Noth Ameica Joual of Fisheies Maagemet 25:93 97, 2005 Copyight by the Ameica Fisheies Society 2005 DOI: 10.1577/M03-129.1 [Aticle] Factos Affectig Regioal Vaiatio i Gowth of Chael Catfish BART W. DURHAM,* KEVIN L. POPE, AND GENE R. WILDE Wildlife ad Fisheies Maagemet Istitute, Mail Stop 2125, Texas Tech Uivesity, Lubbock, Texas 79409, USA Abstact. We elated the legth at age of chael catfish Ictaluus puctatus, a idiect measue of gowth, to thee climatic ad five mophoedaphic vaiables i 144 Texas esevois. Gowth of chael catfish ages 3 though 6 was egatively elated to logitude, a facto that explaied as much as 34% of the vaiatio i legth at age. Chael catfish legth at age was ot sigificatly elated to latitude, coductivity, mophoedaphic idex, mea depth, ad maximum depth i all age-classes. Amog age-7 chael catfish, legth at age was positively elated to esevoi aea, which explaied 35% of the vaiatio i gowth. A quadatic model fo gowig-seaso legth explaied 7 17% of the vaiatio i legth at age i all age-classes. Oveall, legth at age fo chael catfish was geatest i esevois with itemediate gowig seasos (appoximately 270 d i legth) ad was lowe whe the gowig-seaso legth was eithe loge o shote. Ou esults povide the fist evidece that the legth of gowig seaso o a statewide o egioal scale may affect the gowth of chael catfish. Native o itoduced populatios of chael catfish Ictaluus puctatus ae peset i almost all of the 50 states i the USA (Mille 1966). Natiowide, chael catfish is oe of the most fequetly tageted feshwate fishes (U.S. Fish ad Wildlife Sevice ad Bueau of the Cesus 2002); cosequetly, maages i most states ecogize the eed to actively maage chael catfish fisheies (Vadefod 1984). Despite the populaity of chael catfish amog eceatioal agles, most studies of the species have bee diected towads aquacultue. As a esult, factos that ifluece the populatio dyamics of wild chael catfish populatios tageted by agles emai ukow. I a ecet liteatue eview, Hubet (1999) idetified the eed fo moe studies o the factos affectig the gowth of chael catfish. Although gowth of the species vaies substatially acoss its age, it has eve bee elated to egioal vaiatio i climatic factos such as tempeatue o gowigseaso legth (Hubet 1999). I this study, we sought to detemie if gowth of age-1 though age-7 chael catfish i 144 Texas esevois was elated to thee climatic ad five mophoedaphic vaiables. Methods Chael catfish wee collected duig outie spig (Jauay though May) gill-et samplig * Coespodig autho: bat.duham@ttu.edu Received July 10, 2003; accepted July 26, 2004 Published olie Febuay 28, 2005 fom 176 Texas esevois betwee 1975 ad 1995. Pectoal spies wee collected fom a subsample of fish fom each esevoi fo use i age ad gowth aalyses. Spies wee collected haphazadly fom up to five idividual fish pe ichgoup. Because samples oly occasioally cotaied moe tha five fish pe ich-goup, the ages of most collected fish wee estimated. I pepaatio fo age estimatio, pectoal spies wee sectioed distal to the aticulatig pocess ad mouted o glass slides (DeVies ad Fie 1996). This sectioig techique has bee show to educe age estimatio eo of olde catfish specimes (Nash ad Iwi 1999). Mea total legth at age fo chael catfish fom each esevoi was calculated. We etaied fo aalyses oly those esevoi agegoup combiatios fo which a miimum of five age estimates was available followig Pope et al. (2004) ad Wilde ad Muoeke (2001). This esulted i a fial sample of 595 chael catfish aged 1 to 7 yeas fom 144 esevois located thoughout Texas. We used coelatio aalyses ad liea ad quadatic egessio to examie the atue ad stegth of the elatioship betwee mea legth at age ad thee climate-elated ad five mophoedaphic vaiables. Climate-elated vaiables icluded latitude, logitude, ad legth of gowig seaso (defied as umbe of fost-fee days pe yea). Mophoedaphic vaiables icluded coductivity, Ryde s (1965) mophoedaphic idex (MEI), mea ad maximum depth, ad esevoi suface aea. Ispectio of scatteplots of gowth 93
