Effects of hypoxia on oxygen consumption swimming

Authors: Quinn P Fitzgibbon Roger S Seymour Jeffery Buchanan Richard Musgrove John Carragher

Publish Date: 2010/07/14

Volume: 89, Issue: 1, Pages: 59-69

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Abstract

Of the few measurements of the behavioural and physiological responses of tuna to hypoxia most are restricted to shallow diving tropical species Furthermore when wild tuna experience low dissolved oxygen they are likely to have an increased oxygen demand associated with the metabolic cost of food digestion and assimilation specific dynamic action However the response of postprandial tuna to hypoxia has never been examined This study focuses on the metabolic and behavioural responses of both fasted and postprandial southern bluefin tuna Thunnus maccoyii to low dissolved oxygen Fasted T maccoyii were exposed to dissolved oxygen levels of 444 323 249 and 157 mg·l−1 for 20–21 h In moderate hypoxia 444 and 323 mg·l−1 swimming speed was enhanced 15 and 13 times normoxic speed respectively presumably to increase ventilation volume Routine metabolic rate R r was similarly elevated 13 and 12 times normoxic R r respectively most likely due to increased metabolic demand of faster swimming At 249 mg·l−1 swimming speed increased to over double the normoxic speed possibly as an escape response At 157 mg·l−1 both swimming speed and R r were reduced 08 and 09 times normoxic level respectively and tuna failed to survive the entire 20 h exposure period This reveals that the critical oxygen level of T maccoyii is between 157 and 249 mg·l−1 demonstrating that they are remarkably well adapted to low dissolved oxygen Feeding did not greatly influence their hypoxia tolerance with tuna surviving exposure to dissolved oxygen levels of 296 and 181 mg·l−1 for 21 h after ingesting a ration of 67 body weight of sardines Sardinops sagax In a subsequent experiment to determine the effects of hypoxia on digestion rate T maccoyii were fed to satiation and exposed to a dissolved oxygen level of 284 mg·l−1 for 65–8 h There was no significant difference in swimming speed R r and gastric evacuation rates of tuna in hypoxia compared to those in normoxia This demonstrates that in moderate to severe hypoxia T maccoyii are still capable of aerobically supporting maintenance metabolism routine swimming and specific dynamic action It is hypothesized that adaptations which support the large metabolic scope of tuna are also likely to be beneficial for oxygen extraction and delivery in conditions of hypoxiaQPF would like to thank the Breakwater Bay skippers Brenton Ebert John Collinson and Neil Chigwidden for their fine seamanship Divers Kane Williams and Dan Gorman for technical assistance David Ellis Tuna Boat Owners Association of South Australia DI Fishing Pty Ltd and Dave Warland for infrastructure setup and Thunnus maccoyii aquaculture industry support Stephen Clarke for program support and helpful advice Many thanks also to BOC gases for supplying gasses and diffuser This work formed part of a project of Aquafin CRC and received funds from the Australian Government’s CRCs Program the Fisheries RD Corporation and other CRC Participants

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