Huon Aquaculture and the NSW Department of Primary Industries will continue the joint trial of ocean- farmed yellowtail kingfish production albeit under a more stringent maintenance regime.
The farm’s future was thrown into question when 20,000 fish escaped one of three pens in January.
The cause, released in an Investigation Summary on Friday, was put down to a combination of vigorous barnacle growth on the pen’s mooring system and large seas.
“These barnacles are more robust and quicker growing than barnacle species in Tasmania, where Huon’s similar operations have withstood similar weather conditions,” the authors found.
The trial is located seven kilometres off Port Stephens in a Marine Aquaculture Research Lease, within the marine park.
In preparation for the trial Huon engaged independent modelling experts from Norway to identify the engineering specifications required for Providence Bay.
This was based on data collected from a current and wave buoy located by Huon in Providence Bay and back casting Bureau of Meteorology Data.
The results of this modelling indicated that the infrastructure could withstand significant wave heights of 8.5m from the south and 6.5m from the south east.
Between January 14 and 18 the MARL experienced “severe, strong southerly winds and large south to south east swells”. The report noted that this severe weather event was caused by two low pressure systems off the east coast of NSW.
The maximum wave height recorded at the Crowdy Head wave buoy on January 16 was was 11.27m, with “significant wave heights” peaking at 5.35m from the south-south east.
The Sydney wave buoy also recorded similar conditions. At the time of the incident there were five sea pens on site with three stocked with Yellowtail Kingfish, totalling 60,000 farmed fish on site.
Inspections were undertaken once safe, and revealed one of the five sea pens (1602) was seriously damaged, resulting in the escape of 20,000 farmed yellowtail kingfish.
The investigation found that the biofouling growth led to damage of sea pen 1602 in two key ways: Firstly, the barnacles, which appear to have caused damage to a number of ropes, led to the remaining ropes holding the nets becoming overloaded. Secondly, the excessive weight – due to the ‘biofouling’ growth – put extra strain on the net rigging once the initial compromised ropes had been severed.
“Huon is taking steps to regularly inspect the remaining pens and address future risk by updating cleaning procedures as part of the trial,” the report’s authors said
“NSW DPI and Huon will be implementing the recommendations of the full investigation report.”
The Investigation Summary also reviewed the closure of the MARL while Huon staff sought to recapture the fish.
The report authors noted a “large number of recreational and commercial fishers” were frequenting the area around the lease, by January 25, resulting in safety concerns for investigators and staff responding to the incident.
“Despite efforts of NSW DPI, Roads and Maritime Service and Water Police to provide advice and to keep fishers away from recovery efforts, the volume of traffic within the lease area hindered efforts and was a hazard to workers and divers,” the authors found.
“Recreational fishermen were not adhering to the minimum separation distance of 60m from divers in the water.”
In order to enact the Emergency Protocol and recapture the fish a temporary Section 8 Fishing Closure under the Fisheries Management Act 1994 was put in place on the lease.
This was to cease on February 7 but has since been extended to February 28 while recovery efforts continue.