OTOLITH MICROCHEMISTRY OF COASTAL CUTTHROAT TROUT FROM THE MARYS AND WILLAMETTE RIVERS.
Otolith chemistry, including both elemental and isotopic composition, and otolith structure may help to differentiate these life-history patterns as well as identify migrations and habitat use during early life histories. Otolith chemistry has been used to distinguish migratory patterns of other salmonid fishes, including Cutthroat Trout within a watershed or basin (Klaue and others 2002; Wells and others 2003; Zydlewski and others 2009; Muhfield and others 2012), but no studies, to our knowledge, have attempted to distinguish resident from fluvial fish.
The basic question in this preliminary study is, can we use water chemistry and otolith chemistry to distinguish resident trout from those whose mothers reside most of the year in the Willamette River and then migrate into the Marys River? If so, this would help differentiate the relative abundance and habitats of these life histories, so that restoration, monitoring, and management of these different life-history types could be prioritized.
We took water samples for analysis from the Marys River and 5 of its tributaries in March and May 2012 and collected 2 samples from the Willamette River in March and 1 in August 2012 (black dots in Fig. 1, Table 1). Water samples were filtered and analyzed for [.sup.18][delta]O at Oregon State University's (OSU) Stable Isotope Laboratory (http://stable-isotope.coas. oregonstate.edu). Water calcium (Ca), strontium (Sr), and barium (Ba) were quantified with Inductively Coupled Plasma Optical Emission Spectroscopy (317.933 nm for Ca, 421.552 nm for Sr, and 455.403 for Ba). Accuracy was assessed using National Institute of Standards and Technology Standard Reference Material (NIST SRM) 1643: n = 3, Ca = 100% [+ or -] 0.003, Ba = 100% [+ or -] 0.006, and Sr= 100% [+ or -] 0.01. Water [.sup.87]Sr/[.sup.86]Sr was measured using a NuPlasma multi-collector inductively coupled plasma mass spectrometer (MC-ICPMS). Accuracy was assessed by comparison with NIST SRM 987 ([.sup.87]Sr/[.sup.86]Sr = 0.71034) and was 99.98% with an internal precision of [+ or -] 0.000019 ppm (n =10).
We collected juvenile fish by seining in 5 tributaries of the Marys River in May 2012, at the same location where we sampled water, and collected adults at Willamette River RM 151 near Harrisburg, Oregon, in August 2012. Sagittae were removed, acid washed, cleaned, dried, embedded in resin, ground, and polished using the methods described in Miller (2011). Three analytes ([.sup.43]Ca, [.sup.86]Sr, and [.sup.138]Ba) were measured to quantify calcium, strontium, and barium using a Thermo X-series II spectrometer and Photon Machines Analyte G2 laser. The laser was set at a pulse rate of 7 Hz with a 50-|.tm ablation spot size and traveled at 7 [micro]m/s. Life-history transects were collected across the otoliths perpendicular to growth rings to generate time series. Normalized analytes (ion ratios) were converted to molar ratios using standard procedures (Kent and Ungerer 2006; Miller 2009). Instrument precision (mean percent relative standard deviation) was 4.5% for Ca, 4.7% for Sr, and 5.2% for Ba across all samples and days (n = 50), and accuracy for Sr/Ca was 103 [+ or -] 8 % and 111[+ or -] 9 % for Ba/Ca (n = 5) based on USGS MACS-1 and MACS-3.
To quantify otolith [.sup.87]Sr/[.sup.86]Sr, we used a NuPlasma MC-ICPMS and Photon Machines Analyte G2 laser. We used the methods of Woodhead and others (2005) as described in Miller and Kent (2009) to correct for Kr and Rb interferences and monitor for Ca argide/dimer formation. The laser was set at a pulse rate of 10 Hz with a 40-[micro]m ablation spot size and travelled at 5 [micro]m/sec. To assess instrument accuracy, we determined the [.sup.87]Sr/[.sup.86]Sr of a marine gastropod (= 0.70918) and consistently obtained a mean value of 0.70902 [+ or -] 0.000099 2 SE (n = 7); otolith [.sup.87]Sr/[.sup.86]Sr values were corrected for this difference. All elemental and isotopic analyses were completed at OSU's WM Keck Collaboratory for Plasma Mass Spectrometry (http://wmkeck-icpms.coas.oregonstate.edu/). We determined average elemental and isotopic values for the core (100 to 200 microns centered within the otolith core) and edge (50 to 100 microns at the outermost otolith edge) regions for each fish.
