Tonic immobility has been found in multiple shark species but the onset and length of induction can be variable from species to species (Henningsen 1994 Brooks et al. Tonic immobility is frequently used in both wildlife research and aquarium husbandry to sedate shark species during restraint and limit injury to both the animal and personnel (Henningsen 1994 Holland et al. Tonic immobility can be induced by several stimuli, but external pressure and physical restraint are the most common (Bayard 1957 Jones 1986). Tonic immobility causes muscle hypertonicity in terrestrial vertebrates but relaxed muscle tone and a ‘limp’ posture develops in fish species (Thompson et al.
It is characterized by a reversible catatonic motionless posture, immobility, and an unresponsiveness to noxious or injurious stimulation. Tonic immobility is an innate, reversible, coma-like stasis displayed by a large number of wildlife taxa (Gallup 1974 Hennig et al. When capture and restraint is undertaken on wildlife, tonic immobility is often used as a method of calming or sedating the animal. As such, there is a need for the exploration of other non-lethal methods of capture of shark species, which cause less impact to the stress and welfare of captured animals (Barnett et al. 2001 Skomal 2007 Mandelman and Skomal 2008).
2012), which can lead to potentially lethal physiological consequences (Hoffmayer and Parsons 2001 Manire et al. However, although both techniques are potentially less stressful than some other capture methods, they may still result in captured animals struggling dramatically and thrashing violently (Brooks et al. Longline and drumline capture are the most frequent methods used. In order to implant tags to collect biological and movement data on shark populations, capture of target species is usually required. The relatively recent development of methodologies, such as acoustic and satellite telemetry and time depth recorders, have increased our knowledge of migration, distribution and population dynamics in shark populations (Heithaus et al. As such, management of shark populations has emerged as an important conversation priority (Godin and Worm 2010). Over the past half century there has been a dramatic increase in worldwide catches of shark species (Baum et al. Tonic immobility induction and other methods of non-lethal capture deserve continued investigation. Decreased duration of anthropogenic intervention, and minimal physical struggle associated with this capture and restraint method is expected to reduce physiological markers of distress. Divers were then able to collect tissue samples for genetic analysis, and in some cases, maintain the animals in a state of tonic immobility during transport up to the research vessel for additional data collection.
#ZEBRA SHARK LENGTH MANUAL#
Zebra sharks were caught by free diving, and on SCUBA, inducing a state of tonic immobility by quickly applying tight-fisted manual pressure to the caudal fin, instead of the dorso-ventral inversion method. Here, we present a novel, non-lethal capture method of zebra sharks, Stegostoma fasciatum, using tonic immobility, in the field. Tonic immobility is an innate, reversible, coma-like stasis displayed by a large number of taxa, including sharks, and has been used for brief restraint, but is rarely used during capture itself. The pectoral fins are large and broadly rounded.When conducting biological investigations on shark species, capture and brief restraint procedures may be required in order to collect ecological, behavioral and physiological data.
#ZEBRA SHARK LENGTH SKIN#
Adults have longitudinal skin ridges which are lacking in juveniles. Adults are yellow-brown with dark brown spots, young are black with yellow bars and juveniles smaller than 70 cm are dark with white bars and spots. This species is easily recognized by its very long caudal fin, which is almost as long as the rest of the body. Though of minor commercial importance, it is regularly taken in bottom trawls (outside Qatar), gill nets and longlines and utilized for human consumption and fishmeal. The Zebra Shark is widely distributed in the Indo-West Pacific, occurring from the Red Sea and East Africa to New Caledonia and Fiji, north to southern Japan, and south to Australia.Īccording to the IUCN Red List, it is globally Vulnerable (VU). They are normally harmless, but may bite if provoked. Zebra sharks are oviparous, laying eggs in large, dark egg cases. This species is a bottom-dwelling inshore shark, which is common in coral areas, where it mainly feeds on mollusks, but also on crustaceans, small fish, and sea snakes.
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