Hydroacoustic evaluation of the spatial and temporal distribution of fish in the upstream proximity of a dam in a Neotropical reservoir

Abstract

evaluation of the spatial and temporal distribution of fish in the upstream proximity of a dam in a Neotropical reservoir.

Repeatability of Hydroacoustic Results versus Uncertainty in Assessing Changes in Ecological Status Based on Fish: A Case Study of Lake Widryńskie (Poland)

“…The differences between the pelagic fish biomass assessed by the hydroacoustic method during the day and at night may be even more than five times higher (e.g., 62 and 11 kg/ha in Lake Sauka in Latvia) [15]. Hydroacoustic data also show that smaller fish can gather at shallower depths [13]. Clear seasonal differences in habitat use by different fish species have also been observed [16] and population estimates in spring may even be several times higher than ones in summer (e.g., 4.0-8.5 larger in Crystal Lake in Vilas County, Wisconsin) [17].…”

“…However, with typical eutrophic ecosystems, fish densities (>600 fish ha −1 ) in temperate lakes may be significantly lower for 200 kHz systems [12]. Moreover, at night fish usually disperse in the water column, which allows the detection of a single echo and accurate estimation of fish size [13,14]. The differences between the pelagic fish biomass assessed by the hydroacoustic method during the day and at night may be even more than five times higher (e.g., 62 and 11 kg/ha in Lake Sauka in Latvia) [15].…”