Transactions of the American Fisheries Society 136:56–71, 2007 [Article] Ó Copyright by the American Fisheries Society 2007 DOI: 10.1577/T06-127.1

Survival and Growth Responses of Juvenile Salmonines Stocked in Eastern Tributaries

1 2 STEPHEN M. COGHLAN JR.,* MICHAEL J. CONNERTON, NEIL H. RINGLER,DONALD J. STEWART, 3 AND JERRY V. MEAD Faculty of Environmental and Forest Biology, State University of , College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, New York 13210, USA

Abstract.—To evaluate the species-specific and stream-specific suitability of juvenile salmonine habitat in the southern Lake Ontario watershed, we studied the effects of multiple environmental gradients on the first- summer apparent survival and growth of various combinations of Atlantic salmon Salmo salar, rainbow trout Oncorhynchus mykiss, and coho salmon O. kisutch stocked in tributaries. Costocking of either Oncorhynchus species had no detectable effect on the apparent survival or change in cohort biomass of Atlantic salmon, but their growth rates were reduced slightly when they were stocked with rainbow trout. Generally, Atlantic salmon outperformed their putative competitors. Summer temperatures were near the physiological optimum for Atlantic salmon but may have limited the success of rainbow trout and especially coho salmon. Total salmonine biomass was maximized at sites in which only Atlantic salmon were planted. Apparent survival and biomass elaboration of Atlantic salmon varied inversely with stream size, temperature, and the abundance of wild salmonines and piscivores, whereas growth rate responded positively to moderate increases in summer temperature, agricultural development, and nutrient enrichment. These regional and species-specific differences in stocked salmonine success may, in part, be explained by variations in temperature, geomorphology, and anthropogenic influences. We recommend that the feasibility of restoring Atlantic salmon continues to be evaluated, especially in those tributaries considered to be of marginal quality for other salmonines.

Landlocked Atlantic salmon Salmo salar were of Atlantic salmon (Heland et al. 1997; Jones and abundant historically in the Lake Ontario watershed, Stanfield 1993; Scott et al. 2003, 2005; Coghlan and where juveniles occupied nursery habitat in tributaries Ringler 2005b). Evaluating survival, growth, and of Lake Ontario and the Finger Lakes (Webster 1982). habitat suitability for several salmonine species on a Atlantic salmon were extirpated from the watershed in site-specific basis would be useful in predicting the the 1890s because of ecosystem changes resulting from outcomes of Atlantic salmon restoration efforts and anthropogenic activities such as deforestation, dam- assessing the likelihood of competition with natural- ming of rivers, industrial and agricultural pollution, and ized salmonines (e.g., Johnson and Wedge 1999). exotic species invasion (Webster 1982; Ketola et al. In a study of 15 New York tributaries to Lake 2000). Since that time, populations of exotic brown Ontario accessible to migratory salmonines, Wildridge trout S. trutta, steelhead Oncorhynchus mykiss (anad- (1990) classified streams according to wild salmonine romous rainbow trout), coho salmon O. kisutch, and production capacity and identified variation in natural Chinook salmon O. tshawytscha have become natural- production corresponding to physiographic region. ized in portions of the historical range of the Atlantic Because abundance values were point estimates from 1 year, Wildridge (1990) could not determine conclu- salmon (Fausch 1998; Crawford 2001) and may be sively if low densities of wild juveniles in certain affecting survival, growth, behavior, and reproduction streams were due to poor habitat quality, some unidentified factor, or were simply low points in * Corresponding author: [email protected] highly variable cycles of juvenile recruitment (e.g., 1 Present address: Department of Wildlife Ecology, Uni- versity of Maine, 240 Nutting Hall, Orono, Maine 04469, Milner et al. 2003). Alternately, longer-term data sets USA. exist on wild salmonine production in high-quality 2 Present address: New York Department of Environmental tributaries to Lake Ontario in New York (Trout Brook, Conservation, Cape Vincent Fisheries Station, Post Office Orwell Brook, and Little Sandy Creek; McKenna and Box 292, Cape Vincent, New York 13618, USA. 3 Johnson 2005) and Ontario (Bowlby and Roff 1986; Present address: Department of Earth and Environmental Science, University of Pennsylvania, 162 Hayden Hall, Stoneman and Jones 2000). In addition, survival and Philadelphia, Pennsylvania 19104-6316, USA. growth of stocked Atlantic salmon have been estimated Received May 29, 2006; accepted August 30, 2006 in several north-shore Lake Ontario tributaries Published online January 15, 2007 (McCrimmon 1954; Jones and Stanfield 1993; Stan-

56 STOCKED SALMONINES IN LAKE ONTARIO STREAMS 57

FIGURE 1.—Locations of tributaries draining the eastern and southern shores of Lake Ontario where the survival and growth of stocked juvenile salmonines were studied. Stocking treatments included Atlantic salmon only (triangles), coho salmon only (open circles), rainbow trout only (squares), Atlantic and coho salmon (filled circles), and Atlantic salmon and rainbow trout (stars). The dashed lines separate physiographic regions but do not represent watershed boundaries. field and Jones 2003). However, estimates of survival Methods and growth of stocked salmonines across a wide range Study area.—The tributaries flowing directly into of south-shore Lake Ontario tributaries are lacking. Lake Ontario along its southeastern and eastern shore Given the importance of stocked salmonines to the originate in three physiographic regions of New York Lake Ontario fishery (Jones et al. 1993), the absence of State (Wildridge 1990; originally described by Cressey data from many potentially productive tributaries in 1966): (1) the Uplands, (2) the Ontario Ridge New York, and a management interest in Atlantic and Swamplands, and (3) the Ontario Drumlins (Figure salmon restoration, we conducted a study with these 1). The Tug Hill Uplands region (also known as Tug objectives: (1) to test for the effects of stocking regime Hill Plateau) is heavily forested with localized areas of agriculture and minimal urbanization. The Ontario on the survival and growth of stocked Atlantic salmon, Ridge and Swamplands region contains a mixture of rainbow trout, and coho salmon in south-shore Lake forests, agriculture, and some urbanization, and soils Ontario tributaries; (2) to build explanatory models of are generally poorly drained. The Ontario Drumlins Atlantic salmon survival and growth responses using region contains deep, calcareous, and well-drained biotic, thermal, microhabitat, and landscape features; soils, extensive agricultural development, and relative- and (3) to identify site-specific limiting or enhancing ly sparse forests (Table 1). Distinct gradients exist in features of salmonine production capacity and make stream physical habitat, temperature, water quality, and recommendations regarding the suitability of streams fish and macroinvertebrate assemblages and are within each of three physiographic regions. oriented in a northeast-to-southwest direction, corre- 58 COGHLAN ET AL.

