Size‐dependent microhabitat use and intraspecific competition in Cottus gobio

Abstract

An electrofishing survey of daytime shelter microhabitat use of bullhead Cottus gobio in a southern English chalk stream revealed positive selection for moderate water velocity, vegetation cover and coarse substrata. Water depth, other forms of cover, shade and substratum embeddedness had no significant influence on the distribution of fish. Microhabitat use was size-dependent, with patches occupied by adult fish containing coarser substrata and less blanket weed (Cladophora algae) than those occupied by smaller juvenile conspecifics. Differences in substratum use between size-classes were less pronounced in parts of the stream shaded by the tree canopy. In laboratory tanks stocked at low fish density, both juveniles and adults favoured use of cobbles over pebbles. The response of fish to increased conspecific density was size-dependent; juveniles reduced use of the coarse substratum whereas adults maintained their predominance in this habitat. An apparently greater shift by juveniles when in the presence of adults was significant at a ¼ 0Á10 only, as was an apparent reduction in interactions between size-classes under low light intensity. The displacement of small juvenile fish from the preferred cobble substratum is consistent with the hypothesis that intraspecific competition contributes to the size-related microhabitat shift observed in the field. Although there was a tendency for the strength of competition to be reduced at low light levels, the mechanism by which tree canopy cover affects microhabitat use remains uncertain. # 2005 The Fisheries Society of the British Isles

Home range and habitat use of translocated endangered species,Cottus koreanus, in South Korea

“…In general, when selecting habitat, large individuals are stronger competitors than small individuals. Thus, large individuals may have priority to select suitable habitats close to the release site, while small individuals are forced to move further (Davey et al 2005). No such pattern was found in the present study.…”

Can the presence of alien Ponto–Caspian gobies affect shelter use by the native European bullhead?

“…However, it was not possible to determine the sex of the specimens in autumn when sexual dimorphism of the bullhead disappeared (Kobler et al 2012), and we were not allowed to dissect the used fish due to their protected status in Poland. Nevertheless, in autumn, which is the post-spawning period for bullheads (Mills and Mann 1983;Davey et al 2005) as well as for gobies (Pinchuk et al 2003), both sexes will use shelters similarly, for protection against unsuitable environmental conditions and display similar levels of aggression as it was demonstrated by Kobler et al (2011). Therefore, we conducted the autumn treatments without determining sex in bullhead.…”

“…Thus, optimal shelter could be potentially a limited resource especially for species displaying similar territorial and aggressive behaviour, such as bullheads and gobies (Mills and Mann 1983;Davey et al 2009;Grabowska et al 2016), and when species density is high. Bullheads exhibit strong interference competition for a shelter and aggressive interactions between them outside shelters are common (Ladich 1989;Davey et al 2005). This competition increases during the spawning season when a suitable shelter becomes also a nesting place.…”

“…This competition increases during the spawning season when a suitable shelter becomes also a nesting place. Larger males monopolize larger territories than smaller individuals, and even if a sufficient number of nesting places is provided, the dominants (larger males) prevent the smaller males approaching them through aggressive behaviour (Natsumeda 2001;Davey et al 2005;Natsumeda et al 2012). Gobies typically exhibit such territorial and aggressive behaviour (Miller 1984).…”

Selección denso-dependiente de microhabitat en Galaxias platei: un estudio experimental

“…La selección de hábitat, mediada por factores de densidad poblacional y disponibilidad de hábitats, ha sido evaluada preferentemente en peces de interés comercial ya que ello ha permitido defi nir las densidades para distintos sistemas acuáticos (Rangeley & Kramer 1998;Armstrong & Griffi ths 2001;Griffi ths & Armstrong 2002;Davey et al 2005Davey et al , 2009Uglem et al 2009;Camp et al 2011). En otros casos se han realizado estudios de selección de hábitats denso-dependiente orientados a comprender las relaciones interespecífi cas entre especies invasoras y especies nativas, como es el caso de salmónidos y galáxidos en Nueva Zelanda (McIntosh et al 1994;Townsend 2003;Bonnett & McIntosh 2004;McDowall 2006;Crow et al 2010).…”