Fish Roach (Rutilus rutilus; Linnaeus, 1758) are

Fish have adapted to differnt aquatic
habitats, which extend from freshwater to marine water, from cold polar seas to
warm tropical reefs, and from shallow surface waters to the deebest ocean
waters. Unsurprisingly,  fishes represent
the most variable and largest vertebrate group including currently about 33000  species (; {{175 Powers,D.A. 1989}}Powers, 1989; Axelsson et
al., 1992; Johnston et al., 1994). With the exception of about 30 partially endothermic
species, all fishes are ectotherms, i.e. their body temperature is dependent on
and in equilibrium with ambient water temperature (Dickson and Graham, 2004). Adaptation
of fishes to temperature involve different life styles. Some fishes are active
in winter and relatively inactive in summer (e.g. burbot, Lota lota) (Edsall
et al., 1993; Carl et al., 1995; Pääkkönen and Marjomäki, 2000), others are
active in summer and dormant in winter (e.g. crucian carp, Carassius carassuis)
(Holopainen et al., 1997), and still others are active all over the year (e.g. rainbow
trout, Oncorhynchus mykiss).

According to
the upper thermal tolerance limit, fishes can be classified into 3 groups:
stenothermal, mesothermal and eurythermal. Stenothermal fish tolerate only
narrow range of temperatures like the fishes of the Southern Ocean, which live
under the constant cold and maximally tolerate temperature changes of about 10
degrees (Verde et al., 2006; Franklin et al., 2007). The most eurythermal
fishes are able to tolerate temperatures changes between 0°C to 40°C (Bennett and Beitinger, 1997; Rantin et al., 1998; Beitinger and
Bennett, 2000). Salmonid fishes are sometoimes called mesothermal, since their
thermal tolerance range (from 0°C to
22-28°C) is between
those of most stenothermal and most eurythermal fish species (Elliott and
Elliott, 2010).

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Roach (Rutilus rutilus; Linnaeus, 1758) are
cyprinid fishes, which inhabit fresh and brackish waters in most of Europe except
the Mediterranean zone and western Asia. In Finland, roach are the most widely distributed
fish after perch (Perca fluviatilis)
and pike (Esox lucius). They inhabit  freshwaters throughout the country with the
exception of northernmost Lapland. Roach favour eutrophic water bodies and their
numbers have risen with increasing nutrient levels of lakes (
Therefore, roach play an important role in the energy flow and nutrient cycling
of a eutrophic lake (Riemann et al., 1986). Roach are eurythermal fishes tolerating
a wide range of temperatures from the lower critical temperature of 0.5? to the
ultimate upper lethal temperature of 33.5°C  (Cocking, 1959).