Historically, acoustic telemetry studies tracking movement of aquatic organisms have lacked rigorous, long-term evaluations of detection range. The purpose of the present study was to identify potential sources of variability in long-term acoustic telemetry data, focusing specifically on environmental variability. The study was conducted for 15 mo in Gray's Reef National Marine Sanctuary, Georgia, USA, using 2 submersible Vemco VR2W hydrophone receivers and 2 stationary range test transmitters (controls). Tag detections (±1 SE) decreased from 54.2 ± 2.5 to 11.4 ± 0.5 detections d −1 as transmission distance increased from 100 to 300 m. Detections varied seasonally (likely due to stratification), with the direction of flood and ebb tidal currents (12.4 h cycle), and with tidal current speed (6.2 h cycle). Tides explained up to 92% of the short-term variability in hourly detection data. Detections also increased or decreased during episodic weather events depending on the season and type of event. These results suggest that stationary control tags are useful for characterizing variability in sound transmission in open water marine acoustic telemetry studies.

We surgically implanted coded-acoustic transmitters in a total of 46 coral reef fish during a saturation mission to the Aquarius Undersea Laboratory in August 2002. Aquarius is located within the Conch Reef Research Only Area, a no-take marine reserve in the northern Florida Keys National Marine Sanctuary. Over the course of 10 days, with daily bottom times of 7 hrs, saturation diving operations allowed us to collect, surgically tag, release, and subsequently track fishes entirely in situ. Fish were collected using baited traps deployed adjacent to the reef as well as nets manipulated on the bottom by divers. Surgical implantation of acoustic transmitters was conducted at a mobile surgical station that was moved to different sites across the reef. Each fish was revived from anesthetic and released as divers swam the fish about the reef. Short-term tracking of tagged fish was conducted by saturation divers, while long-term fish movement was recorded by a series of acoustic receivers deployed on the seafloor. Though not designed as an explicit comparison with surface tagging operations, the benefits of working entirely in situ were apparent.

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