Density‐dependent territory size and individual growth rate in juvenileAtlantic salmon (Salmo salar)

Abstract

Whether territoriality regulates population size depends on the flexibility of territory size, but few studies have quantified territory size over a broad range of densities. While juvenile salmonids in streams exhibit densitydependent mortality and emigration, consistent with space limitation, there has been relatively little study of how territory size and individual growth rate change over a broad range of densities, particularly in field experiments. Consequently, we manipulated the density (range = 0.25-8 m À2 ) of young-of-the-year (YOY) Atlantic salmon (Salmo salar) in mesh enclosures erected in a natural stream to test whether (i) territory size is fixed, decreases continuously or decreases towards an asymptotic minimum size as density increases; and (ii) individual growth rate decreases as a negative power curve with density as in observational field studies. Territory size decreased with increasing density, consistent with an asymptotic minimum size of about 0.13 m 2 for a 5-cm fish. Individual growth rate also decreased with density, although the magnitude of decrease was steeper than in observational studies. Our results suggest a limit to how small territories can be compressed, which will set the upper limit to the local density in a habitat. The density-dependent changes in territory size and individual growth rate will both play a role in the regulation of stream salmonid populations.

Effect of individuals’ local persistence, and spatial and temporal scale, on density-dependent growth: a study in brown troutSalmo trutta

“…The studies referred to above suggested that density-dependent growth is more intensive in less mobile groups with high survival of individuals due to strong competition for space and food and with a relatively low chance for individuals to achieve ideal free distribution (sensu Fretwell & Lucas 1969). Competition is generally divided into exploitative and interference interactions (Krebs & Davies 1987), but the importance of these interactions in the regulation of density-dependent growth in salmonids is ambiguous (Imre et al 2005(Imre et al , 2010Ward et al 2007;Lindeman et al 2015). Population density on the large scale (several kilometres or the whole stream) can causes depletion of resources and changes the growth of individuals throughout exploitative competition.…”

Coupled geomorphic and habitat response to a flood pulse revealed by remote sensing

“…Capacity was based on the space-limited concept of population regulation in salmonids, in which territorial juveniles each require a minimum area of habitat that is a function of body size (Chapman, 1966;Dunham & Vinyard, 1997;Lindeman, Grant, & Desjardins, 2015;Rosenfeld, 2014;Smith, Baumgartner, Suthers, Fielder, & Taylor, 2013;Steingrimsson & Grant, 1999). Capacity was based on the space-limited concept of population regulation in salmonids, in which territorial juveniles each require a minimum area of habitat that is a function of body size (Chapman, 1966;Dunham & Vinyard, 1997;Lindeman, Grant, & Desjardins, 2015;Rosenfeld, 2014;Smith, Baumgartner, Suthers, Fielder, & Taylor, 2013;Steingrimsson & Grant, 1999).…”

Seasonal effects of macrophyte growth on rainbow trout habitat availability and selection in a low‐gradient, groundwater‐dominated river

“…Hutchins, Engel, Nowlin, & Schwartz, 2016;Kuehne & Olden, 2016;Lindeman, Grant, & Desjardins, 2014). Hutchins, Engel, Nowlin, & Schwartz, 2016;Kuehne & Olden, 2016;Lindeman, Grant, & Desjardins, 2014).…”