Fish hypnosis: Induction of an atonic immobility reflex

Authors: Wells, Rufus M. G.; McNeil, Heather; MacDonald, John A.

Source: Marine and Freshwater Behaviour and Physiology, Volume 38, Number 1, March 2005 , pp. 71-78(8)

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Abstract:

An immobility reflex may be induced in fish by a vigorous flow of water through the branchial chamber. The reflex was observed in 22 species representing bony and cartilaginous fishes from diverse habitats, and was invariably characterised by loss of caudal muscle tone and limp posture. The immobilised state may be maintained for many hours, and revival is instantaneous. The critical flow rate for induction increases with increasing body size in the snapper, Pagrus auratus, and heart rate falls below the resting rate. In addition, haematological parameters, and plasma lactate after 6?h were typical of resting fish. Although the mechanism is unclear, and the selective advantage for the fish unknown, pressure-sensitive receptors in the branchial chamber are likely to be involved. Application in live fish transport, and recovery from handling and exercise stressors is suggested.

Keywords: Immobilisation; Pagrus auratus; heart rate; haematology; lactate; water flow

Document Type: Research article

DOI: http://dx.doi.org/10.1080/10236240400029341

Affiliations: 1: School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand

Publication date: 2005-03-01