Efficiency and Selectivity of Gill Nets for Assessing Fish Community

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North American Journal of Fisheries Management 25:1315±1320, 2005 ᭧ Copyright by the American Fisheries Society 2005 [Management Brief] DOI: 10.1577/M04-104.1

Ef®ciency and Selectivity of Gill Nets for Assessing Fish Community Composition of Large Rivers

DAVID G. ARGENT* AND WILLIAM G. KIMMEL Biological and Environmental Sciences Department, California University of Pennsylvania, 250 University Avenue, California, Pennsylvania 15419, USA

Abstract.ÐTo evaluate the ef®ciency and selectivity netting must be understood to be used to sample of gill netting for assessing ®sh biodiversity in the upper target ®sh communities (TFCs) as part of a tem- Ohio River system, we compared the ef®ciency of ®ve poral monitoring program. gill-net types for sampling large-bodied ®shes (adult total length greater than 250 mm) during fall 2001 and Most existing studies focus on comparisons spring and fall 2002. Mesh sizes ranged from 3.8 cm to among gear types (e.g., gill netting versus elec- 14 cm (bar measure). We set the gill nets in selected tro®shing) rather than ef®ciency within a speci®c pools of the Allegheny, Monongahela, and Ohio rivers gill-net mesh size (Elliott and Fletcher 2001; Col- 186 times over three seasons for a total of 1,644 net- vin 2002) or on one target species or several target hours. Nets were attached to a variety of structures, in- species with the objective of developing selectivity cluding trees and rootwads, bridge pylons, lock and dam chambers, and channel marker buoys. Nets were ®shed curves (Berst 1961; Hamley 1975). Unfortunately, from late evening to ®rst light, and all ®sh captured were these studies provide little information to discern identi®ed, enumerated, and released. A total of 823 in- gill-net ef®ciency for sampling a TFC. dividuals representing 30 species or hybrids were cap- Gill nets are primarily used to monitor ®sh pop- tured. All net types captured common carp Cyprinus ulations in lakes (Minns and Hurley 1988; Colvin carpio and ¯athead cat®sh Pylodictis olivaris, but we 2002), reservoirs (Jensen 1986), and marine en- captured a signi®cantly greater diversity of ®shes in vironments (Carlander 1953; Berst 1961; Murphy graded-mesh gill nets with small mesh (38 m in length with variable-bar mesh and 15.2 m in length with 3.8- and Willis 1996) rather than in large riverine hab- cm-bar mesh). When adjusted for length, smaller-bar itats. The large rivers of the United States are home mesh nets (3.8-cm-bar mesh) were more ef®cient for to a diverse assemblage of ®shes (Lee et al. 1980) capturing target species than graded-mesh nets. To max- and present sampling challenges because of their imize species richness, 200±225 h of effort were nec- size and habitat complexity. We theorized that gill essary to characterize target ®sh communities of large- nets could be used to ef®ciently sample large riv- bodied riverine species. erine habitats, especially for a clearly de®ned TFC. In this study, we de®ned the TFC as those ®shes When sampling for ®sh diversity, electro®shing having an adult total length (TL) greater than 250 (Meador et al. 1993; Angermeier and Smogor mm. This TFC excluded all cyprinids except com- 1995; Heimbuch et al. 1997), rotenoning (OR- mon carp Cyprinus carpio and included a range of SANCO 1978), and gill netting (Minns and Hurley large-bodied riverine ®shes representing several 1988; Colvin 2002) have been widely used by ®sh- feeding (e.g., piscivore and detritivore) and habitat eries biologists but not without issues of cost, ®sh (e.g., benthic and midwater) guilds that are vul- mortality, public perception, and size and species nerable to capture in gill nets. Of particular interest selectivity (Hamley 1975; Hubert 1996; Murphy was the buffalo±carpsucker±redhorse (smallmouth and Willis 1996). Gill netting presents similar is- buffalo Ictiobus bubalus, river carpsucker Carpi- sues of public concern with respect to ®sh mor- odes carpio, redhorse Moxostomus spp.) complex, tality, but can provide a cost-effective method for which includes a number of ``species of special sampling a diversity of ®shes, size-classes, and concern'' in Pennsylvania. Our objective was to habitats. However, studies indicate that gill-net ef- determine which of ®ve selected gill-net types was ®ciency varies with mesh size and material, ®sh most effective for quantifying the large-bodied ®sh morphology (Hamley 1975), and sampling period community composition in a large riverine system. (Carlander 1953). Therefore, the ef®ciency of gill Methods The Ohio River (from Pittsburgh, Pennsylvania, * Corresponding author: [email protected] to Pike Island, West Virginia) and its major trib- Received July 2, 2004; accepted March 5, 2005 utaries, the Allegheny and Monongahela rivers in Published online September 28, 2005 Pennsylvania, consist of a series of navigational

1315 1316 ARGENT AND KIMMEL

TABLE 1.ÐDimensions of gill nets used to sample ®sh community structure in eight pools of the Ohio, Alleghe- ny, and Monongahela rivers from October 2001 through November 2002.

