Movements of blue sharks (Prionace glauca) in depth and course

Abstract

Abstract. Acoustic telemetry was used to follow 22 blue sharks, Prionace glauca (Linnaeus), over the continental shelf and slope in the region between George's Bank and Cape Hatteras between 1979 and 1986. The sharks frequently made vertical excursions between the surface and depths of several hundred meters. The oscillations, which were repeated every few hours, were largest in the daytime and were smaller in amplitude and confined to depths near the thermocline at night. This behavior was prominent in trials from August through March, but was not seen from June through July. Diving is discussed in terms of a hunting tactic and behavioral thermoregulation. Most of the sharks moved in a southeasterly direction from the release point and many maintained a constant course day and night for several days. The sharks may orient to the earth's magnetic field, or to the ocean's electric fields, allowing them to swim on a constant heading in the absence of celestial cues. These possibilities are discussed in the appendix.

Diel movement patterns of ocean sunfish Mola mola off southern California

“…There also may have been some inhibition of vertical movement for a short time following the initial stress-related dive, but it is unclear whether this was due to tagging stress. Carey & Scharold (1990), Block et al (1997) and(1992) observed similar behavior in blue sharks, yellowfin tuna and blue marlin, respectively, wherein diving patterns were less welldeveloped over approximately the first 12 h of tracking. Although it is difficult to determine the degree to which capture stress impacts post-release behavior, the occurrence of diel vertical movement patterns may provide some indication of speed of recovery that may only be obvious over longer tracks.…”

“…This reaction was brief (< 3 h) in most cases, and is well documented as a short-term stress response in various acoustically tagged pelagic fishes (e.g. Sciarrotta & Nelson 1977, Carey & Scharold 1990, Holland et al 1990a, Block et al 1992, Holts & Bedford 1993. There also may have been some inhibition of vertical movement for a short time following the initial stress-related dive, but it is unclear whether this was due to tagging stress.…”

“…Ocean sunfish horizontal movements were often highly directional; 7 of the 8 fish tracked exhibited significantly non-random movements over the entire (Carey & Scharold 1990, Klimley 1993, Holland et al 1999, blue marlin Makaira nigricans (Block et al 1992), and yellowfin tuna (Holland et al 1990b). While the orientation cues of directed movements are difficult to identify, some fish have been shown to orient to (Walker et al 1984, Moore et al 1990, Kobayashi & Kirschvink 1995.…”

“…This diel pattern is likely induced by changes in light intensity. Changes in diel light intensity are thought to initiate similar bounce diving behavior in other pelagic fishes, such as blue sharks Prionace glauca (Carey & Scharold 1990), swordfish Xiphias gladius (Carey & Robison 1981), and some tunas (Holland et al 1990b, Kitagawa et al 2000. Various explanations have been posited for this behavior, most of which focus on prey acquisition as the primary motivation for diving activity.…”

Movements of the reef manta ray (Manta alfredi) in the Red Sea using satellite and acoustic telemetry

“…These results highlight the importance of accurately delineating movements of individuals at scales relevant to species conservation. Advances in electronic tagging equipment provide a range of tracking technologies that enable assessment of the movement and habitat use of marine species ranging from hours (Carey et al 1990) to years (Block et al 2001) and across individual estuaries (Kneebone et al 2012) to ocean basins (Skomal et al 2009). …”