TPWD 1960 F-2-R-7 #635: Underwater Observations of Fish Populations in Clear Water Lakes of Central Texas, including the Effect of Various Sound Frequencies on Fish: Job Completion Report, Din

--- Page 1 --- Le Report of Fisheries Investigations Underwater Observations of Fish Populations in Clear Water Lakes of Central Texas, including the Effect of Various Sound Frequencies on Fish by John E. Tilton Project Leader Gary Wood Assistant Project Leader Dingell-Johnson Project F-2-R-7, Job E-5 February 1, 1959 - January 31, 1960 H. D. Dodgen - Executive Secretary Texas Game and Fish Commission Austin, Texas Marion Toole Kenneth C. Jurgens & William H. Brown Coordinator Assistant Coordinators --- Page 2 --- ABSTRACT Netting studies were conducted to determine the effects of underwater sound on movement of fish in Lake Travis. Three squares of nets of varying mesh sizes were set to enclose a sound source. Five frequencies were transmitted, each for a period of approximately two weeks. Pure frequencies of 720 cps, 4,150 cps and 620 cps apparently had no effect on the movement of fish to the sound source. However, 2, 300/100 eps mixed evenly showed a defi- nite repelling effect and 1,750 cps had some repelling influence although less pronounced than the mixed tone. --- Page 3 --- Job Completion Report State of TEXAS Project No. F-2-R-7 Name: Fisheries Investigations and Surveys of the Waters of Region 6-B Job No. E-5 Title: Underwater Observations of Fish Popu- : —— lations in Clear Water Lakes of Central Texas, including the Effect of Various Sound Frequencies on Fish Period Covered: February 1, 1959 through January 31, 1960 OBJECTIVES To test the response of fish to various frequencies of sound transmitted under- water. In addition, the sound producing capabilities of freshwater fish to be determined by underwater recordings of selected fish species. Underwater observa- tions of fish populations to be continued with the use of SCUBA equipment. PROCEDURE Job E-5 was set up with three distinct phases including: (1) a continuation of visual observations of fish using SCUBA equipment, (2) recording fish sounds and other underwater sounds with subsequent rebroadcasting in an effort to attract fish and, (3) the transmission of pure frequencies underwater in an effort to attract or guide fish to a certain area. Because of the large amount of time required for the broadcast of pure frequencies, only a limited amount of time could be devoted to the other phases of the work. In addition, generally turbid water conditions hampered diving activity. Diving was largely confined to specific needs in con~ junction with other phases of the work. Experimental work was continued in recording underwater sounds, particularly those made by freshwater fish. The limited data obtained will be incorporated with those gathered in forthcoming segments of the project and no attempt will be made to present the results in this report. The greatest time expenditure was used in phase three of the progran, attempting to attract fish with pure frequencies. The experimental procedures used were formulated with the help and advice of Dr. Richard Davis, Texas Agricultural and Mechanical College at College Station in an effort to make the data lend themselves to statistical analysis. The basic experimental procedure is that used in the previous segment and described in Segment ‘Completion Report F-2-R-6, Job E-5. The entire system was expanded and incorporated two complete sampling units replacing the single system previously used. Each unit was composed of nine gill nets hanging 8 feet, including three 1" mesh nets 75' long, three 13" mesh nets 100' long, and three 2" mesh nets 125' in length. Three distinct squares were set, effectively enclosing and blocking access --- Page 4 --- by fish to the sound source from open water. The nets were set with an inner square of 1" mesh, a middle square of 13" mesh, and an outer square of 2" mesh. (In all cases the shoreline makes the fourth side of the square. See Figure 1.) The actual sites chosen for the experiments were shallow flats with a maximum depth of 8 feet and relatively smooth bottom to prevent access under the weighted nets. Although no single square was completely closed because of small holes in the nets:and occasional small openings at the corners, the unit was considered tight enough to effectively block the sound source. The purpose in using two complete units operated simultaneously, was to increase the collected data and to provide a simultaneous control which was not possible with the single unit sampling method used in the previous segment. Because the sound system used for transmission had a range of approximately one mile underwater, the two sampling units were always set over one mile apart to prevent sound overlap. The experiments consisted of setting up the two units in similar environmental situations and alternating sound transmissions between the two on successive nights. Only complete overnight collections were found practical and the sound was trans~ mitted continuously for a period of approximately 14 hours, being started late in the afternoon and taken in the following morning. The net squares were set up on the same time basis. The two unit system thus gave two possible comparisons with controls. That is, the data from a collection with sound could be compared both to that of the second unit, or simultaneous collection, or back on the previous night's collection at the same location. Data collected included numbers of fish taken by species, including total lengths of all individuals, the