TABLE 1.—Selected geographic and climatological variables for three physiographic regions of New York State. Thermal data are from NOAA (2001), snowfall data from Muller (1966), approximate elevation ranges from U.S. Geological Survey 7.5’ maps, land-use data from M. J. Connerton (unpublished), and soil data from Cline (1955).

Physiographic region

Variable Tug Hill Uplands Ontario Ridge and Swamplands Ontario Drumlins

Mean temperature (8C; Jan 2001) 5to3.8 3.2 to 1.2 1.8 to 0.3 Mean temperature (8C; Jul 2001) 19.2–21.2 20.1–21.6 20.3–21.7 Mean annual snowfall (cm) 330–460 260–350 200–260 Elevation range (m) 140–550 110–160 100–150 Forest cover (%) 58.6 45.1 30.6 Agriculture (%) 2.3 2.5 10.7 Urban development (%) 1.7 2.2 3.1 Dominant soil associations Worth–Empeyville–Westbury, Sodus–Ira Sodus–Ira, Fulton–Toledo Ontario, Sodus–Ira sponding to the three physiographic regions (Coghlan normal hatchery production schedules in the region and 2004. Many tributaries contain barriers impassable to thus would be typical in most stocking events. Between fish migration and experience municipal or agricultural 21 May and 29 May 2003, salmonines were scatter- water diversions during the summer. stocked in sites to approximate a total density of 1.0 Field studies.—In May 2003, we selected 34 study fish/m2; at sites stocked with two species, density of sites on 15 tributaries, including at least 10 sites within each species approximated 0.5 fish/m2. We based our each physiographic region (Figure 1), to encompass a stocking densities upon work by Murphy (2003) and variety of points located along various environmental Millard (2005), who found little evidence of density- gradients.We selected sites based on past studies (i.e., dependent survival and growth in Atlantic salmon Wildridge 1990; Coghlan 2004), present accessibility, stocked at these and higher densities in cold streams of and observation of seemingly suitable habitat for the northeastern Tug Hill Plateau. In streams where juvenile salmonines (e.g., coarse substrate, juxtaposi- wild salmonine production has been identified previ- tion of moderate-velocity and low-velocity microhab- ously, typical late-summer densities of wild age-0 itats, riparian vegetation present, and maximum salmonines range from 0.05 to 1.03 fish/m2 (Tug Hill), summer temperatures ,278C). Sites that appeared 0.01–0.54 fish/m2 (Ontario Ridge and Swamplands), completely unsuitable for juvenile salmonines were and 0.02–0.46 fish/m2 (Ontario Drumlins) (Johnson deliberately excluded (e.g., beaver impoundments with and Ringler 1980; Wildridge 1990; Coghlan 2004). summer temperatures .308C) to focus our efforts. Site We visited each site between 16 July and 8 August lengths ranged from 50 to 125 m, and mean wetted 2003 and sampled physical habitat, water chemistry, widths at time of site selection ranged from 4 to 16 m. and the fish and benthic macroinvertebrate communi- We assigned one of five stocking treatments to each ties. Before collecting fish, we chose two sampling site: Atlantic salmon only, rainbow trout only, coho points within each site randomly. At each point, we salmon only, Atlantic salmon with rainbow trout, and selected a sampling reach (10–21 m long) that seemed Atlantic salmon with coho salmon; each physiographic to encompass a distinct ‘‘habitat unit’’ as described by region contained at least two sites receiving each Wildridge (1990). Because most of our sites did not stocking treatment. At 1–2 weeks before stocking, we contain classic riffle–pool sequences, the sampled surveyed for wild juvenile salmonines in all sites that reaches are best described as predominately riffle were accessible to migratory adults from Lake Ontario habitat interspersed with areas of deeper pocket waters, (i.e., reaches below impassable barriers) and noted the and demarcated by obvious features such as chutes and presence and relative abundance of spawning adults, channel restrictions. Maximum depths in these reaches redds, or emergent fry. Temperature monitors were did not exceed 1.0 m. Based upon known summer placed at each site to record hourly stream temperatures habitat preferences of age-0 Atlantic salmon and (nearest 0.18C) during the study period (Figure 2a). We rainbow trout (e.g., DeGraaf and Bain 1986; Johnson obtained the landlocked Lake Mephremagog strain of and Kucera 1985; Hearn and Kynard 1986; Morantz et Atlantic salmon (mean mass, 0.22 g) from the Ed Weed al. 1987; Beland et al. 2004), all of our sampled reaches Fish Culture Station (Grand Isle, Vermont) and appeared to offer at least some suitable habitat. rainbow trout (0.45 g) and coho salmon (2.1 g) from Because of the potential for species-specific habitat the Hatchery (Altmar, New York). segregation (i.e., coho salmon prefer relatively slow Although body size varied considerably among the and deep microhabitats; Hartman 1965), whenever three species, this interspecific variation was a result of possible we deliberately included slower and deeper STOCKED SALMONINES IN LAKE ONTARIO STREAMS 59