Net Net Panels Panel Net depth length (num- length type (m) (m) ber) (m) Bar mesh (mm) 1 2.4 38.1 5 7.62 38, 64, 89, 114, and 140 2 1.8 45.7 5 9.12 38, 64, 89, 114, and 38 3 1.8 15.2 1 15.20 38 4 2.4 30.5 1 30.50 140 5 2.4 30.5 1 30.50 102

that varied by pool. Deployment frequency varied by net type as part of a multigear sampling strategy directed toward assessing population status of paddle®sh Polyodon spathula in Pennsylvania (Table 2). All gill nets were deployed perpendicular to ¯ow and the residual end of each net was anchored and identi®ed with marker buoys. Gill nets were typically set once in the early evening, checked after 3±4 h, and then redeployed overnight. Nets ®shed overnight were checked immediately after FIGURE 1.ÐLocations of eight pools in the Ohio, Al- ®rst light. All captured ®sh were identi®ed to spe- legheny, and Monongahela rivers in southwestern Penn- cies, measured to the nearest millimeter TL, enu- sylvania where ®sh community structure was sampled merated, and released. from October 2001 through November 2002. Filled cir- cles indicate locations of lock and dam chambers. Catches were scaled by net length to permit comparisons of catch rate among each net type. First, we used one-way analysis of variance (AN- pools maintained by a basinwide lock and dam OVA) to compare species catch rate, size of ®sh system (Figure 1). Pool lengths vary from 9 to 67 captured, and species composition (dependent var- km and pool widths vary from 140 to 437 m. Flu- iables) among net types (independent variable). vial dynamics and mean depths of these pools are Fisher's least-signi®cant-difference (LSD) test was constantly changing from the operation of the var- then used to determine which net types differed ious locks for maintaining navigable channels. Our whenever the ANOVA was signi®cant (P Յ 0.05; study area encompassed lock and dam chambers bounded to the west by Pike Island, West Virginia, TABLE 2.ÐSampling protocol (number of net sets per to the south by Grays Landing, and to the north net type) used to sample ®sh community structure in eight by Lock and Dam No. 3 in Pennsylvania (Figure pools of the Ohio, Allegheny, and Monongahela rivers 1). from October 2001 through November 2002. Dimensions To assess their relative capture ef®ciencies in of net types are shown in Table 1, and pool locations are these large rivers, we deployed ®ve gill-net types shown in Figure 1. of different lengths and mesh sizes (Table 1) from Net type 5 October to 9 November 2001 and from 5 April to 11 November 2002, employing a strati®ed ran- Pool 12345Total dom sampling design for pool selection and net- Pike Island 54244 19 set location. Eight pools were randomly selected Montgomery 20 8 6 30 4 68 Dashields 42272 17 from a total of 11 in the study area (the Pittsburgh Lock and Dam pool was considered as one, even though it in- No.3 54332 17 cludes all three major rivers). The ®ve gill-net Braddock 43333 16 Elizabeth 42232 13 types were randomly assigned to available ®xed Lock and Dam points (e.g., large woody debris, bridge abutments, No.4 53343 18 barge pylons, island back channels, tributary Maxwell 43353 18 mouths, gravel bars, and lock and dam chambers) Total 51 29 24 59 23 186 MANAGEMENT BRIEF 1317

TABLE 3.ÐNumbers of ®sh captured in ®ve gill-net types (Table 1) used to sample ®sh community structure in eight pools of the Ohio, Allegheny, and Monongahela rivers from October 2001 through November 2002. Pennsylvania status codes are as follows: E ϭ endangered, T ϭ threatened, and C ϭ candidate for listing.

