As part of Australia’s Integrated Marine Observing System (IMOS) acoustic data is being collected at basin scales from ships of opportunity (BASOOP). Since July 2010, 137 transects from 17 vessels covering 310,634 km have been processed and available on-line (http://imos.org.au/). These acoustic data give wide spatial and temporal coverage of scattering layers in the southern ocean for use in the MESOPP project (Figure 1). Key uses of the data will be to interpret scattering layers into biological units (such as dominant functional groups, biomass and size) using ecological and observational models. To assist in interpreting scattering layers into biological units, nets are often used. Nets have known catchability issues for a range of taxa where small sized individuals (e.g. fish) and gelatinous organisms can be grossly underrepresented in the catch, biasing interpretations. To investigate this bias and further explore scattering layer composition in situ acoustic and optical methods are also used.

IMOS bio-acoustic transects with an underlay of the annual net primary production daily average for 2015

Figure 1 Map of the southern ocean highlighting the IMOS bio-acoustic transects with an underlay of the annual net primary production daily average for 2015 (source 0regon State). The pink dot highlights the location of the IN2017_V02 voyage where detailed trials were done with

To advance in situ acoustic and optical methods a profiling lagrangian acoustic optical system (PLAOS) has been developed (Figure 2). In March the PLAOS was trialed in the southern ocean on the research vessel RV Investigator IN20167_V02 incorporating broadband echo sounders with some interesting video observations. Predator prey interactions are very important and dynamic in the pelagic realm with squids observed to be very optimistic feeders (https://blog.csiro.au/squid-attack-clip-mystery-still-unsolved/ ). The video shows the PLAOS as it is descending to 1000 m with a calibration sphere suspended at 5 m and white tags for optical reference every 1 m. Data collected from this voyage will be used to assist in the interpretation and conversion of the IMOS broad scale acoustic returns into biological units within the MESOPP project.

The profiling lagrangian acoustic optical system (PLAOS)

Figure 2. The profiling lagrangian acoustic optical system (PLAOS) being retrieved on IN2017_V02.

Recent reference material

  • Davison, P., Koslow, T. A., and Kloser, R. J. 2015. Acoustic biomass estimation of mesopelagic fishes: backscattering from individuals populations, and communities. ICES J. Mar. Sci.
  • Kloser, R. J., Ryan, T. E., Keith, G., and Gershwin, L. 2016. Deep-scattering layer, gas-bladder density, and size estimates using a two-frequency acoustic and optical probe. ICES Journal of Marine Science: Journal du Conseil, 73: 2037-2048.
  • Marouchos, A., Sherlock, M., Kloser, R., Ryan, T., and Cordell, J. 2016. A profiling acoustic and optical system (pAOS) for pelagic studies; Prototype development and testing. In OCEANS 2016-Shanghai, pp. 1-6. IEEE.