FIGURE 2.—(a) Mean daily temperatures of tributaries draining the eastern and southern shores of Lake Ontario, May–August 2003, and (b) and the discharge (m3/s) of three other nearby creeks. Temperatures were averaged over all study sites within each physiographic region; the data from the warmest (Wolcott Creek) and coolest (Little Sandy Creek) sites are included to illustrate the degree of thermal variation across sites. The horizontal lines indicate the optimum temperatures for the growth of Atlantic salmon, rainbow trout, and coho salmon. Mean daily streamflows were obtained from U.S. Geological Survey (USGS) gauging stations for streams representative of the Tug Hill Uplands (South Sandy Creek [USGS reference 4250750]), Ontario Ridge and Swamplands (Oneida Creek [4243500]), and Ontario Drumlins physiographic regions (Onondaga Creek [4240010]). habitats in our sampled reaches at sites stocked with LeCren 1967) with backpack electrofishers. Wetted coho salmon. At the few sites containing distinct riffle– sampling areas ranged from 78 m2 to 280 m2 and pool sequences, we chose reaches that included one encompassed between 15% and 52% of the original complete sequence. stocking areas. All fish were identified to species and We isolated each reach with 4-mm-mesh seines and measured for total length (TL; mm) and wet mass (0.1 conducted a two-pass depletion sampling (Seber and g). If no stocked salmonines were collected in either 60 COGHLAN ET AL. reach, we conducted exploratory sampling in likely thereafter as response variables. Because stocked coho habitats within 25 m downstream of the site’s lower salmon were collected at only one site, we omitted boundary. After collecting fish in each reach, we coho salmon from further analyses. established 6–10 transects across each sampling reach From the fish community data, we calculated the at regular intervals and measured wetted width at each species richness, Shannon–Wiener species diversity, transect. At 10 discrete points along each transect we and density and biomass of wild salmonines; the measured depth and velocity and characterized sub- density and biomass of piscivores (defined here as strate composition according to White and Brynildson salmonines and cyprinids .150 mm TL and centrarch- (1967). We measured pH, total dissolved solids (TDS; ids and yellow perch Perca flavescens .100 mm TL); mg/L), conductivity (COND; ls/cm), and dissolved and total fish density and biomass. From the benthic oxygen (DO; mg/L) at the upstream boundary of each macroinvertebrate assemblage data we calculated taxa site. Finally, using kick-screens in the thalweg riffle at (genera) richness; Shannon–Wiener diversity (genera); the upstream boundary of the site, we collected the percentages of Ephemeroptera, Plecoptera, Tri- approximately 200 benthic macroinvertebrates for choptera, Diptera, and noninsects (mostly crustaceans); preservation in 70% ethanol; later we identified all and a generic biotic index (GBI; Coghlan and Ringler benthic macroinvertebrates to genus, except those in 2005a, as adapted from Hilsenhoff 1982), where GBI the family Chironomidae. indicates the relative degree of organic and agricultural Because Atlantic salmon no longer reproduce in pollution. The GBI is strongly correlated with COND, New York’s Lake Ontario tributaries, we were certain TDS, and agricultural development (Pearson’s product- that all of the Atlantic salmon caught were from our moment correlation coefficients, .0.80), and increas- stocking. At sites where both stocked and wild ing values of GBI indicate reduced water quality due to Oncorhynchus could be present, we retained age-0 anthropogenic perturbation. Means of site width, depth, rainbow trout and coho salmon and froze them for velocity, percent cover of each substrate category, and future identification. Several weeks later, we removed daily temperature were calculated, along with weekly sagittal otoliths from all frozen salmonines and maximum temperatures, weekly minimum tempera- polished the otoliths in the sagittal plane to reveal tures, thermal coefficients of variation (100SD/mean), early growth increments. Using otoliths from known and number of days with water temperatures greater wild individuals (from sites in which that species was than 258C. From digital elevation and land-cover maps, not stocked) and known stocked individuals (from sites we calculated landscape-level attributes at each site, upstream of impassable barriers in which wild including elevation, slope, and percent land use in each populations are absent; authors’ unpublished data) as subcatchment devoted to agriculture, forest, and urban– references, we distinguished between stocked and wild suburban development. Daily stream discharge data fish according to criteria described by Brothers (1990). were available from U.S. Geological Survey (USGS) Only three sites yielded both stocked and wild rainbow gauging stations for only one stream in our study trout, and none yielded both stocked and wild coho (South Sandy Creek), and logistical constraints pre- salmon. vented us from monitoring discharge at regular Preliminary data analysis.—We estimated popula- intervals. Therefore, we present USGS data from tion size (N; Seber and LeCren 1967), population nearby streams merely to illustrate representative flow density (N/m2), and standing biomass (B; g/m2) of all regimes across the three regions (Figure 2b). fish species within sampled reaches, and data from All variables were tested for normality, and both reaches within each site were pooled to yield site necessary transformations were made before analysis means (Coghlan and Ringler 2004). For stocked (Zar 1974). From each of the two data sets described salmonines, we divided estimated density by initial above (i.e., abiotic and biotic variables), we used (stocking) density to yield apparent survival (SURV; principal components analysis to extract a smaller e.g., Elliott 1994; apparent survival is similar to number of explanatory variables to better summarize Nislow’s et al. (2000) ‘‘proportional retention’’). environmental gradients encountered across streams. Because different stocking treatments contained differ- For further consideration and analyses, we retained ent initial biomasses of stocked salmonines, we only those principal components with eigenvalues calculated the proportional change in biomass (DB) greater than those derived from a broken-stick model from time of stocking as (B2 B1)/B1, where B1 is the (McCune and Grace 2002). We examined Pearson’s initial estimate and B2 the final estimate. Mean product-moment correlation coefficients between the instantaneous growth rate (Ginst) was calculated original variables and each principal component (PC) according to Ricker (1968). For each species–site score to make inferences regarding the position of each combination, SURV, B, DB, and Ginst were considered site in gradient space. STOCKED SALMONINES IN LAKE ONTARIO STREAMS 61

