Availability of toothfish to predators – sea ice-based survey

Sea ice-based toothfish surveys have been carried out in McMurdo Sound since 2014.

Sea ice-based toothfish surveys have been carried out in McMurdo Sound since 2014. The surveys document the spatial distribution, relative abundance, diet and reproductive status of toothfish in McMurdo Sound. Antarctica New Zealand provides logistical support. [NIWA]

Toothfish sampling sites are generated randomly in depths deeper than 500 m, and then sampled if access is safe. [NIWA]

Video - underwater observations of Antarctic toothfish

This is the first ever recording of toothfish swimming and interacting with each other. This video has been filmed in McMurdo Sound at a depth of 587 m. Video observations of this species can teach us about their ecology by the way they swim, how they interact with bait, and how they interact with each other. [Simone Pietro Canese]

Video - sampling toothfish

Sampling toothfish on sea ice can be uncomfortable. A fish hut provides protection from the weather and allows scientists to collect many samples.

Video - new technology used to study distribution and abundance of toothfish

In collaboration with our Italian colleagues, we plan to use acoustics - and possibly video techniques - to study the distribution and abundance of Antarctic silverfish in McMurdo Sound and in Terra Nova Bay.

Catch rates of Antarctic toothfish from Ainley et al 2012 plus catch rates observed by NIWA since 2014

Throughout the period where adequate data were collected, the average size of toothfish was about 135 cm, including during 2014 and 2015. There is no lack of large or small fish. [NIWA]

Age composition of Antarctic toothfish samples in November 2015 in McMurdo Sound.

 

In collaboration with Italian colleagues, we have collected toothfish stomach samples for diet, ovaries for reproductive studies, and additional tissue samples for physiological studies including stable isotope indicators of long term diet. We have also collected sensory organs to learn about sensory physiology and prey detection, and blood plasma for endocrine studies. [NIWA]

 

Using calibrated acoustics, we have measured the target strength of individual toothfish during capture. These data can be useful in identifying toothfish in other regions of the Ross Sea, when conducting acoustic surveys for other species such as macrourids (rattails). [NIWA]

 

We have trialled a real-time video image processing system that detects motion in the hole in the ice when a seal surfaces. We then record the following two 2 minutes to document when and how seals use the hole and if they bring toothfish they’d caught to the surface for processing (They can’t eat toothfish underwater). We plan to use this system to document and monitor the sampling sites, to look for a correlation between the presence of seals and toothfish catch rates. [NIWA]

Research subject: Antarctica