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, Pro

mm. ill: Report of Fisheries Investigations Underwater Observations of Fish Populations in Clear water Lakes of Central Taxas, including the Effect of various Sound Frequencies on Fish by John E. Tilton Project leader Gary WOod Assistant Project Leader Dingoll-thnson Project F—2-R-7, Jdb E-5 February 1, 1959 - January 31, 1960 H. D. Dodgen - Executive Secretary Texas Game and Fish Commission Austin, Texas ‘Harion Toole Kenneth C. Jurgens & William H. Brown Coordinator Assistant Coordinators A B S T R A.C T 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, h,l§0 cps and 620 cps apparently had no effect on the movement of fish to the sound source. However, 2,300/h00 cps mixed evenly showed a defiu nite repelling effect and 1,750 cps had some repelling influence although less pronounced than the mixed tone. JOb Completion Report State of TEXAS Project No. F-2-R-7 Name: Fisheries Investigations and Surveys of _ the Waters of Region -B \ Job No. E-5 . Title:_ Underwater Observations of Fish Po u— . ‘ ' lations in Clear water Lakes of Central Texasz including the Effect of various Sound Frequencies on Fish Period Covered: February 12 1959 through_January 312 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 observe“ 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 he 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 tine expenditure was used in phase three of the program, 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-2wR-6, Job EmS. 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 1%” mesh nets 100‘ long, and three 2" mesh nets 125' in length. Three distinct squares were set, effectively enclosing and blocking access by fish to the sound source from open water. The nets were set with an inner square of l" mesh, a middle square of 1%” mesh, and an outer square of 2” mesh. (In all cases the shoreline makes the fourth side of the square. See Figure l.) 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 netsaand 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 trance mitted continuously for a period of approximately 1h 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 cf fish taken by species, including total lengths of all individuals, the specific not 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 lhm night period. Because of equipment failure and weather conditions which prohibited work, actual experimental periods vary from 10 to 1h 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 free quencies to transmit was largely a random selection. 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. The June experiment was conducted with a frequency of 720 cps; 2,300/h00 cps mixed evenly in July; 1,750 cps in August; h,l50 cps 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 experim mental situations showed random catches. These data are presented in Graphs 1 through 3. The July experiment using 2,300/h00 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 h. 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. Prepared by John E. Tilton _ Approved by - .h4/’5}z¢’éi:;w Project Leader Director inland Fisheries Division Gary Wood -Assistant Project Leader Date August 12, 1960 _ Table l. - Checklist of species, Lake Travis Scientific name Lepisosteus productus Lepisosteus osseus Dorosoma cepedianum Ictibbus bubalus Carpiodes carpio Moxostoma congestum Cyprinus carpio Ictalurus punctatus Ictelurus furcatus Pylodictus olivaris Egg}; cephalus _ Roccus chrysops Micropterus punctulatus Micropterus treculi Micropterus salmoides Chaendbryttus gulosus Lepomis cyanellus Lepomis microlophus Lepomis macrochirus Lepomis megalotis Pomoxis annularis Aplodinotus gaunniens 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 Figure 1. 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