Individual variations in habitat use and morphology in brook charr

Abstract

The specific objectives of this study were to determine if there is individual specialization in habitat use by lacustrine brook charr Salvelinus fontinalis and if so, if specialization is related to fish morphology. Localizations of 28 brook charr equipped with thermosensitive radiotransmitters were recorded during three summers (1991, 1992, and 1993) in two lakes of the Mastigouche Reserve (Québec, Canada). Fifty per cent of the fish were found mainly in the benthic zone (hereafter benthic individuals), 18% in the pelagic zone (pelagic individuals), and 32% travelled regularly between the two zones (generalist individuals). The observed interindividual differences in habitat preference were related to differences in body morphology and coloration: (i) the pectoral fins of benthic and generalist individuals were significantly longer than those of pelagic ones; and (ii) the coloration of the lower flank of benthic and generalist individuals was silver-grey while that of pelagic individuals was red. The results of this study suggest that brook charr inhabiting oligotrophic lakes of the Canadian Shield exhibit trophic polymorphisms, where some individuals are specialists better adapted to feeding in the littoral zone whereas others are specialists better adapted to feeding in the pelagic zone. The potential for reproductive isolation between the two morphs is discussed. 1997 The Fisheries Society of the British Isles 1997 The Fisheries Society of the British Isles

Ecomorphology and use of food resources: inter- and intraspecific relationships of fish fauna associated with macrophyte stands

“…The main goal of ecomorphology is to understand the response of organisms to environmental challenges, by comparing patterns of variations in morphological and ecological characters (Motta et al, 1995). Ecomorphological analysis can be used to describe patterns along niche dimensions, since the body shape provides relevant information about the use of resources by organisms (Bourke et al, 1997;Fugi et al, 2001;Pagotto et al, 2009Pagotto et al, , 2011Oliveira et al, 2010;Sampaio et al, 2013). For example: the depressed and elongated body of armored catfishes (Siluriformes: Loricariidae) permits a more efficient occupation of the bottom in lotic habitats, since this adaptation compensates the difficulties caused by the current, eliminating the effect of drag forces that tend to elevate their body .…”

Impacts des coupes forestières sur l'alimentation de l'omble de fontaine (Salvelinus fontinalis) et la structure trophique de lacs en forêt boréale /

“…On remarque cependant que tous les lacs échantillonnés, sauf un, possèdent des valeurs moyennes d'isotopes stables de carbone associées à la zone littorale. Des différences interindividuelles dans l'utilisation de l'habitat chez l'omble de fontaine permettent d'expliquer cette constatation (Bourke et al 1997). …”

“…Le meunier étant un spécialiste benthivore, il est beaucoup mieux adapté, d'un point de vue comportemental et morphologique, que l'omble de fontaine pour s'alimenter sur les proies benthiques (Magnan et FitzGerald 1984, Magnan 1988, Tremblay et Magnan 1991. La compétition avec l'omble de fontaine pour cette ressource amène un déplacement de niche écologique de ce dernier vers la zone pélagique afin de s'y alimenter de zooplancton (Bourke et al, 1997).…”

“…Conversely, fish from other lakes seemed to be associated with littoral and benthic zones. Brook trout could exhibit interindividual differences in habitat use; some are typically pelagic and others are typically benthic (Bourke et al 1997) Stable nitrogen isotope ratios-Stable isotope analyses yield a time-integrated signal of trophic position. It is however necessary to estimate nitrogen stable isotope ratio at the ecosystem baseline, which is represented by primary producers.…”

“…Brook trout coexists in many lakes with introduced species, especially the white sucker, a specialist benthivore (Scott and Crossman 1973). It has been demonstrated that brook trout shift their niche from zoobenthos to zooplankton when living in sympatry with white sucker in response to interspecific competition for resources (Magnan 1988, Bourke et al 1997, Laçasse and Magnan 1992, Magnan and Rodriguez 1994.…”