This study reports on the fine-scale movements of swordfish (Xiphias gladius) outfitted with pop-off satellite archival transmitters (PSATs) in the Southern California Bight (SCB). PSATs were deployed on basking swordfish using traditional harpoon methods from 2004 to 2006. Transmitters were programmed for short-term deployment (2-90 days) and re-acquired using a signal direction finder. High-resolution (min )1 ) depth and temperature data from nine swordfish (approximately 45-120 kg) were collected (>193 days). All swordfish displayed diurnal vertical movements similar to those reported for other geographic locations. The dominant diurnal movement pattern entailed swordfish remaining below the thermocline (>68 ± 15 m) during the day and near the surface, within the upper-mixed layer, at night. Collectively, the average daytime depth (±SE) was 273 ± 11 m and the average night depth 31 ± 5 m. Three distinct vertical behaviors were recorded: 35% of the records following a strict diurnal pattern, with the entire day below the thermocline and the entire night near the surface; 52% of the records revealed routine surface-basking events during the day, with an otherwise similar distribution at night; and 13% of the records exhibited surface-oriented activity during the day and night. Surface basking (<3 m during the day) was recorded for eight individuals and occurred on 131 of the 193 days (68% of the dataset). Collectively, surface basking accounted for 8% of the total daytime records. The relevance of these vertical behaviors to SCB fisheries is discussed.
Little is known about the role that patterns of habitat selection play in mediating movement of Atlantic cod Gadus morhua, particularly in off-shore environments. We used acoustic telemetry to study the movement of adult cod tagged at deep boulder reefs (DBRs) in the western Gulf of , and data on each fish were recorded for up to 95 d post-release. Twenty-three cod (35.4% of tagged fish) exhibited high site fidelity to the DBR where they were caught and released (recorded in > 82% of the 1 h time bins), while 33 cod (50.8% of tagged fish) appeared to depart the area rapidly following release (recorded in < 20% of the 1 h time bins). Cod with high site fidelity exhibited no pattern of diel activity. Cod movement among DBRs was recorded in both sampling periods (maximum linear distance of at least 24 km). Patterns of site fidelity and movement did not differ significantly with fish total length, among individual DBRs, or between sampling periods. Understanding the spatial dynamics of fish populations with both resident and transient components that are linked to particular habitats can aid in development of unique management strategies for both sustainable fisheries and conservation of biological diversity.
A B S T R A C TA variety of video and photographic imaging platforms are used to survey seafloor habitats and organisms beyond the effective depth of most SCUBA diving (>30 m). Each platform has benefits and shortcomings, with the most frequently limiting factors being (a) access to the most advanced instruments, (b) response of organisms, and (c) resolution of organism identification. Here, we describe the approaches used to collect, process, and analyze video imagery collected with a simple towed camera sled in the Monterey Bay National Marine Sanctuary as part of a larger, ongoing characterization project that began in 2006. We describe the details of deployment, imagery collection, postprocessing, and analyses gleaned from hundreds of hours of underwater video. Data extracted from camera sled imagery have been analyzed using multivariate model comparison techniques and have been represented in a variety of forms to support management needs and public outreach efforts.
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