TPWD 1966 F-6-R-13 #1024: Appraisal of Various Mesh Sizes in Taking Fishes at Lake Corpus Christi, Texas

. JDE COMFLEIIDN REPORT As required by FEDERAL AID IN FISHERIES RESIDRAIIDN ACT TEXAS Federal Aid Project New Fm6-R-13 FISHERIES INVESTIGATIONS AND SURVEYS OF THE WATERS 0F REGIOR 5-D Job Non D-3 (let of 2 segments} Appraisal of Various Mesh Sizes in Taking Fishes at Lake Corpus Christi, Texas Project Leader: John C, Barron Ja Weldon Wetson Executive Director Parks and Wildlife Department Austin3 Texas Marion Tomle QEugene AA Walker D~J Coordinator Director, Wildlife Servicee February 9, 1966 ABSTRACT Bimonthly gill netting with straight mesh nets was conducted at Lake Corpus Christi in 1965” Nets with mesh ranging from one to four inches were useda The purpose of the operation was to determine which species of fish would be taken in the various mesh sizes? This information would cast light on the assumption that_gill netting is harmful to sport fishesi The job is to be conducted for another year, and the results of the col- lecting will be pooled, analyzed, and publishedo The data collected in this first segment shows that less than two per cent of the species which anglers ordinarily seek were taken in legal size (three-inch or above) gill nets, JOB COMPLETION REPORT State of‘ Texas immmmm Project N00 “End-Rig} _mmwfl Name: fisherigsfllgvestigations and Sure“ .r.srs_at‘=tas_tsisas_ei_tsaiesi§;¥2_ Job Non Dw3 (.st of 2 “agil. Title; épp£aisal_§i_yariou§_Mesh_§i§es in latices 'm-F.._1:- assist$213,399. r. .Bas___._.__.., Christi Texas mm: .m,,.‘_m..,t_.__ i1...- m..._1_____l_ Period Covered: January 13 1965 to December_§l£ml2§fi___mflmm__fl _mwmmm_ 'W‘u as: “w.mmI—nnm ”mums-1“— Objective; To appraise the effectiveness of various mesh sizes in taking rough or commercial species of fish at Lake Corpus Christi, Texaso Procedures: Bimonthly netting tripS'were made to Lake Corpus Christi during this segmento Straight mesh gill nets were used to collect fish specimensc Six different mesh sizeS'were used. la, 2:, 2%«, 3m3 3%”? and Quinch har measureo The nets were 100 feet long and 8 feet deepu The gill nets were set in a radial pattern about a staked This insured that each mesh size was available in each locations Three collection sites 'were usedo These were at Pernitas Creek, Miller's island, and Ramirena Creeko The latter site was near the headwaters of the lake; the former near the dame and the middle site was between the other twoc The fish collected were separated according to the mesh size in which they'were takeno Length and'aeight measurements were recorded for most individuals9 although at times it was necessary to weigh some species as a groupo Results and Discussion: It is intended that this job will he conducted for another segment; therew fore, since these data collected this year represents only half of the scheduled totalj only a cursory examination and analysis will he attemptedo Table 1 presents the numbers of fishes collected in the varioas mesh sitesa The species are grouped into convenient units of commercial} catfishss ysince in some counties they are commercial and in others are sportfc sport {those commonly sought after by anglers)? and Othersu This grouping is somewhat arbitrary, but for the present it is adequateo -.,-fiouefl epsmhwimMMIiilJ s . am .N HaammsHe m .. 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QOH ow Humflhsu msmnoo mqu om wouoeaaoo.mogmflm mo Hoaesz H oHQwH Unfortunately, these data collected will not satisfy the stated objectives of the jobo Effectiveness (=efficiency) of the various meshes was to have been appraiseda In order to test this, one must at least have an estimate of popu- lation sizes; however, no such estimates were attempted or availableo The objective was restated in the job description submitted for the coming segment to read: To determine the relation between mesh size of gill nets and species composition of the catchs Thesedata thus collected will be considered with this objective in mindu Actually, this job is intended to answer the question: ”Does gill netting hurt game fish populations?” In the counties where commercial fishing with large mesh gill nets is allowed many sportsmen contend that these nets damage the game fish populationsa The preliminary analysis of these data which we have collected, however, does not uphold this claimo Table 2 better illustrates this pointa Of the 529 sport and catfishes taken, less than 2 per cent were collected in legal size (threewinch or more) gill netso The legal size seems to be buffered too, since less than 4 per cent of the catch was taken in the next smaller net sizeu Inspection of the catch frequencies over the various mesh sizes leads to the belief that they are distributed in the form of one of the theoretical discrete distributions (probably the Poisson36 The validity of this assumption cannot be tested, however, due to the unfortunate exclusion of the ls-inch mesh size, This omission gives the l- and 2minch mesh sizes larger sampling in— tervals than the other groupsc This breakdown in experimental design illuSw trates the need of statistical counsel when preparing research jobs, since it would be very desirable to know the hypothetical probabilities of the various mesh sizes instead of just the sampling probabilities shown in Table 20 Of course the capture of fish in a gill net is a bilateral function of not only net mesh size but fish size aS'wella Io obtain data on this aspect, it will be necessary to show the weight of the groups taken in the various mesh sizesa The weight percentages taken in the-legal size nets will probably be greater than the frequency percentages, due to the fact that the larger indi- viduals are usually caught in the larger mesh siresa No attempt now will be made to analyze or present data on weight per mesh size, but it will be a part of the job completion report for the coming segmento Recommendations: This job should be conducted for another segment then the results pooled and analyzed The job compl.etion report should be published in the departmental magazine, Iexas Parhg Egg and later reprinted as a bulletino This would give maximum circulation and would publicly answer the question of come mercial fishing on the inland'waters of the Stateo \ /"/'"'" M/é/ {if @M'fl/ W1: -. Prepared by irishslgo Barrsslrrllmlll_ Approved by” lrt_l.l_r._m Project Leader ! Coordtlator Date _____tssrssr 9, l966l_m_llr__ll, “will” .. Keiasismsl.aa£slss_l_rl - Malonal Supervisor Table 2 Percentages of Sport and Catfishes Collected in 2%—inch and Larger Gill Nets - €1.11 Sizes ; Channel catfish 10901 1,90% Blue catfish ‘ 3,80 1 1090 1 Flathead catfish 6606? 66067 White bass . 2,83 g 0.00 _ Largemouth bass t 0000 ; 0000 White and black crappie : 5064 L 2642 :Total (percentage) 1 3578 : la89 .....m