Is the water chemistry different between the tributaries of the Marys River and the main stem of the Willamette River?
The answer is "yes", based on lower values of [delta][.sup.18]O and [.sup.87]Sr/[.sup.86]Sr and higher Sr/Ca ratios in Willamette River water than most tributaries of the Marys River (Table 1). [delta][.sup.18]O is a measure of the ratio of [.sup.18]O to [.sup.16]O. As water vapor in the atmosphere moves from the coast to the Cascade Range, it becomes depleted in the heavier isotope or more negative (Rayleigh Fractionation, see Arag uas-Araguas and others 2000). Hence, the lower values of [delta][.sup.18]O are expected in precipitation falling over tributaries east of the mainstem Willamette River than tributaries west of the river. Plots of both water Sr/Ca versus Ba/Ca and water [.sup.87]Sr/[.sup.86]Sr versus Sr/Ca show strong positive relationships during both March and May (Fig. 2). The Sr/Ca ratios in the Willamette River were very similar during March (3.15, 3.16 mM/M) and August 2012 (3.1 mM/M, Table 1), suggesting little seasonal change in this ratio.
Overall, there was overlap in Sr/Ca and Ba/Ca in the Willamette and Marys rivers (Table 1). The Willamette River had moderate to low levels of Ba/Ca and moderate levels of Sr/Ca compared to some sites in the Marys River and its tributaries. Water samples in headwaters of the Tumtum and Marys rivers at Blodgett also had high Ba/Ca and Sr/Ca ratios, water chemistries different from other tributaries and the mainstem Willamette River. Water [.sup.87]Sr/[.sup.86]Sr was consistently lower in the Willamette River (mean = 0.70400 [+ or -] 0.00017 SD; 95% CI = 0.70377 to 0.70423) than in the Marys River (mean = 0.70639 [+ or -] 0.00141 SD; 95% CI = 0.70526 to 0.707517) (Table 1). Additional data on the Willamette River show that water [.sup.87]Sr/[.sup.86]Sr is consistently [less than or equal to]0.70450 (Bourret 2013), and no Marys River water sample was <0.70450.
How does the microchemistry of cutthroat otoliths compare with that of the water where they were caught?
Elemental data were collected from the otoliths of 10 juvenile Cutthroat Trout collected from tributaries of the Marys River and from 6 adult fish from the Willamette River at Harris-burg. Strontium isotopic data were collected from 6 of the 10 juveniles and 5 of the 6 adults (Table 2). The elemental and isotopic composition of otolith edges, which is the product of recent growth, was expected to be the most similar to those ratios in the water when these fish were collected.
Sr/Ca (mM/M) and Ba/Ca ([micro]M/M) were always much higher for proximate water than for the otolith edges (Table 3), which is expected because of elemental partitioning; hence otolith elemental ratios are typically a fraction of ambient water (Campana 1999; Miller 2011). The otolith edge chemistry (Sr/Ca and Ba/Ca) of the juveniles was positively correlated with water chemistry (r = 0.937, n = 8, P = 0.001 for Sr/Ca, and r = 0.872, n = 8, P= 0.005 for Ba/Ca), although the relationships were primarily driven by the high Sr/Ca and Ba/Ca at 1 site (Tumtum at Blodgett) (Tables 1 and 3). Otolith edge [.sup.87]Sr/[.sup.86]Sr was also positively correlated with water [.sup.87]Sr/[.sup.86]Sr (r = 0.740, n = 11, P < 0.01). However, unlike elemental incorporation, [.sup.87]Sr/[.sup.86]Sr is incorporated into the otolith with no partitioning (Kennedy and others 2000; Weber and others 2005) (Tables 2 and 3).
Are values for the edges versus the core of the otoliths similar, or do they exhibit changes over time, suggesting maternal effects, changes in distribution, or differential incorporation?
