Context-dependent responses of juvenile Atlantic salmon (Salmo salar) to forestry activities at multiple spatial scales within a river basin

2007 ◽  
Vol 64 (8) ◽  
pp. 1069-1079 ◽  
Author(s):  
Julie Deschênes ◽  
Marco A Rodríguez ◽  
Pierre Bérubé

We used classification trees and regression trees to relate the incidence and density of juvenile Atlantic salmon (Salmo salar) to forestry activities measured at four spatial scales (subbasin and 8, 2, and 0.5 km radii upstream of study sites) and environmental features in 120 stream reaches of the Cascapedia River basin, Québec, Canada. At all scales, incidence increased with reach size and accessibility to the reach from the river mainstem. Incidence declined with areal coverage of logging at all scales, but only in larger reaches. The time horizon over which logging effects were detected increased with spatial scale. At all scales, density in salmon-bearing reaches increased with accessibility. Density in more accessible reaches was negatively related to logging over the preceding 9 years at the subbasin and 8 km scales, but no effects of logging on density were detected at the 2 and 0.5 km scales. Overall, apparent effects of logging activities on salmon incidence and density were mostly negative and strong, but were both markedly scale-dependent and conditional on environmental context.

1987 ◽  
Vol 44 (1) ◽  
pp. 120-129 ◽  
Author(s):  
D. L. Morantz ◽  
R. K. Sweeney ◽  
C. S. Shirvell ◽  
D. A. Longard

This study was designed to define the microhabitats selected in summer by juvenile Atlantic salmon (Salmo salar). Curves were developed describing the preference of 880 young salmon for water velocity at the fish's position (nose velocity), mean water column velocity, total water depth, and stream substrate size. Study sites were chosen in six morphologically diverse streams in Nova Scotia and New Brunswick during 1982–84. Of the four variables measured, only nose velocity chosen by both fry and parr was not significantly different among years or rivers. Atlantic salmon fry (< 65 mm) most frequently selected nose velocities between 5 and 15 cm∙s−1, small parr (65–100 mm) between 5 and 25 cm∙s−1 and large parr (> 100 mm) between 5 and 35 cm∙s−1. Apparently, juvenile salmon utilized water depths and stream substrates which varied within tolerable limits according to their availability in conjunction with preferred water velocities. Significant differences in the body shape and size of the pectoral fin of Atlantic salmon parr in different rivers did not influence the selection of nose velocities within the range of flow conditions sampled.


1982 ◽  
Vol 60 (7) ◽  
pp. 1647-1659 ◽  
Author(s):  
R. G. Randall ◽  
U. Paim

The production rate of juvenile Atlantic salmon (Salmo salar) was estimated at four sites in two tributary streams of the Miramichi River, New Brunswick, during the period September 1976 to October 1978. Annual production ranged between 0.27 and 5.12 g∙m−2∙year−1. Growth was largely restricted to a 4-month period in early summer. Among the four sites, age 0+ salmon attained a mean weight of between 0.95 and 3.50 g by the end of their first growing season (September) and densities in July ranged between 0.3 and 3.1 fry∙m−2∙Age 1+ parr grew to mean weights between 4.95 and 12.45 g by September, and June–July densities ranged between 0.03 and 0.6 parr∙m−2. Marking information indicated that most parr remained in the study sites from July to September, but larger proportions of migrant parr were recorded in October. Production during summer was directly and positively related to initial population densities. Production rates at these sites were lower than most other recorded values for juvenile Atlantic salmon. Biomass of salmon may have been below the carrying capacity of the environment at all four sites.


1998 ◽  
Vol 55 (S1) ◽  
pp. 9-21 ◽  
Author(s):  
Carol L Folt ◽  
Keith H Nislow ◽  
Mary E Power

The Atlantic salmon (Salmo salar) is a model species for studying scale issues (i.e., the extent, duration, and resolution of a study or natural process) in ecology. Major shifts in behavior and habitat use over ontogeny, along with a relatively long life span and large dispersal and migration distances, make scale issues critical for effective conservation, management, and restoration of this species. The scale over which a process occurs must be linked to the research design and we illustrate this with a discussion of resource tracking by Atlantic salmon. Identifying scale inconsistencies (e.g., when a process is evident at one scale but not another) is shown to be an effective means by which some scale-dependent processes are understood. We review the literature to assess the temporal and spatial scales used in Atlantic salmon research and find most current studies appear to sacrifice spatial and temporal extent for increased resolution. Finally, we discuss research strategies for expanding the temporal and spatial scales in salmon research, such as conducting multiple scales studies to elucidate scale inconsistencies, identifying mechanisms, and using techniques and approaches to generalize across studies and over time and space.


2015 ◽  
Vol 41 (4) ◽  
pp. 1029-1051 ◽  
Author(s):  
Kirsten O. Hannesson ◽  
Elisabeth Ytteborg ◽  
Harald Takle ◽  
Grethe Enersen ◽  
Grete Bæverfjord ◽  
...  

1999 ◽  
Vol 56 (12) ◽  
pp. 2397-2403 ◽  
Author(s):  
Sveinn K Valdimarsson ◽  
Neil B Metcalfe

Traditionally, behavioural studies on juvenile Atlantic salmon, Salmo salar, have been conducted during the day in summer. It is known that Atlantic salmon become nocturnal in winter, but very little is known about their behaviour at that time. Therefore, observations in a seminatural stream were carried out during the day and night, from February to June, comparing diel and seasonal differences in behaviour between fish adopting alternative life history strategies. The results showed a general trend for more activity in spring than in winter, and the fish were found to be foraging at surprisingly low light levels. There were differences in relative feeding rate between the life history strategies; the early migrant fish foraged mostly during the day whereas the delayed migrant fish did more foraging at night. There is some evidence that the early migrant fish made fewer feeding attempts over the winter, which is surprising, since they grow faster over that period. This suggests differences in foraging efficiency, which could contribute to the separation into these two life history strategies.


2001 ◽  
Vol 15 (6) ◽  
pp. 701-711 ◽  
Author(s):  
B. JONSSON ◽  
T. FORSETH ◽  
A. J. JENSEN ◽  
T. F. NAESJE

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