94 DURHAM ET AL. TABLE 1. Miima (Mi) ad maxima (Max) fo thee climatic ad five mophoedaphic vaiables, umbe of esevois (), ad coelatio coefficiets () elatig chael catfish legth at age 1 though age 7 ad climatic ad mophoedaphic vaiables i Texas esevois. Coductivity ad the mophoedaphic idex (MEI) wee log 10 tasfomed. Coelatio coefficiets fo gowig-seaso legth ae based o quadatic models. Asteisks idicate sigificat coelatios based o the sequetial Bofeoi test (P 0.05). Vaiable Mi Max Age 1 Latitude ( N) 25.9 35.8 57 0.21 111 0.08 121 0.02 110 0.06 Logitude ( W) 93.6 103.7 57 0.04 111 0.24 121 0.05* 110 0.39* Gowig seaso (d) 187.0 341.0 57 0.17 111 0.26* 121 0.33* 110 0.36* Coductivity ( S/cm) 1.8 3.7 55 0.17 107 0.08 116 0.28 107 0.36 MEI 1.3 3.8 53 0.09 104 0.08 110 0.10 102 0.02 Mea depth (m) 0.3 16.0 55 0.22 107 0.00 114 0.02 104 0.09 Maximum depth (m) 0.9 61.0 57 0.27 108 0.03 115 0.04 106 0.14 Aea (ha) 0.4 74925.0 57 0.11 111 0.13 121 0.13 110 0.06 Age 2 Age 3 Age 4 vesus each idepedet vaiable idicated liea elatioships fo all vaiables except fo coductivity ad MEI, fo which logaithmic tasfomatios wee used, ad gowig-seaso legth, fo which a quadatic elatioship was most appopiate (Miada ad Duoche 1986; Wilde ad FIGURE 1. Relatioships betwee mea legth at age ad gowig-seaso legth fo 144 Texas chael catfish populatios. Symbols epeset the meas of five o moe obsevatios fo each esevoi ad ae defied as follows: ope upight tiagles age-1 fish; solid squaes age-2 fish; cicles age-3 ad age-4 fish; ope squaes age-5 fish; solid upight tiagles age- 6 fish; ad ope iveted tiagles age-7 fish. Muoeke 2001; Pope et al. 2004). I all cases, thee was o evidet depatue fom omality amog esiduals. Legth of gowig seaso was obtaied fom Ramos (1995). Ifomatio fo all othe vaiables was obtaied fom Texas Paks ad Wildlife Depatmet s Lake Categoizatio File, a database of wate quality ad mophometic data fo Texas esevois. To cotol the pobability of falsely ejectig ull hypotheses, we used the sequetial Bofeoi test with a tablewide sigificace of 0.05 to evaluate test statistics (Rice 1989). Regadless of statistical sigificace of idividual coelatios, two-tailed biomial tests (Siegel 1956) wee used to detemie whethe thee was a excess popotio of positive o egative coelatios betwee legth at each age ad climatic ad mophoedaphic vaiables. Ude the ull hypothesis of o coelatio, we expected 50% of the coelatios to be positive ad 50% to be egative fo each age-class. Exact P-values fo the biomial test ca be calculated by expadig the biomial pobability fuctio, o fo small ( 25) sample sizes, P-values ae peseted i tables i Siegel (1956). All statistical aalyses wee pefomed with SAS softwae (SAS Istitute, Cay, Noth Caolia). Results Acoss all study esevois, mea SE total legths at captue (ad ages) of chael catfish wee as follows: age 1, 234 6.9 mm (161 401 mm; N 57) ; age 2, 277 7.1 mm (152 552 mm; N 111); age 3, 327 8.0 mm (178 599 mm; N 121); age 4, 365 7.5 mm (234 646 mm; N 110); age 5, 396 7.9 mm (229 560 mm; N 96); age 6, 430 10.5 mm (277 606 mm; N 62); ad age 7, 437 12.2 mm (298 592 mm; N 38). Legth at age amog age-3 (
