TPWD 1957 F-6-R-4 #319: Inventory of Fish Species Present in Falcon Reservoir

Report of Fisheries Investigations Inventory of Fish Species Present in .‘Falcon Reservoir by Lou Guerra Project Leader Dingell-Johnson Project F-6-R-h, Job B—h February 1, l95h - June 30, 1957 H. D. Dodgen - Executive Secretary Texas Game and Fish Commission Austin, Texas Marion Toole William H. Brown Coordinator Asst. Coordinator JOB COMPLETION-REPORT State of TEXAS Project No. F6Rh Name: Fisheries_Investia of Region 3-B.. Inventor_.of.FiSh_S_ ation8.and Surve.s_of.the_Waters Job NO- _ _§:h .. Title: 'ecies.Present.in_Falcon,BeserVOir Period Covered: .h‘. J15111830 _ 19.7.” . _ . . ABSTRACT: Falcon Reservoir, an international lake on the Rio Grande between Texas and Mexico was studied from February 1, 195M through June 30, 1957. A total of 370 floating experi» mental gill net sets was made at ten locations. Seining and rotenone collections were made sporadically to augment data obtained with nets. Thirtynseven species of fish representing 13 families and 18 genera were recorded from Falcon Reservoir. Fish activity peaks were apparent in October and in January and February, aquatic vertebrates, inverts» brates and parasites are discussed. Regulations for the control of commercial fishing are recommended. Quarterly vegetation checks should be made to prevent the re-introduction of harmful aquatic plants. ”PeriOdic fisheries checks are recommended to determine the progress and.status of bass that spawned last spring (1957). fiRJECTIVES: To determine the fish species present and their relative numbers in Falcon Reservoir. PROCEDURE: The investigations of Falcon Reservoir was divided into two jobs: Job Auk, Basic Survey of Falcon Reservoir, objectivetto gather fundamental data on the chemical and physical characteristics of the lake and JOb Bah, Inventory of the Fish Present in Falcon Reservoir. Because of the many problems encountered, principally water lewel fluctuations and heavy commercial fishing, the project was carried on for a period of four years. The present job consisted of making monthly netting collections at the ten designated stations on the lake (Map 1). Other types of nets were also used occasionally to augment the data gathered from the regular stations. The information gathered was kinds and numbers of fish, sizes and Coeffecient of condition, sex and sexual condition, feeding characteristics, parasites, and seasonal and yearly changes in the whole population. Rem cords were kept on fish collection cards and netting collection forms. a. Netting Collections 1. Ten stations as Shown in Map l were selected in Falcon Reservoir to represent different locations and ecological conditions. Station 1 had a normal depth of 65 feet with a brush covered bottom. Station 2,=west of the submerged town of Old Falcon was 20 feet deep under normal water conditions. The bottom was sand and sandy silt. This station was exposed to south and southeast winds. Station 3 was located in the middle of the Arroyo Tigre Chico, and was generally exposed to south and south» east winds. This station had a normal water depth of to fact. The bottom was brush covered. This station was exposed to south and scutheast winds. Station 5, was near the river channel and the water at normal water depth was 50 feet. The bottom was brush covered. Station 6 was located at the Arroyo Clareno over some old culm tivated fields. The bottom was sandy silt and fine silt. The normal depth at this station was 30 feet. This station was exposed to southeast winds in the summer and spring and northwest winds in the fall and winter. Station 7 was located at the Arroyo Boleno four miles west of where U. S. Highway 83 creases the Arroyo Boleno. It was situated on the old Arroyo bed and the bottom was of sandy silt. The'depth' of water was 32 feet at normal water level. The nets were set in the area where the Arroyo Boleno entered the lake, and had good wind protection from all sides.. Station 8 at normal lake level was 18 feet deep and bottom Was brush covered with occasional areas of fine sandy silt.‘ Station 9 was 12 miles dOWnstream from San lgnacio. The lake was over bed rock out channel and had a normal depth of 15 feet, with bluffs on the east side of the river; Station 10 below San anac 0 Where the Rio Grande entered the lake had a normal water depth of 8 feet. The bottom was fine sandy silt with an area of deposited top soil. Station 7, 8, 9 and 10 had good wind protection”bee cause of their position in relation to prevailing winds and banks of the Arroyos. All stations with the exception of station 9 and 10 had some form of fish cover. The cover present was usually in the form of trees and brush submerged or partly ems mergent that were inundated by the impounded waters of Falcon Lake. Due to all this vegetation present in the lake bottom nets sets were seldom made. Experimental gill nets, 125 feet long and 5 feet deep varying mesh (1", 1%", 2", '%", and 3" square mesh) each twentymfive feet long were set at each station every month except when low water stages made it impossible. From September 1956 through June 1957 stations 7, 8, 93 