Quantifying the exposure, protection and recovery of seafloor habitats in Spencer Gulf to prawn trawling
University of Adelaide
Gretchen L. Grammer
An independent review (FishListic Pty Ltd. 2019) identified knowledge gaps that need to be addressed for the SGPF to have a successful re-assessment of their MSC certification. The review found that detailed information was needed on the percentage of key seafloor habitat types within and outside the trawl footprint. The review highlighted the need to visually monitor the SGPF’s associated habitats to address knowledge gaps of habitat extent, regeneration, detailed mapping, sensitivity and understanding of gear impacts. Specific knowledge gaps are: a) the presence/extent of sponge and rhodolith habitats currently in medium to high-intensity trawl areas; b) regeneration of sponge and rhodolith habitats previously subjected to high-intensity trawling; c) post-capture survivability of rhodolith pavement; and d) impact of gear on specific habitats. The MSC Fisheries Standard for Habitats (PI 2.4) requires explicit assessment of the fishery’s impact on commonly encountered habitats, vulnerable marine ecosystems (VMEs) and minor habitats. While VMEs are not currently designated in Spencer Gulf, the common, sensitive and minor habitats associated with the SGPF need to be evaluated. Data are needed on the amount of exposure of these habitats to prawn trawling in Spencer Gulf, as well as on their protection and recovery, to determine their status. In order for the SGPF to maintain its status as one of the world’s best managed prawn trawl fisheries and retain its social licence to operate, the requirements of MSC Principle 2: Habitat (2.4) need to be addressed. Seafloor habitat types found within the trawl grounds need to be visually monitored, described, quantified, and impacts from prawn trawling assessed. New understanding of the spatial and temporal distribution of key habitats and impacts from fishing in the context of the entire Spencer Gulf is needed to protect fisheries resources and the environment that supports them, and for integrated ecosystem-based management to be implemented in the future.
1. Estimate the proportion of key seafloor habitats (namely sponge gardens, rhodolith pavements and seagrass) and selected by-catch species that occur inside and outside the SGPF trawl footprint;
2. Quantify the spatial distribution of cumulative trawl intensity and time-since-trawled across Spencer Gulf;
3. Quantify the exposure and protection of seafloor habitats and by-catch species to trawling;
4. Estimate the potential regeneration timeframes of key seafloor habitats and assess their current status.