Movements and behaviors of swordfish in the Atlantic and Pacific Oceans examined using pop‐up satellite archival tags     

HEIDI DEWAR  ERIC D. PRINCE  MICHAEL K. MUSYL  RICHARD W. BRILL  CHUGEY SEPULVEDA  JIANGANG LUO  DAVID FOLEY  ERIC S. ORBESEN  DERKE SNODGRASS  R. MICHAEL LAURS  JOHN P. HOOLIHAN  BARBARA A. BLOCK  LIANNE M. MCNAUGHTON 《Fisheries Oceanography》2011,20(3):219-241

Swordfish are highly specialized top‐level predators that have been challenging to study. In this paper, data from 31 pop‐up satellite archival tags attached to swordfish from (i) the eastern Pacific, (ii) central Pacific, and (iii) western North Atlantic‐Caribbean were analyzed. Common across locations was a pronounced diel vertical pattern with daytime hours spent primarily below the thermocline and nighttime hours spent in warmer waters, close to the surface. One exception to this pattern was periodic daytime basking events which were most common in cooler waters off California. Maximum daytime depths were significantly correlated with light penetration as measured by the diffuse attenuation coefficient at 490 nm. Temperature did not appear to influence daytime depths, and swordfish tolerated both extremely low temperatures (4°C) and rapid and dramatic temperature changes (>20°C). Temperature did appear to influence the nighttime depths in the Pacific where fish typically remained in the surface mixed layer. In contrast, in the warm tropical Atlantic this was not the case, and nighttime depths were much deeper. In all areas, nighttime depth increased around the full moon. Given the parallels between the vertical movement patterns of swordfish and those of the deep sound scattering layer we suggest that swordfish vertical distribution patterns, especially during daytime, are influenced largely by resource availability. At night, when swordfish are typically targeted by fisheries, both ambient light and temperature influence movements. Understanding vertical movement patterns of swordfish can help evaluate gear vulnerability, improve population assessments, and potentially reduce fisheries bycatch.  相似文献   

Fine‐scale movements of the swordfish Xiphias gladius in the Southern California Bight     

CHUGEY A. SEPULVEDA  ASHLEY KNIGHT  NICOLE NASBY‐LUCAS  MICHAEL L. DOMEIER 《Fisheries Oceanography》2010,19(4):279-289

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.  相似文献