NOAA TR NMFS SSRF-660 T NOAA Technical Report NMFS SSRF-660 U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Marine Fisheries Service A Freshwater Fish Electro-Motivator (FFEM)- Its Characteristics and Operation JAMES E. ELLIS and CHARLES C. HOOPES iwarine efologbi utboratt^ry" LIBRA RV ftfll61973 *Woocl$Hol«, ivwisf. ■"»l.»Jii'ii' SEATTLE, WA November 1972 NOAA TECHNICAL REPORTS National Marine Fisheries Service, Special Scientific Report-Fisheries Series The major responsibilities of the National Marine Fisheries Service (NMFS) are to monitor and assess the abundance and geographic distribution of fishery resources, to understand and predict fluctuations in the quantity and distribution of these resources, and to establish levels for optimum use of the resources. NMFS is also charged with the development and implementation of policies for managing national fishing grounds, develop- ment and enforcement of domestic fisheries regulations, surveillance of foreign fishing off United States coastal waters, and the development and enforcement of international fishery agreements and policies. NMFS also as- sists the fishing industry through marketing service and economic analysis programs, and mortgage insurance and vessel construction subsidies. It collects, analyzes, and publishes statistics on various phases of the industry. The Special Scientific Report — Fisheries series was established in 1949. The series carries reports on scien- tific investigations that document long-term continuing programs of NMFS, or intensive scientific reports on studies of restricted scope. The reports may deal with applied fishery problems. The series is also used as a medium for the publication of bibliographies of a specialized scientific nature. NOAA Technical Reports NMFS SSRF are available free in limited numbers to governmental agencies, both Federal and State. They are also available in exchange for other scientific and technical publications in the marine sciences. Individual copies may be obtained (unless otherwise noted) from NOAA Publications Section, Rockville, Md. 20852. Recent SSRF's are: 604. The flora and fauna of a basin in central Florida Bay. By J. Harold Hudson, Donald M. Allen, and T. J. Costello. May 1970, iii -|- 14 pp., 2 figs., 1 table. 605. Contributions to the life histories of several penaeid shrimps (Penaeidae) along the south Atlantic Coast of the United States. By William W. Anderson. May 1970, iii + 24 pp., 15 figs., 12 tables. 606. Annotated references on the Pacific saury, Colol- abis saira. By Steven E. Hughes. June 1970, iii -I- 12 pp. 607. Studies on continuous transmission frequency modulated sonar. Edited by Frank J. Hester. June 1970, iii 4- 26 pp. 1st paper. Sonar target classification experiments with a continuous- transmission Doppler sonar, by Frank J. Hester, pp. 1-20, 14 figs., 4 tables; 2d paper, Acoustic target strength of several species of fish, by H. W. Volberg, pp. 21-26, 10 figs. 608. Preliminary designs of traveling screens to col- lect juvenile fish. July 1970, v -|- 15 pp. 1st paper. Traveling screens for collection of juvenile salmon (models I and II), by Daniel W. Bates and John G. Vanderwalker, pp. 1-5, 6 figs., 1 table; 2d paper. Design and operation of a canti- levered traveling fish screen (model V), by Dan- iel W. Bates, Ernest W. Murphey, and Earl F. Prentice, 10 figs., 1 table. 609. Annotated bibliography of zooplankton sampling devices. By Jack W. Jossi. July 1970, iii + 90 pp. 610. Limnological study of lower Columbia River, 1967-68. By Shirley M. Clark and George R. Snyder. July 1970, iii + 14 pp., 15 figs., 11 tables. 611. Laboratory tests of an electrical barrier for con- trolling prodation by northern squawfish. By Galen H. Maxfield, Robert H. Lander, and Charles D. Volz. July 1970, iii -|- 8 pp., 4 figs., 5 tables. 612. The Trade Wind Zone Oceanography Pilot Study. Part VIII: Sea-level meteorological properties and heat exchange processes, July 1963 to June 1965. By Gunter R. Seckel. June 1970, iv + 129 pp., 6 figs., 8 tables. 613. Sea-bottom photographs and macrobenthos col- lections from the Continental Shelf off Massa- chusetts. By Roland L. Wigley and Roger B. Theroux. Augu.st 1970, iii + 12 pp., 8 figs., 2 tables. 614. A sled-mounted suction sampler for benthic or- ganisms. By Donald M. Allen and J. Harold Hudson. August 1970, iii + 5 pp., 5 figs., 1 table. 