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The 1995 mass mortality of pilchard: no role found for physical or biological oceanographic factors in Australia

journal contribution
posted on 2023-05-16, 10:29 authored by Griffin, DA, Thompson, PA, Bax, NJ, Bradford, RW, Gustaaf HallegraeffGustaaf Hallegraeff
An unprecedented mass mortality of pilchard, Sardinops sagax, occurred in Australia in 1995, spreading east and west from the Great Australian Bight at approximately 0.5 m s-1 and 0.3 m s-1 respectively to span the 6000-km range of the species from Noosa, Queensland, to Geraldton, Western Australia. Mortalities with the same clinical signs of hypoxia also occurred in New Zealand. Upwelling and phytoplankton blooms preceded the first mortalities, leading to widely publicized speculation that environmental stress caused the mortalities. However, upwellings as strong as in February 1995 off Eyre Peninsula occur as often as once every three or four years, and environmental conditions surrounding mortalities elsewhere were normal. Phytoplankton blooms were absent through much of the range; where they did accompany mortalities they were of widely differing species. Hence, the hypothesis that environmental stress caused the mortalities is quite confidently rejected. The hypothesis that ocean currents were a vector of an aeteological agent is also rejected, since the Leeuwin and East Australian currents were both flowing strongly against the spread of mortalities. Other potential vectors exist, however, so the hypothesis that an introduced pathogen was responsible cannot be rejected.

History

Publication title

Marine Freshwater Research

Volume

48

Pagination

27-42

ISSN

1323-1650

Department/School

School of Natural Sciences

Publisher

CSIRO

Place of publication

Victoria, Australia

Repository Status

  • Restricted

Socio-economic Objectives

Assessment and management of terrestrial ecosystems

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