Effects of stream-adjacent logging in fishless headwaters on downstream coastal cutthroat trout

Abstract

To investigate effects of headwater logging on downstream coastal cutthroat trout (Oncorhynchus clarkii clarkii) populations, we monitored stream habitat and biotic indicators including biomass, abundance, growth, movement, and survival over 8 years using a paired-watershed approach. Reference and logged catchments were located on private industrial forestland on ∼60-year harvest rotation. Five clearcuts (14% of the logged catchment area) were adjacent to fishless portions of the headwater streams, and contemporary regulations did not require riparian forest buffers in the treatment catchment. Logging did not have significant negative effects on downstream coastal cutthroat trout populations for the duration of the sample period. Indeed, the only statistically significant response of fish populations following logging in fishless headwaters was an increase in late-summer biomass (g·m−2) of age-1+ coastal cutthroat trout in tributaries. Ultimately, the ability to make broad generalizations concerning effects of timber harvest is difficult because response to disturbance (anthropogenically influenced or not) in aquatic systems is complex and context-dependent, but our findings provide one example of environmentally compatible commercial logging in a regenerated forest setting.

Season‐specific survival rates and densities of coastal cutthroat trout across stream sizes in southwestern British Columbia

“…Our density estimates of 0.034–0.238 fish/m 2 were in line with other studies of cutthroat trout that provided estimates of 0.04–0.36 fish/m 2 (Bateman et al, 2016) and 0.18–0.3 fish/m 2 (Buehrens et al, 2014). In this study of resident cutthroat trout, all age classes were present in streams, with trout densities and distributions reflecting age‐related habitat preferences with occupancy of specific habitat types (e.g.…”

“…Mean monthly survival probabilities did not differ greatly between stream populations (means 0.87 – 0.94 per month, annualized 0.19 to 0.46), which were very similar to the annual survival rates of 0.19 to 0.50 found by Bateman et al, (2016) and 0.322 (Berger & Gresswell, 2009) for PIT‐tagged coastal cutthroat trout in Oregon. However, even small difference in survival rates among streams can reflect a biologically meaningful difference (White & Burnham, 1999).…”

“…As a result, aquatic fauna may be threatened by stream disturbances due to habitat and connectivity loss, especially during periods of reduced surface flows, including predicted climate change (e.g. Bateman et al, 2016). These current and future environmental issues create challenges for the conservation of freshwater species (e.g.…”

Loss of riparian forests from wildfire led to increased stream temperatures in summer, yet salmonid fish persisted

“…The density of age 1 and older salmonids (cutthroat trout and O. mykiss together) in our study reaches in July 2021 were 0.14 fish m −2 in Middle South Fork Hinkle Creek (MSFHC) and 0.11 fish m −2 in Lower South Fork Hinkle Creek (LSFHC). This was largely consistent with an earlier study from this area in which salmonid densities in the SFHC mainstem in late summer averaged 0.18 fish m −2 over a 5‐year period (Bateman et al, 2016). Although our July 2021 abundance estimates were slightly below those reported by Bateman et al (2016), this earlier study sampled only from pools, and we sampled from all habitats in our survey reaches.…”

Evaluating Coexistence of Fish Species with Coastal Cutthroat Trout in Low Order Streams of Western Oregon and Washington, USA

“…In this region, highly valued salmonids are the focus of much policy and research to understand how they are influenced by land management practices [3,4]. With respect to the question of forestry and fish [5][6][7], the salmonid most often considered is the coastal cutthroat trout (Oncorhynchus clarkii clarkii). This is likely because, among Pacific Northwest salmonids, coastal cutthroat trout predominates in smaller streams [8,9] and such streams comprise a vast majority of the length of streams [10].…”