Stocking treatment and species comparisons.—First, ranged from 0 to 0.54. Individuals were recovered from we conducted separate two-way analyses of variance 11 of 12 sites, and the absolute numbers ranged from 0 on the SURV, B, and DB of stocked salmonines, to 12. The standing biomass of stocked rainbow trout considering species (Atlantic salmon versus rainbow ranged from 0 to 0.98 g/m2, DB ranged from 1 to 1.49 trout) and stocking treatment (stocked with or without a (5 of 12 sites yielded a net gain in biomass), and Ginst heterospecific) as the main effects. We did not include ranged from 0.01 to 0.035. Stocked coho salmon were coho salmon in this analysis because of their extremely recovered from one site only (N ¼ 6); apparent survival low apparent survival. Where significant effects were was 0.16, the proportional change in biomass was found, we conducted post hoc, Bonferroni-adjusted 0.33, and Ginst was 0.02. With respect to apparent mean separation tests (MSTs). Because of species- survival and standing biomass, there were no statisti- specific differences in initial body size, interspecific cally significant effects of species (Atlantic salmon comparisons of Ginst would have little meaning, so we versus rainbow trout) or stocking regime (with or conducted one-way ANOVAs on the effect of stocking without heterospecifics; 0.11 , all P , 0.95); treatment on Ginst, separately for each species. Finally, however, Atlantic salmon stocked alone were nomi- to determine the relative success of each stocking nally the most successful. With respect to the treatment in contributing to overall salmonine SURV, proportional change in biomass, Atlantic salmon were

B, and DB, we conducted one-way ANOVAs with more successful than rainbow trout overall (F3,24 ¼ stocking treatment as the main effect. Calculating a 6.53, P ¼ 0.017), but stocking regime was not mean salmonine growth rate here would be of little significant (F3,24 ¼ 0.01, P ¼ 0.95). Atlantic salmon value, so again, we omitted Ginst. exhibited higher growth rates when stocked alone than Multiple regression models.—Due to restrictions in when stocked with rainbow trout (F1,15 ¼ 8.15, P ¼ sample sizes, we limited regression analyses to stocked 0.013), but this stocking effect was not significant for

Atlantic salmon. Using stocking treatment (stocked rainbow trout (F1,11 ¼ 0.59, P ¼ 0.54). At sites in which alone, with rainbow trout, or with coho salmon) as a Atlantic salmon and rainbow trout were stocked dummy variable, we conducted bivariate regressions of together, total salmonine biomass ranged from 0.03 each Atlantic salmon response variable (SURV, B, DB, to 1.1 g/m2, which was intermediate to the biomass for and Ginst) with each PC axis score. No significant effect each species stocked separately but not significantly due to stocking treatment was found (all p . 0.10), so different from that of either species stocked alone (F2,19 thereafter we pooled data from all stocking treatments. ¼ 0.38, P ¼ 0.69). The proportional change in biomass Bivariate plots were also inspected visually for any of both species stocked together ranged from 0.95 to potential nonlinear relations; none were obvious. Next, 2.32, which was intermediate to the values for each we conducted multiple linear regressions of each species stocked separately but not statistically signif- response variable with PC scores generated from biotic icant (F2,19 ¼ 1.69, P ¼ 0.21). and abiotic data sets via stepwise selection, where thresholds of P ¼ 0.10 were used for a variable to enter Principal Components Analysis and Regression or leave each model. We also conducted regressions Models using all possible combinations of independent vari- For the abiotic habitat variables, the first three ables and evaluated competing models using Akaike’s principal components accounted for about 60% (34.7, information criterion (AIC) and the criteria suggested 14.6, and 10.1%, respectively) of the total variance in by Shaw (2003). Principal components analyses were the original data set. PC1 was correlated most conducted with PC-ORD version 4.10 (McCune and positively with elevation, slope, percent forested land, Mefford 1999), and all other statistical procedures were thermal variation, and percent gravel and most conducted with SAS 9.0 (SAS 2003). negatively with percent agricultural and urban devel- opment, mean temperature, minimum temperature, Results maximum temperature, and water chemistry measures Apparent Survival, Biomass, and Growth Summary (pH, TDS, and conductivity; Table 2; Figure 4a). Thus, The apparent survival of Atlantic salmon ranged PC1 implied a transition from upland, forested, cool from 0.01 to 0.66; parr were recovered from all 22 sites but thermally variable, and nutrient-poor sites to stocked. The absolute numbers of Atlantic salmon lowland, developed, warm but thermally stable, and recovered from each site ranged from 1 to 45. Standing nutrient-rich sites. PC2 was correlated most positively biomass ranged from 0.03 to 1.08 g/m2, DB ranged with temperature and measures of stream size (width, from 0.75 to 6.1 (13 of 22 sites yielded a net gain in depth, and velocity) and most negatively with pH. biomass), and Ginst ranged from 0.029 to 0.048 (Figure Thus, PC2 implied a gradient from small, shallow, 3). The apparent survival of stocked rainbow trout slow-flowing, cool streams to large, deep, fast-flowing, 62 COGHLAN ET AL.

FIGURE 3.—Survival, standing biomass, proportional change in biomass, and instantaneous growth rates of Atlantic salmon and rainbow trout stocked in study streams. The names of the physiographic regions comprising the study area are abbreviated as follows: TUG ¼ Tug Hill Uplands, ORS ¼ Ontario Ridge and Swamplands, and DRU ¼ Ontario Drumlins. STOCKED SALMONINES IN LAKE ONTARIO STREAMS 63