specific net each individual was taken from, direction of movement (into or away from the sound source), and wind direction during the collection period. Simultaneous data was collected from both sampling units. Because the majority of fish taken were considered undesirable, all fish were removed from the lake. Frequencies Utilized In order to compare results and analyze the collected data, it was necessary to maintain a constant frequency covering as many collection nights as possible. Because observations from previous segments indicated a sharp reduction in the number of fish taken after 10 or more night's netting in the same locality, it was considered necessary to set the limit of continuous operation at a maximum 1h night period. Because of equipment failure and weather conditions which prohibited work, actual experimental periods vary from 10 to 14 days. The variance in time was inconsequentail since each experimental period was a separate entity and no cross comparisons between experiments were contemplated. The frequency generator and transmitting equipment utilized in the experiment had a frequency range of 200 to 20,000 cps. Because of the infinite numbers of pure frequencies and mixed frequencies possible to produce, the selection of fre- quencies to transmit was largely a random selection. --- Page 5 --- Sounds produced by freshwater fish and recorded in Lake Travis have shown a predominance of low frequency on the order of 90 to 1,000 cps. To try and simulate natural sources, half of the experimental work was conducted with frequencies below 1,000 cps. However, all frequencies utilized within this range were picked at random. A frequency meter was incorporated into the sound system and frequency drift was observed to be less than 0.01 percent for all frequencies used. The June experiment was conducted with a frequency of 720 cps; 2,300/400 eps mixed evenly in July; 1,750 cps in August; 4,150 eps in November; and 620 cps in December. FINDINGS The pure-frequencies transmitted in June, November, and December apparently had no effect on the movement of fish as the numbers taken in the control and experi- mental situations showed random catches. These data are presented in Graphs 1 through 3. The July experiment using 2,300/400 cps mixed evenly apparently repelled a segment of the fish population as the experimental situations with sound took 2 percent less fish than did the control situations. Each sampling unit consisting of the averaged figures for a two-night period (one experimental and one control at each location) shows a significantly lower catch with sound than without. The collected data involves the total nettable fish population. The fish species involved are shown in Table 1. No attempt will be made to ascertain the size ranges repelled or the individual species most affected until more experiments are conducted. The data for the July experiment are presented in Graph 4. The August experiment using a frequency of 1,750 cps also indicates a limited effect on the nettable fish population. Graph 5 shows the results of the August experiments. ‘CONCLUSIONS In the experiments conducted during July and August, the frequencies utilized exhibited a significant repelling effect on the nettable fish population. The frequencies used in the June, November, and December experiments showed no effect on the movement of the fish population. Other collected data including direction of movement, species and sizes repelled, and species and size ranges collected in the three mesh sizes will be compiled and statistically analyzed with additional data compiled at a later date. RECOMMENDATIONS It is felt that the result of the experiments conducted during the segment show enough promise to justify the continuance of the project. It is recommended that all phases be continued. --- Page 6 --- Prepared by John E. Tilton approves ty “Piper. & poten Director Inland Fisheries Division Project Leader Gary Wood Assistant Project Leader Date August 12, 1960 --- Page 7 --- Table 1. - Checklist of species, Lake Travis Scientific name Lepisosteus productus Lepisosteus osseus Dorosoma cepedianum Ictiobus bubalus Carpiodes carpio Moxostoma congestum Cyprinus carpio Ictalurus punctatus Ictalurus furcatus Pylodictus olivaris Mugil cephalus Roccus chrysops Micropterus punctulatus Micropterus treculi Micropterus salmoides Chaenobryttus gulosus Lepomis cyanellus Lepomis microlophus Lepomis macrochirus Lepomis megalotis Pomoxis annularis Aplodinotus grunniens Common name Spotted gar Longnose gar Gizzard shad Smallmouth buffalo River carpsucker Gray redhorse sucker European carp Channel catfish Blue catfish Flathead catfish Striped mullet White bass Kentucky spotted bass Texas spotted bass Largemouth black bass Warmouth Green sunfish Redear sunfish Bluegill sunfish Longear sunfish White crappie Freshwater drum --- Page 8 --- Figure 1. Diagram of Sampling Unit Open Water (25 Gill Net, (2%mesh) on foot 400 U1. mesh) ys ‘(1 mesh) Fansmitter vm s00° J (imesh) (“4g “mesh) tO see sh) re" (0 meshl yoo’ (74 mesh) fas (2% presh) Qeen Warvter --- Page 9 --- ish Taken Number of F Graph 1. June Netting Results. Z alg) --- Page 10 --- ish Taken umber of F N Graph 2. November Netting Results. Sr Ril as sitet Wie ina ts tae a Wetting Dates --- Page 11 --- Decenber p Netbing Results. 11S 10-44 8&9 (2-13 $5 Nettino Nateae 00 Oo 8 R 8 Number of Fish Te he re al - / 90 50 40 3 --- Page 12 --- . Graph '. July Netting Results. 10. 70 TTT Number of Fish Taken 12°73 Netting Dates --- Page 13 --- Number of Fish Taken Graph 5. August Netting Me-t9 18-19 Netting Dates