Using a 3-D positioning acoustic system to study the behaviour and habitat use of largemouth bass (Micropterus salmoides Lacépède, 1802) in a Mediterranean reservoir

Abstract

In the Mediterranean region, the largemouth bass (Micropterus salmoides Lacépède, 1802) is a non-indigenous species of high interest for recreational fisheries, but the knowledge about its movement patterns is still very scarce. The main objective of this study is to analyse the behaviour and habitat use of largemouth bass in a typical Mediterranean reservoir. With this purpose we used a biotelemetry acoustic system for 3-D positioning, the VEMCO Positioning System (VPS) to continuously track largemouth bass movements along the 19 ha of the Nascentes reservoir. An array of six fixed VR2tx acoustic receivers and two V9 reference tags were deployed with a design set according to the reservoir’s bathymetric and morphologic characteristics. Detection Efficiency and Positioning Error of the deployed acoustic system were measured through a range test revealing a Detection Efficiency of 95% and a Positioning Error around 6 m. After validation of this system, 10 fishes were tagged with V9P acoustic transmitters that provide their position and depth every 120 s. The study began in June 2018 and will continue for a 1-year period. Preliminary results for the first three months provided a total of 93 304 positions, an average of 10 367 per fish. Kernel Density Estimation (KDE) analyses on individual positions allowed to identify larger home ranges for this species during daytime (Day: 12 ha; Night: 10 ha, on average). Linear regression on water temperature and depth of the fish revealed a significant negative relationship between these two variables, meaning that during low temperature hours largemouth basses tend to occupy deeper areas within the reservoir. The information obtained in this study can be very important for the management of the target species and small/medium size reservoirs, more specifically regarding the promotion of recreational fishing in the Mediterranean region.