The Tucker Trawl is an opening and closing mid-water zooplankton trawl. It is typically equipped with a full suite of instruments, including inside and outside flow meters, CTD, pitch sensor and stepper motor. Open Seas supplies the Tucker Trawl with their Bioness data logger, which can open and close nets either in real time or autonamously based on descending or ascending depth or specific time intervals. If a conducting tow cable is available, the deck software provides real-time graphing of CTD data, as well as displaying all other sensor data.
Tucker Trawl sizes are typically specified by their “effective mouth area”. A one meter (1 m) Tucker Trawl will present a one square meter mouth opening to the water column while under tow, at a nominal 45 deg actual mouth pitch angle. The onboard pitch sensor corrects swept volume for any actual deviation from the nominal angle.
Standard sizes are 1 m, 2 m and 2.5 m effective mouth areas. The smaller size is suitable for deployment from small vessels, while the large nets require a vessel of significant size.
Scientific Net Systems
Tucker Trawl Specifications
1. One Tucker Trawl (2.5 m2 standard or 1.0 m2 ) frame made from galvanized steel. Other sizes can be provided. Complete with stainless steel trigger net drop system, net counting bar, and net locking unit. All components rated to 1,000 metres.
Windows software displays all sensor readings in real engineering units and provides real-time graphing of CTD data, as well as calculating and displaying speed, swept volume, net efficiency and battery voltage. Each net drop command and net drop sensed is recorded on the graph. Autonomous mode setup can be programmed if a conducting tow cable is not available.
2. One stepping motor in oil filled pressure compensated housing, connected through a flexible drive belt to the net bar trigger shaft.
3. Four footer weights which control pitch of a Tucker Trawl, by adding or removing the provided weights from the footer bar, and by ship speed. Typical pitch under tow is 45°.
4. One electronics/battery pressure case with removable end cap, of 6061 aluminum, which contains the Bioness Data Logger which monitors and records on internal Flash Rom (4 meg standard) the following for each net: net drop, conductivity, temperature, pressure, pitch, inside net flow and outside net speed, as well as up to 4 additional CTD sensors, and up to 3 additional sensors on 12-bit A/D channels. All connectors and molded cables included.
5. CTD probes. The data logger allows for user selection of the following CTDs:
- Applied Microsystems Ltd, STD12+
- Applied Microsystems Ltd, Smart Sensor
- Sea-Bird SBE-19, 0 to 4 optional sensors
- Falmouth Scientific CTDs
Other CTDs can be accommodated. Conductivity, pressure and temperature accuracies and resolutions are dependent on the CTD selected.
6. One net drop sensor – reed switch, to confirm that the net has opened.
7. One pitch sensor – Humphrey Instruments oil damped precision pendulum, with a range of ± 60°, with accuracy of ± 1°.
8. Two flow meters – General Oceanics model No 2031H, with a range of 1 to 5 knots, with an accuracy of ± 3%.
9. One shipboard module – containing power supply, battery charger, and communications hardware. Operates on either 110V 60Hz, or 220V 50Hz power.
10. Deck Software -Windows software enables monitoring of real-time net operation, with real-time graphing of CTD outputs. Nets can be dropped on command, or underwater electronics can be programmed in Autonomous Mode, before a tow, to drop nets. A deck computer or laptop with Windows™ 95/98, NT, ME or 2000 operating system is required. Pentium 133 or better, with CDROM is recommended. mso-bidi-font-size:10.0pt;font-family:”CG Times”‘>
Sensor calibration coefficients and operating parameters can be user set. Software is switchable between real time and autonomous modes.
Discrete data is saved for each net as printable ASCII files in raw data format. All sensor coefficients and user preference selections are saved in the file header. The Bioness Deck Software can use the coefficients from the raw data file header to post-process run files into real engineering units, either:
a) Saving a converted data file for each net. Converted data files are comma de-limited, and can be imported into most database and spreadsheet programs.
b) Running the data through the run screen graphical interface to view data as if in real time.
11. Operating Modes
Real Time Mode requires use of a conductive tow cable. It displays scrolling sensor data in real engineering units. CTD data is graphed in real time. Also displayed are current net number; data at time of opening; and cumulative data for the current net (swept volume, time open, net efficiency, etc). Nets can be opened on command.
Self-Contained Mode allows operation without conductive tow cable. The deck software is used to select sensor sampling rates and net drop criteria, by time or by depth, either ascending or descending. Sensor data is uploaded in raw format at the end of each deployment.
12. One battery pack – NICAD rechargeable “D” cells, contained in the electronics case, with sufficient power for dropping up to 80 nets and operating electronics for up to 8 separate 3-hour tows. Batteries can be recharged in less than 2 hours, using the deck unit.
Other Items Included in Basic Price
a) One nylon stepper motor belt
b) One net drop sensor
c) One battery charge cable
d) One RS232 serial cable
e) One deck communications cable
Plankton sampling nets. Minimum of 1 required. Standard is white, with end user specified mesh size. Nets seams are reinforced with nylon webbing. Filtration rates of ±6:1, depending on mesh size.
14. Optional Items
A. Field Kit, with all item specifications as outlined under standards, which includes:
1) One net drop sensor
2) One pitch sensor
3) One flow meter
4) One spare of each type connector
5) One nylon stepper motor belt
6) Two cans of wet suit cement
7) Two rolls of bi-seal tape
8) .5 metres heat shrink, with electrical tape
9) One spare of each size of O-ring
10) Two metres silicone tension cord
B. Cable Modems (two required) for coaxial or CTD conductive tow cable. Also recommended for multi-conductor cable over 2500m long.
C. Spare Shipboard Module
D. Spare Stepper Motor
E. Spare Battery Pack
F. CTD can be supplied with the system, based on user specification
G. Additional sensors can be accommodated, including ambient light, flourometers, optical particle counters, dissolved oxygen, etc.