Allometric and environmental correlates of territory size in juvenile Atlantic salmon (Salmo salar)

1995 ◽  
Vol 52 (1) ◽  
pp. 186-196 ◽  
Author(s):  
Ernest R. Keeley ◽  
James W. A. Grant
Keyword(s):  
Body Size ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Territory Size ◽  
Environmental Correlates ◽  
Atlantic Salmon Salmo Salar ◽  
Juvenile Atlantic Salmon ◽  
Wide Range ◽  
Body Sizes ◽  
Young Of The Year

We observed juvenile Atlantic salmon (Salmo salar) over a wide range of stream conditions and body sizes to determine the relative importance of environmental factors and body size as predictors of territory size. Defended and foraging areas were virtually identical in size. Eighty-eight percent of the variation in territory size was explained by differences in body size and age; territory size increased with body size, but young-of-the-year salmon had relatively larger territories for their body size than older fish. Territory size was inversely related to food abundance, the only significant environmental correlate of territory size, but food only explained an additional 2% of the variation in territory size. Intruder pressure, visual isolation, and current velocity were not significantly related to territory size. The allometric scaling of territory size was consistent with the hypothesis that Atlantic salmon maintain a maximum daily ration of drift flowing over their territory. Atlantic salmon in Catamaran Brook have larger territories than is reported in the literature for other stream-dwelling salmonids of a similar size.

Mechanisms underlying the increase in young-of-the-year Atlantic salmon (Salmo salar) density with habitat complexity

2008 ◽  
Vol 65 (9) ◽  
pp. 1956-1964 ◽  
Author(s):  
Oscar Venter ◽  
James W.A. Grant ◽  
Michelle V. Noël ◽  
Jae-woo Kim
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Habitat Complexity ◽  
Indirect Evidence ◽  
Growth Potential ◽  
Territory Size ◽  
Complex Environments ◽  
Atlantic Salmon Salmo Salar ◽  
Direct Support ◽  
Young Of The Year

We tested three hypotheses used to explain the increase in young-of-the-year (YOY) Atlantic salmon ( Salmo salar ) density with habitat complexity: the territory-size, predator-refuge, and foraging-benefits hypotheses. We manipulated habitat complexity in three different treatments (boulder-removed, control, and boulder-added) at eight sites in Catamaran Brook and the Little Southwest Miramichi River, New Brunswick. The density of juvenile salmon was two times higher in the boulder-added treatment than in the other treatments. Our data were consistent with the territory-size hypothesis; visual isolation was highest and territory size was smallest in the boulder-added treatment, and salmon selected microhabitats to maximize their field of view. Our results showed partial support for the predator-refuge hypothesis; salmon in the boulder-added sites were closer to cover and showed a reduced reaction distance to a novel stimulus, but did not preferentially select microhabitats closer to cover. We found no direct support for the foraging-benefits hypothesis; however, there is indirect evidence that boulders may improve the growth potential of instream habitat. Our results suggest that YOY Atlantic salmon may be attracted to complex environments for the increased cover and that the decreased visibility of these sites causes a reduction in territory size, allowing a higher density of fish.

Changes in the Selection of Microhabitat by Juvenile Atlantic Salmon (Salmo salar) at the Summer–Autumn Transition in a Small River

1984 ◽  
Vol 41 (3) ◽  
pp. 469-475 ◽  
Author(s):  
D. M. Rimmer ◽  
U. Paim ◽  
R. L. Saunders
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Water Depth ◽  
Water Velocity ◽  
Bottom Surface ◽  
Age Classes ◽  
Atlantic Salmon Salmo Salar ◽  
Juvenile Atlantic Salmon ◽  
Wide Range ◽  
Maximum Water

Over three summers we used direct underwater observation to examine the summer to autumn differences in seven microhabitat properties of three age-classes of juvenile Atlantic salmon (Salmo salar) in the Little Sevogle River of northeastern New Brunswick. Salmon of all three age-classes occupied a wide range of water depths during summer, but were concentrated mainly in depths of 24–36 cm. In autumn, they occurred in this range almost exclusively. The streambed stones most closely associated with the individual positions of all ages were always <20 cm in summer and mostly (84–92%) <10 cm in diameter. In autumn, all ages were associated with home stones up to 40 cm in diameter, with 65–83% of the stones exceeding 20 cm; the size of home stones selected increased with fish age in autumn. There was no apparent relationship between the water depth and home stone size distributions occupied by all age-classes and available in the stream during either summer or autumn. Summer focal water velocity (velocity at the fish's snout) was predominantly 10–30 cm∙s−1 for 0+, 10–40 cm∙s−1 for 1+, and 30–50 cm∙s−1 for 2+ salmon, but during autumn it was almost always <10 cm∙s−1 for all ages. The bottom and surface water velocities as well as the maximum water velocity within 1 m of fish stations increased with fish age during summer and autumn. At the summer–autumn transition, 0+ salmon selected higher bottom, surface, and maximum water velocities, 2+ salmon selected lower velocities, but selection by 1+ salmon remained unchanged. We view substrate size followed by water depth as the primary properties influencing stream suitability for juvenile Atlantic salmon in autumn.