For juveniles, there was extensive variability in otolith chemistry within both the core and edge signatures (Tables 2 and 3). Mean core Sr/Ca ranged from 0.38 [+ or -] 0.03 SD to 2.02 [+ or -] 0.24 SD mM/M, and mean edge Sr/Ca ranged from 0.36 [+ or -] 0.02 SD to 2.07 [+ or -] 0.18 SD mM/M. Juvenile core Ba/Ca ranged from a mean 2.7 [+ or -] 0.36 SD to 43.8 [+ or -] 5.80 SD uM/M, and edge Ba/Ca ranged from a mean of 1.0 [+ or -] 0.34 SD to 28.2 [+ or -] 2.71 SD [micro]M/M (Table 2). Juvenile core [.sup.87]Sr/[.sup.86]Sr values were also variable, ranging from a mean of 0.70366 [+ or -] 0.00036 SD to 0.70612 [+ or -] 0.00046 SD. Juvenile edge [.sup.87]Sr/[.sup.86]Sr values ranged from 0.70428 [+ or -] 0.00133 SD to 0.70590 [+ or -] 0.00028 SD (Table 3).
For adults, there was also extensive variability in otolith chemistry within both the core and edge signatures (Tables 2 and 3). Core Sr/Ca ranged from 0.20 [+ or -] 0.04 SD to 0.76 [+ or -] 0.07 SD mM/M, and the edge Sr/Ca ranged from 0.65 [+ or -] 0.05 SD to 0.72 [+ or -] 0.06 SD mM/M. Core Ba/Ca of adults ranged from 0.9 [+ or -] 0.20 SD to 9.0 [+ or -] 1.35 SD [micro]M/M in adult otoliths, and the edge Ba/Ca ranged from 1.9 [+ or -] 0.17 SD to 6.8 [+ or -] 2.38 SD [micro]M/M (Table 2). Adult core [.sup.87]Sr/[.sup.86]Sr values were also variable, ranging from a mean of 0.70387 [+ or -] 0.00036 SD to 0.70733 [+ or -] 0.00029 SD. However, adult edge [.sup.87]Sr/[.sup.86]Sr values were similar (0.70365 [+ or -] 0.00019 SD to 0.70396 [+ or -] 0.00015 SD) (Table 3).
Several juveniles (fish 3, 4, and 7) had relatively low otolith core values of [.sup.87]Sr/[.sup.86]Sr (mean = 0.70366 to 0.70408), which fell within the 95% CI for Willamette River water (0.70377 to 0.70423) (see Fig. 3 for example). Core chemistry reflects the maternal environment during egg incubation (Volk and others 2000; Zimmerman and Reeves 2002; Miller and Kent 2009). Therefore, given that Marys River water (mean = 0.70639 [+ or -] 0.00141 SD) and juvenile otolith edge [.sup.87]Sr/[.sup.86]Sr (mean = 0.70512 [+ or -] 0.00060 SD) are consistently greater than the core [.sup.87]Sr/[.sup.86]Sr values, those juveniles with lower core [.sup.87]Sr/[.sup.86]Sr likely originated in the Willamette River or an area with similar water chemistry, or are the offspring of Willamette River mothers or mothers that completed oogenesis in a location with water [.sup.87]Sr/[.sup.86]Sr similar to the Willamette River.
For adults, based on the relatively large differences between core and edge Sr/Ca (0.20 versus 0.72 mM/M) or Ba/Ca (8.0 versus 2.0 [micro]M/M), it appears that fish 1, 3, and 5 moved to a chemically distinct habitat after early rearing. Similarly, these fish, based on the relatively high core [.sup.87]Sr/[.sup.86]Sr values ([greater than or equal to]0.70460), likely reared in a tributary before moving into the Willamette River later in life.
Does the chemistry of otoliths of "resident" fish caught above the Rock Creek dam differ from fish that may be "fluvial" below the dam?
Otolith edge values of fish from Rock Creek 1 above the dam, where fish cannot make downstream migrations, were higher for fish 1, 2, and 5 (Ba/Ca ratios of 5.7 to 8.3 [micro]M/M) than fish 3 and 4 below the dam (Ba/Ca ratios of 0.0 to 1.7 [micro]M/M) (Table 2, Fig. 4, Fig. 5). This reflects the higher Ba/Ca ratios in the water above the dam compared to water below the dam.
The highest core [.sup.87]Sr/[.sup.86]Sr was for a fish above the dam (fish 1, mean = 0.70612), clearly separating it from the possible fluvial fish below the dam (fish 3 mean = 0.70366, fish 4 mean = 0.70399). These low core values for fish 3 and 4, collected in Rock Creek below the dam, provide evidence that these 2 fish originated in the Willamette River or were spawned by mothers who completed oogenesis in waters with [.sup.87]Sr/[.sup.86]Sr values similar to the Willamette River. Based on water [.sup.87]Sr/[.sup.86]Sr data, residents that spawned in the Marys River are expected to have different core [.sup.87]Sr/[.sup.86]Sr than fluvial fish.
