Where: Port Macquarie, Lighthouse Beach
When: 25th August 2023
Shark: Great White, Adult. (approx. 4mtrs)
Water Temp: 18 degrees
Chl.a: 4mg/m
Injuries: Serious
There are several strong indicators of increased risk for the Port Macquarie area leading up to this incident. With Bite Metrix reports analysing oceanographic factors and seasonality of previous shark incidents, we outline below these indicators that would warrant a high level of risk.
Seasonality
Previous shark-human interactions in nearby locations can provide an indication of shark movement patterns. These statistics are analysed by Bite Metrix to assist in establishing risk levels to create reports. Below is a list of negative interactions by Great White sharks near the location of the incident and the season.
Date: 22nd of August 2015, (2 days prior as per calendar year)
Where: Lighthouse Beach, Port Macquarie NSW. (same beach)
Shark: Great White Shark (same species)
Water Temp: 18 degrees (same temp)
Chl.a: 2mg/m
Injuries: Serious
Date: 15th August 2020, (10 days prior as per calendar year)
Where: Shelley Beach, Port Macquarie NSW (same city)
Shark: Great White Shark (same species)
Water Temp: 18 degrees (same temp)
Chl.a: 3mg/m
Injuries: Serious
Date: 5th September 2021, (10 days after as per calendar year)
Where: Coffs Coast, Emerald Beach (100kms north)
Shark: Great White Shark
Water Temp: 20 degrees
Chl.a: 2mg/m
Injuries: Fatal
Date: 5th July 2021, (31 days prior as per calendar year)
Where: Crescent Head, (25km north)
Shark: Great White Shark
Water Temp: 20 degrees
Chl.a: 2mg/m
Injuries: Serious
Oceanographic Factors
A strong upwelling event rotating and dredging nutrient rich cool waters from the deep ocean off the continental shelf for over a month made its way onto the shelf in the days leading up to the incident on the 25th of August.
Image via IMOS https://oceancurrent.aodn.org.au/
Image via IMOS https://oceancurrent.aodn.org.au/
Image via IMOS https://oceancurrent.aodn.org.au/
The above 3 images show the upwelling at 10 days prior, 5 days prior and the day of the attack. The black arrows indicate nutrient rich upwelling water and the current direction. As is shown in the second image, the cooler nutrient rich water is beginning spilling onto the shelf between Coffs and Laurieton, while the third image shows the nutrient rich cooler water spreading on top and along the shelf in the immediate area of the incident.
Image via IMOS https://oceancurrent.aodn.org.au/
The above image displays the ocean colour and density of Chlorophyll (phytoplankton) present in the water on the day of the incident. The green and yellow colouring identifies a large area of phytoplankton present in the water due to the high nutrient levels dredged from the ocean depths over a 3-week period. The red colouring indicating a dense phytoplankton bloom along the coast.
Conclusion
As is demonstrated in the above bite file, the strong indicators to establish a high-risk warning are present for the area where the incident took place. To confirm the presence of white sharks in the area there were also two white sharks between 2 and 3 metres caught on SMART drumlines in Port Macquarie in the five days leading up to the attack.
These conditions can take place along the coast at times when there are people in the water and thankfully there are no shark-human interactions however, as this shark-human interaction proves, when these conditions are present there is no doubt the risk level of an incident occurring is increased.
