Relative importance of size-based competitive ability and degree of niche overlap in inter-cohort competition of Atlantic salmon (Salmo salar) juveniles

2011 ◽  
Vol 68 (6) ◽  
pp. 969-976 ◽  
Author(s):  
Sigurd Einum ◽  
Eli Kvingedal
Keyword(s):  
Body Size ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Niche Overlap ◽  
Size Class ◽  
Atlantic Salmon Salmo Salar ◽  
Ontogenetic Niche Shifts ◽  
Niche Shifts ◽  
Ontogenetic Niche ◽  
Competitive Abilities

The competitive effect of older cohorts on younger cohorts may strengthen with increasing size differences owing to increasing differences in competitive abilities. Alternatively, it may weaken owing to increasing partitioning of resources as a result of ontogenetic niche shifts. Here, we test this by creating spatial variation in densities of one size class of overyearling Atlantic salmon ( Salmo salar ) and assess the effects on two size classes of young-of-the-year (YOY). The positive relationship between growth of overyearlings and final body size of YOY (a proxy for their growth) was steeper for the larger size class of YOY than for the smaller size class, which would be expected if the degree of niche overlap between two cohorts depended on their size difference. The negative relationship between overyearling density and YOY body size was also steeper for the larger size class (at least for body mass), suggesting that effects of body size differences on relative competitive abilities appear to be of less importance than the effects on degree of niche overlap. YOY should thus experience relatively less competition from older cohorts in rapidly growing populations, and this may also apply to many other fish species with ontogenetic niche shifts.

Relationship of upstream migrating adult Atlantic salmon (Salmo salar) and stream discharge within Catamaran Brook, New Brunswick

2007 ◽  
Vol 64 (3) ◽  
pp. 563-573 ◽  
Author(s):  
Sean C Mitchell ◽  
Richard A Cunjak
Keyword(s):  
Body Size ◽  
Atlantic Salmon ◽  
New Brunswick ◽  
Salmo Salar ◽  
Predictive Ability ◽  
River System ◽  
Low Flow ◽  
Stream Discharge ◽  
Atlantic Salmon Salmo Salar ◽  
Adult Abundance

Stream discharge has long been associated with abundance of returning adult spawning salmonids to streams and may also affect body size distribution of adult salmon as low flows interfere with returns of larger-bodied fish. We examined these relationships of abundance and body size within Catamaran Brook, a third-order tributary to the Miramichi River system of New Brunswick, Canada, to investigate the causes of a declining trend in annual returns of Atlantic salmon (Salmo salar) to this stream. Regression models of adult abundance, proportion of the run as grilse, and body size of returning adults as functions of maximum daily stream discharge during the period of upstream spawner migration were constructed. Adult abundance shows a logarithmic relationship with stream discharge and provides good predictive ability, while appearing to not be significantly related to adult abundance in the larger Miramichi system. The proportion as grilse in the run and female body size are also logarithmically related to stream discharge, with low flow years being very influential in the regressions. These relationships of Atlantic salmon population abundance and body size characteristics have implications with respect to stock integrity and production of the following generation.

Hierarchical analysis of wild Atlantic salmon ( Salmo salar ) fecundity in relation to body size and developmental traits

2019 ◽  
Vol 96 (2) ◽  
pp. 316-326
Author(s):  
Nora Hanson ◽  
James Ounsley ◽  
Tim Burton ◽  
Sonya Auer ◽  
James H. Hunt ◽  
...  
Keyword(s):  
Body Size ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Hierarchical Analysis ◽  
Atlantic Salmon Salmo Salar ◽  
Developmental Traits

scholarly journals Character Displacement Through an Evolutionary Change in Ontogenetic Niche Shifts

