|Hypoxia increases the behavioural activity of schooling herring: a response to physiological stress or respiratory distress?|Herbert, N.A.; Steffensen, J.F. (2006). Hypoxia increases the behavioural activity of schooling herring: a response to physiological stress or respiratory distress? Mar. Biol. (Berl.) 149(5): 1217-1225. hdl.handle.net/10.1007/s00227-006-0284-6
In: Marine Biology. Springer: Heidelberg; Berlin. ISSN 0025-3162, more
|Authors|| || Top |
- Herbert, N.A.
- Steffensen, J.F.
Atlantic herring, Clupea harengus, increase their swimming speed during low O2 (hypoxia) and it has been hypothesised that the behavioural response is modulated by the degree of “respiratory distress” (i.e. a rise in anaerobic metabolism and severe physiological stress). To test directly whether a deviation in physiological homeostasis is associated with any change in behavioural activity, we exposed C. harengus in a school to a progressive stepwise decline in water oxygen pressure (PO2=20.4,15.2,12.7,10.6,8.5,6.4and4.2kPa) and measured fish swimming speed and valid indicators of primary and secondary stress (i.e. blood cortisol, lactate, glucose and osmolality). Herring in hypoxia increased their swimming speed by 11–39% but only when PO2 was <8.5 kPa and in an unsteady (i.e. declining) state. In parallel with the shift in behaviour, plasma cortisol also exhibited an increase with PO2=8.5kPa, plasma osmolality was subject to a transient rise at 8.5 kPa and plasma glucose was generally reduced at PO2=12.7kPa. However, without any rise in anaerobically derived lactate levels, there was no evidence of respiratory distress at any set PO2. We show that a shift in physiological homeostasis is indeed linked with an increase in the swimming speed of herring but the physiological response reflects a hypoxia-induced shift in metabolic fuel-use rather than respiratory distress per se. The significance of this behavioural–physiological reaction is discussed in terms of behavioural-energetic trade-offs, schooling dynamics and the hypoxia tolerance of herring.