We used a retrospective approach to identify hydrologic metrics with the greatest potential for ecological relevance for use as resource management tools (i.e., hydrologic indicators) in rapidly urbanizing basins of the Puget Lowland. We proposed four criteria for identifying useful hydrologic indicators: (1) sensitive to urbanization consistent with expected hydrologic response, (2) demonstrate statistically significant trends in urbanizing basins (and not in undeveloped basins), (3) be correlated with measures of biological response to urbanization, and (4) be relatively insensitive to potentially confounding variables like basin area. Data utilized in the analysis included gauged flow and benthic macroinvertebrate data collected at 16 locations in 11 King County stream basins. Fifteen hydrologic metrics were calculated from daily average flow data and the Pacific Northwest Benthic Index of Biological Integrity (B-IBI) was used to represent the gradient of response of stream macroinvertebrates to urbanization. Urbanization was represented by percent Total Impervious Area (%TIA) and percent urban land cover (%Urban). We found eight hydrologic metrics that were significantly correlated with B-IBI scores (Low Pulse Count and Duration; High Pulse Count, Duration, and Range; Flow Reversals, TQmean, and R-B Index). Although there appeared to be a great deal of redundancy among these metrics with respect to their response to urbanization, only two of the metrics tested – High Pulse Count and High Pulse Range – best met all four criteria we established for selecting hydrologic indicators. The increase in these high pulse metrics with respect to urbanization is the result of an increase in winter high pulses and the occurrence of high pulse events during summer (increasing the frequency and range of high pulses), when practically none would have occurred prior to development. We performed an initial evaluation of the usefulness of our hydrologic indicators by calculating and comparing hydrologic metrics derived from continuous hydrologic simulations of selected basin management alternatives for Miller Creek, one of the most highly urbanized basins used in our study. We found that the preferred basin management alternative appeared to be effective in restoring some flow metrics close to simulated fully forested conditions (e.g., TQmean), but less effective in restoring other metrics such as High Pulse Count and Range. If future research continues to support our hypothesis that the flow regime, particularly High Pulse Count and Range, is an important control of biotic integrity in Puget Lowland streams, it would have significant implications for stormwater management.

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Anadromous salmonid populations are particularly vulnerable to migration blockages, such as dams and culverts, because access to historic spawning and rearing habitats is prevented. The process of salmonid recolonization has not been well documented for river systems where anthropogenic migration barriers have been removed or where fish passage facilities have been constructed. In September 2003, Seattle Public Utilities completed construction of a fish passage facility that circumvented Landsburg Dam on the Cedar River, Washington. Chinook Salmon Oncorhynchus tshawytscha spawned in newly available main‐stem habitats immediately after fish passage facility construction and in all subsequent years. Further dispersal into tributary habitats occurred 5 years after construction. Redds tended to be concentrated in the downstream third of the available habitat above the dam, although some fish did utilize suitable spawning sites throughout the main stem, even in the uppermost reaches of the newly available habitat. Median spawn timing for redds observed above the dam was not significantly different from spawn timing for the source population, indicating that migration delays through the fish passage facility were minimal. Male Chinook Salmon consistently outnumbered females, with annual sex ratios ranging from 1.3:1 to 4.7:1. Chinook Salmon spawning above the dam contributed between 2.7% and 14.7% of the total annual redd count (2003–2010) for Cedar River Chinook Salmon; upstream redds as a percentage of total redds increased over time, indicating that a new, naturally reproducing population above the dam was growing. The proportion of hatchery‐origin fish spawning above the dam decreased over the duration of the study but was consistently higher than the hatchery component observed below the dam.

We conducted field experiments in the nearshore area of two urban lakes (Lake Washington and Lake Sammamish) in western Washington to test the attractive quality of artificial nighttime lighting to subyearling salmonids Oncorhynchus spp. In both lakes, experimental trials were conducted along a uniform 156‐m shoreline section twice a month (one night with lights and one control night without lights) from March to May to correspond with peak nearshore rearing of subyearling salmonids. We examined the effects of three light intensities on nearshore fish abundance: (1) no light, (2) dim light (maximum, 5.0 lx), and (3) bright light (maximum, 50.0 lx). These were compared with abundances from control nights without light treatments. Beach seining was used to determine fish abundance. For each month, the total number of subyearling salmonids (Chinook Salmon O. tshawytscha, Coho Salmon O. kisutch, and Sockeye Salmon O. nerka combined) was greater on the lighted nights (all treatments combined) than it was on the control nights. In both lakes, the most subyearling salmonids were collected in the bright‐light treatments, an intermediate amount in the dim‐light treatments, and few in the no‐light treatments. In some instances, subyearling salmonid abundances in the bright‐light treatments were more than 10 times greater than in the no‐light treatments. The effect of nighttime artificial lighting was generally more pronounced in March than in April or May. The results support our hypothesis that subyearling salmonids exhibit nocturnal phototaxic behavior when exposed to elevated nighttime lighting. A major concern of artificial nighttime lighting for subyearling salmonids is the potential for an increased predation risk, and we believe the prudent management goal would be to minimize artificial nighttime lighting. Received October 23, 2016; accepted March 7, 2017 Published online May 26, 2017