Optimal territory size models predict a decrease in territory size with increasing food abundance. However, most of these models may not be applicable to juvenile salmonids in streams, because they defend contiguous territories at high densities. The optimal size of a contiguous territory is predicted to (1) be independent of food abundance when food is rare and (2) decrease only when food abundance is high enough to induce a reduction in territory size below the contiguous optimum. To test these predictions, we raised equal densities of juvenile steelhead trout in outdoor stream channels over a 32-fold range of food abundance in the absence of emigration for 25 days. Increasing competition for scarce food resulted in increasing mortality, higher willingness to emigrate, higher variance in body mass, lower growth, lower population density and lower biomass. The size of territories decreased with increasing local population density, and increased with increasing body size. However, territory size did not change with food abundance, a result consistent with the prediction of a contiguous territory size model. On average, total salmonid biomass increased 5.7 times in response to the 32-fold increase in food abundance. Our data provide strong support for an earlier quantitative relationship between the abundance of stream salmonids and their food.
This is a preview of subscription content, access via your institution.
Buy single article
Instant access to the full article PDF.
Price excludes VAT (USA)
Tax calculation will be finalised during checkout.
Adams ES (2001) Approaches to the study of territory size and shape. Annu Rev Ecol Syst 32:277–303
Askenmo C, Neergaard R, Arvidsson BL (1994) Food supplementation does not affect territory size in rock pipits. Anim Behav 47:1235–1237
Boutin S (1990) Food supplementation experiments with terrestrial vertebrates: patterns, problems, and the future. Can J Zool 68:203–220
Dill LM, Ydenberg RC, Fraser AHG (1981) Food abundance and territory size in juvenile coho salmon (Oncorhynchus kisutch). Can J Zool 59:1801–1809
Elliott JM (1994) Quantitative ecology and the brown trout. Oxford University Press, Oxford
Grant JWA (1997) Territoriality. In: Godin J-GJ (ed) Behavioural ecology of teleost fishes. Oxford University Press, Oxford, pp 81–103
Grant JWA, Kramer DL (1990) Territory size as a predictor of the upper limit to population density of juvenile salmonids in streams. Can J Fish Aquat Sci 47:1724–1737
Grant JWA, Noakes DLG (1987) Escape behaviour and use of cover by young-of-the-year brook trout, Salvelinus fontinalis. Can J Fish Aquat Sci 44:1390–1396
Grant JWA, Noakes DLG, Jonas KM (1989) Spatial distribution of defence and foraging in young-of-the-year brook charr, Salvelinus fontinalis. J Anim Ecol 58:773–784
Grant JWA, Steingrímsson SÓ, Keeley ER, Cunjak RA (1998) Implications of territory size for the measurement and prediction of salmonid abundance in streams. Can J Fish Aquat Sci 55 [Suppl 1]:181–190
Hixon MA (1980) Food production and competitor density as the determinants of feeding territory size. Am Nat 115:510–530
Imre I, Grant JWA, Keeley ER (2002) The effect of visual isolation on territory size and population density of juvenile rainbow trout (Oncorhynchus mykiss). Can J Fish Aquat Sci 59:303–309
Keeley ER (2000) An experimental analysis of territory size in juvenile steelhead trout. Anim Behav 59:477–490
Keeley ER (2001) Demographic responses to food and space competition by juvenile steelhead trout. Ecology 82:1247–1259
Keeley ER, Grant JWA (1995) Allometric and environmental correlates of territory size in juvenile Atlantic salmon (Salmo salar). Can J Fish Aquat Sci 52:186–196
Keeley ER, McPhail JD (1998) Food abundance, intruder pressure, and body size as determinants of territory size in juvenile steelhead trout (Oncorhynchus mykiss). Behaviour 135:65–82
Keenleyside MHA (1979) Diversity and adaptation in fish behaviour. Springer, Berlin Heidelberg New York
Le Cren ED (1973) The population dynamics of young trout (Salmo trutta) in relation to density and territorial behaviour. Rapp Cons Int Explor Mer 164:241–246
Łomnicki A (1978) Individual differences between animals and the natural regulation of their numbers. J Anim Ecol 47:461–475
Łomnicki A (1988) Population ecology of individuals. Princeton University Press, Princeton, N.J.
Martin P, Bateson P (1993) Measuring behaviour: an introductory guide, 2nd edn. Cambridge University Press, Cambridge
McNicol RE, Noakes DLG (1984) Environmental influences on territoriality of juvenile brook charr, Salvelinus fontinalis, in a stream environment. Environ Biol Fish 10:29–42
Myers JP, Conners PG, Pitelka FA (1979) Territory size in wintering sanderlings: the effects of prey abundance and intruder density. Auk 96:551–561
Newton I (1998) Population limitation in birds. Academic Press, New York
Norman MD, Jones GP (1984) Determinants of territory size in the pomacentrid reef fish, Parma victoriae. Oecologia 61:60–69
Schoener TW (1981) An empirically based estimate of home range. Theor Popul Biol 20:281–325
Schoener TW (1983) Simple models of optimal-feeding territory size: a reconciliation. Am Nat 121:608–629
Sinclair ARE (1989) The regulation of animal populations. In: Cherrett JM (ed) Ecological concepts: the contribution of ecology to an understanding of the natural world. Blackwell, Oxford, pp 197–241
Slaney PA, Northcote TG (1974) Effects of prey abundance on density and territorial behaviour of young rainbow trout (Salmo gairdneri) in laboratory stream channels. J Fish Res Bd Can 31:1201–1209
StatSoft Inc (1995) Statistica for Windows, Vols 1–5, 2nd edn. StatSoft, Tulsa, Okla.
Symons PEK (1971) Behavioural adjustment of population density to available food by juvenile Atlantic salmon. J Anim Ecol 40:569–587
Tricas TC (1989) Determinants of feeding territory size in the corallivorous butterflyfish, Chaetodon multicinctus. Anim Behav 37:830–841
We thank S.Ó. Steingrímsson, C.A. Johnson, I.L. Girard, L. Weir, C. Breau, and two anonymous referees for constructive comments on the manuscript, and Michelle Noël for help in conducting the experiment. We are grateful to D. Larson and K. Scheer (Fraser Valley Trout Hatchery) for supplying the fish, to B. Stanton (Chilliwack River Hatchery) for the loan of equipment, to E. Parkinson (B.C. Ministry of Fisheries) and Cultus Lake Laboratory (Department of Fisheries and Oceans) for their generous logistical support. The research was financially supported by an operating grant from the Natural Sciences and Engineering Research Council of Canada (NSERC) to J.W.A. Grant, and a Grant-in-Aid-of-Research from Sigma Xi to I. Imre. I. Imre was supported by an FCAR postgraduate fellowship and a Concordia graduate fellowship during this study. This experiment complies with the Animal Care Guidelines of Concordia University and the applicable laws of Canada.
Rights and permissions
About this article
Cite this article
Imre, I., Grant, J.W.A. & Keeley, E.R. The effect of food abundance on territory size and population density of juvenile steelhead trout (Oncorhynchus mykiss). Oecologia 138, 371–378 (2004). https://doi.org/10.1007/s00442-003-1432-z
- Contiguous territory
- Juvenile salmonids