Dot's otolith chemistry vary across life-history transects?
In addition to the difference between edge and core values of elements, other variations are notable across otoliths. Scans of otoliths showed several peaks in Ba/Ca ratios, and sometimes Sr/Ca ratios between the core and edges in juveniles and adults (Figs. 4 to 8). These Ba/Ca and Sr/Ca peaks in the scans of adult otoliths often appeared to correspond with the clear annular growth rings (Figs. 6 to 8). In addition to differences owing to movement into waters with distinct elemental composition, otolith elemental incorporation can be affected by seasons and by changes in temperature and habitats (Kalish 1989; Radtke and Shafter 1992; Elsdon and Gillanders 2002; Miller 2011). These factors may have contributed to the patterns we observed.
Are growth rates of juveniles and adults during their 1st year similar?
Juveniles (90-135 mm in length) were assumed to be age 1 or 1+ (Moring and Yonker 1979). All adults appeared to be age 2+ or 3+. The mean and range of the otolith width at the 1st annulus was smaller in Marys River juveniles (mean = 839 [micro]m; range = 633 to 945 [micro]m) than in adults (mean = 923 [micro]m; range = 740 to 1150 [micro]m), although the difference was not significant (t = -1.21; P = 0.257). However, otolith width at the 2nd annulus was significantly smaller in the Marys River juveniles (mean = 1177 [micro]m [+ or -] 69.8 SE) than in the fluvial Willamette River adults (mean = 1490 [micro]m [+ or -] 78.9 SE) (t = -2.98; P = 0.016). This suggests potential interannual or habitat differences in growth or life-history variation, with adults having a more nutritious prey base or a different thermal regime. Sloat and Reeves (2014) found that thermal conditions influence somatic growth rates and the prevalence of resident or migratory salmonids.
Coastal Cutthroat Trout are widely distributed in tributaries of the Willamette River (Dimick and Merryfield 1945). Moring and Yonker (1979) stated that age 0 and 1 fish were rarely caught in large rivers like the Willamette, whereas these age groups account for the majority of fish in small tributaries. Whether these small fish represent recent downstream migrants from tributaries or spawning in the Willamette River is not known, but they concluded that large rivers rely on fish from tributaries for recruitment. Given the observed variation and overlap in elemental composition (Sr/Ca and Ba/Ca) of the Willamette and Marys rivers, accurately reconstructing movement patterns or life history based solely on otolith Sr/Ca and Ba/Ca is unlikely. However, there was no overlap in water [.sup.87]Sr/[.sup.86]Sr and there were clear differences in otolith edge [.sup.87]Sr/[.sup.86]Sr of fish in the Willamette and Marys rivers. We determined that otolith [.sup.87]Sr/[.sup.86]Sr ratios in the core region of adults collected in the Willamette River show that 3 of the 5 individuals with [.sup.87]Sr/[.sup.86]Sr data likely reared in the Marys River or another tributary with relatively high [.sup.87]Sr/[.sup.86]Sr. Thus, otolith [.sup.87]Sr/[.sup.86]Sr ratios hold promise for reconstructing movement history and identifying fluvial versus resident individuals within these river systems.
Although resident Cutthroat Trout populations were considered secure in most coastal streams in Oregon (Hooten 1997), they were thought to be declining in western Oregon streams where habitat has been lost and pool complexity has decreased (Reeves and others 1997). A lack of information about the status of Cutthroat Trout west of the crest of the Cascade Range, especially the fluvial types, made them a stock of concern by Wevers and others (1992). Fluvial fish were once abundant in the Marys River (Nicholas 1979) and declines are probably a result of loss of habitat complexity and pools (Reeves and others 1997). More recently, Good-son (2008) concluded that the Species Management Unit of Willamette River Coastal Cutthroat was not at risk.
Based on the otolith core values of [.sup.87]Sr/[.sup.86]Sr of the 6 juveniles sampled in the Marys River, 3 appeared to be offspring of mothers who may have resided in the Willamette River, or another tributary with similarly low [.sup.87]Sr/[.sup.86]Sr values. Thus, a preliminary estimate is that 50% of the juvenile fish from the Marys River appear to have originated from outside or from mothers that came from outside the Marys River.
