FOCI Standard Operating Instructions

January 2002
3.2.2 MARMAP Bongo Tows - A 60-cm aluminum bongo frame with a 0.505-mm mesh net, (or 0.333 mm before mid May), hard plastic codends, and a 40-kg lead weight for a depressor will be used in standard Marine Assessment Monitoring and Prediction (MARMAP) Bongo tows. The nets will be deployed at a constant wire speed of 40-45 meters per minute to a maximum depth of 100 meters (or 200 meters before mid May), or 5-10 meters off bottom in shallower waters. However, at stations on Lines 8, 16 and 17 in Shelikof Strait, nets will be towed from 10 m off bottom to the surface. In addition, one side of the 60-cm bongo will be changed to 0.333-mm mesh net. Furthermore, the 20-cm bongo with 0.150-mm mesh nets will be attached to the wire one meter above the 60-cm bongo frame at line 8 and at selected other stations.

The winch should be one of the ship's Markey oceanographic winches equyipped with slip rings and at least 2,000 meters of 0.322, 2-layer, 3-conductor oceanographic wire.  A Sea-Bird Electronics SBE 19 SEACAT profiler or SBE 39 Temperature and Pressure Recorder will be attached to the wire above the bongo frame(s) to provide real-time tow data. The primary SEACAT, or SBE 39, will be provided by the Pacific Marine Environmental Laboratory (PMEL) and the backup SEACAT will be provided by the ship.  Before the SEACAT is terminated on the wire by the ship's electronic technician and the survey technician, a PMEL scientist will note the identification number of the unit and provide the proper calibartion file for the computer when the SEACAT from PMEL is used; however, if the ship's equipment is used, current calibrations should be available.  Personnel from PMEL will provide the acquisition computer and monitor.  There is no requirement for the SEACAT data to be displayed on the Scientific Computer System (SCS).

After the bridge gives permission, the survey technician and one or two scientists will deploy and recover the bongo array.  A scientist will be stationed in the ship’s DataPlot compartment to monitor the SEACAT and to inform the ship’s survey technician and winch operator when the desired gear depth is reached.  The bridge will then be instructed either by the scientist in DataPlot or the survey technician to enter the position in the Electronic Marine Observation Abstract (E-MOA).  Afterwards, the winch operator is instructed from DataPlot to retrieve the nets at a wire speed of 20 meters per minute.  The ship’s speed should be adjusted to maintain a wire angle of 45(±5)° during the entire tow, which is accomplished by the survey technician relaying wire angles to the bridge by radio.  When the nets reach the surface, they are brought aboard and hosed with saltwater to wash the sample into the cod-end.  The sample is preserved as specified in the FOCI Field Manual or sample collection request forms.  In some cases, larvae are sorted and preserved separately.  Flow meters in the nets record the amount of water filtered, and the SBE 19 SEACAT, or SBE 39, records the depth history of the tow.  The scientists on watch are responsible for recording times, maximum depth, wire outs, and flow meter counts on the Cruise Operations Database (COD) forms.  Tows not meeting specifications (i.e., hit bottom, poor wire angles, nets tangled, etc.) may be repeated at the discretion of the scientific watch.

allen.macklin@noaa.gov