TABLE 2.—Pearson’s product-moment correlation coeffi- biomass, wild salmonine density and biomass, and cients between habitat variables and habitat principal compo- piscivore biomass. Thus, PC2 implied a gradient in fish nents (PCs) for streams draining the eastern and southern community structure. PC3 was correlated most posi- shores of Lake Ontario. Correlation coefficients greater than 0.5 are shown in bold italics. tively with piscivore density and biomass and most negatively with percent Diptera (Table 3; Figure 4b). Variable PC1 PC2 PC3 In all multivariate regressions modeling Atlantic Percent urban development 0.69 0.36 0.51 salmon responses as functions of principal component Percent agricultural development 0.70 0.35 0.16 scores derived from abiotic and biotic data, the best Percent forest 0.91 0.22 0.15 Elevation 0.66 0.31 0.54 models as determined by stepwise selection were Stream channel slope 0.34 0.15 0.25 identical to those chosen using AIC and Shaw’s Week 1 temperature (2003) criteria. The apparent survival of stocked Mean 0.82 0.47 0.11 Minimum 0.82 0.47 0.01 Atlantic salmon was a function of all three habitat Maximum 0.64 0.39 0.38 principal components and all three biotic principal a Mean CV 0.42 0.22 0.33 components (overall model adjusted R2 ¼ 0.89, P , Week 7 temperature Mean 0.87 0.32 0.10 0.0001; Table 4). The standing biomass of stocked Minimum 0.87 0.39 0.06 Atlantic salmon was a function of habitat PC2, habitat Maximum 0.45 0.01 0.36 2 Mean CVa 0.57 0.47 0.18 PC3, and biotic PC2 (overall model adjusted R ¼ 0.75, Number of days . 258C 0.81 0.41 0.22 P , 0.0001; Table 4). The proportional change in the Mean width 0.03 0.61 0.06 biomass of stocked Atlantic salmon was a function of Mean depth 0.03 0.68 0.04 Mean velocity 0.23 0.52 0.02 habitat PC2, habitat PC3, biotic PC2, and biotic PC3 Mean percent boulder 0.27 0.37 0.62 (adjusted R2 ¼ 0.84; P , 0.0001; Table 4). The Mean percent cobble 0.10 0.27 0.24 instantaneous growth rate of stocked Atlantic salmon Mean percent gravel 0.51 0.45 0.09 Mean percent sand 0.23 0.33 0.54 was a function of habitat PC1, habitat PC3, and habitat Mean percent silt 0.14 0.03 0.08 PC4 (adjusted R2 ¼ 0.58; P ¼ 0.0011; Table 4). Mean percent bedrock 0.01 0.10 0.43 Mean percent woody material 0.36 0.43 0.28 pH 0.42 0.60 0.44 Discussion Conductivity 0.79 0.41 0.13 Overall Survival and Growth Responses Total dissolved solids 0.76 0.43 0.11 The apparent survival estimates of stocked Atlantic a CV ¼ coefficient of variation, computed as 100SD/mean. salmon fell within the range previously reported in the Lake Ontario watershed (McCrimmon 1954; Murphy warm streams. PC3 was correlated most positively with 2003; Stanfield and Jones 2003; Coghlan and Ringler percent urban development and percent sandy substrate 2004, 2005a, 2005b; Millard 2005) and elsewhere in andmostnegativelywithelevationandpercent the northeastern United States (Bley and Moring 1988; boulder, implying a similar gradient as PC1. The Orciari et al. 1994; Whalen and LaBar 1994; Nislow et thermal regime at most sites (Figure 2a) appeared al. 1999; Raffenberg and Parrish 2003). The apparent survival estimates of stocked rainbow trout and suitable for Atlantic salmon growth (optimal temper- especially coho salmon were low compared with those ature, ;198C; Murphy 2003) but higher than the obtained in studies in other geographic regions (e.g., physiological optimum for rainbow trout (;178C; Wentworth and LaBar 1984; Hume and Parkinson Hokanson et al. 1977) and especially coho salmon 1987; Close and Anderson 1992; Bilby and Bisson (;158C; Stewart et al. 1981). 1987; Bisson et al. 1988), but similar estimates in Lake For the biotic variables, the first three principal Ontario tributaries are lacking—hence one rationale for components accounted for about 61% (26.3, 18.6, and conducting this study. 16.3%, respectively) of the total variance in the original data set. PC1 was correlated most positively with Species and Stocking Effects invertebrate taxa richness, invertebrate diversity, and Costocking putative competitors (i.e., rainbow trout percent Ephemeroptera and most negatively with and coho salmon) had no significant effect on the percent noninsects and GBI. Thus, PC1 implied a apparent survival or biomass of Atlantic salmon, gradient from diverse macroinvertebrate assemblages although growth rates were slightly lower in the predominated by mayflies and intolerant taxa to presence of stocked rainbow trout. Other authors have taxonomically depauperate assemblages predominated documented depressing effects of putative salmonine by crustaceans and tolerant taxa. PC2 was correlated competitors on Atlantic salmon in laboratory and field most positively with percent Trichoptera and most settings (Gibson 1980; Hearn and Kynard 1986; negatively with fish taxa richness, fish density and Heland et al. 1997; Jones and Stanfield 1993; Coghlan 64 COGHLAN ET AL.

FIGURE 4.—Principal components analyses of (a) the abiotic and (b) the biotic variables used to characterize environmental gradients across tributaries of Lake Ontario in three physiographic regions. The implied gradients are indicated by arrows. and Ringler 2005b). Substituting an equal number of and affected apparent survival. It is also possible that heterospecifics for conspecifics (Fausch 1998) might mortality or emigration of coho salmon and rainbow have either enhanced or depressed Atlantic salmon trout occurred immediately after stocking (e.g., Bilby responses, depending on the relative intensities of and Bisson 1987; see below), rather than gradually interspecific and intraspecific competition (Isely and over the summer, such that potential interspecific Kempton 2000). Perhaps our initial stocking densities competitors were not present in numbers sufficient to were lower than those at which interspecific compet- affect Atlantic salmon apparent survival. Alternatively, itive interactions overpowered intraspecific interactions the outcomes of any competitive interactions might STOCKED SALMONINES IN LAKE ONTARIO STREAMS 65