Net type Species 1 2 3 4 5 Status Longnose gar Lepisosteus osseus 18 21 10 0 0 C Mooneye Hiodon tergisus 64000T Skipjack herring Alosa chrysochloris 158800E Gizzard shad Dorosoma cepedianum 19 16 8 0 0 Common carp Cyprinus carpio 48 3 40 11 4 River carpsucker Carpiodes carpio 30100E Quillback C. cyprinus 81100 High®n carpsucker C. velifer 00100 White sucker Catostomus commersonii 10000 Smallmouth buffalo Ictiobus bubalus 170400C Bigmouth buffalo I. cyprinellus 00001E Silver redhorse Moxostoma anisurum 20000 River redhorse M. carinatum 10100E Black redhorse M. duquesnei 10000 Golden redhorse M. erythrurum 136500 Shorthead redhorse M. macrolepidotum 421000 Channel cat®sh Ictalurus punctatus 114 27 41 3 1 Flathead cat®sh Pylodictis olivaris 16 4 6 13 11 Northern pike Esox lucius 10000 Tiger muskellunge (Northern pike ϫ muskellunge E. masquinongy) 01000 White bass Morone chrysops 93700 Hybrid striped bass (White bass ϫ striped bass M. saxatilis)265 222 0 Rock bass Ambloplites rupestris 13000 Smallmouth bass Micropterus dolomieu 04000 Spotted bass M. punctulatus 6131200 Black crappie Pomoxis nigromaculatus 21000 Sauger Sander canadensis 20 5 18 0 1 Walleye S. vitreus 252901 Saugeye (sauger ϫ walleye) 10 1 7 0 0 Freshwater drum Aplodinotus grunniens 155765 Total 401 135 218 45 24

Ott 1988). Second, we used catch data to estimate (23%), common carp (13%), and hybrid striped the time (effort) necessary to adequately sample bass (7%) dominated the catches. Several state en- the TFC. Accumulated catch was plotted against dangered or threatened ®shes were caught, includ- accumulated effort to empirically evaluate the re- ing longnose gar, mooneye, skipjack herring, river sultant asymptotic relationship. Last, we compared carpsucker, high®n carpsucker, bigmouth buffalo, our TFC with a data set derived from the Penn- and smallmouth buffalo (Table 3). sylvania Fish and Boat Commission's (PFBC Catch rates were signi®cantly higher in graded- 2000) list of ®shes expected to occur here and with mesh or small-mesh gill nets (types 1±3) than larg- a list of ®shes collected over a 20-year period by er-mesh types (F ϭ 15.7; df ϭ 4; P Ͻ 0.001; Figure means of electro®shing (EAEST 2001). We pruned 2). Catch rates did not differ signi®cantly between the PFBC (2000) and EAEST (2001) ®sh lists to the two graded-mesh gill-net types (types 1 and 2) include only those ®shes that met our TFC criteria or between the two large-mesh gill nets (types 4 and were native to the Ohio River drainage or had and 5; Fisher's LSD). We captured 88% of ®shes been stocked for sport®shing purposes. that were expected to occur in the Allegheny, Mo- nongahela, and Ohio rivers (PFBC 2000; EAEST Results 2001). Sampling effort in eight randomly selected Fish ranged in length from 139 to 1,280 mm TL, pools of the Allegheny, Monongahela, and Ohio 66% of the total catch being in the 250- to 500- rivers included 186 net sets for 1,644 net-hours mm length-class (Figure 3). Fish shorter than 500 (Table 2). Catches included 823 individuals of 30 mm TL were captured signi®cantly more often in species or hybrids (Table 3). Channel cat®sh graded-mesh (types 1 and 2) and small-mesh nets 1318 ARGENT AND KIMMEL

FIGURE 3.ÐSize frequency of ®sh captured in ®ve gill- net types (Table 1) used to sample ®sh community structure in eight pools of the Ohio, Allegheny, and Monon- gahela rivers from October 2001 through November FIGURE 2.ÐCatch per unit effort (CPUE), scaled by 2002. net length, in ®ve gill-net types (Table 1) used to sample ®sh community structure in eight pools of the Ohio, Allegheny, and Monongahela rivers from October 2001 tured signi®cantly more often in our graded-mesh through November 2002. Error bars denote one standard (types 1 and 2) and small-mesh nets (type 3) than deviation from the mean. in our large-mesh nets (types 4 and 5), while the large-mesh nets were more ef®cient at capturing (type 3) than in larger net types (types 4 and 5; F ®shes greater than 500 mm TL (Figure 3). Minns ϭ 43.5; df ϭ 4; P Ͻ 0.001). Larger-mesh net types and Hurley (1988) concluded from their study of (types 4 and 5) caught signi®cantly more ®sh larg- the ®sh community in Bay of Quinte, Lake On- er than 500 mm TL than smaller-mesh net types tario, that ``use of gill-net catches as indices of (types 1, 2, and 3; Figure 3; Fisher's LSD). ®sh abundance must be validated species by spe- Species richness was maximized at different cies.'' numbers of species and at different levels of sam- Species richness varied with net type and sampling effort among net types. For graded-mesh and pling effort with graded-mesh and small-mesh small-mesh nets (types 1±3), species richness was nets, reaching higher species asymptotes over lon- maximized at about 25 species by 200±225 h of ger time periods (Figure 4). Tejerina-Garro and net time (Figure 4). In contrast, for larger-mesh Merona (2001), studying ®sh communities of large nets (types 4 and 5), species richness was maximized at about 5 species by 100 h of net time.

