Diel Migration and Spatial Distribution of Fish in a Small Stratified Lake

Abstract

The diel migration and spatial distribution of fish were explored using six sequential 4-h sample gillnettings in the pelagic and littoral zones of Lake Verevi (Estonia, 12.6 ha, max. depth 11 m, hard-water, deoxygenated hypolimnion) in August 2001 and July 2002. Considering abundance, two-thirds of the total fish moved to the littoral zone. The biomass of fish was distributed evenly between the littoral and pelagic zones, where the topmost epilimnion accounted for 80-85% leaving 10-15% for the lower epilimnion in the pelagic zone. Just above the thermocline only some large specimens of perch Perca fluviatilis (L.) and roach Rutilus rutilus (L.) (1-5%) during the daytime were captured. No fish movements were recorded under the thermocline. Rudd Scardinius erythrophtalmus (L.) inhabited only the littoral zone; all the other species were captured in both zones. Juvenile perch stayed in the littoral zone, whereas juvenile roach was caught in both zones and was active over a 24-h period. Piscivores, perch and pike Esox lucius L., were inactive in the dark. Perch inhabited mostly the littoral zone and the duration of its activity increased with age. In summer-stratified Lake Verevi, sharp change in the values of oxygen in the metalimnion along with species interaction affected the spatial distribution of fish, while diel migration was light-dependent.

Pelagic underyearling communities in a canyon-shaped reservoir in late summer

“…In artificially destratified, deep reservoirs fish inhabited the whole volume (Prchalová et al 2006). In the sharply stratified Římov Reservoir the highest fry density was usually observed in the surface layer as has also been observed for adult fish in other stratified lakes and reservoirs Järvalt et al 2005;Kahl & Radke 2006;Prchalová et al 2008).…”

“…Sharp gradients in the oxygen content, food availability and temperature in the metalimnion determine the vertical distribution of fish in lakes (Järvalt et al 2005). In artificially destratified, deep reservoirs fish inhabited the whole volume (Prchalová et al 2006).…”

“…Cyprinids strongly dominated in the surface stratum (0-3 m depth) whereas percids dominated catches around the thermocline (3-6 m depth). Perch usually prefer clean-water lakes (Järvalt et al 2005), while cyprinids, including roach, are known to thrive under more eutrophic and turbid conditions (Jeppesen et al 2000). This could be an explanation for the dominance of roach and other cyprinid fish in the turbid and more eutrophic upper area of Římov Reservoir, whereas percid fish prefer the less eutrophic middle area of the reservoir.…”

Hydroacoustic estimates of fish stocks in temperate reservoirs: day or night surveys?

“…Fish species in manmade reservoirs have rarely been observed below the thermocline during summer thermal stratification (Kubečka and Wittingerová 1998;Matthews et al 2004;Vašek et al 2004;Järvalt et al 2005), except for larval and juvenile perch (Čech et al 2005). Diel vertical migration was not observed at the studied reservoirs, most likely because strict temperature and oxygen stratification of the water column prevent fish from swimming to deeper layers.…”

Opposing diel migration of fish and zooplankton in the littoral zone of a large lake

“…Not only zooplankton but also fish as their main predators are looking for the same compromise between feeding and predatory pressure and were observed to perform diel migration (Wang & Eckmann, 1994;Imbrock et al, 1996;Järvalt et al, 2005). In juvenile fish, in particular, this diurnal migration can be superimposed on a longer-term ontogenetic habitat shift.…”