Summary

Shelf and ocean-basin scale methods of characterising mid-trophic level organisms (meso-zooplanktonic and micronekton communities ~2 to 20 cm length including small fish, crustaceans, squids and gelatinous) will provide valuable inputs to ecosystem-based fisheries management, marine planning and monitoring impacts of climate change. These mid-trophic level organisms regulate the primary production involved in biogeochemical cycles (e.g. CO² fixation) and are forage for top predators (e.g. tunas, seals, birds). Despite the enormous pelagic realm these organisms occupy and their pivotal role in the functioning of ecosystems linking biogeochemistry to the distribution and abundance of predators they remain one of the least known components of the ecosystem. Recent coupled ocean-biogeochemical-population models have identified a gap in knowledge of this area (Lehodey, 2004; Fulton et al., 2005). Ecosystem models need observations on the distribution and abundance of these micronekton mid-trophic functional groups at shelf and basin scale to validate predictions, but there are very few observations in southern hemisphere waters. These sparse observations come from a variety of sampling devices of limited spatial and temporal extent making it difficult to compare biomass estimates or determine the value of the data as an ecological indicator. The development of a cost effective bio-acoustic observation program that provides both large basin scale distribution and abundance coupled with targeted biological sampling for biodiversity, connectivity, trophic interactions and life history characteristics has been demonstrated to be achievable (Kloser et al. 2009). Kloser et al. (2009) demonstrated that the use of research and fishing vessels on transit can provide sustained repeatable basin scale observations of micronecton communities (Fig. 1). See example of fishing vessel data collection methods here.

Background

The Bio-Acoustic sub-facility is part of a major international effort that aims to develop a global ocean Mid-trophic Automatic Acoustic Sampler (MAAS) being proposed as part of the CLimate Impacts on Oceanic TOp Predators (CLIOTOP) program. CLIOTOP is a ten year programme implemented under the international research programmes GLOBEC (2005 to 2009) and IMBER (2010 to 2014), two components of the International Geosphere-Biosphere Programme (Handegard et al., 2009). CLIOTOP focuses on oceanic top predators within their ecosystems and is based on a worldwide comparative approach among regions, oceans and species. It requires a substantive international collaborative effort to identify, characterise, monitor and model the key processes involved in the dynamics of oceanic pelagic ecosystems in a context of both climate variability and change and intensive fishing of top predators (e.g. Lehodey et al. 2008 (Fig. 2). The goal is to improve knowledge and to develop a reliable predictive capacity combining observation and modelling for single species and ecosystem dynamics at short, medium and long term scales. It is proposed that observational platforms equipped with multi-frequency acoustics will provide data for identification and quantification of marine life on a global scale, and reliably transfer data to the users. It is envisaged that this will be achieved through a combination of existing components and expertise (e.g. ARGOS buoys, vessels of opportunity, moorings, etc.) capable of large scale monitoring of mid-trophic level prey organisms, their horizontal and vertical size-resolved distribution and abundance in the pelagic environment.

Several other international groups are focused on this area of work where the ICES Working Group Fisheries Acoustic Science and Technology provides key advice on standard protocols for calibration and data processing through its working and study groups. Calibration of acoustic instruments and standard processing protocols have been developed in this area over a number of years and published as cooperative research reports (http://www.ices.dk/products/cooperative.asp). This group meets annually to advance the science of bio-acoustics and further develop and check protocols (http://www.ices.dk/workinggroups/ViewWorkingGroup.aspx?ID=141). Likewise the CCAMLR sub group ASAMS meets to discuss specific issues of bio-acoustic surveys in the Southern Oceans.