The ages of brook trout Salvelinus fontinalis are typically estimated using scales despite a lack of research documenting the effectiveness of this technique. The use of scales is often preferred because it is nonlethal and is believed to require less effort than alternative methods. To evaluate the relative effectiveness of different age estimation methodologies for brook trout, we measured the precision and processing times of scale, sagittal otolith, and pectoral fin ray age estimation techniques. Three independent readers, age bias plots, coefficients of variation (CV = 100 × SD/mean), and percent agreement (PA) were used to measure within‐reader, among‐structure bias and within‐structure, among‐reader precision. Bias was generally minimal; however, the age estimates derived from scales tended to be lower than those derived from otoliths within older (age > 2) cohorts. Otolith, fin ray, and scale age estimates were within 1 year of each other for 95% of the comparisons. The measures of precision for scales (CV = 6.59; PA = 82.30) and otoliths (CV = 7.45; PA = 81.48) suggest higher agreement between these structures than with fin rays (CV = 11.30; PA = 65.84). The mean per‐sample processing times were lower for scale (13.88 min) and otolith techniques (12.23 min) than for fin ray techniques (22.68 min). The comparable processing times of scales and otoliths contradict popular belief and are probably a result of the high proportion of regenerated scales within samples and the ability to infer age from whole (as opposed to sectioned) otoliths. This research suggests that while scales produce age estimates rivaling those of otoliths for younger (age < 3) cohorts, they may be biased within older cohorts and therefore should be used with caution.

The physiological well‐being or condition of fish is most commonly estimated from aspects of individual morphology. However, these metrics may be only weakly correlated with nutritional reserves stored as lipid, the primary form of accumulated energy in fish. We constructed and evaluated bioelectrical impedance analysis (BIA) models as an alternative method of assessing condition in amphidromous Dolly Varden Salvelinus malma collected from nearshore estuarine and lotic habitats of the Alaskan Arctic. Data on electrical resistance and reactance were collected from the lateral and ventral surfaces of 192 fish, and whole‐body percent lipid and moisture content were determined using standard laboratory methods. Significant inverse relationships between temperature and resistance and reactance prompted the standardization of these data to a constant temperature using corrective equations developed herein. No significant differences in resistance or reactance were detected among spawning and nonspawning females after accounting for covariates, suggesting that electrical pathways do not intersect the gonads. Best‐fit BIA models incorporating electrical variables calculated from the lateral and ventral surfaces produced the strongest associations between observed and model‐predicted estimates of proximate content. These models explained between 6% and 20% more of the variability in laboratory‐derived estimates of proximate content than models developed from single‐surface BIA data and 32% more than models containing only length and weight data. While additional research is required to address the potential effects of methodological variation, bioelectrical impedance analysis shows promise as a way to provide high‐quality, minimally invasive estimates of Dolly Varden lipid or moisture content in the field with only small increases in handling time.Received June 17, 2013; accepted December 3, 2013

In partially migratory salmonid populations, growth and condition of migratory fish may be different than that of residents. To ascertain if a similar phenomenon exists in fluvial brook trout, Salvelinus fontinalis (Mitchell), populations, the growth and condition of fluvial and resident brook trout was measured in four Appalachian stream networks. Sites were sampled during summer, cohorts separated via scale analysis and differences in length and condition were investigated. Age-1 and -2 fluvial fish were significantly longer (P < 0.001) than residents of the same cohort. Additionally, age-2 fluvial fish had significantly greater condition (P < 0.005) than resident fish of the same cohort. This suggests that the use of spatially segregated resources can result in growth and condition advantages. However, potentially greater rates of mortality as suggested by low abundance in main stem sites may limit the fitness advantages of this energetically profitable, but ultimately risky, behaviour.

Annual winter water level drawdown (WD) is a common lake management strategy to maintain recreational value by controlling nuisance macrophytes and preventing ice damage to shoreline infrastructure in lakes of the northeastern United States. The state of Massachusetts provides general guidelines for lake managers to implement and practice WDs. However, WD management reporting is not required and as such empirical water level records are scarce, making it difficult to assess guideline adherence and link these management actions to littoral habitat conditions. We monitored water levels bihourly in 18 lakes with ongoing WD regimes and 3 non-drawdown lakes over 3-4 yr. Our results show an interlake drawdown magnitude gradient of 0.07-2.66 m with intralake consistency across years. Corresponding WD magnitudes generated exposure of 1.3-37.6% for entire lakebeds and 9.2-71.1% for littoral zones. WD durations averaged 171 d and ranged widely from 5 to 246 d. Longer recession and refill phase durations and faster recession rates were moderately to strongly correlated with drawdown magnitudes. WDs were predominantly initiated prior to the state of Massachusetts 1 November starting guideline (83.1%) and refilled to summer reference levels after the recommended date of 1 April (70.6%). To minimize ecological impacts while still meeting recreational goals, WD performance guidelines may require a more fine-scale approach that integrates local hydrogeomorphic features and the presence of WD-sensitive littoral biotic assemblages. However, climate change model projections of warmer and wetter winters in the Northeast indicate increasing uncertainty for WD as an effective and worthwhile macrophyte control tool.

The accuracy of population statistics and the validity of management actions they motivate are in part dependent on the acquisition of quality age determinations. Such data for northern‐form Dolly Varden Salvelinus malma have been traditionally garnered using otoliths, despite little research investigating the consistency of this or alternative nonlethal techniques. To address these gaps, the precision of age determinations generated from scales, otoliths, and fin rays was examined for 126 amphidromous Dolly Varden collected from two Arctic rivers. Three independent readers, age‐bias plots, coefficients of variation (CVs), and percent agreement (PA) were used to estimate bias and precision for among‐reader, within‐structure comparisons and within‐reader, among‐structure comparisons. Among‐reader, within‐structure tests of CVs suggested that otoliths produced more precise age determinations than fin rays. Furthermore, the CV for scales was intermediate to and not significantly different from those for otoliths and fin rays. Age‐bias plots suggested that, scales consistently underestimated age relative to otolithsbeginning at age 6. Underestimation was also apparent, but less distinct, within fin ray–otolith and scale–fin ray comparisons. Potential sources of error and management implications are discussed. Because scale and otolith ages exhibited little bias within cohorts younger than age 6, age may be determined nonlethally in these cohorts using scales; otoliths should be used otherwise.Received April 27, 2012; accepted May 13, 2013