615. Distribution of fishing effort and catches of skip- jack tuna, Katsuwonus pelamis, in Hawaiian waters, by quarters of the year, 1948-65. By Richard N. Uchida. June 1970, iv -1- 37 pp., 6 figs., 22 tables. 616. Effect of quality of the spawning bed on growth and development of pink salmon embryos and alevins. By Ralph A. Wells and William J. Mc- Neil. August 1970, iii -|- 6 pp., 4 tables. 617. Fur seal investigations, 1968. By NMFS, Ma- rine Mammal Biological Laboratory. December 1970, iii -I- 69 pp., 68 tables. 618. Spawning areas and abundance of steelhead trout and coho, sockeye, and chum salmon in the Columbia River Basin - past and present. By Leonard A. Fulton. December 1970, iii -|- 37 pp., 6 figs., 11 maps, 9 tables. 619. Macrozooplankton and small nekton in the coastal waters off Vancouver Island (Canada) and Washington, spring and fall of 1963. By Donald S. Day, January 1971, iii 4- 94 pp., 19 figs., 13 tables. 620. The Trade Wind Zone Oceanography Pilot Study. Part IX : The sea-level wind field and wind stress values, July 1963 to June 1965. By Gunter R. Seckel. June 1970, iii + 66 pp., 5 figs. Continued on inside back cover. ,,O^MOSP^ "L'fNT 0(- U.S. DEPARTMENT OF COMMERCE Peter G. Peterson, Secretary NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Robert M. White, Administrator NATIONAL MARINE FISHERIES SERVICE Philip M. Roedel, Director NOAA Technical Report NMFS SSRF-660 A Freshwater Fish Electro-Motivator (FFEM)- Its Characteristics and Operation JAMES E. ELLIS and CHARLES C. HOOPES SEATTLE, WA November 1972 The National Marine Fisheries Service (NMFS) does not approve, rec- ommend or endorse any proprietary product or proprietary material mentioned in this publication. No reference shall be made to NMFS, or to this publication furnished by NMFS, in any advertising or sales pro- motion which would indicate or imply that NMFS approves, recommends or endorses any proprietary product or proprietary material mentioned herein, or which has as its purpose an intent to cause directly or indirectly the advertised product to be used or purchased because of this NMFS publication. CONTENTS Page Introduction 1 Characteristics and operation of the freshwater fish electro-motivator ... 2 Pulser 2 Pulse control logic 2 Pulse selection logic 3 Switching circuits 5 Power supply 9 High voltage 9 Low voltage 9 Summary of field testing 10 Discussion 10 Acknowledgment H Literature cited H A Freshwater Fish Electro-Motivator (FFEM)— Its Characteristics and Operation by JAMES E. ELLIS, Fishery Biologist' National Marine Fisheries Service Fish Farming Development Center P.O. Box 711 Rohwer, AR 71666 and CHARLES C. HOOPES, Ph.D.^ Research Engineer University of Michigan Ann Arbor, MI 48104 ABSTRACT A prototype Freshwater Fish Electro-Motivator (FFEM) system was developed as a research tool to test the application of electricity for use with active and passive fishing gear for increasing the gear's catching efficiency. The system's basic characteristics and operating modes are explained. The prototype system is extremely sophisticated, and its versatility permits single or multiple time-sequenced electrode loading and various pulse patterns, and allows duty cycles over a wide dynamic electrode load range. A summary of the field testing is discussed. INTRODUCTION In 1966, investigations into the application of electricity in conjunction with fishing gear were undertaken by the National Marine Fisheries Service at Ann Arbor, Mich. The specific aim of these investigations was to develop an electrical appciratus for researching the application of electricity for commercial fishing of all fresh- water fish stocks in the Great Lakes. In essence, this gear was to be designed for any freshwater species found in the contiguous 48 States. 1 Wildlife, Fish Farming Development Center, Rohwer, AR 71666. 2 Present address: Cyphernetics Corporation Product Manager, Ann Arbor, MI 48104. Work by other investigators had demonstrated that bottom trawls lost up to 60% of their catch due to fish escapement back through the trawl's mouth area (Kreutzer, 1964). McRae and French (1965) and Shentaykov (1965) demon- strated that the overall catch rate of an electrified bottom trawl was increased by as much as 2.0 to 2.5 times. EUis (1972) showed that electricity increased an electrical trawl's catch rate up to 1.86 times that of a standard control trawl. Seidel (1969) showed that a commercially feasible shrimp fishery in daylight hours was practical if electricity was used in conjunction with a trawl. Our review