SARDI have now completed their investigation into the mortalities of snapper larvae, oyster spat and barramundi broodstock and fingerlings at South Australian Aquatic Sciences Centre (SAASC) at West Beach.
The investigation was led by three highly experienced SARDI researchers, and has been independently reviewed by Professor Michael Goodsite, who has expertise in civil and environmental engineering.
Multiple lines of evidence were explored as part of the investigation, which included pathology reports, environmental water quality data, oceanographic analysis of coastal water movement, location and quantities of dredged sand placement, and site maintenance activities. The investigation found the cause of the mortalities to be inconclusive.
Pathology testing on affected larvae, spat, and fingerlings returned negative results for notifiable diseases and did not reveal any further clues to explain the mortalities.
Further, no direct evidence has been identified to link the mortalities to dredged sand placement or dredging activities conducted by the Department for Environment and Water (DEW).
The independent review by Professor Goodsite has confirmed the findings from the SARDI investigation.
Early life stages of fish and oysters are more vulnerable to environmental stressors than older life stages due to differences in physiological development, Due to their weak immune systems and sensitivity to water quality, stress and nutrition, it is not uncommon for larval fish to have high mortality rates both in the wild and in an aquaculture setting such as the one at the SAASC.
SARDI is working to mitigate future risks at the site by implementing a range of operational measures including inline water quality sensors with data logging capability and alarms on SARDI's raw seawater intake.
Despite the loss of some snapper larvae, the Malinauskas Government's $1.2 million snapper restocking program will continue, with a new batch of fingerlings set to be produced and released next summer. The program aims to release close to one million snapper fingerlings into South Australia's gulfs, with more than 600,000 already released.
PIRSA-SARDI are working closely with the privately owned barramundi hatchery on site as it returns to its normal operations.
As put by Clare Scriven
SARDI researchers, particularly marine sciences, are highly regarded in their field of expertise.
The mortalities of larvae, spat, fingerlings and broodstock at the SAASC were unfortunate, and disappointing for all involved, not least the team at SARDI who dedicate their careers to our world class research and breeding programs at the West Beach site.
While there are times when causes for events such as these cannot be conclusively found, learnings can still be applied for future activities. SARDI is already implementing mitigation measures for any future events.
