A 1-km reach of Brierly Brook, Nova Scotia, was studied from 1995 to 2004 to determine if the addition of artificial structures mimicking large woody debris could enhance Atlantic salmon populations. In 1995, digger logs (which mimic fallen trees) and deflectors (which narrow the channel) were constructed in a 250-m section of the brook devoid of woody debris (Old Restored Site). In 2003, 5 more digger logs and defectors were built in a previously unrestored section of the stream (New Restored Site). A third control site was left unchanged. Physical changes caused by the structures were monitored at the New Restored Site. Densities of juvenile and spawning Atlantic salmon were also monitored. At all sites, woody debris structures in the brook were important and effective in creating complex salmonid habitat. The structures narrowed the channel, scoured pools and undercut banks. They created habitat that parr used for summer and winter refuge and adult spawners used for cover and resting during upstream migration and spawning. The structures caused gravels to accumulate that spawning adults used to build redds and fry used for shelter. The reaches with structures had higher spawning densities than reaches without them; spawning increased in the New Restored Site relative to the control site. The absence of woody debris may be a bottleneck for salmonid populations in streams of the Atlantic Northeast. For streams with a small or immature riparian zone and little woody debris in the channel, woody structures may be an effective tool for restoring salmonid populations.

In a restored, third-order stream in northern Nova Scotia, Canada, we used redd counts over 12 years to examine the influence of beaver dams and the timing and intensity of autumn rains on spawning activity of Atlantic salmon. Most beaver dams in most years had no detectable effect on the distribution of spawning redds, but in 2004 the density of redds downstream from a threedam complex was significantly greater than that above, suggesting the dams were a barrier to many fish. A second complex of dams blocked salmon passage completely in 2003 and 2004 until they were notched to provide access upstream. The length of stream used by salmon for spawning was linearly correlated with total precipitation in the basin in October plus November (R 2 ¼ 0.60), to a ceiling of 325 mm, above which the fish had access to the entire brook, if beaver dams were notched. Number of redds in the whole brook was strongly correlated (R 2 ¼ 0.94) with the coefficient of variation (CV) of daily rainfall in October, but only for 7 of 11 years. This relationship disappeared when the impassable beaver dam complex failed in 2005, allowing salmon free access to 4 km of the upper brook. Variation in rainfall, and hence discharge, in this flashy brook evidently influences migration and spawning of Atlantic salmon in conjunction with channel blocking by beaver dams.

Although large woody debris from streamside vegetation has profound influences on channel morphology and habitat for salmonid fishes, it has often been depleted by channelization or deforestation of the riparian zone. We installed artificial structures mimicking naturally fallen trees in a third‐order stream in northern Nova Scotia from 1992 to 2004 to determine whether the structures enhanced spawning success of Atlantic salmon Salmo salar. In total, 250 digger logs (which mimic fallen tree trunks and stimulate formation of pools) and bank deflectors (which encourage meandering) were constructed in degraded reaches of Brierly Brook beginning at the downstream end. We monitored spawning each year by counting redds during the fall spawning season. Spawning rates (redd counts) in the whole brook increased exponentially for the first 4 years after restoration work began, from 43 in 1992 to 592 in 1996. By 1996, the entire length of Brierly Brook contained redds, and Atlantic salmon were using gravel that accumulated behind digger logs to build redds. Thereafter, redd counts remained high (502–605) but no longer increased, suggesting that restoration near the mouth of the brook removed an impediment to upstream migration. In 2004, reaches with artificial structures had significantly more redds (336) than reaches without the structures (280). In reaches with artificial structures, 48% of the redds were associated with gravel pool tails or the heads of riffles, 44% were near artificial structures, and 7% were near natural large woody debris. In reaches without artificial structures, almost 89% of the redds were associated with pool tails and the remainder were associated with natural large woody debris. Large woody debris, whether natural or artificial, appears to be an important source of spawning habitat for Atlantic salmon. Artificial structures mimicking naturally fallen wood are effective in the restoration of spawning habitat.

Stream restoration is often undertaken with the goal of improving habitat for one focal species, most often a salmonid fish such as trout or salmon. Improvements in channel structure, especially the flushing of silt from sediments, should also benefit benthic invertebrate communities, but studies to date suggest substantial changes in benthic communities following restoration are not common. In a third-order Nova Scotia stream, we examined the effect of successful restoration to improve habitat for spawning Atlantic salmon on benthic invertebrate communities at sites where clogging of the bottom cobble with fine silt had been alleviated.  In a long-term comparison of two restored sites and two degraded sites, only six of 24 insect taxa showed increased population density five or seven years after restoration. In a second comparison of a comparatively undisturbed site against a newly restored site and a site restored eight years earlier, only three invertebrate taxa appeared to respond positively and consistently to restoration. In both studies there were no substantial changes in total invertebrate density, taxa richness, Simpson’s diversity index or other community metrics over five years, except for a decline in the EPT/Chironomids ratio in the second study. Ordination of sites by correspondence analysis showed that, in both studies, benthic communities at unrestored control sites and restored sites were clearly different and did not become more similar through time. A long-term restructuring of the benthic community in the entire brook is suggested by the appearance of silt-intolerant shredders (Lepidostoma, Leuctra) among the most abundant members of the benthos in the second study, replacing silt-tolerant collectors (Tricorythodes, Optioservus) that dominated the earlier study. Habitat factors unaffected by in-stream restoration (frequent high discharge, lack of woody debris) limit benthic communities more than substratum quality.