From the tropics to the ice edge, Investigator's nets are deployed while the vessel is underway to capture tiny species at every level of the water column to better understand the life cycle and ecosystems of marine plants and animals.
A larval lobster moulting
The EZ Net has a one metre square mouth area and is used to sample plankton and micro-nekton at discrete depths in the water column. It is towed through the water on a conductive cable, which enables remote control and monitoring of system performance. Real time data of system performance and environmental variables are displayed in the operations room. During a deployment the nets are remotely released at chosen depth intervals or times. The volume of water is measured, calculated and logged by the employment of flow sensors inside and outside the net frame. This enables the number of animals per cubic metre of water to be determined at the various depths. The system operates to 1000m and usually has 335 micron nets fitted (larger sizes are available) and holds 10 nets. Various other sensors can also be fitted such as a CTD or optical plankton counter.
The surface net consists of a 1m2 steel frame constructed from 50mm box section galvanised steel. A net with a mesh size between 335 micron and 1mm2 is laced on. The system towed from a boom mounted on the starboard side of the fore-deck of the vessel with the net mid-ships using a stainless steel wire. The net is designed to fish the surface waters for plankton and fish larvae, using the boom to keep the net clear of the vessel.
Updated: 17 December 2014