene alluvial sedimentation with particular effects on the ichthyofauna distribution. In accord with Silva et al [3] is visible the adjustment of an ample hydrographic net of the low Amazon basin to a system of successive acquired fractured geologic sites. The Amazonian rivers are, observed by Sternberg [4], aligned in northeast-southwest direction following a line of small resistance of early crystalline ancient soil with influence on the ichthyofauna distribution. The flood lowlands include two kinds of landscape: 1) the “Igapó” (having dense arboreal inundate vegetation along most of the year), and 2) the “Várzea” (an extensive field of low vegetation, sometimes intermittent flood and playing important rule on ichthyofauna distribution)

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Conclusion