Hydroacoustic measurements at two frequencies: 70 and 120kHz – consequences for fish stock estimation

Fish density and target strength distribution of single fish echoes in varying light conditions with single and split beam echosounding and trawling

“…This resulted in a good compatibility in TSdistribution comparison between single and split beam devices of differing frequencies. The result is in line with Rudstam et al (1999), who found the differences between single and split beam echo sounders of the same frequency to be small, and Godlewska et al (2009), who found that 70 and 120 kHz split beam transducers gave similar estimates of fish TSdistribution.…”

“…Its technique evolved from single to dual and split beam transducers along with the increase in data processing capacity. The dual beam turned out to be an intermediate technique, and during the last 15 years split beam echosounding has been almost a standard in acoustic fish studies (e.g., Rudstam et al, 1999;Godlewska et al, 2009). In spite of some imprecision in acoustic surveys (e.g., the European Standard, 2013), establishing the relevance of time series in these studies is an important task in fisheries research.…”

Can pelagic forage fish and spawning cisco (Coregonus artedi) biomass in the western arm of Lake Superior be assessed with a single summer survey?

“…The vast majority of the November acoustic data were gathered with the 70 kHz system, except along transect 4 where a second 70 kHz split-beam transducer with a 5.3 • cone was employed. Studies comparing fish densities measured with these two frequencies have generally shown good agreement (Rudstam et al, 1999;Mason and Schaner, 2001;Guillard et al, 2004;Godlewska et al, 2009). Periodic field calibrations with tungsten carbide standard spheres (Foote et al, 1987) showed that the three echosounders provided high quality data throughout the study.…”

Hydroacoustics as a relevant tool to monitor fish dynamics in large estuaries

“…Building on previous recommendations made by Samedy et al (2013) this study also brought up a range of technical and methodological issues relating to sampling methods and estuarine fish dynamics. Firstly, while hydroacoustics is effective in estimating biomass and fish size, we still used ABC and TS metrics as density and size proxies, in order to avoid any uncertainty stemming from conversion methods to fish weight or fish length (Rose et al, 2000;Godlewska et al, 2009). The most of fishing techniques mainly provide information on the composition and size of fish (Godø, 1998) and have been widely used in fish monitoring over the last few decades due to their versatility.…”

“…Although we collected data at both 70 and 120 kHz, we used only the results of the latter, since this frequency would appear to be the most commonly used in the literature (MacLennan et al, 2002;Guillard et al, 2004;Jech and Michaels, 2007;Godlewska et al, 2009). …”