Although Coastal Cutthroat Trout have phenotypically different life histories within a watershed, these life-history types are thought to be flexible, without a genetic basis for anadromous versus resident fish (Johnson and others 2010). This means that resident forms may become fluvial and vice versa. A better understanding of the relative recruitment of both resident and fluvial Cutthroat Trout to the population of the Marys River and other tributaries is needed to prioritize restoration, monitoring, and management of the different spawning and rearing habitats of these life-history types. Given the observed water and otolith edge [.sup.87]Sr/[.sup.86]Sr values, the generation of a more comprehensive watershed map of [.sup.87]Sr/[.sup.86]Sr values throughout the mainstem Willamette River (Bourret 2013) and its tributaries would be a valuable tool for reconstructing Cutthroat Trout life histories. A strontium isoscape that covers the range of Cutthroat Trout could be combined with additional fish sampling to further elucidate the relative proportions of resident and fluvial fish across the basin.
We are indebted to Karen Hans (Oregon Department of Fish and Wildlife) and Steve Trask (Bio-Surveys LLC) for their help in collecting juvenile fish from the Marys River, Randy Wildman for collecting adults in the Willamette River, Chris Romsos (Oregon State University) and Kathleen Westly (Marys River Watershed Council) for editing and formatting the manuscript, and reviewers for helpful comments.
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WILLIAM G PEARCY AND JESSICA A MILLER
College of Earth, Ocean, and Atmospheric Sciences and Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR 97337 USA; email@example.com
Submitted 9 August 2017, accepted 22 March 2018. Corresponding Editor: Tara Chestnut.
TABLE 1. Water chemistry data collected from the Marys River and tributaries in March and May 2012, and the Willamette River in March and August 2012. "NA" = data not available. Site Collection month Ba/Ca ([micro]M/M) Tumtum River at Ellmaker March 2500 Tumtum River at Blodgett March 1190 Rock Creek March 300 Rock Creek August 190 Rock Creek 2 August 120 Rock Creek 2 August 50 Blair Creek at Hwy 20 August 180 Wood Creek March 210 Marys River at Blodgett March 1750 Willamette River Park March 220 Willamette River at Irish Bend March 160 Willamette River near Harrisburg August NA Site Sr/Ca (mM/M) [.sup.87]Sr/[.sup.86]Sr Tumtum River at Ellmaker 7.69 0.70793 Tumtum River at Blodgett 4.35 0.70746 Rock Creek 1.18 0.70478 Rock Creek 1.82 NA Rock Creek 2 1.23 NA Rock Creek 2 1.29 NA Blair Creek at Hwy 20 1.96 0.70509 Wood Creek 1.34 0.70551 Marys River at Blodgett 6.11 0.70756 Willamette River Park 3.16 0.70412 Willamette River at Irish Bend 3.15 0.70388 Willamette River near Harrisburg 3.1 NA Site [delta][.sup.18]O Tumtum River at Ellmaker -7.8 Tumtum River at Blodgett NA Rock Creek -8.9 Rock Creek NA Rock Creek 2 NA Rock Creek 2 NA Blair Creek at Hwy 20 NA Wood Creek -9.1 Marys River at Blodgett -8.2 Willamette River Park -11.1 Willamette River at Irish Bend -11.4 Willamette River near Harrisburg NA TABLE 2. Fish identification number (ID), size, collection site, and mean ([+ or -] standard deviation) for [.sup.87]Sr/[.sup.86]Sr in the otolith core and edge for juveniles collected in March and May, and for the adults caught