TABLE 3.—Pearson’s product-moment correlation coeffi- play a role in mediating apparent survival and biomass cients between biotic variables and biotic principal component elaboration during the summer for the less heat-tolerant (PC) scores for streams draining the eastern and southern Oncorhynchus species. Atlantic salmon are the most shores of Lake Ontario. Correlations greater than 0.5 are shown in bold italics. heat-tolerant of the juvenile salmonines (Grande and Andersen 1991) and, thus, should perform better in Variable PC1 PC2 PC3 relatively warm sites. Thermal regimes at most sites Invertebrate taxa richness 0.76 0.02 0.38 appeared suitable for Atlantic salmon growth but Invertebrate taxa diversity 0.81 0.02 0.35 higher than the physiological optimum for rainbow Percent Ephemeroptera 0.86 0.25 0.13 Percent Plecoptera 0.46 0.05 0.20 trout and especially coho salmon (Figure 2a). Further- Percent Trichoptera 0.15 0.52 0.29 more, the summer average of mean daily temperature Percent Diptera 0.27 0.38 0.70 was correlated negatively and significantly with both B Percent non-insects 0.70 0.01 0.26 Generic biotic index 0.83 0.20 0.08 and DB of stocked rainbow trout; coho salmon Fish taxa richness 0.34 0.43 0.40 survived and grew (albeit with a net loss in cohort Fish taxa diversity 0.28 0.10 0.37 biomass) only in the coldest site (Coghlan 2004). Fish density 0.18 0.52 0.47 Fish biomass 0.34 0.73 0.15 Coghlan and Ringler (2005b) demonstrated that Wild salmonine density 0.40 0.67 0.32 temperature influenced the outcomes of interactions Wild salmonine biomass 0.45 0.66 0.30 Piscivore density 0.19 0.46 0.72 between Atlantic salmon and rainbow trout and that, as Piscivore biomass 0.16 0.61 0.62 summer temperatures increased, Atlantic salmon bio- mass became increasingly favored at the expense of rainbow trout biomass. vary along environmental gradients (e.g., Dunson and Travis 1991) and obscure detectable patterns in Emigration Atlantic salmon responses. Considering effects on Movement of stocked salmonines from our study growth, competition from the larger stocked rainbow sites would have been interpreted as mortality and thus trout could have forced the smaller Atlantic salmon apparent survival would be downwardly biased. into energetically unfavorable foraging microhabitats, Gowan et al. (1994) stressed the importance of thus reducing growth rates (e.g., Fausch and White accounting for the migration of lotic salmonines 1981). Imre et al. (2005) found that intraspecific because, although this phenomenon is probably densities affected growth but not survival of Atlantic widespread, it often remains undetected in studies salmon at low population densities; perhaps in our encompassing small spatial and temporal scales. The study, interspecific effects from stocked rainbow trout literature on juvenile Atlantic salmon suggests ex- exerted a similar effect (i.e., on growth but not apparent tremely variable propensity for movement among survival) of Atlantic salmon. individuals and populations. For example, Steingrims- Atlantic salmon were more successful than rainbow son and Grant (2003) found that during the first trout in elaborating biomass, and both species outper- summer of life, about 97% of all tagged Atlantic formed coho salmon, which generally experienced a salmon remained within 5 m of their point of capture, complete loss of cohort biomass. Temperature may similar to other findings (Juanes et al. 2000), in which

TABLE 4.—Regression models generated by stepwise selection relating Atlantic salmon responses to habitat and biotic principal component (PC) scores for streams draining the eastern and southern shores of Lake Ontario.

Dependent variable Independent variable Estimate SE Type II sums of squares Partial R2 F-value P-value

Apparent survival Habitat PC2 0.082 0.0099 0.408 0.43 15.33 ,0.0001 Habitat PC3 0.0622 0.011 0.197 0.14 6.23 ,0.0001 Biotic PC2 0.054 0.011 0.136 0.25 25.05 0.0002 Habitat PC1 0.027 0.0096 0.046 0.02 2.09 0.014 Biotic PC1 0.036 0.016 0.03 0.023 2.56 0.0407 Biotic PC3 0.027 0.015 0.015 0.025 3.38 0.0858 Standing biomass Habitat PC2 0.12 0.02 1.081 0.424 38.16 ,0.0001 Habitat PC3 0.1 0.022 0.58 0.183 20.46 0.0003 Biotic PC2 0.07 0.024 0.298 0.145 10.51 0.0045 Proportional change in biomass Habitat PC2 0.969 0.13 58.37 0.43 58.81 ,0.0001 Habitat PC3 0.76 0.13 32.46 0.21 32.7 ,0.0001 Biotic PC2 0.59 0.14 17.52 0.19 17.65 0.0006 Biotic PC3 0.28 0.19 2.23 0.02 2.25 0.05 Instantaneous growth rate Habitat PC1 0.0013 0.00032 0.0003571 0.33 17.1 0.0006 Habitat PC3 0.0016 0.00059 0.0001532 0.18 7.33 0.0144 66 COGHLAN ET AL.

