Utilização do método acústico passivo para avaliar sons de peixes marinhos e continentais em ecossistemas tropicais brasileiros

Abstract

Communication is omnipresent in aquatic animals, especially in those capable of producing different types of acoustic signals. This cacophony, called soundscape has allowed to evaluate both the distribution and behavior of organisms, simply recording and evaluating the sounds produced by them using the passive acoustic method. The objective of this work was to use innovative methods of noninvasive research, such as passive acoustics, in the sample and analysis of acoustic data in continental and marine aquatic environments, for monitoring, conservation and management of the living resources in these environments, mainly fish. In marine environment, the soundscape were evaluated of two coastal reef areas on the southern coast of the State of Pernambuco. Porto de Galinhas, an area already impacted by free access for tourism and fishing, and another in Tamandaré, within the Coastal Corals Protection Area, in the Marine Life Preservation Zone, used for research only. In a freshwater environment, the sounds production was appraise of five species of commercial importance of the order Characiformes in the Madeira River, southern Amazonia. The results of the marine experiments indicated that the sounds in both study areas occurred mainly in the late afternoon and at night, where six recurrent fish chorus were found, with a frequency band between 200 and 2000 Hz, without overlapping and with different acoustic characteristics between species. The chorus presented high energy in the open sea, after the last reef line in the Tamandaré protected area (~ 130 dB re1μPa2 Hz-1). However, fish coral presented low energy levels in Porto de Galinhas, with a difference of 30 dB re1μPa2 Hz-1. In addition, characteristic sounds of invertebrates were detected with a dominant frequencies band of 2 and 3 kHz, besides noise produced by different types of fishing vessels, recreational boats and ships, that can masked and interfere in the fish communication. The monitoring of the complex soundscape found in Tamandaré during the summer showed a constant temporal overlap of fish chorus produced in the late afternoon. The fish chorus occurrence were related to different lunar phases, influencing in a different way both the initial and detection time, with variation mainly during the first quarter moon. This also occurred in the noises of detected vessels, with fishing vessels reporting mostly early in the morning, during the crescent and waning gibbous moon, and frequency bands <200 Hz with high energy peaks of easily distinguishable. In continental waters, passive acoustics allowed the evaluation of five characiform sounds of commercial importance (Potamorhina latior, P. altamazonica, Psectrogaster amazonica, Semaprochilodus insignis and Prochilodus nigricans). The sounds presented differences between genus and even between species, showing the specificity of sounds. Underwater recordings in areas of river confluences in the Madeira basin during the reproductive period in the high waters (January and February) indicated that P. latior and S. insignis produced similar sounds, using the same ecologic niche in the Guaporé River. P. latior preferred the confluences of the river and was the main sound producing species during the study period, being found in most of the evaluated sites. It was observed that only the males of these species have an extrinsic sonic muscle associated with the first ribs and fixed in an aponeurosis that surrounds the lateral swimbladder. These results can help identify and differentiate underwater sounds by monitoring and evaluating areas of occurrence, indicating the use of the method as a complementary tool for the monitoring of aquatic organism populations, mainly marine and freshwater fish species.