A wireless communication system for determining site fidelity of juvenile dusky groupers Epinephelus marginatus (Lowe, 1834) using coded acoustic transmitters

• Published in: Hydrobiologia 2002-09, Vol.483 (1-3), p.249-257
• Main Authors: LEMBO, G, SPEDICATO, M. T, ØKLAND, F, CARBONARA, P, FLEMING, I. A, MCKINLEY, R. S, THORSTAD, E. B, SISAK, M, RAGONESE, S
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Conservation, protection and management of environment and wildlife; Epinephelus marginatus; Fundamental and applied biological sciences. Psychology; Hydrophones; Marine; Parks, reserves, wildlife conservation. Endangered species: population survey and restocking; Protected species; Site fidelity; Tagging; Threatened species; Transmitters; Wave action; Wireless communications
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1023/A:1021360419150

The value of marine reserves to protect threatened and vulnerable species, such as the dusky grouper (Epinephelus marginatus), is often uncertain because of a lack of knowledge about their ecology and habitat utilisation. To address this issue, a Wireless Communication System for location-based positioning of fish tagged with coded acoustic transmitters was installed to determine site fidelity of juvenile dusky groupers (mean total length = 30.4 cm, range: 20.5-40.0 cm; mean total weight = 470 g, range: 113-950 g) within a marine reserve (Island of Ustica, Sicily, Italy). The system was based on five wireless hydrophones distributed approximately 200 m apart along the coastline of the reserve, each monitoring acoustic signals from transmitters within a reception cell. The hydrophones retransmitted detected signals as a radio signal to a land-based receiver and data logger. Unique identifiers for each hydrophone permitted the identification of the detection cell containing the tagged fish. The wireless hydrophones had partly overlapping detection ranges, dividing the marine reserve into more than five different detection cells. The average detection range was 232 m, but coverage varied from site to site and with time, depending on many factors, such as ambient noise, wave action and signal strength of the transmitters. Despite some limitations, the Wireless Hydrophone System (WHS) combined with manual tracking provided a valuable tool for investigating site fidelity in the dusky grouper. Preliminary home ranges for the fish were estimated by the kernel method (probability level of 95%), based on a limited set of manual tracking data, to be a median 5312 m^sup 2^ (range 1673-18626 m^sup 2^).[PUBLICATION ABSTRACT]