Discussion Variability in catch per unit effort (CPUE) among net mesh size, net length, depth of deployment, soak time, and season has been documented in a number of studies (Minns and Hurley 1988; Van den Avyle et al. 1995; Hansen et al. 1998). However, these studies (along with most of the pertinent literature) describe surveys directed at a particular species or size or age-group within the target species (Pierce et al. 1994; Van den Avyle et al. 1995) and are conducted mostly in standing waters. Assessments of large-river ichthyofauna utilizing serial gill netting, such as that of Tejerina- Garro and Merona (2001), are rare. FIGURE 4.ÐCumulative number of species captured The in¯uence of ®sh body length, girth, and en- in ®ve gill-net types (Table 1) used to sample ®sh community structure in eight pools of the Ohio, Allegheny, counter probability is also well documented (Red- and Monongahela rivers from October 2001 through No- din 1986; Spangler and Collins 1992; Paukert and vember 2002. Net type 1 ϭ square; net type 2 ϭ asterisk; Fisher 1999; Anderson and Neumann 2000). We net type 3 ϭ plus sign; net type 4 ϭ triangle; and net found that ®shes less than 500 mm TL were cap- type 5 ϭ circle. MANAGEMENT BRIEF 1319 rivers in French Guiana, concluded that gill-net Geri and Dick Morgan from the Groveton Boat mesh sizes of 15±35 mm adequately sampled their Club for their hospitality in providing boat launch target communities. facilities; Edwin L. Cooper for con®rming ®sh Using total species asymptotes as determinants, identi®cations; and the West Virginia Division of our results indicate that serial gill netting with a Natural Resources (Chris O'Bara) for partial fund- mix of mesh sizes and net lengths can adequately ing of this survey work. assess species richness of large-bodied riverine ®shes. This strategy allowed us to capture the ma- References jority of species of this TFC that were expected Anderson, M. R., and R. M. Neumann. 2000. Indirect to occur in the Ohio, Allegheny, and Monongahela estimates of gill-net mesh size selectivity for land- rivers. Among these were 7 species recognized as locked alewives. Journal of Freshwater Ecology 15: ``endangered or threatened'' in Pennsylvania. Ex- 491±496. Angermeier, P. L., and R. A. Smogor. 1995. Estimating ceptions were ®shes that the PFBC recognizes as number of species and relative abundances in stream ``uncommon'' in Pennsylvania (e.g., river carp- ®sh communities: effects of sampling effort and dis- suckers) and ®shes that are not vulnerable to cap- continuous spatial distributions. Canadian Journal ture in gill nets (e.g., centrarchids; R. Lorson, of Fisheries and Aquatic Sciences 52:936±949. PFBC, personal communication). While many ®sh Berst, A. H. 1961. Selectivity and ef®ciency of exper- were missing scales and exhibited signs of stress imental gill nets in South Bay and Georgian Bay of upon release, survival was exceptionally high, Lake Huron. Transactions of the American Fisheries Society 60:413±418. even among alosines. Gill nets are widely used as Carlander, K. D. 1953. Use of gill nets in studying ®sh a passive capture technique in standing waters but populations, Clear Lake, Iowa. Proceedings of the are selective in regard to ®sh size and morphology Iowa Academy of Science 60:621±625. (Hamley 1975). Users can minimize selectivity by Colvin, M. 2002. A comparison of gill netting and elec- employing graded-mesh nets to capture ®shes of tro®shing as sampling techniques for white bass in varying lengths. However, our data suggest that Missouri's large reservoirs. North American Journal of Fisheries Management 22:690±702. nets with small-bar single-mesh panels were com- EAEST (EA Engineering, Science, and Technology). parable in ef®ciency to graded-mesh nets for sam- 2001. Final report 2000: Ohio River ecological re- pling the diversity of the ichthyofauna of the Al- search program. EAEST, Deer®eld, Illinois. legheny, Monongahela, and Ohio rivers. These re- Elliott, J. M., and J. M. Fletcher. 2001. Comparison of sults suggest that an appropriately designed gill- three methods for assessing the abundance of Arctic net sampling strategy can be comparable to costly charr, Salvelinus alpinus, in Windermere (Northwest England). Fisheries Research 53:39±46. boat electro®shing for the characterization of this Hamley, J. M. 1975. Review of gill-net selectivity. Jour- TFC. nal of the Fisheries Research Board of Canada 32: The major weakness of this gill-net sampling 1943±1969. approach is that some species are not vulnerable Hansen, M. J., R. G. Schorfhaar, and J. H. Selgeby. 1998. to capture in gill nets. This may be a critical issue, Gill-net saturation by lake trout in Michigan waters especially if decisions regarding ®sheries man- of Lake Superior. North American Journal of Fish- agement objectives require frequency of capture eries Management 18:847±853. Heimbuch, D. G., H. T. Wilson, S. B. Weisberg, J. H. or proportional data. However, if the primary ob- Volstad, and P. F. Kazyak. 1997. Estimating ®sh jective is to characterize diversity, then gill netting abundance in stream surveys by using double-pass may offer a low-cost alternative to other more ex- removal sampling. Transactions of the American pensive and labor-intensive techniques. If the man- Fisheries Society 126:795±803. agement objective demands data on those ®shes Hubert, W. A. 1996. Passive capture techniques. Pages that are not vulnerable to capture in gill nets, then 157±192 in B. R. Murphy and D. W. Willis, editors. Fisheries techniques, 2nd edition. American Fish- we suggest the use of multiple sampling gears to eries Society, Bethesda, Maryland. adequately characterize the community. The re- Jensen, J. W. 1986. Gill-net selectivity and the ef®ciency sults of our study suggest that graded-mesh and of alternative combinations of mesh sizes for some small-mesh nets can ef®ciently sample the diver- freshwater ®sh. Journal of Fish Biology 28:637± sity of ®shes in our de®ned TFC (Ͼ250 mm TL). 646. Lee, D. S., C. R. Gilbert, C. H. Hocutt, R. E. Jenkins, Acknowledgments D. E. McAllister, and J. R. Stauffer, Jr. 1980. Atlas of North American freshwater ®shes. North Caro- We thank Adam Smith, Patrick Kocovsky, Rob- lina State Museum of Natural History, Raleigh. ert Carline, Justin Fowler, Greg Huchko, and Dan Meador, M. R., T. F. Cuffney, and M. E. Gurtz. 1993. Counahan for their assistance with ®sh collections; Methods for sampling ®sh communities as part of 1320 ARGENT AND KIMMEL