and 10 were abandoned because of low_water and inaccesse ability. A total of 370 not sets were made.. Normally two or four stations were set at one time starting about 2 P. M. and the nets were picked up the next morning between 6 and 9 A» M. 2. Gill nets of 2" and 3" square mesh and 100 feet long and 8 feet deep were set at various times and at different locations to try and locate spawning and feeding areas. During the second segment six nets 100 feet long _8 feet wide of 3” square ' mesh were set in an effort to locate spawning buffalo with negative results. Most of these were set close to station A over some old plowed_fields. The information '. gathered from these nets was recorded in the same manner as those from experimental note, but because of their selectivity for size the information was not used in the statistical analysis. 3. Four 1" square mesh hoop nets, seven feet long, four feet wide and with two throats were set during the project period at various places. The nets were baited with meat scraps and cottonseed cake pellets. The results Obtained were inconclusive as only 6 soft shell turtles and 13 sunfish were caught. h. The fish taken in all gill nets were worked in the field. All fish measuring was.done by one of the field assistants, while the other weighed the fish and made the 3. internal examination. The assistant project leader recorded all the data. "K” factors and contents of stomachs were determined later in the laboratory. b. Seining Collections Seining collections were almost impossible to make because of the heavy brush growth on the lake. Only four areas were found where collections could be made. One was in the cleared area of the boat ramp at the International Boundary and water Commission camp in Falcon Village (A) Seining station "B" was located close to netting station No. 3 where old Highway 83 went into the lake. Seining station "C" was located opposite seining station No. 2 on the Arroyo Tigre Grands over old Highway 83. Sein~ ing station "D" was located in front of Bill Neale Fishing Camp on the Arroyo Boleno. Five rotenone collections were also made. The results of the seining and rotenone collections are shown in Table 13. Whenever possible the coining was done with a 30' by 6' seine with i” mesh. Whenever stumps or brush prevented the use of this seine a ten by four foot common sense minnow seine was used. Samples of the fish seined were preserved in one quart fruit jars containing 10% formalin solution. The fish seined were sorted, identified and counted later in the laboratory. Excessive numbers of a single species or fish too large for the fruit jar were counted, recorded on Fish Cards and discarded at the time of collection. c. Data Data concerning weather and water conditions and other observations were kept on Fish Cards and Fish Collection Sheets. A description of the lake and its chemical and physical characteristics was given in Job Completion Report for deb A-h. FINDINGS: The seasonal variations of fish activity as reflected by comparison of monthly netting catches expressed numerically and by weight may be seen in Tables 2 through 9. Tables 10 through 12 show the relative success of experimental gill netting in Falcon Lake. Table 1h shows the ranks, lengths, weights and "K" factors of the most common fish species caught in gill note from Falcon Reservoir. Table 15 shows the number and percentages of the common fish species caught from Falcon Lake in experimental gill nets during the project period. Table 16 shows the rough and gamefish population trends during the study period. Tables 17, 18 and 19 show the sexual condition of eight common fish species taken from Falcon Reservoir. Table 20 shows the stomach analysis of fish which contained food in their stomachs. Fish activity periods from the relative not catch are shown Tables 10 through 12. Peak periods are evident in the late winter (October and early spring (January, February) months in the second segment. Only the spring peak was evident in the first and third segments and this is correlated with inflow of waters raising the level of the lake, and bringing in a new food supply. It appears that peak periods are correlated to spring water temperature rises, spawning and feeding runs and the inflow of water into the lake. Sexual condition chart numbers are based on the numbers one to five. Condition 1 indicates the eggs and sperm were flowing, 2, gonads well developed, 3, sexes discernible, h, sexes indiscernible, 5, indicates that the fish had just spawned. DISCUSSION OF INDIVIDUAL SPECIES: Lepisosteus spatula — Alligator Gar. Rather common and some of very large size, occurring in all parts of the lake. One taken in experimental nets was Té-feet long and weighed 18% pounds. Among other items in its stomach were sixteen fish hooks. Adults were usually found infected with visceral tape worms and fish lice and small leeches were around the gills on some specimens. Almost all of the very large specimens were caught near submerged high and heavy brush. This species ranked fifth by number and first by weight. Lepisosteus productus, Spotted Gar. A common gar in Falcon Lake, found in