MIDOC: An improved open and closing net system for stratified sampling of mid-water biota

In support of ecosystem and fisheries studies the CSIRO has deployed a variety of towed and tethered systems to collect quantitative data to understand the distribution and makeup of mid-water biota. A series of platforms have been developed at the CSIRO which incorporate both imaging and acoustics to augment the physical samples. Although these systems provide high fidelity data, they often require specialised technical staff to operate, which limits their use on commercial vessels and vessels of opportunity where it is impractical and/or too costly to dedicate staff to their use. As such it was necessary to develop a self-contained system which could collect stratified physical samples and be deployed in a flexible manner from a variety of vessels with minimal to no technical supervision. A self-contained MIDwater Open and Closing net system (MIDOC) was developed with the ability to conduct self-contained sample collection via pre-programmed sequence or via direct vessel command using acoustic link or electrical connection. The system is designed to be flexible and can be towed with a single wire from the stern of a ship, incorporated as a cod end in a larger commercial net system, or dropped vertically to profile the water column. This paper will discuss the design, development and testing of an open and closing net system for midwater sample collection. Finally, the paper discusses the next phases of development for the system.