of prior work indicated that available fish shockers were not fully utilizing electrical currents for obtaining maximum power outputs at optimum pulse characteristics. In addition, this review pointed out the advantages of designing a circuit using SCR (silicon-controlled rectifier) static switching in conjunction with capacitor-discharge pulses. This design would allow us to produce fast rise flat-topped rectangular pulses with exponential trailing edges of durations of 1 msec or more. Pulses having this shape are considered to give the optimum neurophysiological effect for fish taxis (Vibert, 1970). As a result of our literature survey, we con- cluded that a versatile research tool could be devised to study ways of increasing the catching efficiency of freshwater fishing gear using elec- tricity. Consequently, developmental work was started on the Freshwater Fish Electro-Motiva- tor (FFEM) system. Four basic modes of oper- ation were considered in the initial design. These operating modes were: 1) phased array — use of electrical stimuli to herd or direct fish into active or passive fishing gear; 2) increasing net aperture — use of stimuli to increase the effec- tive aperture of a net by confining the fish to a region wherein they will be caught by the me- chanical fishing gear; 3) confinement — use of electrofishing techniques to prevent fish from es- caping once they are trapped by the fishing gear; and 4) concentric spheres — use of electrical stimulus in conjunction with a fish pump-light for removing fishes that are positively photo- tactic. To achieve this goal, we contracted with the University of Michigan to work with us on the development of an FFEM. Two main studies were conducted: the development of a proto- type FFEM and its field testing. In this paper we will cover the design characteristics and oper- ation of the FFEM and give a summary of the field test. Another report covers the field test in detail (Ellis and Pickering, in press). CHARACTERISTICS AND OPERATION OF THE FRESHWATER FISH ELECTRO-MOTIVATOR The FFEM system as shown in Figure 1 is divided into a pulser and a power supply. The physical and electrical parameters of each system are as follows. Pulser The FFEM pulser is by far the most complex portion of the system (Figure 2). Its physical characteristics are shown in Figure 3. The pulser housing is an aluminum tube, 165.1 cm in length, 20.3 cm nominal diameter with 1.3 cm walls, and weighs 116.1 kg including electronic components. It consists of three bulkhead plates, PI, P4, and P8 along with two tubes, Tl and T2, as shown in Figure 3. The bulkheads and tubes are held in compression by two sets of four aluminum connection rods, Rl and R2. The right bulkhead end plate has an air check valve which permits the pulser to be pressurized with air to about 13.6 kg/cm". This pressuriza- tion tests the O-ring seals for leaks before submerging the unit. A cap is placed over the check valve to prevent water from entering the housing since external water pressure will at times exceed the internal air pressure. The left bulkhead end plate has six bulkhead electrical connectors and mating plugs. One connector is for supplying external electrical power to the pulser while the other five connectors are for supplying power to the electrode arrays in sequential or single mode firing orders. The firing circuits and power silicon-con- trolled rectifiers (SCR) of the FFEM pulser contained within the aluminum housing are shown schematically in Figure 4. The pulser has a maximum voltage of 300 volts^ peak output with the capability of any intermediate voltage level. A minimum load resistance presented by the electrodes to the pulses should be 1.5 to 2.0 ohms. For an "effective duty cycle" of 100% (equivalent to an on-time of 1 msec and an off-time of 7 msec) at full voltage, the pulser is capable of an average output of 7,500 watts with a peak pulse power output of 60,000 watts. Pulse control logic— The pulse control logic (Figure 1, items 8 and 9) generates the gate input pulses to the firing circuits (Figure 1, item 6) which controls the firing of the SCR for the desired output pulse parameter. To achieve the basic 8-msec timing cycle, a l-KH^, clock is used with a three-stage binary counter which divides This maximum was dictated by the size and availability of electrolytic capacitors. 