the National Water Quality Assessment Program. Pierce, R. B., C. M. Tomcko, and T. D. Kolander. 1994. U.S. Geological Survey, Open File Report 93-104, Indirect and direct estimates of gill-net size selec- Raleigh, North Carolina. tivity for northern pike. North American Journal of Minns, C. K., and D. A. Hurley. 1988. Effects of net Fisheries Management 14:170±177. length and set time on ®sh catches in gill nets. North Reddin, D. G. 1986. Effect of different mesh sizes on American Journal of Fisheries Management 8:216± gill-net catches of Atlantic salmon in Newfound- 223. land. North American Journal of Fisheries Man- Murphy, B. R., and D. W. Willis. 1996. Fisheries tech- agement 6:209±215. niques, 2nd edition. American Fisheries Society, Spangler, G. R., and J. J. Collins. 1992. Lake Huron Bethesda, Maryland. ®sh community structure based on gill-net catches ORSANCO (Ohio River Sanitation Commission). 1978. corrected for selectivity and encounter probability. Summary of Ohio River ®sh surveys. ORSANCO, North American Journal of Fisheries Management Cincinnati, Ohio. 12:585±597. Ott, L. 1988. An introduction to statistical methods and Tejerina-Garro, F. L., and B. Merona. 2001. Gill-net analysis, 3rd edition. PWS-Kent Publishing Com- pany, Boston. sampling standardisation in large rivers of French Paukert, C. P., and W. L. Fisher. 1999. Evaluation of Guiana (South America). Bulletin FrancËais de la paddle®sh length distributions and catch rates in Peche et de la Pisciculture 357±358:227±240. three mesh sizes of gill nets. North American Jour- Van den Avyle, M. J., G. R. Ploskey, and P. W. Bettoli. nal of Fisheries Management 19:599±603. 1995. Evaluation of gill-net sampling for estimating PFBC (Pennsylvania Fish and Boat Commission). 2000. abundance and length frequency of reservoir shad Pennsylvania ®shes. PFBC, Educational Media Sec- populations. North American Journal of Fisheries tion, Harrisburg, Pennsylvania. Management 15:898±917.