Southern Ocean Fisheries
Much of the research our group did when I was based at the Australian Antarctic Division was aimed at providing scientific input into the ‘ecosystem approach’ used to manage commercial harvesting of Antarctic marine living resources through the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). This includes our work on seabird diet, both for ecosystem monitoring using indicator species (e.g. Adélie penguin diet) and for examining direct interactions between seabirds and fisheries (e.g. black-browed albatross work done by Julie McInnes). In the laboratory we also did some other CCAMLR related work (A) the population genomics of Antarctic toothfish to look at population connectivity and (B) fish bycatch in the Antarctic krill fishery.
(A) Population genomics of Antarctic toothfish
Antarctic toothfish are long-lived, late-maturing and highly adapted to cold Antarctic waters. They utilise a broad range of habitats throughout their lifespan, from the epipelagic as planktonic larvae to benthopelagic slope habitats in excess of 2000 m depth. They are also fished at several sites around Antarctic and this international fishery is managed by CCAMLR
This project was run with the AAD fisheries research group and is funded through FRDC. The goal was to provide a better understand the spatial stock structure of the Antarctic toothfish and document how fishing mortality is distributed across the stock(s). Essentially, trying to answer the question: can we manage this fishery as a single stock, or does each distinct region represent a separate population? Another outcome of the project will be development of a large number of new genetic markers for this species and an initial evaluation of the feasibility of using close-kin mark-recapture to estimate population size (see an example of this approach here).
The work was led by Dale Maschette (pictured below). Dale spent two months in 2018 on the Southern Ocean collecting samples on a fishing vessel operated by Australian Longline Pty Ltd.
Hundreds of toothfish samples were collected from sites throughout the Southern Ocean and these have been genotyped at thousands of loci (using DArT sequencing). The project was covered in the Australian Antarctic Magazine (here) . Results showing very limited population structuring was presented as CCAMLR progress report, a final FRDC project report and published in peer-reviewed literature (PDF)
(B) Fish bycatch in the Antarctic krill fishery
Determining the scale and taxonomic identity of fish bycatch in the krill fishery has been a focus in CCAMLR for many years. Juvenile/larval fish, typically less than 60 mm, make up the vast majority of the fish that are caught as bycatch and taxonomic identification of these early life stages can be challenging.
Figure: Photos taken of juvenile fish bycatch by an observer on the FV Saga Sea
Our study examined the accuracy of juvenile fish taxonomy as reported by fishery observers. We used DNA barcoding to provide independent identification of a subset of samples from those identified by observers based on morphology. Although generally the taxonomy matched, there were a few common misidentifications made by the observers. In addition, DNA barcoding allowed many specimens to be assigned to species level that were only recorded to family-level by observers. Overall the diversity of fish identified by observers (5 families; 8 species) was considerably lower than with DNA barcoding (7 families; 20 species). The impact of potential taxonomic misidentifications on fish bycatch datasets needs to be considered. Developing standardised field guides and additional observer training many improve the accuracy of observer taxonomic assignments. This study was submitted as a CCAMLR paper to the Working Group on Ecosystem Monitoring and Management.