The effect of turbulence on the cost of swimming for juvenile Atlantic salmon (Salmo salar)

2003 ◽  
Vol 60 (9) ◽  
pp. 1149-1160 ◽  
Author(s):  
Eva C Enders ◽  
Daniel Boisclair ◽  
André G Roy
Keyword(s):  
Atlantic Salmon ◽  
Turbulent Flow ◽  
Flow Velocity ◽  
Turbulent Flows ◽  
Salmo Salar ◽  
Forced Swimming ◽  
Mean Flow ◽  
Atlantic Salmon Salmo Salar ◽  
Juvenile Atlantic Salmon ◽  
Wide Range

Fish activity costs are often estimated by transforming their swimming speed in energy expenditures with respirometry models developed while forcing fish to swim against a flow of constant velocity. Forced swimming models obtained using a procedure that minimizes flow heterogeneity may not represent the costs of swimming in rivers characterized by turbulence and by a wide range of instantaneous flow velocities. We assessed the swimming cost of juvenile Atlantic salmon (Salmo salar) in turbulent flows using two means (18 and 23 cm·s–1) and two standard deviations of flow velocity (5 and 8 cm·s–1). Twenty respirometry experiments were conducted at 15 °C with fish averaging 10 g. Our results confirmed that swimming costs are affected by the level of turbulence. For a given mean flow velocity, swimming costs increased 1.3- to 1.6-fold as turbulence increased. Forced swimming models under estimated actual swimming costs in turbulent flow by 1.9- to 4.2-fold. Spontaneous swimming models overestimated the real cost of swimming in turbulent flow by 2.8- to 6.6-fold. Our analyses suggest that models in which both the mean and the standard deviation of flow velocity are explicitly represented are needed to adequately estimate the costs of swimming against turbulent flows.

Nocturnal activity of juvenile Atlantic salmon (Salmo salar) in late summer: evidence of diel activity partitioning

1997 ◽  
Vol 54 (6) ◽  
pp. 1408-1413 ◽  
Author(s):  
Gabe Gries ◽  
Kevin G Whalen ◽  
Francis Juanes ◽  
Donna L Parrish
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Late Summer ◽  
Diel Activity ◽  
Juvenile Salmon ◽  
Time Budgets ◽  
Nocturnal Activity ◽  
Atlantic Salmon Salmo Salar ◽  
Juvenile Atlantic Salmon ◽  
Young Of The Year

Paired day-night underwater counts of juvenile Atlantic salmon (Salmo salar) were completed on tributaries of the West River, Vermont, U.S.A., between 28 August and 10 September 1995. At water temperatures ranging from 13 to 23°C, the relative count of juvenile salmon was greater at night. Nocturnal counts differed for young-of-the-year and post-young-of-the-year (PYOY) salmon, with PYOY exhibiting almost exclusive nocturnal activity. Nocturnal activity in late summer may enable salmon to maintain population densities when space and suitable feeding areas may be limited. Nocturnal activity of juvenile salmon should be considered in studies of habitat use, competition, time budgets, and associated bioenergetic processes.

Microhabitat use by juvenile Atlantic salmon (Salmo salar ) sheltering during the day in summer

1998 ◽  
Vol 76 (8) ◽  
pp. 1441-1449 ◽  
Author(s):  
Gabe Gries ◽  
Francis Juanes
Keyword(s):  
Atlantic Salmon ◽  
Water Column ◽  
Salmo Salar ◽  
Maximum Temperature ◽  
Juvenile Salmon ◽  
Microhabitat Use ◽  
Atlantic Salmon Salmo Salar ◽  
Juvenile Atlantic Salmon ◽  
Young Of The Year ◽  
And Behavior