90% of all tagged fry moved less than 20 m. However, outright mortality, emigrating fish probably would individual fish that did migrate often traveled long have lower survival and growth rates than would distances (up to 400 m; Juanes et al. 2000). Some resident fish (Hartman 1959; Elliott 1994; Nislow et al. confusion exists regarding fitness correlates of resident 2000; but see Gowan and Fausch 2002; Steingrimsson individuals versus those that moved. Elliott (1994) and Grant 2003), such that overall site quality still suggested that emigrating age-0 brown trout were would be poor. Similarly, our regression analyses were competitively weak individuals that could not establish simply attempts to identify important abiotic and biotic or maintain a feeding territory, whereas Gowan and factors related to stocked salmonine apparent survival Fausch (2002) found that emigrating brook trout and growth rather than to predict those attributes at any Salvelinus fontinalis were most likely dominant specific location. individuals in search of new energetically profitable Emigration of stocked Oncorhynchus spp., which foraging stations, especially as hydrologic conditions also would have been interpreted as mortality, may changed. Although there are many conditions that have occurred, as it did in the case of Atlantic salmon. favor emigration (e.g., floods or droughts, high density Close and Anderson (1992) concluded that such of conspecifics, inadequate invertebrate production or emigration is density-dependent for steelhead stocked drift, lack of suitable physical habitat, unsuitable in Lake Superior tributaries, although their stocking temperatures), it is clear that the frequency and densities were 5–10 times greater than ours. Emigration magnitude of movements are related inversely to the rates of steelhead fry stocked in British Columbia quantity and quality of available habitat (Belanger and streams at densities similar to our study were negligible Rodriguez 2002; Gowan and Fausch 2002). Those sites compared with losses from mortality (Hume and that provide the most habitat or highest quality habitat Parkinson 1987). Bisson et al. (1988) stocked coho should contain and retain the most fish (e.g., Urabe and salmon in volcanically perturbed streams at higher Nakano 1999; Nislow et al. 2000). densities than we did in our study, but they obtained Our estimates of apparent survival most likely higher survival and biomass estimates. Temperatures in include losses from emigration, but we do not have many Lake Ontario tributaries exceeded the physio- the data to distinguish between movement and logical optimum for rainbow trout and coho salmon mortality. However, the objective of our study was to (Figure 2; Coghlan 2004), which may have caused compare the relative productive potentials of many early emigration or high mortality (e.g., Hartman sites over a wide geographic range, rather than to 1959), but those temperatures did not exceed temper- quantify actual production at any one site. As such, our atures observed by Bisson et al. (1988). estimates of SURV, B, and DB are indices of the The virtual failure of coho salmon in this study may capacity of each site to retain a given density or have resulted from artificial selection within hatchery biomass of salmonines, assuming high-quality sites populations. Most coho salmon returning to the Salmon would retain more salmonines (whether measured by River hatchery were stocked originally in Lake Ontario density or biomass) than would low-quality sites. as smolts (New York State Department of Environ- Belanger and Rodriguez (2002) argue that movement mental Conservation, unpublished stocking data) and patterns provide a better measure of habitat quality than experienced no prior stream residence. Therefore, does density. Because our sites received an initial selection for high lacustrine survival could be signif- stocking of salmonines, the magnitude of emigration of icant within hatchery-derived populations, but selection individuals from each site would indicate habitat pressures associated with lotic survival are probably quality, even if we measured the net effect of relaxed (Kostow 2004). Furthermore, because the emigration (and mortality) in terms of resultant density. Salmon River Hatchery rears fish in cold, thermally Because stocking densities were low, intraspecific stable groundwater (;5–78C), there are no selective interactions were probably negligible (Millard 2005), pressures or acclimation regimes favoring adaptation to and few significant differences were found that could the high, variable temperatures found naturally in many be attributed to the presence of stocked Oncorhynchus; Lake Ontario tributaries. Other authors have docu- considering that, variation in Atlantic salmon responses mented the importance of woody material and deep would be a function of site quality as determined by pools to juvenile coho salmon (e.g., Hartman 1965; habitat parameters. Nielsen 1992), and the relative paucity of such habitat A related objective was to rank sites in terms of their in our study sites could have contributed to either potential to retain stocked Atlantic salmon fry so that emigration or mortality of this species. However, we could identify the most suitable areas for future exploratory sampling in seemingly suitable reaches restoration attempts. Even if a site was ranked as low adjacent to our study sites yielded no coho salmon. quality because of high emigration rates rather than Clearly, additional studies are needed to identify the STOCKED SALMONINES IN LAKE ONTARIO STREAMS 67 mechanism behind this high apparent mortality in some derived from biotic (fish and invertebrate) data Lake Ontario streams, but temperature probably is exhibited less explanatory power than those derived important. from habitat data. Biotic PC axis 2 was significant in three of four regression models and represents a Environmental Gradients gradient in density and biomass of all fish, wild Principal components and regression analyses sug- salmonines, and piscivores. Here, we interpret apparent gested that several important environmental gradients survival, biomass, and proportional change in biomass affected Atlantic salmon responses. These gradients as inverse functions of the density and biomass of most likely were a product of interactions at several potential competitors and predators. Taken together, spatial scales (e.g., geomorphic variables affecting these regression analyses suggest that apparent survival microhabitat characteristics; Poff and Huryn 1998). and biomass elaboration responded to somewhat The first habitat PC axis (representing a distinct different predictor variables than did growth rate. geomorphic transition from high-elevation, forested sites to low-elevation, developed sites and correspond- Stream-Specific Assessments ing changes in temperature regime, pH, and conduc- Distinct gradients in abiotic and biotic variables tivity), explained much variation in growth rates. corresponding to geomorphology were apparent across Although not measured here explicitly, nutrient our study region (Figure 4; Coghlan 2004) and concentration and, hence, benthic macroinvertebrate probably were responsible for the patterns seen here. productivity usually are correlated positively to the Furthermore, significant regional differences exist in variables we measured, such as agricultural develop- production potential of wild salmonines in the southern ment and conductivity (e.g., Krueger and Waters 1983; catchment of Lake Ontario (Wildridge 1990). North- Hunsaker and Levine 1995; Aguiar et al. 2002; Shieh east-to-southwest gradients exist (i.e., from Tug Hill to et al. 2003). Therefore, our measures of GBI, Ontario Ridge and Swamplands to Ontario Drumlins), conductivity, and percent agricultural development such that stream temperature, organic enrichment, and probably provide an adequate, albeit rough, estimate total fish community biomass (which presumably are of potential benthic macroinvertebrate productivity all correlated with benthic productivity; Krueger and across our sites. Thus, moderate increases in agricul- Waters 1983) increase with a concomitant decrease in tural development, nutrient enrichment, or benthic wild salmonine biomass (Wildridge 1990; Coghlan productivity can stimulate juvenile salmonine growth 2004). These gradients may be affected by climatic, rates, as other studies suggest (e.g., Kennedy et al. geomorphic, and anthropogenic variation (Cressey 1983; Bowlby and Roff 1986; Bergheim and Hestha- 1966; Sly 1971; Wildridge 1990; Coghlan 2004). gen 1990; Richardson 1993; Weng et al. 2001; Nislow Densities and production of wild salmonine juveniles et al. 2004). Presumably no sites exceeded the level of in several Tug Hill streams may approach or exceed deforestation, organic enrichment, or temperature those of high-quality Pacific coast tributaries (Johnson beyond which salmon growth would be reduced, either and Ringler 1980). Wildridge (1990) considered Tug due to metabolic stress or shifts in the macroinverte- Hill streams to have the greatest production potential of brate assemblage towards taxa that do not provide all New York tributaries of Lake Ontario. Growth rates many foraging opportunities for young salmonines of stocked Atlantic salmon were lowest in Tug Hill (e.g., Scott et al. 1986; Rader 1997; Kilgour 1998; streams, presumably due to low temperatures and Wang et al. 2003; Coghlan and Ringler 2005a). perhaps low nutrient levels. However, apparent sur- Furthermore, relatively high temperatures might have vival in many Tug Hill streams was high enough to favored growth in Atlantic salmon by excluding offset slow growth and resulted in the greatest biomass potentially competing wild or stocked rainbow trout elaboration. Skinner, Lindsey, and Deer creeks may (Coghlan and Ringler 2005b), provided that adequate offer the best juvenile rearing habitat for future Atlantic food was available. salmon restoration efforts because summer tempera- The second habitat PC axis appeared to reflect tures appear to be optimal for Atlantic salmon but stream size and was related inversely to the apparent slightly higher than optimal for wild rainbow trout survival, biomass, and proportional change in biomass (Coghlan and Ringler 2005b). However, these streams of Atlantic salmon. Small streams replete with shallow, are relatively small, so absolute production potential is low-velocity habitats provide Atlantic salmon fry with probably limited. The prospect for restoring Atlantic energetically profitable foraging habitats (Nislow et al. salmon to the coldest streams in Tug Hill may be 1999, 2000) and exclude large piscivores (McCrimmon limited by the abundance of wild rainbow trout and the 1954; Bowlby and Roff 1986), thus favoring survival desire to manage accordingly for that species (Johnson or retention of young fish. Principal components and Wedge 1999; McKenna and Johnson 2005; 68 COGHLAN ET AL.