CHANNEL CATFISH GROWTH VARIATION 95 TABLE 1. Exteded. Vaiable Age 5 Latitude ( N) 95 0.15 62 0.10 38 0.16 Logitude ( W) 96 0.49* 62 0.51* 38 0.59 Gowig seaso (d) 96 0.37* 62 0.41* 38 0.39 Coductivity ( S/cm) 92 0.02 62 0.23 38 0.46 MEI 87 0.14 60 0.06 37 0.20 Mea depth (m) 90 0.16 60 0.06 37 0.01 Maximum depth (m) 93 0.17 62 0.12 38 0.41 Aea (ha) 96 0.04 62 0.05 38 0.59* Age 6 Age 7 0.35; N 121; P 0.0001), age-4 ( 0.39; N 110; P 0.0001), age-5 ( 0.49; N 96; P 0.0001), ad age-6 ( 0.51; N 62; P 0.0001) chael catfish was sigificatly egatively coelated with logitude ad explaied 13 34% of the vaiatio i legth at age (Table 1). Legth at age amog age-1 ad age-2 ( 0.24 to 0.04; N 57 121; P 0.10 0.76) chael catfish was ot sigificatly coelated with logitude. Legth of age-7 chael catfish was positively coelated ( 0.59; N 38; P 0.0001) with esevoi aea, which explaied 35% of the vaiatio (Table 1). Fo each chael catfish agegoup, afte Bofeoi adjustmet, legth at age was ot sigificatly elated to latitude, gowig seaso, coductivity, MEI, mea depth, o maximum depth ( 0.16 to 0.46; P 0.05). A quadatic model fo gowig-seaso legth was sigificatly coelated with legth at age amog age-2 (F 7.67; df 2, 108; P 0.0066), age-3 (F 14.20; df 2, 118; P 0.0003), age- 4(F 14.32; df 2, 107; P 0.0003), age-5 (F 10.17; df 2, 93; P 0.0019), ad age-6 (F 8.15; df 2, 59; P 0.0066) chael catfish ad explaied 7 17% of the vaiatio i legth at age (Table 1). Fo all age-goups, the elatioship betwee chael catfish legth at age ad gowigseaso legth was dome shaped (Figue 1). Legth at age was geatest i esevois with a gowigseaso legth of about 270 d ad deceased i esevois with shote o loge gowig seasos. This patte was cosistet acoss all age-goups. Populatios distiguished by slow gowth ates fo age-1 fish cotiued to gow slowly ad failed to each the statewide aveage legth i subsequet yeas. Chael catfish gowth geeally deceased with logitude ad MEI ad geeally iceased with mea ad maximum depth. Fo all ages, egadless of the sigificace of idividual coelatios, a excess popotio of coelatios betwee gowth ad mea depth ad maximum depth wee positive (P 0.016), ad a excess popotio of coelatios betwee gowth ad logitude wee egative (P 0.016). Thee was o sigificat (P 0.124) excess i the popotio of positive (o egative) coelatios betwee legth at age ad latitude, gowig-seaso legth, coductivity, ad esevoi aea. Discussio Ou esults povide the fist evidece that legth of gowig seaso may affect the gowth of chael catfish o statewide o egioal scales. Climatic factos ae kow to ifluece gowth ad yield of fish species with boad geogaphic distibutios. Howeve, the degee to which climatic factos affect fish gowth at egioal ad local scales is ot well documeted (Schlesige ad Regie 1982). Calade (1969) obseved that faste gowig chael catfish populatios typically occued i the southe potio of the species age, but he cocluded that moe compehesive evidece was eeded to detemie if egioal diffeeces i gowth commoly occu. Gowigseaso legth has bee show to be a sigificat pedicto of gowth i both white bass Mooe chysops (Wilde ad Muoeke 2001) ad white cappie Pomoxis aulais (Pope et al. 2004) i Texas. Howeve, Miada ad Duoche (1986) foud o sigificat elatioship betwee gowigseaso legth ad gowth of lagemouth bass Micopteus salmoides i Texas. Thus, it appeas thee is o geeal elatioship acoss species betwee gowig-seaso legth ad gowth. Gowig-seaso legth diffes by as much as
96 DURHAM ET AL. 160 d amog Texas esevois (Ramos 1995). We foud gowth of chael catfish was geatest i esevois with itemediate gowig-seaso legths (about 270 d). Gowth of chael catfish also was egatively elated to logitude. I Texas, elevatio iceases ad pecipitatio deceases fom southeast to othwest (Miada ad Duoche 1986; Goud ad Goege 1994; Wilde ad Muoeke 2001), possibly explaiig the logitudial elatioship with gowth. Relatioships betwee gowth ad gowig seaso ad logitude suggest that chael catfish gowth may be affected by seveal eviometal gadiets acoss the state; howeve, gowig-seaso legth appeas to have the geatest effect o chael catfish gowth. Gowth of chael catfish i oth Texas esevois is likely