220 VAC Shipboard Power -o^o— - -o^o— cr-o- Isolahon Transformer Shipboard AC Power Input I HV Power Supply — ;: — LV Power Supply Underwater Cable J 28 VC -tTJ^ -* To — ^ Underwater ^ Electronics I FFEM Power Supply (a) FFEM Primary Power Supply Shipboard Supply Reverse Discharee Protection CCT Enerpy Storage Ener|^ Storage CCT r _j Logic Power Supply (15) .12V, LV , .5V, GND. I LV on Detector Liii LV Drop Detector il*} External Selection Pulse Selection Logic lai Control Logic iSl Overload Current Detector 1121 High Power Switching Circuits liiSI External Selection Mode of Operation Selection ta. Output to ■>■ Maximum of 5 Grids Firing 'irculis Emergency Shut Down CCT,,,, FFEM Pulser Uttderwater Electronics (b) FFEIri Pulser Figure 1. — Basic electrical system block diagram. Commutatior CCTS Lm the clock rate by eight. Decoding logic is used to generate the required timing waveforms. Pulse selection logic— The pulser has logic for 1-msec output pulses at selectable duty cycles, selectable periods, and distribution to one (two electrode arrays) to four (five electrode arrays) loads in a selectable sequential order. To select a desired pulse pattern the left bulkhead end plate is removed exposing three female plugs; one for selecting pulse pattern, one for selecting the desired load distribution, smd one for bench testing. Prewired male mating plugs are inserted to produce the desired performance. The pulse parameters available are as follows: The number of on-pulses ^q„ is 2 (Sgjj) where S^^ is selectable in seven steps from 1 to 7. The number of off-pulses N^ff is (S^^) times (Sgff) where S^jf is selectable in eight steps from 0 to 7 and S^,, is the same as above. The combination of N pulses followed by N^jj-f missing pulses is referred to as a "pulse set." The number of pulse sets distributed to a Figure 2. — Freshwater Fish Electro-Motivator (FFEM) pulser with and without protective aluminum housing. given electrode load N^ist before switching to another load is selectable in 15 steps from 1 to 15. Also, the order of pulsing electrode pairs is selectable after N^ist sets of pulses to a given load. The above pulse parameters are all based on the 1-msec on, 7-msec off basic pattern. As examples of pulse parameters possible, we will give situations where a single load (2 elec- trode arrays) and two loads (3 electrode arrays) are fired (Figure 5). For a single load, suppose Son = 2, Soff = 3, and Ndist = 1- The output to this load would appear as shown in Figure 5a. In this example, the pulse set Non and Noff equals 10 and produces a total pulse period of 80 msec and an effective duty cycle of 40%. In all situ- ations the number of basic pulse groups (No,^ Noff) can be varied with Non = 2X and Noff = YX where X can be selected 1 through 7, and Y can be selected 0 through 7. For the basic pulse pattern in Figure 5 with tp (total pulse or pulse _R1^ 1.3 cm- -1.3 cm NOTE: VI. H4, F8 V2. P3, P5, H6, F7 PIO F9 Tl, T2 HI H2 H3 H4 HS bulkhead plates divider plates insulated connectiun plate insulated cover plate outside cover tubes resistor heat sink SCR heut sink semiconductor ins. & heat sinks Rl R2 outside tie rods R3 R4, R6 inside support rods CI. C7 chambers R5 centering rod ORl, OR2, OR3, OR4 bulkhead plate "O" rings Bl, B2 firing CCT support burs HI 1 tie point plate PI 2 current transformer plate Figure 3. — Mechanical layout sectional drawing of Freshwater Fish Electro-Motivator (FFEM) pulser. set) = 8 msec, the pulse parameter has an effec- tive on-time of ton = ^on times tp = 32 msec and an off-time of toff = Noff times tp = 48 msec. Thus the effective duty cycle while being pulsed for the pulse parameter shown (Figure 5) is expressed as follows: Percent effective duty cycle: T 100 on + T off Non V 100 Non tp + Nofftp Non 100 2X 1 00 XY 200 N -1- on Noff 2X + 2 -H Y From the above equation the percen t effect duty cycle "^ is 100% for Y = 67% for Y = 50% for Y = 40% for Y = 33% for Y = 29% for Y = 0 1 2 3 4 5 Actual duty cycle is only one-eighth of the effective duty cycle. 25% for Y = 6 22% for Y = 7 For two loads which are to be pulsed alter- nately, suppose Son = 2, Soff = 3, and N^w^t ~ 2. The output to these loads would appear as shown in Figure 5b. In this example, the pulse set Non = 4 and Noff = 6 will give a total pulse period of 80 msec for each set (Son ~ 2 and Soff = 3) and in this example there are two sets per load; thus, the duty cycle is 40% per load Num- ber 1 and 40% per load Number 2 when being pulsed or an overall duty cycle of 20% because of the sharing between the two loads. Switching circuits.