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INT2021-02 Characterisation of protected coral interactions (PDF, 29,035K)

Summary

This study focused on analyzing the spatio-temporal distribution of observed coral captures in New Zealand’s commercial fisheries between the 2007–08 and 2019–20 fishing years.The majority (99%) of reported coral catch was attributed to bottom trawl fisheries. The study specifically examined trends in protected coral species groups, including black corals, gorgonians, lace corals, and stony corals.

The study suggests that the current grouping of protected coral species into stony corals, black corals, lace corals, and gorgonians is currently adequate to assess coralfisheries interactions broadly at a high taxonomic level. However, we recommend further differentiating of stony corals into stony cup corals and stony branching corals, as the latter have higher catch rates within bottom trawl fisheries. Further, disaggregating the stony coral group revealed that branching corals were typically caught within Fishery Management Areas (FMAs) 6 and 9, while cup-forming corals were typically caught
within FMA 4.

The analysis highlights the limitations of using catch weight as a measure of the impact of fishing on coral habitats. Large coral captures are often subjectively estimated, and the accuracy of reported catch weights is questionable. Therefore, catch weight is not considered a reliable indicator of fishery impact on coral communities. We suggest assessing the risk of commercial fishing on corals based on presence-absence data of coral captures.

The evaluation of coral bycatch data and presence-absence data suggests that stony corals are the most commonly reported group of corals in observed bycatch within and outside the Exclusive Economic Zone (EEZ), with much lower occurrences in observed bycatch of the other groups. Further, stony corals are predominantly caught in bottom trawl fisheries that target orange roughy in the North-East Chatham Rise region. The analysis of stony coral catch weights did not reveal a clear pattern over the assessed period, although the first three years stood out with particularly high reported catch weights. However, caution is necessary when interpreting these findings due to inconsistent methods of determining catch weights. While the analysis of presence-absence data can help identify risk areas of coral catch in commercial fisheries, it does not provide a comprehensive measure of the actual impact on coral communities. Factors such as habitat destruction, physical damage, and post-capture mortality should be considered. The study emphasizes the need for standardized protocols for determining coral catch weights and exploring alternative indicators that capture the broader ecological implications of fishing on coral habitats.

Publication information

Meyer, S. 2023. Characterisation of protected coral interactions. INT2021-02 final report prepared by Proteus for Conservation Services Programme, Department of Conservation 173 p.