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Last night we deployed the MIDOC trawl system. This is a fishing net fitted with a device that switches 6 different “cod ends” (essentially: the small net at the end of the large net which collects the catch) at different times during the trawl.
In this way, we know the approximate depth that the creatures that we are catching, actually came from. For our operation, we take the net down to 1000m depth which requires about 2500m of cable let out from the ships trawl winches. The first net is open on the descent which means it will catch anything between the surface and 1000m. Upon reaching 1000m, the first net is closed and the second one opens for 30 minutes while we raise the net from 1000m to 800m.
This process is repeated at 200m intervals until we reach the surface, The net result (yes – I’m aware of the pun) is that we get a sample of the sea life between the surface and 1000m which can then be used to fine tune acoustic readings of the biota under the vessel.
Last night, we got a very good catch. Lots of sea creatures including jelly fish and one rather large (>30cm) fish whose scientific name I will extract from the scientific staff for a later sitrep. The fishing operation itself is a very impressive operation and demands great concentration from the winch operator for up to 4.5 hours. Last night’s cast proved to be extremely accurate in term of the depths achieved. This was a fantastic result given that we lost live depth data at between 800m and 1000m leaving Robbie steering blind for quite a while.
Another MIDOC cast was made this morning. We are just getting it on deck right now.
Lloyd and Brett
Map
A map showing Australia and Antarctica. The map shows the journey of one voyage that has occured in the season, with each route highlighted in a distinct colour.