ASFB Home > The effects of spatial and temporal factors on the abundance of seven key finfish species along south-western Australia.

The Effects of Water Temperature on Spacial Distribution and Burst Swimming in Some MDB Fishes

Jarod Lyon, Tom Ryan and Ruth Lennie

Arthur Rylah Institute For Environmental Research, HEIDELBERG, AUSTRALIA

THEME: ASFB (Poster)

Behavioural and physiological responses of fish to cold water releases can partly explain the reduced distribution & abundance of many Australian species. Thermal preferences and burst swimming performances were determined for two key native fish species, and compared to data obtained for an introduced predatory fish. The results will be used to assess the implication of thermal barriers to fish migration, evaluate the current fish distribution patterns in relation to rivers with impacted thermal regimes, and discover impacts on predator prey interactions within these areas. Temperature preference trials were conducted on golden perch (Macquaria ambigua), Murray cod (Maccullochella peelii peelii) and rainbow trout (Oncorhynchus mykiss) using a temperature gradient tank. M. ambigua (50 - 68 mm) and M. peelii (57 - 72 mm) demonstrated a preference for warm water with median occurrences from 24 - 31 oC and 24 to 33 oC respectively. In contrast juvenile rainbow trout (45 - 68 mm) demonstrated a preference for water with a median occurrences from 10 to 21 oC. Burst swimming trials were conducted under different temperatures on M.ambigua and M.peelii. M. ambigua of statistically similar size classes (p=0.05) were acclimatised for 21 days at the test temperatures. Results revealed swimming performances were significantly lower at 10 oC and 12.5 oC than at the higher temperatures (15.5 oC, 18.5 oC, 21.5 oC, 24.5 oC). Despite possible size related effects, M. peelii acclimatised for 3 months to each of the test temperatures were significantly faster at 24.5 oC than at 12.5 oC and 15.5 oC. Results obtained from northern-hemisphere tests of O.mykiss show a greater ability to perform fast starts at lower temperatures than M.peelii and M.ambigua. This study demonstrates the competitive advantage that O.mykiss have in cold water conditions compared to the native species tested and provides information on the optimal temperature conditions in terms of biological and physiological performance.