Tipo
Documentos Académicos
Tipo de Documento
Dissertação de Mestrado
Título
Evaluation of the utilization pattern of fish aggregation devices, installed in a reservoir in south Portugal
Participantes na publicação
Miguel Encarnado (Author)
Bernardo Quintella (Co-adviser)
Dep. Biologia Animal
MARE
Carlos Alexandre (Adviser)
Resumo
This study aimed to evaluate the patterns of use of prototype fish aggregation devices (FADs). It was carried out at the Nascentes reservoir (Crato), a small-to-medium Mediterranean reservoir (ca. 10 ha) in the south of Portugal. These FADs were installed to enhance the refuge habitat for fish species of interest for recreational fisheries, especially Largemouth bass (Micropterus salmoides Lacepéde, 1802) and Cyprinus carpio L and, consequently, promote the occurrence of trophy specimens. Two typologies of FADs were deployed and tested: 1) Bank FADs (TREES), used in shallow waters near the margins; 2) Pelagic FADs (DAP), suspended in the water column in deeper areas at the center of the reservoir. Two different methodologies were used to evaluate the pattern of use of these structures by fish. Underwater sonar equipment (i.e., ARIS EXPLORER 1800) was used to evaluate the patterns of use of FADs by all the fish assemblage occurring in the reservoir. The data was collected throughout 1 year, by counting the fish and classifying them by size class, in both types of FADs and respective control areas. Fish between 10 and 30 cm were the main users of pelagic devices, and the overall number of fish using these devices was higher when compared to the respective control areas. Acoustic telemetry based on a tridimensional positioning system was also used, by installing a network of receivers in the reservoir and tagging a total of 20 largemouth bass, 10 before the FADs deployment and 10 after. The results indicate strong evidence of the use of DAPs by fish, but not the use of TREES. Significant differences were found in the vital areas of tagged largemouth bass before and after FADs deployment. In the presence of FADs, fish reduced their vital areas and movement amplitudes, becoming more associated with these artificial habitats. Several environmental variables were also related to fish behavior in the presence of the artificial refuges, namely the day period, moonlight intensity, and depth use. The outcomes of this study are expected to contribute to defining guidelines for refuge habitat promotion in small-to-medium Mediterranean reservoirs, to foster the interest of these water bodies for recreational fishing activities.
Data de Publicação
2025-03-07
Instituição
INSTITUTO SUPERIOR DE AGRONOMIA
Identificadores da Publicação