3.2.5.1 Deck Machinery - The Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS) is deployed whenever possible from the stern platform using the A-frame and the ship’s Rowe winch equipped with 600 to 1,500 meters of single conductor wire of at least 0.375” diameter. On cruises where the trawl ramp is used, the MOCNESS may be carefully lowered and retrieved over the ramp under calm sea conditions. In addition, a set of slip rings is requested for the winch. The manufacturer states that the maximum drag observed on a 1-m2 MOCNESS system was 3,000 pounds.
3.2.5.2 Electronics - The MOCNESS telemeters, in real time, conductivity, temperature, depth, and flow meter data to the surface. FOCI owns two separate electronic systems for the MOCNESS frame. The older system consists of two 6-inch outer diameter (OD) pressure cases that sit in separate cradles on the net frame. This system telemeters data to the ship at one frame every four seconds. The signal is received in the ship’s DataPlot compartment by a data acquisition deck box that simultaneously routes the data to a computer and a Video Cassette Recorder (VCR) for analog signal backup. A dot matrix printer is used to print data from every other scan. RS-232 serial input from the ship’s scientific Global Positioning System (GPS) receiver is required to obtain continuous position data for the data stream. The Data Acquisition System (DAS) software requires an NMEA-0183 $GPGGA Sentence Set for input to the computer’s COM2 serial port. All acquisition programs are written in Borland TurboPascal version 5.0 and exist as both source code and compiled executable code. All DAS hardware components sit in the electronics rack in the DataPlot compartment.
The newer system consists of two 4-inch OD pressure cases that sit in the same cradle on the MOCNESS frame and telemeter data to the ship as fast as one frame per second. The signal is received in DataPlot by a serial modem and is routed to a Pentium-based personal computer located under the bench on the starboard bulkhead. With this newer system, the signal from the underwater unit is digital instead of analog. The MOCNESS acquisition station shares a monitor with the Sea-Bird Electronics SBE 19 SEACAT data acquisition system. Serial input of GPS data is required, as for the older system. The data acquisition software is written in Microsoft Visual Basic running under Windows 3.1; however, we only have the compiled executable file on board. Data scans and tow summaries require a color printer.
3.2.5.3 Launch, Fishing, and Recovery - The movable MOCNESS support frame (cart) will be used, as in the past. On cruises not using trawl gear, the MOCNESS is launched and recovered from the stern grating. We request that the deck crew construct a 4-foot by 16-foot plywood platform with 2" x 4" side rails to attach to the stern platform. On these non-trawl cruises, the support frame will be secured to the deck near the net reel when not in use. On cruises where trawling occurs, the MOCNESS is launched just forward of the trawl ramp and stored off the trawl way between the crane and sorting table.For safe, efficient launch and recovery of the MOCNESS, the survey technician is asked to lead those events, giving orders to the trawl house while the scientific watch handles the tag lines. When the weather is rough, a member of the fishing crew may be requested to assist in the deployment and recovery.
A scientist designated as the MOCNESS pilot in the ship’s DataPlot compartment will relay instructions to the winch operator and the bridge to control the descent and ascent rate of the net system. It is essential that the ship maintain a constant speed through the water during the tow. Wire payout and haul back rates must be available to the winch operator and should be displayed in DataPlot as well. The MOCNESS is deployed and recovered while under way cruising at 1.5 knots. Height off the bottom should be 10 meters in the Gulf of Alaska and 5 meters on the Bering Sea shelf. Wire is paid out at a rate of 5-25 meters per minute and is retrieved at 5-20 meters per minute under the direction of the pilot. If a GPS signal is not available to the DAS, then the MOCNESS pilot will inform the bridge as each net is closed and request that the bridge record the position in the Electronic Marine Observation Abstract (E-MOA). After recovery, the MOCNESS nets are washed down on the aft deck. It may be necessary to remain on a course that minimizes waves coming up the stern trawl ramp during net washing.