PIRSA: Surveying, searching and promoting cuttlefish spawning activity in northern Spencer Gulf
SARDI Food Safety and Innovation
Mike A. Steer
Given the iconic nature of the Point Lowly cuttlefish population there is a need to provide a robust assessment of its annual status to inform management and the general public. Currently, management has initiated a spatial closure for upper Spencer Gulf (North of Wallaroo) as a precautionary measure to ensure that the cuttlefish population is not unnecessarily compromised by commercial and recreational fishing. Although, fishing has not been specifically identified to detrimentally affect the population it was the most amenable factor to control. It is therefore important to assess the relative status of the Point Lowly cuttlefish population to inform management and assist in the development of the most appropriate management strategies. Quantifying cuttlefish by-catch in association with this closure will provide greater resolution in regard to fishing pressure. There is also a need to determine whether there are alternate spawning grounds for the Giant Australian cuttlefish in northern Spencer Gulf to determine the relative conservational significance of Point Lowly and whether other areas within the region may require additional management consideration. It is clear that cuttlefish aggregate on the reef fringing Point Lowly, however, the specific characteristics and preferred dimensions of their dens and spawning substrate is unknown. For example, the preferred orientation, surface texture, depth range and exposure of natural spawning dens is not understood. Also there is a requirement to understand whether coastal pollutants play a role in shaping the distribution and relative abundance of aggregating cuttlefish. This level of information is required prior to the development and deployment of artificial spawning habitat that may be required to either mitigate habitat loss in the future or promote spawning in other areas where the habitat may be limited.
1. To use the standard survey methodology described in Steer et al. (2013) to estimate cuttlefish abundance and biomass of the Point Lowly spawning aggregation, characterise the spawning habitat and analyse the ambient water quality.
2. To explore and assess the potential of alternate cuttlefish spawning areas in northern Spencer Gulf.
3. Characterise the natural spawning substrate during the 2013 spawning season.
4. Use the ‘natural spawning preference’ information to design and develop artificial habitat with the intention of strategically deploying it in northern Spencer Gulf prior to the 2014 spawning season.
5. Determine the potential impact of fishing on giant cuttlefish in northern Spencer Gulf.
6. To assess whether there are abnormally high levels of metals accumulating in giant cuttlefish in northern Spencer Gulf.
Protection Authority through combined State and Federal funding. There is a commitment by all levels of government to understand more about the biology and ecology of this species to assist in determining the future management actions required to ensure its sustainability. The specific focus of this study’s research related to determining the relative significance of the Point Lowly aggregation within Northern Spencer Gulf; the impact of commercial fishing and industrial pollution (heavy metals) within the area on the population; and if spawning activity could be promoted in other areas away from historic breeding grounds through the use of artificial spawning habitat. The scope of research was diverse, involving extensive diver-based and video-based surveys; design, construction and deployment of artificial habitat; broad-scale collection of biological samples; and close collaboration with the commercial fishing industry within northern Spencer Gulf throughout 2013 and 2014.
Key Words: Giant Australian Cuttlefish, spawning, aggregation, population dynamics, by-catch, heavy metals, Spencer Gulf.