ASFB Home > 2003 > Biological Invasions: Consequences for Parasites, Pathogens, Emerging Diseases, and Fisheries in the Marine Environment.

Can egg strontium content be used to differentiate between sea-run and resident brown trout spawning redds?

Gerard P. Closs¹, Mohammad Reza Sangi², and Joathan Kim³

¹Department of Zoology, University of Otago, PO Box 56, Dunedin, New Zealand.
²Department of Chemistry, Arak Univesity, Arak, Iran
³Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand
Email: gerry.closs@stonebow.otago.ac.nz

The strontium (Sr) content of eggs was used to identify redds formed by either sea-run or resident brown trout in tributaries of the Taieri River, South Island, New Zealand. Eggs were collected from 106 redds distributed across the lower reaches of 13 tributaries of the Taieri River. Sites sampled ranged from 35 km inland and 20 m above sea level, to sites 239 km inland and 560 m above sea level. In addition, eggs were collected from 3 redds known to have been formed by sea-run trout from the Water of Leith stream to provide a measure of the expected Sr content in eggs of sea run fish. 41% (n = 17) and 43% (n = 16) of redds from Silverstream (35km inland) and Big Stream (58km inland) were identified as sea-run redds. Single redds from sea-run fish were recorded in each of Christmas Creek (n = 7; 62km inland) and Sutton Stream (n = 9; 95km inland). The results suggest that the Sr content of eggs can be used to differentiate between the spawning redds of sea-run and resident brown trout, and that sea-run brown trout form a significant proportion of spawning trout in the lower reaches of the Taieri River catchment.

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