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Efficiency and Selectivity of Gill Nets for Assessing Fish Community

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Efficiency and Selectivity of Gill Nets for Assessing Fish Community North American Journal of Fisheries Management 25:1315±1320, 2005 q 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 to- tal 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 pad- dle®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 # 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 5 endangered, T 5 threatened, and C 5 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 3 muskellunge E.
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