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Summary
Theme 1 of the Conservation Services Programme’s Medium-Term Research Plan (MTRP) for protected corals highlights the requirements for species-level data in determinations of susceptibility to commercial fishing impacts. However, most protected gorgonian corals (Cnidaria: Anthozoa: Octocorallia) known to occur in the territorial seas of Aotearoa New Zealand (NZ) have not been documented at the species-level and many represent undescribed taxa that lack formal scientific names. The ubiquitous sea-fans of the family Paramuriceidae are recognised as one of the most diverse groups of gorgonians within the EEZ but there are currently only two records of described species from this group in NZ, despite being a regular component of bottom trawl bycatch in commercial fishing operations.
This research addresses Biodiversity and Distribution aspects of Theme 1 of the coral MTRP, using genetic delimitation of species that are distributed across spatially explicit regions of relevance to commercial fishing activities. Genomic DNA sequencing using target-bait enrichment was applied to available specimens of the Paramuriceidae held in the NIWA Invertebrate Collection, which were obtained from both bycatch and non-bycatch sources on the Chatham Rise (Fisheries Management Area (FMA4) and Campbell and Bounty plateaus (FMA6). DNA sequencing was used to objectively determine the number of distinct taxa present in each region and examine fishing-related impacts on protected coral diversity. Fifty-one specimens were successfully sequenced, and 32 distinct taxa were discriminated, including a distinct genetic lineage that may represent a new family of protected gorgonians. The two FMA regions shared representatives of most major lineages, but one lineage was confined to the Chatham Rise and the members of the tentative new family were confined to the Campbell and Bounty plateaus, where they were obtained primarily as bycatch. Overall, all major genetic lineages were represented among sampled bycatch, with the exception of the lineage found only on the Chatham Rise. In combination with previous genetic characterisation efforts, the current project brings the total number of protected octocorals represented in trawl bycatch that have been genetically detected or confirmed to 43 taxa (genera and species) distributed amongst at least seven families (five described, one in question, one undescribed).
The continued use of genomic approaches in the characterisation of coral bycatch is warranted by its ability to produce large amounts of informative data that can resolve relationships at multiple taxonomic levels, and its resilience to highly degraded sample sources that include dried and aged archival tissues. While the current and previous studies support target-bait enrichment as an effective means of characterising the identity and relationships of bycatch specimens, recent advances and cost reductions in whole genome ‘skimming’ make it an attractive method for generating comparable genomic and genetic data for protected corals, which can be implemented within NZ, without need for specialised overseas providers.
Publication information
Bilewitch, J. 2024. High-resolution estimation of species diversity for a protected coral family commonly occurring as trawl bycatch. INT2023-05 final report prepared by NIWA for Department of Conservation. 31 p.