all areas. Some showed well developed gonadal development during all months of the year. many had visceral tape worms. Rich lice and leeches were found around the gills. This species ranked eighteenth by number and ninth by weight over the fournyear period. Legisosteus_osseus, Longnose Gar. This species was common in all of the stations in the lake. Most specimens, upon internal examination, had visceral tape worms. Fish lice around the gill area were common. This species was observed to be mainly a night feeder on several night jugfishing trips. Longnose gars ranked seventh by number and ' eighth by weight. Their small size, nocturnal feeding habits, small elongated mouth, makes this species a real pest to trotline fishermen and difficult to control. Dorosoma petenenses , Threedfin Shad. This is one of the least common forage fish found in the lake. Seining collections showed only nineteen specimens. Dorosoma cepedianum, Giszard‘Shad was common at all of the seining areas and netting stations. This species is one of the principal forage fish found in Falcon Reservoir and constitutes one of the major items of diet of the short and longnose gars as evidenced by stomach analysis of these species. Gizzard shad ranked fourth by number and sixth by weight of all fish caught in experimental gill nets. ' Astyanem fasciatus mexicanus, ‘Rio Grande Tetra. Very common around the shoreline areas of Falcon Reservoir. In fact, this species is so prolific that its trapping,_sale and export as a bait minnow is a big and growing business in this area. Seining collections show that this species spawns on the average of three times a year in Falcon Reservoir, apparently in the months of February, May and July. Although some tetras were taken in open water they usually occur most commonly along shallow beaches. leiobus bubalus, Smallmoutthuffalo. Very common throughout the lake and all during the year. Commercial fishermen on both sides of the lake took an estimated one million pounds per year of this species from the lake during the project period. This estimate is baSed on records from beicois Secretary of marine Resources, U. S. Custom“s import records and buyer records from the commercial fishermen on the United States side. ' This species ranked first by number caught and second by weight. Smallmouth Buffalo had a low percentage of 5.7h by number during the first segment, 35.02 percent during the second year, 50.08 per cent during the third year and 39.26 during the last year of the“ project study. All growth stages of Smallmouth Buffalo were taken all year long, indicaw tion that this fish has an average spawn about every four months, which may be related to slight water temperature variation during the year, inflow of water, and abundant food' supply. Carpiodes carpio, River CarpSucker has been present in Falcon Reservoir every segment of the project period. All growth stages were caught in gill nets, but the average was lTA mm in standard length. River carpsucker ranked eleventh by number and eleventh by weight. Corgis, Carp. Very common at all stations in the lake. All growth stages were Cyprinus .ught during the period of stndy also indicating it spawns at least three times a year. Weight ranges from #5 to h7.67*grams. Carp ranked sexth by number and fifth by weight. Eybopsis aestivalis, Speckeled Dace, was present in all seining and rotenone collections. A total of 92 specimens was captured during the project period. Notropis.amabilis, Texas Shiner, was recorded during the first, third and fourth segment ' on Falcon Reservoir. Present but not in large numbers as only 55 specimens were captured during the project period. ‘ \ Notropis lutrensis, Redhorse Shiner, was common during all segments of the proiect period. The males of the redhorse shiner exhibit breeding coloration and tubercles almost- all year around, except in mid winter. Notropis jemesanus, Rio Grande Shiner, was recorded in small numbers during the first and fourth segments othhe project period. Only seven specimens were obtained during this time. ' ' hgroserfinus, Proserpine Shiner, was present during all segments of the project period, but the numbers caught in seines and rotenone collections was small. It was usually found on shallow sandy beaches. Notropis braytoni, Tamaulipas Shiner, very common in Falcon Lake, and one of the hardier species present. The Tamaulipas Shiner occurred in large numbers during all segments of the project period, at all stations, but numbers caught were small during the winter months. _talurus punctatus, Southern Channel Catfish, very rare in seining and rotenone collections made in Falcon Lake, and somewhat prevalent in gill net collections. Channel Catfish ranked tenth by number and twelfth by weight of all fish caught in gill net collections. Channel Catfish has been taken in large numbers by commercial fishermen and trotline fishermen. Ictalurus furcatus affinisc Blue Catfish. A very common species found at all stations during the project period. Very large numbers have been caught in Falcon Reservoir by' commercial fishermen on both sides of the lake. Spawning of Blue Catfish took place during