Daytime snorkeling surveys were conducted in the Wardsboro Branch, a tributary of the West River, Vermont, U.S.A., in July and August 1996. We documented microhabitat use by 245 juvenile Atlantic salmon (Salmo salar) sheltering (i.e., concealed beneath the stream substrate) at water temperatures ranging from 17 to 23°C, well above 10°C, the maximum temperature at which young salmon are thought to shelter during the day. The majority (92%) of sheltering salmon were young-of-the-year salmon (YOY). Of the YOY observed, 45% were sheltering, while 55% were in the water column. In comparison, only 10% of post-young-of-the-year salmon (PYOY; age 1 or older) observed were sheltering, while 90% were in the water column. Sheltering PYOY occupied greater water depths and were found under larger substrate stones than were YOY. Sheltering salmon (YOY and PYOY) were not distributed in proportion to the available microhabitat. Salmon only sheltered beneath unembedded cobble or boulder substrate, and sheltering salmon were found in pool habitats 43% of the time. Daytime sheltering suggests that the current interpretation of juvenile salmon habitat use and behavior during summer is incomplete. The availability of suitable sheltering habitats may be a factor affecting juvenile salmon production.

Impact of exposure to a simulated predator (Mergus merganser) on the activity of juvenile Atlantic salmon (Salmo salar) in a natural environment

2002 ◽  
Vol 80 (11) ◽  
pp. 2006-2013 ◽  
Author(s):  
Mélanie Dionne ◽  
Julian J Dodson
Keyword(s):  
Grain Size ◽  
Body Size ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Natural Environment ◽  
Juvenile Salmon ◽  
Short Term ◽  
Sediment Grain Size ◽  
Atlantic Salmon Salmo Salar ◽  
Juvenile Atlantic Salmon

Some laboratory studies suggest that the presence of predators influences the short-term behaviour of juvenile Atlantic salmon. However, few studies have been conducted in the natural environment to confirm these observations and to document how biological and environmental factors influence the behaviour of fish faced with a predator. Of the many potential predators of juvenile Atlantic salmon, Salmo salar, the common merganser, Mergus merganser, is a major one. This study was designed to investigate the immediate and short-term impact of exposure to a simulated avian predator on the activity of juvenile Atlantic salmon in their natural habitat. The influence of riverbed sediment grain size, a major determinant of habitat choice in salmon, and body size of juvenile salmon on the nature and intensity of their response to the predator was also investigated. Observations were made before and after exposure to a model of M. merganser in three situations: (1) fry (young salmon during their first summer of life) on fine sediment, (2) fry on coarse sediment, and (3) parr (young salmon during their second or third summer of life) on coarse sediment. Observations were also made on fry exposed to a harmless floating stimulus to evaluate if the decoys were perceived as threat. Following exposure, the feeding rate of juvenile salmon decreased by 25–39% and the moving rate increased by 123–386%. Sediment grain size influenced the nature of the immediate response of juvenile salmon, while body size influenced the intensity of the moving response. Parr moved significantly more than fry after exposure to the simulated predator.

scholarly journals Seasonal shift in the effects of predators on juvenile Atlantic salmon (Salmo salar) energetics

2011 ◽  
Vol 68 (12) ◽  
pp. 2080-2089 ◽  
Author(s):  
Darren M. Ward ◽  
Keith H. Nislow ◽  
Carol L. Folt
Keyword(s):  
Population Density ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Large Scale ◽  
Balance Model ◽  
Atlantic Salmon Salmo Salar ◽  
Juvenile Atlantic Salmon ◽  
Wide Range ◽  
Salmon Population ◽  
Predator Effects

Predator effects on prey populations are determined by the number of prey consumed and effects on the traits of surviving prey. Yet the effects of predators on prey traits are rarely evaluated in field studies. We measured the effects of predators on energetic traits (consumption and growth rates) of juvenile Atlantic salmon ( Salmo salar ) in a large-scale field study. Salmon fry were released at 18 sites that encompassed a wide range of predatory slimy sculpin ( Cottus cognatus ) abundance. We sampled salmon after 21 and 140 days to measure salmon growth and estimate consumption using a mass-balance model of methylmercury accumulation. Salmon population density was reduced fivefold at sites with abundant sculpin. Over the early season, salmon consumed less where sculpin were abundant, suggesting that reduced foraging under predation risk contributed to predator-caused mortality. In contrast, over the late season, salmon grew more where sculpin were abundant, suggesting that compensatory growth at reduced salmon population density moderated predator-caused mortality. Predator effects on prey energetics can drive variation in survival and growth, with important consequences for population dynamics.

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