educed because these populatios expeiece the shotest gowig seasos, wheeas i southe esevois, gowth is pesumably educed because summe wate tempeatues exceed the optimum (30 32 C) fo gowth of chael catfish (Kilambi et al. 1971; Adews ad Stickey 1972). High wate tempeatue also may affect gowth by causig chael catfish to stop feedig as it does i othe species such as stiped bass Mooe saxatilis (e.g., Lochmille et al. 1989; Zale et al. 1990), o by iceasig metabolic demads to a level ot compesated fo by iceased food cosumptio as i white cappie (e.g., Haywad ad Aold 1996). Gowth of chael catfish was weakly associated with mea ad maximum depth, as evideced by sigificat excesses of positive coelatios. This esult is cotay to the ivese elatioship betwee fish poductio ad depth that typically is obseved i lakes ad esevois (Rawso 1952; Ryde 1965; Calie 1986). It is possible that gowth of chael catfish is uelated to depth ad poductivity. Alteatively, the captue efficiecy of gill ets used to sample chael catfish may vay amog lakes diffeig i mophometic chaacteistics (e.g., Blackwell ad Bow 2000), obscuig ay elatioship betwee gowth ad depth. Ou aalyses coside oly esevoi populatios ad povide o diect isight ito geogaphic vaiatio i the gowth of iveie chael catfish populatios. Although iveie populatios ae likely to gow at a diffeet ate tha lake ad esevoi populatios, thee is o easo to aticipate ay diffeece i the atue of the elatioship betwee gowth ad gowig-seaso legth betwee these habitats. Additioal study of iveie populatios is eeded to claify gowth pattes at a egioal scale i lotic systems. Seveal life histoy chaacteistics of chael catfish (icludig matuity, fecudity, ad motality) ae elated to legth (Appleget ad Smith 1951; Jeald ad Bow 1971; Hubet 1999). Theefoe, geogaphic vaiatio i gowth may affect local populatio dyamics ad the legth of time eeded fo chael catfish to each havestable size (Miada ad Duoche 1986). Igoig geogaphic pattes i gowth (ad hece populatio dyamics) may simplify fishey maagemet but may esult i agle dissatisfactio i aeas with extemely log o shot gowig-seaso legths. I such cases, egioal o wate bodyspecific maagemet pactices ad egulatios may be pefeable to maagemet with statewide egulatios. Ackowledgmets We thak Texas Paks ad Wildlife Depatmet Ilad Fisheies pesoel fo collectio of the data epoted i this pape. Chis Chiziski ad Todd Byely commeted o ealie dafts of this mauscipt. This is cotibutio umbe T-9 1010 of the College of Agicultual Scieces ad Natual Resouces, Texas Tech Uivesity. Refeeces Adews, J. W., ad R. R. Stickey. 1972. Iteactios of feedig ates ad eviometal tempeatue o gowth, food covesio, ad body compositio of chael catfish. Tasactios of the Ameica Fisheies Society 101:94 99. Appleget, J., ad L. L. Smith, J. 1951. The detemiatio of age ad ate of gowth fom vetebae of the chael catfish, Ictaluus lacustis puctatus. Tasactios of the Ameica Fisheies Society 80: 119 139. Blackwell, B. G., ad M. L. Bow. 2000. A compaiso of fish distibutios i simple ad complex lake basis. Joual of Feshwate Ecology 15:353 362. Calade, K. D. 1969. Hadbook of feshwate fishey biology. Iowa State Uivesity Pess, Ames. Calie, R. F. 1986. Idices as pedictos of fish commuity taits. Pages 46 56 i G. E. Hall ad M. J. Va De Avyle, editos. Resevoi fisheies maagemet: stategies fo the 80 s. Ameica Fisheies Society, Southe Divisio, Resevoi Committee, Bethesda, Maylad. DeVies, D. R., ad R. V. Fie. 1996. Detemiatio of age ad gowth. Pages 483 512 i B. R. Muphy ad D. W. Willis, editos. Fisheies techiques, 2d editio. Ameica Fisheies Society, Bethesda, Maylad. Goud, T. A., ad A. W. Goege. 1994. Chemical classificatio ad tophic chaacteistics of Texas es-
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