Science Centres: Fisheries

Antarctic silverfish (Pleuragramma antarcticum), one of the key components of foodwebs in the Ross Sea. (Photo: Richard O’Driscoll, NZ IPY-CAML)

The recent New Zealand International Polar Year – Census of Antarctic Marine Life (NZ IPY-CAML) survey to the Ross Sea will produce the first-ever abundance estimates for Antarctic silverfish (Pleuragramma antarcticum) using acoustics.

Silverfish are a small pelagic (free-swimming) fish that act as a key link between plankton and the top predators such as seals,penguins, and toothfish, in the shelf waters of the Ross Sea. Very little is known about their distribution and abundance.

Because they don’t have a gas-filled swim bladder, silverfish produce a very weak echo at the low frequencies commonly used for acoustic surveys in New Zealand waters. But they do form distinctive acoustic marks at higher frequencies.

“We were able to distinguish between the different species in the Ross Sea using a four-frequency echosounder system,” says NIWA fisheries scientist Richard O’Driscoll, who led the research. “We found silverfish distributed across most of the Ross Sea shelf.”

Specimens were collected for modelling acoustic target strength. These data will be used to convert observed acoustic scattering values into estimates of silverfish biomass. The estimates will form an important part of a Ross Sea ecosystem model, currently being developed.

The NZ IPY-CAML voyage was funded by Land Information New Zealand.