We propose to implement a random, depth-stratified vertical longline survey conducted through the annual sea ice in McMurdo Sound to monitor the age composition, diet, maturity, and local abundance of Antarctic toothfish. A pilot season was carried out in 2014, where sampling gear and methodology for a standardised hook and line survey were trialled in McMurdo Sound. Data collected will be integrated with ongoing collaborative research programmes to determine the importance of toothfish to mammalian predators in the area. Age composition, physiology, and diet objectives can be met with the current design. However, power analysis based on historical catch data suggests that the sample size (number of stations sampled per season) needed to detect a moderate change in the abundance index is likely to be higher than feasible at this stage. Therefore, techniques and additional infrastructure will be developed and tested to obtain the sample size and experimental design necessary to index abundance in the future.
Dr Rohan Currey (New Zealand)