2021 ◽  
Author(s):  
Jaime Anaya-Rojas ◽  
Ronald Bassar ◽  
Blake Matthews ◽  
Joshua Goldberg ◽  
David Reznick ◽  
...  
Keyword(s):  
Body Size ◽  
Poecilia Reticulata ◽  
Character Displacement ◽  
Trophic Niche ◽  
Niche Shift ◽  
Ontogenetic Niche Shifts ◽  
Ontogenetic Niche Shift ◽  
Significant Difference ◽  
Niche Shifts ◽  
Ontogenetic Niche

In communities structured by body size, coexistence can occur through combinations of ontogenetic changes in competitive ability and dietary niche. Using stable isotopes, we examined ontogenetic niche shifts in Trinidadian guppies (Poecilia reticulata) and killifish (Rivulus hartii) in three types of natural communities (both species with predators, KGP; both without predators, KG; killifish only, KO) and four experimental KG communities, initiated with KGP guppies and KO killifish between 13 and 45 years ago. In all communities, killifish occupied higher trophic positions and changed their diet (δ^13 C) with body size. Only KGP guppies displayed an ontogenetic niche shift. The KG guppies displayed a significant difference in trophic niche from KGP guppies, a character displacement that can facilitate coexistence with killifish. In the experimental communities, the guppy trophic niche was intermediate between those in KGP and KG communities, indicating that evolution has driven the niche shift in KG guppies.

Influence of Body Size on Silvering of Atlantic Salmon (Salmo salar) at Parr–Smolt Transformation

1970 ◽  
Vol 27 (5) ◽  
pp. 983-987 ◽  
Author(s):  
C. E. Johnston ◽  
J. G. Eales
Keyword(s):  
Body Size ◽  
Atlantic Salmon ◽  
Water Temperature ◽  
Salmo Salar ◽  
Atlantic Salmon Salmo Salar ◽  
Salmon Parr ◽  
Negligible Influence ◽  
Atlantic Salmon Parr

Large yearling Atlantic salmon parr turn silvery more quickly than small parr when held under a series of controlled temperature and photoperiod regimes. Photoperiod appeared to exert a negligible influence on silvering, and water temperature was the main controlling variable.

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 Spawning history influence on fecundity, egg size, and egg survival of Atlantic salmon (Salmo salar) from the Miramichi River, New Brunswick, Canada

2012 ◽  
Vol 69 (9) ◽  
pp. 1678-1685 ◽  
Author(s):  
Jenny E. Reid ◽  
Gérald Chaput
Keyword(s):  
Body Size ◽  
Atlantic Salmon ◽  
New Brunswick ◽  
Salmo Salar ◽  
Egg Size ◽  
Positive Association ◽  
Egg Survival ◽  
Wild Female ◽  
Atlantic Salmon Salmo Salar ◽  
Egg Diameter

Abstract Reid, J. E., and Chaput, G. 2012. Spawning history influence on fecundity, egg size, and egg survival of Atlantic salmon (Salmo salar) from the Miramichi River, New Brunswick, Canada. – ICES Journal of Marine Science, 69: 1678–1685. There is an increasing abundance of repeat spawners in the Atlantic salmon (Salmo salar) population in the Miramichi River that, owing to their larger size, can be expected to contribute greater egg depositions and better offspring survival than primarily maiden spawning populations. Currently, there is little information on the reproductive contribution of repeat-spawning salmon. In this study, the fecundity, egg size, and egg survival for 235 maiden and repeat-spawning wild female Atlantic salmon were examined over a period of 3 years. Relative fecundity did not differ among the largest body size group of salmon, but consecutive repeat spawners had a higher fecundity than maiden 2SW salmon and alternate repeat spawners. Egg diameter also increased with body size, but consecutive repeat spawners had significantly smaller eggs, in absolute terms and relative to their body size, than maiden 2SW salmon and alternate repeat spawners. The egg survival rate of consecutive repeat spawners was significantly lower than that of 2SW maiden salmon and alternate repeat spawners. Consecutive repeat spawners are different in that egg diameter and egg survival did not follow the general positive association with female body size, probably because of the short time that they spend reconditioning in the ocean and consequently their available energy reserves.

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