in August. For juveniles, bold text denotes individuals whose core chemistry indicates a probable Willamette River maternal origin. For adults, bold text denotes individuals that appeared to rear outside of the Willamette River in waters similar to portions of the Marys River and its tributaries. The mean Willamette River otolith edge [.sup.87]Sr/[.sup.86]Sr = 0.70377 [+ or -] 0.00019 SD (957r CI = 0.70361-0.70393). The mean otolith edge [.sup.87]Sr/[.sup.86]Sr for juveniles collected in the Marys River basin = 0.70512 [+ or -] 0.00066 SD (95% CI = 0.70458-0.70565). Fish ID Fork length (mm) Collection site juveniles 1 124 Rock Ck. 1 2 90 Rock Ck. 1 3 115 Rock Ck. 2 4 101 Rock Ck. 2 5 190 Rock Ck. 1 6 135 Wood Ck. 1 7 102 Wood Ck. 2 10 110 Tumtum at Blodgett 11 85 Blair Ck. 14 98 Wood Ck. 2 Adults 1 315 Willamette R. 2 220 Willamette R. 3 223 Willamette R. 4 268 Willamette R. 5 303 Willamette R. 6 294 Willamette R. [.sup.87]Sr/[.sup.86]Sr Fish ID Otolith core Otolith edge juveniles 1 0.70612 ([+ or -]0.00046) 0.70590 ([+ or -]0.00028) 2 NA NA 3 0.70366 ([+ or -]0.00036) 0.70470 ([+ or -]0.00028) 4 0.70399 ([+ or -]0.00052) 0.70428 ([+ or -]0.00133) 5 0.70474 ([+ or -]0.00025) 0.70556 ([+ or -]0.00051) 6 0.70567 ([+ or -]0.00032) 0.70563 ([+ or -]0.00063) 7 0.70408 ([+ or -]0.00046) 0.70462 ([+ or -]0.00041) 10 NA NA 11 NA NA 14 NA NA Adults 1 0.70574 ([+ or -]0.00038) 0.70393 ([+ or -]0.00012) 2 0.70387 ([+ or -]0.00036) 0.70396 ([+ or -]0.00015) 3 0.70461 ([+ or -]0.00097) 0.70352 ([+ or -]0.00013) 4 NA NA 5 0.70732 ([+ or -]0.00029) 0.70379 ([+ or -]0.00034) 6 0.70392 ([+ or -]0.00025) 0.70365 ([+ or -]0.00019) TABLE 3. Fish identification number (ID), size, collection site, and mean and standard error for otolith Ba/Ca ([micro]M/M) and Sr/Ca (mM/M) at the core and edge (juveniles in March and May) and for the core and edge during rearing for the adults caught in August. Otolith core Fish ID (mm) Collection site Ba/Ca ([micro]M/M) Sr/Ca (mM/M) Juveniles 1 124 Rock Ck 1 4.8 (0.39) 0.60 (0.04) 2 90 Rock Ck 1 7.0 (0.52) 0.39 (0.02) 3 115 Rock Ck 2 3.0 (0.44) 0.45 (0.05) 4 101 Rock Ck 2 3.8 (0.37) 0.74 (0.06) 5 140 Rock Ck 1 2.7 (0.36) 0.44 (0.04) 6 135 Wood Ck 1 4.3 (0.40) 0.38 (0.03) 7 102 Wood Ck 2 8.8 (0.95) 0.73 (0.06) 10 110 Tumtum at Blodgett 43.8 (5.8) 2.02 (0.24) 11 85 Blair Ck 6.0 (0.52) 0.45 (0.03) 14 98 Wood Ck 2 3.5 (0.52) 0.48 (0.04) Adults 1 315 Willamette R. 9.0 (0.62) 0.33 (0.02) 2 220 Willamette R. 4.4 (0.33) 0.54 (0.04) 3 223 Willamette R. 0.9 (0.11) 0.20 (0.04) 4 268 Willamette R. 1.2 (0.11) 0.56 (0.04) 5 303 Willamette R. 9.0 (1.35) 0.76 (0.07) 6 294 Willamette R. 8.0 (0.90) 0.70 (0.06) Otolith edge Fish ID Ba/Ca ([micro]M/M) Sr/Ca (mM/M) Juveniles 1 6.0 (0.56) 0.59 (0.08) 2 5.7 (1.09) 0.36 (0.02) 3 1.7(0.21) 0.54 (0.05) 4 1.0(0.34) 0.42 (0.06) 5 8.3 (1.59) 0.56 (0.47) 6 13.0 (1.36) 0.55 (0.05) 7 5.6 (0.66) 0.39 (0.02) 10 28.2 (2.71) 2.07 (0.18) 11 2.6 (0.23) 0.42 (0.03) 14 2.0 (0.52) 0.41 (0.02) Adults 1 1.9 (0.17) 0.69 (0.05) 2 5.5 (0.70) 0.67 (0.07) 3 6.8 (2.38) 0.72 (0.06) 4 2.1 (0.32) 0.70 (0.05) 5 2.3 (0.25) 0.66 (0.05) 6 2.0 (0.19) 0.65 (0.05)
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|Author:||Pearcy, William G.; Miller, Jessica A.|
|Publication:||Northwestern Naturalist: A Journal of Vertebrate Biology|
|Date:||Sep 22, 2018|
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