— The high power switching circuitry in Figure 1 is composed of three sets of SCR: 1) routing, 2) timing, and 3) commutation. There are eight routing SCR, one timing SCR, and three commutation SCR. A simplified diagram of the routing and timing circuits is given in Figure 6. For discussion purposes, we represent the SCR with single-pole, single-throw switches. As noted, the switches (SCR) are grouped into: 1) routing switches and 2) a timing switch. (The commutation SCR are not shown.) Three modes of operation are shown. Referring to Figure 6a, if only one electrode pair is used, one is connected to point 9 and the other is connected to point 10, then when the switch is closed, the voltage E will appear across the two electrodes and current will flow from ° 1 J "V^ r^f— vW^ -^ rr T t ♦ t ♦ M ♦ ' cf ^ iH/v\^ 5 (— 1(— vV^ T- rlt-WAAi ^ / -»?^-^ 01 u. O I g^ ij' ^/^ J jl r a V- < O I- Q Ul ^ U tj I- u t 9 sua O Z u- , O O 03 + ; ,- r ij »; S??3 » <^<^ ® a i" b O U x I (a) "off JLfUUL _1 I I I L .^LLfl "dist- 1 _l I I I L. "dist' •< — "dist"^ Load #1 JULXJL n ,, = 6 off J I I I L. (b) J I I I \ I I ] 1 1 I I I'll dist Set 1 _] I I I I I I I 1 L. Set 2 I I I 1_1 L. n = 6 off JUL J I I I I L. _l I I I ■ Load #2 Set 1 Set 2 Note: Each division corresponds to the 8 msec basic control cycle. Figure 5. — Examples of Freshwater Fish Electro-Motivator (FFEM) pulse patterns: (a) one load, Son = 2, Soff = 3, Ndist = 1 and (b) two loads, Son = 2, Soff = 3, Njist = 2. point 9 (anode) to point 10 (cathode) via the water path surrounding the two electrodes. For multiple loads having a common anode, the switching arrangement is shown in Figure 6b. If we use point 9 as the anode and points 4, 5, 6, and 7 as the cathodes, then current will flow in the electrode load whenever any of the switches e, f, g, or h is closed and switch i is closed. Current can only flow when the timing switch is closed. For multiple loads, where a given electrode may be used as an anode and at a different time be used as a cathode, such as in the phased array, the switching arrangements Eire shown in Figure 6c. If electrodes are attached to points 7, 1, 2, 3, and 8 with points 1 and 4, 2 and 5, and 3 and 6 jumpered, then when a single pair of swatches (a-e loading i; b-f loading i), current will flow between a pair of electrodes. For example, if only routing switches b and f are closed, then current will flow between the anode electrode (point 2) and the cathode electrode (point 1 or 4) when switch i is closed. Now if routing switch c and g are closed, then current flows between the anode electrode, point 3 and the cathode electrode (point 2 or 5) when the switching SCR is closed. In the first case, the electrode at point 2 served as the anode, and in the second case, it became a cathode. To achieve the greatest versatility, the arrangement shown in Figure 6c is used, and a subset of the switches are used for the other alternatives. In reality SCR are used in place of the switches. An SCR is basically an on-off switch which can be turned on by momentary application of current to the gate which causes current to flow from anode to cathode only. Once turned on, the gate cannot be used to turn off the SCR. Thus, for turning off the SCR in the load distribution and switching logic, a reverse voltage is applied across the anode and cathode of the SCR. To accomplish the turn-off we use a self -commutation circuit. The commutation circuit consists of three SCR, a capacitor (C2), and inductor (L2) (Figure 7). The commutation is performed as follows: assume that there is no current flowing in the circuit and that C2 is discharged. Now, if 10 y (a) Single Load Timing ' Switch (SCH) lOo- ■^s fi \\ 7^ 4^ 59 6 V Y Y Y I . Routing Switches (SCRs) 9 h (SCR) (b) Multiple Loads (common anode) °J lllmln 7 / Switc J ' /C/'D 10 o- r (c) Multiple Loads (phased array) "^1 1 I 1. 