Identifying vulnerable invertebrates in toothfish bycatch
Information on vulnerable marine invertebrates caught as bycatch in the Ross Sea toothfish fishery is helping to assess the environmental impacts of the fishery. It also contributes to knowledge of vulnerable species distribution in Antarctic waters.
NIWA is providing classification guides and training for Ministry of Fisheries (MFish) scientific observers aboard commercial toothfish vessels. This will help them to accurately identify especially vulnerable invertebrates accidentally caught on toothfish longlines.
Structure-forming benthic invertebrates (those that provide three-dimensional structure in seafloor habitats) may be especially vulnerable to disturbance by bottom longlines used to catch Antarctic toothfish. These longlines can be up to 20 kilometres long and carry thousands of hooks.
The Committee for the Conservation of Antarctic Marine Living Resources (CCAMLR) has identified 23 groups of invertebrates that are considered especially vulnerable, including sponges, corals, basket stars, and bryozoans. Some of these groups may be very similar in appearance, highlighting the need for at-sea guides and training.
Improving identification of vulnerable invertebrates
MFish funded NIWA in 2008 to produce an identification guide for invertebrate taxa caught as bycatch in the Ross Sea. The laminated guide has been well received by observers and has been translated into several languages for use internationally.
In addition, NIWA taxonomists have evaluated invertebrate identifications made by MFish observers on four commercial toothfish vessels for the past two years. Last summer, the observers identified 88% of 4555 specimens accurately using the VME guide, with mistakes mainly confined to groups that appear very similar.
To further improve accuracy, NIWA scientist Di Tracey and assistant collection manager Sadie Mills recently ran a training session for observers about to join toothfish vessels heading to the Ross Sea. The training focussed on distinguishing easily confused sponges; separating sponges from ascidians (sea squirts); and identifying corals that are specifically regulated (most corals, including red hydrocorals and the precious coral Corallium)
Spatial distributions of vulnerable invertebrates
Nelson-based NIWA fisheries scientist Steve Parker uses the bycatch data to analyse the spatial distribution of several vulnerable benthic invertebrate groups. The analyses also use data from underwater video transects collected during the 2008 International Polar Year – Census of Antarctic Marine Life voyage.
The research shows that, although longlines are not well designed to sample benthic invertebrates, longline bycatch data do map invertebrate distributions within the areas fished. Spatial analyses show that some areas in the Ross Sea will be more vulnerable than others, due to the composition of benthic communities inhabiting particular seafloor features.
Learning about which organisms live in the Ross Sea, and the areas they are likely to be found, is necessary to develop spatial protection measures to manage fishery impacts on benthic ecosystems in Antarctic waters.