April and May in the hollow sections of the flood control gates of Falcon Dam. Blue Catfish ranked third by number and fourth by weight. This, at the present time, is the' most important game fish in the lake, but percentagewise there has been a decrease in the numbers caught in the nets during the third and fourth segments of the project, in all probability brought about by extensive commercial catches. .A T2 pound specimen has been recorded from Falcon Reservoir. lctalurus melas, Black Bullhead, present in all but the first segment in seining and' rotenone collections. Many were taken in gill nets but the numbers were small. Probably present in the lake from some of the flooded stock tanks that were in the impounded water area. Black Bullheads, ranked nineteenth by number and fifteenth by weight of all the species caught in experimental gill nets. Pilodictus olivaris, Flathead catfish, very common in all parts of the lake. Caught during all segments of the project period in gill nets. Some Flathead Catfish were caught near a river channel that weighed up to 60 pounds. This species ranked ninth by number and c-9enth by weight of all species caught in experimental nets. Anguilla rostrata, American Eel. One specimen was caught in the dry spillway at Falcon Lake. Some were caught by commercial fishermen in the same area by hand. To date none have been recorded from the lake. Cyprinodon K; varigatus, Sea Pupfish. Many were caught in coining and rotenone collections made in isolated pools left by the receeding water level in Falcon Lake. Mngil cephalus, Striped Mullet, this salt and brackish water inhabitant has been caught in small numbers in Falcon Lake. Some of the specimens caught weighed as much as six pounds. : Menidia beryllina, Silversides, very common in all of the coining collections. -Silverside minnows furnish food for some of the game fish in the lake, although it is not one of the preferred items of diet, as the*numbers found in stomachs of Elue Catfish.were small. Chaenobryptus 3 _ Vermouth Bass, no specimens were caught in coining or rotenone collections. None were caught in nets during the first segment of the project period? seven during the second part, eleven during the third part and none during the fourth segment of the project. warmouth Bhss ranked thirteenth by number and sixteenth by weight' of all the fish caught in gill nets. Roccus chgysops, White Bass, was first caught in gill nets in January 1955, during the . second segment of the project'periOd. Although only a few were caught, some weighed as much as three and oneehalf pounds. 'One four and one-half pound specimen was caught in the river below the dam by commercial fishermen. .Apparently white bass have entered the river from flooded Lake walk and Devil's‘River above Del Rio. White been ranked seventeenth by number and thirteenth.by weight. Micropterus salmoides, Largemouth'Black_hass was first caught in experimental gill nets in November 1955. At first, this species was being caught in the upper lake stations. During the first three years of the project earnest efforts were made to locate and capture" bass fry and fingerlings to see if a spawn had taken place with negative results. During the last months of the fourth period repeated reports of bass fry were investigated and“ proved fruitless. In August 1957 reports of bass fry and young in the Arroyo holeno area were investigated and several juveniles, apparently from a late spring spawn, were captured which indicated that a bass spawn. had taken place. The lake had a period of constant low water level from April 12 to April 26, 1957 and the bass were able to get a spawn. Black bass caught in the gill nets ranged from 295 to 333 an. in standard lenght and from 907 to 1928 grams in weight. Largemouth bass ranked fourteenth by number and tenth by weight of all fish caught in experimental gill nets. A rather high "K” factor was found on this species of bass. The average “K" factor for fish of this species from Falcon‘ Reservoir ran 3.23. A comparative list of this same species in some of the major lakes in Texas is given below. ‘ Lake PW Falcon Lake 3.23 Bentsen Lake, near Mission 2.00 Delta Orchards lake, near We's'laco 1.61 Olmito Lake, near Brownsville“ 2.73 WOodlawn Lake, San Antonio 3.19 Bolton Reservoir, Bolton 2.60 Brownswood Lake 2.59 Lake Texoma 2.h9 Lake Levon 2.68 Average "K? factor in other Texas Lakes 2.h3 spomis c anellus, Green sunfish, was common in all parts of the lake. Sizes ranged from 9 to 115 mm in standard length. This species was the most common of the sunn fishes caught in seines and gill note. The green sunfish ranked sixteenth by number and nineteenth by weight. Lepomis macrochirus, Bluegill, common in all parts of the lake. Taken a1 all stations during the project period. Bluegills ranked eighth by number and fourteenth by weight of all fish taken in experimental gill nets. Although present in lake, neither the numbers nor the Size are large enough to attract the pan fishermen. Lepomis auritus, Yellowbelly Sunfish, rare in Falcon Lake, only two specimens were recorded and these were caught in seines, around coining station "A". Pomoxis annularis, White Crappie, common in all parts of the lake by the fourth segment. At first White Crappie was found only in the central part of the lake, but specimens began to show up in other parts of the lake by the end of the project period. White Crappie ranked fifteenth by number and eighteenth'by weight. Fishing for Crappie has not been too heavy in the lake. Aplodinotus grunniens, Freshwater Drum, next to most common species caught in nets in the lake. Infection with parasites (Visceral nematodes) of this species in this lake is not as common as in the other lakes of South Texas. Freshwater Drum ranked second by number and third by weight. Cichlasoma c ano uttatum, Rio Grande Perch, common in all parts of the lake but more so some of the samll isolated pools left when the lake receeded, brush piles and under road culverts. This fish ranked twelfth by number and seventeenth by weight. Electric pisonis, Spiny Cheek Sleeper, no specimen of this species has been caught in“ nets in the lake, but many have been caught by fishermen below the dam in the tailrace section. This strange looking brackish water fish has caused a lot of controversy among fishermen. The Spiny Cheek Sleeper has been called everything from a Mexican trout to a bowfin, and walleye pike. many young were seen and taken when the water was running over the spillway. This species is very highly regarded as a fighting fish by spin and baitm casting fishermen. Only two invertebrates were found in Falcon Lake that could possible be construed as a source of food supply for some of the game fish in the lake. This is the River Prawn, Macrobrachium 32;. which occurs in all parts of the lake in small numbers. Insects that" ' undergo an aquatic larval stage are not common, probably due to fluctuating water levels and relative absence of aquatic vegetation. Crayfish are common in the lake, but their relative numbers are very small. Large flocks of ducks and geese winter on the lake, staying mostly in the central part and around the Arroyo Boleno area. Small populations of anhingas, Mexican Cormonants, coots, great blue herons, snowy egrets, green herons, sea gulls, and terns are found almost the year around on the lake. Bird populations, especially coots and anhingas, increase slightly during the fall and winter months. Two species of turtles (Amyda sp. 3 and the slider (Pseudemyss scripts. )are found in the lake and the lake shore areas. A few frogs inhabit the lake, mostly leOpard frog (Rana pipiens). Their relatively small numbers are probably due to the high rate of predation by coons, as evidenced by their tracks around the isolated pools that the frogs inhabit. Toads found in the lake shore are Bufoc compactilus, Bufo woodhousei, Bufo marinus. Some alligators have been reported in the lake, but none have been caught. PARASITES: Two external parasites have been noticed on the fish from Falcon Lake, fish lice .Argulus lepidostei, and a small brown leech Glossiphenia §p__ The fish lice were found almost exclusively on gars usually around the head and gill covers. Leashes were found mostly on catfish. Internal visceral rOund worms and tape worms were also found in the stomach, intestine, and liver area of gore and on a few white bass. No infections were noticed on largemouth bass. RECOMMENDATIONS: The principal fisheries management problem on Falcon Reservoir is the lack of” adequate laws or regulations to govern the commercial fishing on this lake. A joint international meeting will be necessary between the Secretary of Marine Resources of Mexico, the U. 8. Fish and Wildlife Service and the Texas Game and Fish Commission in order to formulate regulatory measures or controls on Falcon Reservoir. Texas laws would help and are necessary in lieu of an international agreement. Fluctuating water levels in Falcon Reservoir due to extensive demands for irrigam tion water in the Rio Grande Valley have prevented the yearly spawn of game fish. However, during the spring of 1957, during a low water stage, a bass spawn was possible. Since bass have spawned in this lake, future stockings form the state fish hatcheries should be reduced or discontinued, because the quantities available from the hatchery are negligm ible compared to natural spawns in a lake of this size. Detrimental vegetation such as water hyacinths should be prohibited from intro= duction either by state or county laws. Occasional checks should also be made of the lake to prevent propagation of water hyacinths that might be accidently introduced by' well meaning but uninformed individuals. Spring and Fall netting and coining samples should be taken to determine the status and spawning success of game fish in the lake. The proposed state park areas with their accompanying boat ramps docks, cabins, playground and swimming area should be developed to provide much needed recreational facilities for this area. Public access to this lake is very limited. When the Diablc International Dam at Del Rio is built, Falcon Lake may become a rather constant level lake and management programs should be developed and carried out until a fish population balance is attained.