1 1 ' 1 ' I ' 1 6 r 6 , O o r r f f o Routing Switchot (SCR») Timing Switch ^SCH) Figure 6. — Switch representation of high power switching circuit. SCR k and SCR i are turned on, the current flows from voltage source E through path L^, Rl, SCR k, L2, C2, and SCR i. The series con- nected inductors Li and L2 limit the rate of change of current, and the resistance R^ limits the maximum current. As current flows, C2 is charged to the source voltage E. At this time, the voltage across SCR k and SCR i is near zero, and the current is necir zero; thus these two SCR turn off, and C2 has a voltage E with the right hand plate of C2 positive. Next, assume routing SCR a and SCR e are turned on. At this time current flows from E through the path L^, Rx, SCR a, water load, SCR e, and SCR i. Again the inductance Li limits the rate of current change, and Rl in series with the water load limits the maximum current through the electrodes. At the end of 1 msec (the pulse-on time), SCR j is turned on. This places charged capacitor C2 in parallel with SCR i. Discharge current flows from Co through the path L2, SCR j, SCR i, and back to C2. This negative current through SCR i cancels the original electrode load current in SCR i, and SCR i turns off. Current continues to flow through Li, Ri, SCR a, electrode load, SCR e, C2, L2, and SCR j even though SCR i is off. However, this current charges the capacitor C2 in the opposite direction to a voltage near E at which time the current through SCR a, SCR e, and SCR j drop below the holding current and these SCR self-commutate. The charge left on C2 makes the left plate of C2 positive which is the wrong polarity for the next commutation; thus, the cycle begins again with SCR i and SCR k turned on. This allows C2 to discharge and recharge with the correct polarity (right plate positive). Again SCR i and SCR k self-com- mutate. SCR 1 is used to insure self-commu- tation of SCR a, SCR e, and SCR j independent of the water load. It is turned on shortly after SCR j is fired and forces self-commutation with- in the correct time limit. The various safety checks and circuits designed into the FFEM system which will automatically shut the system down are: 1) high or low current overload, 2) reverse discharge of capacitor banks, and 3) loss of high or low voltage. In addition, all systems are electrically isolated from the primary electrical source. Power Supply The FFEM power supply consists of the following: 1) a vjiriable high voltage supply capable of 0 through 300 v DC at 25 amp DC and 2) a fixed low voltage power supply producing 28 v DC at 7 amp DC (Figure 8). These power supplies share a common ground; thus a three-conductor number 10-wire power cable is required to interconnect the FFEM power supply with the FFEM pulser. High voltage.— The high voltage supply is basically a slave full-wave rectified L-C (L-inductor, C-capacitor) filter power supply. The input is 230 v AC single phase power applied at the main input. This output is connected to a 0-300 v AC variac. The high voltage power supply output is floating relative to shipboard ground. Low voltage.— The low voltage power supply consists of a 28 v DC 7 amp, regulated power supply and a step-down transformer. An interlock exists between the high voltage and low voltage supplies. This interlock prevents the low voltage from being applied to the pulser SCR before the high voltage is properly adjusted to approximately 25 v. Also, the interlock removes the low voltage if there is a failure in the high voltage supply. The FFEM power supply uses a 0-300 v panel volt meter and a double set point 0-30 amp meter for monitoring output parameters. The oV bi ci dV p 'VW o o *-* o <) 9 9 •X ;? w 1? ^ O 6 6- * w Switching C ircuit Commufotion Circuit Figure 7. — High power switching and commutation circuit. Figure 8. — Freshwater Fish Electro-Motivator (FFEM) power supply. double set point meter will detect current which is either above or below normal limits and trip an alarm of either red or amber lamps respectively. Other pilot lamps indicate when the main power is on and when the low voltage is on. Summary of Field Testing The FFEM system was tested for reliability in 21 10-min fishing drags and 22 15-min voltage plotting drags aboard the RV Kaho in the Sagi- naw Bay area of Lake Huron. Ellis and Pickering (in press) give a complete discussion of an exper- iment involving the use of this gear and allied ICATHOOe eiEMENTS Figure 9. — Diagram of electrical trawl showing arrangement of electrode arrays in mouth of net. equipment. During the field testing, the maxi- mum power output was limited to 90 v DC due to an anomalous electronic signal in the pulse generator which shut the power supply down when this limit was exceeded. However, this signal presented no problem in our test. A 21.3-m (headrope) wing trawl, rigged with an electrode array as shown in Figure 9, was used. The spacing between arrays was 1.5 m and between electrode array elements was 0.3 m. We experienced no problems with the FFEM during the voltage