Coghlan and Ringler 2005b). Another Lake Ontario poor water quality; improvements in water quality in tributary in the Tug Hill region, the main-stem Salmon the most impaired streams (e.g., Wolcott Creek) might River, was the subject of a previous study (Coghlan increase the potential for Atlantic salmon restoration and Ringler 2004). Although apparent survival of (Coghlan and Ringler 2005a). In addition, the numer- stocked Atlantic salmon was relatively low there, the ous low-head dams in these streams increase water sheer amount of available habitat provided by this large temperatures downstream (e.g., England and Fatora river makes it a likely candidate for restoration 1978), favor invertebrate assemblages relatively invul- attempts. nerable to salmonine predation (Rader 1997; Tiemann The virtual failure of Atlantic salmon in Ontario et al. 2005), and prevent upstream migrations of Ridge and Swamplands streams is puzzling. Johnson spawning adults and juveniles. Removal of these dams and Wedge (1999) mentioned that poor water quality may improve downstream habitat accordingly (but see may render Grindstone Creek unsuitable for Atlantic Mistak et al. 2003) and also open up suitable habitat salmon, but they did not elaborate. Coghlan and upstream for future colonization. Ringler (2005a) found that variation in water quality Management efforts applied towards maximizing the could alter the energy balance of juvenile Atlantic salmonine biomass produced in eastern and southern salmon and reduce apparent survival and growth. Lake Ontario streams should account for thermally Biotic indices derived from invertebrate communities marginal or unsuitable conditions (Coghlan and Ring- indicated slightly impacted water quality in Ontario ler 2005b). Given existing physiological information Ridge and Swamplands streams compared with Tug on each species (e.g., Hokanson et al. 1977; Stewart et Hill streams (Coghlan 2004), but one would expect al. 1981; Murphy 2003), summer temperatures at most streams in the highly perturbed Ontario Drumlins sites appeared to be nearly optimal for Atlantic salmon region, rather than in the Ontario Ridge and Swamp- but above optimal for rainbow trout and especially lands region, to be most affected in this manner. coho salmon. Perhaps the cold Tug Hill streams such as Because of the poor drainage capacity of soils in the Trout Brook, Orwell Brook, and Little Sandy Creek region, Ontario Ridge and Swamplands streams may (Johnson and Ringler 1980; Wildridge 1990; McKenna experience extreme fluctuations in discharge after a and Johnson 2005) could continue to be managed storm (S. M. Coghlan and M. J. Connerton, personal solely for natural reproduction of wild salmonines, observations)—that is, freshets large enough to dis- whereas Atlantic salmon restoration efforts might place newly planted fry (e.g., Egglishaw and Shackley target the more thermally marginal streams that have 1980) or reduce the amount of energetically profitable less potential for producing other salmonines, espe- foraging habitat (Nislow et al. 2004). However, cially in the Ontario Drumlins region. Based on our although many Ontario Ridge and Swamplands results, tributaries of Lake Ontario along its southern streams possess seemingly suitable thermal and and eastern shores, such as Skinner, Lindsey, Deer, physical habitat for juvenile Atlantic salmon, our Black, Rice, Eightmile, and Red creeks, appear to be results and previous evidence (Wildridge 1990; promising candidates for Atlantic salmon reintroduc- Johnson and Wedge 1999; Murphy 2003) clearly tion programs. indicate that most streams in the region offer little or no potential for future restoration attempts. Acknowledgments The Ontario Drumlins region demonstrates high Our sincerest thanks go to Kevin Kelsey and crew variability in rearing potential among streams, which (Ed Weed Fish Culture Station, Grand Isle, Vermont), may result from the high intensity and occurrence of Andy Gruelich and crew (Salmon River Fish Hatchery, agriculture and other human activities in the landscape Altmar, New York), Ed Grant and crew (Adirondack (e.g., Kilgour 1998). All streams studied in the region Fish Hatchery, Saranac Lake, New York), and Walt contain at least one artificial barrier and impoundment, Zelie and crew (Carpenter’s Brook Fish Hatchery, and water diversion for agricultural and municipal Elbridge, New York) for graciously providing salmo- purposes is widespread. At least some of these streams nines for our studies. We thank Phil Hulbert, Jeff contain high-quality salmonine habitat, provided ade- Robins, Les Wedge, Al Schiavone, Web Pearsall, Paul quate flow is available. For example, Atlantic salmon Moore, and Fran Verdoliva (New York State Depart- were relatively successful in Eightmile and Rice creeks ment of Environmental Conservation) for their helpful during our study. However, in a pilot study during the advice and technical support. We thank Gerrit Cain, previous year (summer of 2002), drought and munic- Rich Chiavelli, Tara Crast, Liz DeAngelo, Kate ipal water diversions dried both streams to standing Dukette, Liz Enriquez, Jess Fischer, Jenny Felske, pools, and no stocked salmonines survived (Coghlan Dave Galinski, Jen Lund, Marc Maynard, Dave 2004). This region also contains streams with relatively Messmer, Karen Stainbrook, and Chrisman Starczek STOCKED SALMONINES IN LAKE ONTARIO STREAMS 69 for their dedication in the field and laboratory. Fred dependent effects of rainbow trout on growth of Atlantic Utter and three anonymous reviewers offered many salmon parr. 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