plotting. We had a heterogen- eous electrical field which ranged from 21.1 v within 38.1 cm of the cathode array to 1.0 v midway and then rose to 16.9 v within 38.1 cm of anode array. The FFEM did shut down at the end of the 21st fishing drag probably due to the electronic anomaly which we knew was present. The catch rate in kilograms of the trawl with power on was 1.65 times or 65.6% more than the catch rate in kilograms with power off. DISCUSSION The prototype FFEM system fully utilizes electrical currents for obtaining maximum power outputs at optimum pulse characteristics. The system permits multiple time-sequenced loads (from 1 to 4), varying pulse patterns and duty cycles, varying load distribution patterns, and variable output voltages and operates over a wide dynamic load range. Its versatility as a research tool is almost endless; however, it must 10 be pointed out that its pulse width is fixed at 1 msec cuid its pulse shape is also fixed. These were designed into the system after we made a study of capacitator-discharge pulse generators. If time and funds were available, these two fixed characteristics could be redesigned for flex- ibility. In designing a follow-up FFEM, a consid- erable savings can be realized through the use of polyvinal chloride pipe in place of the high impact aluminum tube. In addition, for a commercial application the system could be designed without the sophistication and versa- tility of our prototype thus realizing a considerable savings. The catch rate of the electrical trawl possibly could have been increased with a more homogeneous electrical field and/or more power to the array system during our field tests. ACKNOWLEDGMENT The authors wish to thank the National Marine Fisheries Service, Remote Sensing Group under the direction of Bill Stevenson for their invaluable assistance with the electronic circuitry . LITERATURE CITED ELLIS, J. E. 1972. The use of electricity in conjunction with a 12.5-meter (headrope) Gulf-of-Mexico shrimp trawl in Lake Michigan. NOAA Tech. Rep. NMFS SSRF653, 10 p. ELLIS, J. E., and E. N. PICKERING. In press. The catching efficiencies of a 21.3-meter (headrope) standard wing trawl and a 21.3-meter electrical wing trawl in the Saginaw Bay area of Lake Huron. Trans. Am. Fish. Soc. KREUTZER, C. O. 1964. Utilization of fish reaction to electricity in sea fishing. In Modern Fishing Gear of the World 2, p. 545-551. Fishing News (Books) Ltd., Lon- don. McRAE, E. D., JR., and L. E. FRENCH, JR. 1965. An experiment in electrical fishing with an electric field used as an adjunct to an otter-trawl net. Commer. Fish. Rev. 27(6): 1-11. SEIDEL, W. R. 1969. Design, construction, and field testing of the BCF electric shrimp-trawl system. U.S. Fish Wildl. Serv., Fish. Ind. Res. 4:213-231. SHENTAYKOV, V. A. 1965. On the possibilities of electric fishing in large bodies of water. [In Russian.] Rybn. Khoz. 41(2):53-57. VILBERT, R. 1970. Fishing with electricity: its application to biology and management. Int. Mar. Publ. Co., Camden, Maine, 304 p. ^GPO 796.147 II lllI^BL JVHOI Ubra, Serials 5 WHSE 01840 621. Predation by sculpins on fall chinook salmon, Oncorhynchiis tshawytscha, fry of hatchery or- igin. By Benjamin G. Patten. February 1971, iii 4- 14 pp., 6 figs., 9 tables. 622. Number and lengths, by season, of fishes caught with an otter trawl near Woods Hole, Massa- chusetts, September 1961 to December 1962. By F. E. Lux and F. E. Nichy. February 1971, iii + 15 pp., 3 figs., 19 tables. 623. Apparent abundance, distribution, and migra- tions of albacore, Thunnus alalunga, on the North Pacific longline grounds. By Brian J. Rothschild and Marian Y. Y. Yong. September 1970, v -f- 37 pp., 19 figs., 5 tables. 624. Influence of mechanical processing on the quality and yield of bay scallop meats. Bv N. B. Webb and F. B. Thomas. April 1971, ii'i + 11 pp., 9 figs., 3 tables. 625. Distribution of salmon and related oceanographic features in the North Pacific Ocean, spring 1968. By Robert R. French, Richard G. Bakkala, Ma- sanao Osako, and Jun Ito. March 1971, iii + 22 pp., 19 figs., 3 tables. 626. Commercial fishery and biology of the fresh- water shrimp, Macrobrachium, in the Lower St. Paul River, Liberia, 1952-53. By George C. Mil- ler. February 1971, iii -|- 13 pp., 8 figs., 7 tables. 627. Calico scallops of the Southeastern United States, 1959-69. By Robert Cummins, Jr. June 1971, iii -t- 22 pp., 23 figs., 3 tables. 628. Fur Seal Investigations, 1969. By NMFS, Ma- rine Mammal Biological Laboratory. August 1971, 82 pp., 20 figs., 44 tables, 23 appendix A tables, 10 appendix B tables. 629. Analysis of the operations of seven Hawaiian skipjack tuna fishing vessels, June-August 1967. By Richard N. Uchida and Ray F. Sumida. March 1971, v + 25 pp., 14 figs., 21 tables. For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - 35 cents. 630. Blue crab meat. I. Preservation bv freezing. July 1971, iii -|- 13 pp., 5 figs., 2 tables." II. Effect of chemical treatments on acceptability. By Jurgen H. Strasser, Jean S. Lennon, and Fred- erick J. King. July 1971, iii -f- 12 pp., 1 fig., 9 tables. 631. Occurrence of thiaminase in some common aquat- ic animals of the United States and Canada. By R. A. Greig and R. H. Gnaedinger. July 1971, iii -f- 7 pp., 2 tables. 632. An annotated bibliography of attempts to rear the larvae of marine fishes in the laboratory. By Robert C. May. August 1971, iii + 24 pp., 1 ap- pendix I table, 1 appendix II table. For sale by the Superintendent of Documents, U.S. Govern- ment Printing Oflice, Washington, D.C. 20402 - 35 cents. 633. Blueing of processed crab meat. II. Identification of some factors involved in the blue discoloration of canned crab meat Callinectes sapidiis. By Melvin E. Waters. May 1971, iii -|- 7 pp., 1 fig., 3 tables. 634. Age composition, weight, length, and sex of her- ring, Clnpea pnllasii, used for reduction in Alas- ka, 1929-66. By Gerald M. Reid. July 1971, iii -I- 25 pp., 4 figs., 18 tables. 635. A bibliography of the blackfin tuna, Thunnus atlanticus (Lesson). By Grant L. Beardsley and David C. Simmons. August 1971, 10 pp. For sale by the Superintendent of Documents, U.S. Government Printing Oflice, Washington, D.C. 20402 - 25 cents. 636. Oil pollution on Wake Island from the tanker R. C. Sinner. Bv Reginald M. Gooding. May 1971, iii + 12 pp., 8 figs., 2 tables. For sale by the Superintendent of Documents, U.S. Govern- ment Printing Office, Washington, D.C. 20402 - Price 25 cents. 637. Occurrence of larval, juvenile, and mature crabs in the vicinity of Beaufort Inlet, North Carolina. By Donnie L. Dudley and Mayo H. Judv. August 1971, iii + 10 pp., 1 fig., 5 tables. For sale by the Superintendent of Documents, U.S. Govern- ment Printing Office, Washington, D.C. 20402 - Price 25 cents. 638. Length-weight relations of haddock from com- mercial landings in New England, 1931-55. By Bradford E. Brown and Richard C. Hennemutli. August 1971, V -I- 13 pp., 16 fig., 6 tables, 10 appendix A tables. For .sale by the Superintend- ent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price 25 cents. 639. A hydrographic survey of the Galveston Bay system, Texas 1963-66. By E. J. Pullen, W. L. Trent, and G. B. Adams. October 1971, v + 13 pp., 15 figs., 12 tables. For sale by the Super- intendent of Documents, U.S. Government Print- ing Office, Washington, D.C. 20402 - Price 30 cents. 640. Annotated bibliography on the fishing industry and biology of the blue crab, Callinectes sapidus. By Marlin E. Tagatz and Ann BouTnan Hall. August 1971, 94 pp. For sale by the Superinten- dent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.00. 641. Use of threadfin shad, Dorosoma petenense, as live bait during experimental pole-and-line fish- ing for skipjack tuna, Katsuwonus pelamis, in Hawaii. By Robert T. B. Iversen. August 1971, iii -f- 10 pp., 3 figs., 7 tables. For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price 25 cents. 642. Atlantic menhaden Brevoortia tyrannus resource and fishery — analysis of decline. By Kenneth A. Henry. August 1971, v -F 32 pp., 40 figs., 5 appendix figs., 3 tables, 2 appendix tables. For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price 45 cents. 646. Dissolved nitrogen concentrations in the Colum- bia and Snake Rivers in 1970 and their efi'ect on Chinook salmon and steelhead trout. By Wesley J. Ebel. August 1971, iii -1- 7 pp., 2 figs., 6 tables. For sale by the Superintendent of Doc- uments, U.S. Government Printing Office, Wash- ington, D.C. 20402 - Price 20 cents. UNITED STATES DEPARTMENT OF COAAMERCE NATIONAL OCEANIC & ATMOSPHERIC ADMINISTRATION NATIONAL MARINE FISHERIES SERVICE SCIENTIFIC PUBLICATIONS STAFF BLDG. 67, NAVAL SUPPORT ACTIVITY SEATTLE, WASHINGTON 98115 POSTAGE AND FEES PAID U.S. DEPARTMENT OF COMMERCE 210 OFFICIAL BUSINESS • 1 f, V MAR INK BIOLmrcAL LABORATORY ^ -".LT'li.f^ARY - periodicals; - rV tr^^l^MCr .yfi WQ&I)S HOLE, • '..ij, ■•.',- iL'* VJT' « - UA 02543 .JcS."