Full Description

"Suction feeding in conjunction with forward swimming, as employed by brown trout and rainbow trout, had a maximum acoustic energy in the frequency range 4–6 kHz and feeding sounds were measurable only for short periods (less than 1 s) in between two pellet distributions by hand."

"For both trout species, feeding activity starts as feed pellets hit the water surface but, within the 0–2 kHz frequency band, feeding sounds are masked by pellet impacts on the water surface (Figs. 4 and 5)."

"For brown trout, feeding sounds are clearly distinguishable from ambient noise between 2.5 and 4 kHz (Fig. 4) and between 4 and 10 kHz, the acoustic energy decreases. The signal/noise ratio reached a maximum (about 15 dB) between 4 and 7 kHz. Sonograms (Fig. 6) confirmed the rapidity of the brown trout’s reaction to distributed feed: the average duration of feeding (including feed throw) was about 1400 ms, whereas the throwing periodicity was about 1800 ms."

"However, acoustic energy produced by fish feeding also concerned higher frequencies (2–10 kHz). Within this higher frequency band, the two feeding strategies analysed (suction (turbot) and suction+ forward swimming (trout)) were easily identifiable."

"For feeding turbot, the maximum signal/noise ratio observed was between 6 and 9 kHz at 15–20 dB and was consistent with our previous results (Lagarde`re and Mallekh, 2000). The comparison between turbot and trout showed that frequency spectra were similar within the frequency band of 2–5 kHz. The 7–9 kHz frequency band seems to be characteristic of feeding turbot and, furthermore of the exclusive suction feeding mode."

Observation Environment Quotes

"Groups of rainbow trout (Oncorhynchus mykiss (Walbaum, 1792)) with a body weight of about 500–600 g (ca 1300 kg biomass) and brown trout (Salmo trutta Linnaeus, 1758) with a body weight of approximately 600–700 g (ca. 800 kg biomass) were used in this study. The fish were held in 6 m diameter circular-concrete tanks of 0.8–1 m depth, and were hand-fed with Biomar feed pellets (diameter: 6 mm; 5200 pellets/kg)."

Full Description

"Suction feeding in conjunction with forward swimming, as employed by brown trout and rainbow trout, had a maximum acoustic energy in the frequency range 4–6 kHz and feeding sounds were measurable only for short periods (less than 1 s) in between two pellet distributions by hand."

"For both trout species, feeding activity starts as feed pellets hit the water surface but, within the 0–2 kHz frequency band, feeding sounds are masked by pellet impacts on the water surface (Figs. 4 and 5)."

"For rainbow trout (Fig. 5), the frequency band in which feeding activity can be clearly distinguished was from 2 to 5 kHz and the highest signal/noise ratio recorded was between 4 and 6 kHz (15–20 dB)."

"However, acoustic energy produced by fish feeding also concerned higher frequencies (2–10 kHz). Within this higher frequency band, the two feeding strategies analysed (suction (turbot) and suction+ forward swimming (trout)) were easily identifiable."

"For feeding turbot, the maximum signal/noise ratio observed was between 6 and 9 kHz at 15–20 dB and was consistent with our previous results (Lagarde`re and Mallekh, 2000). The comparison between turbot and trout showed that frequency spectra were similar within the frequency band of 2–5 kHz. The 7–9 kHz frequency band seems to be characteristic of feeding turbot and, furthermore of the exclusive suction feeding mode."

Observation Environment Quotes

"Groups of rainbow trout (Oncorhynchus mykiss (Walbaum, 1792)) with a body weight of about 500–600 g (ca 1300 kg biomass) and brown trout (Salmo trutta Linnaeus, 1758) with a body weight of approximately 600–700 g (ca. 800 kg biomass) were used in this study. The fish were held in 6 m diameter circular-concrete tanks of 0.8–1 m depth, and were hand-fed with Biomar feed pellets (diameter: 6 mm; 5200 pellets/kg)."

Full Description

"Exclusive suction, as used by turbot, is characterised by a maximum acoustic energy in the frequency range 7–9 kHz and a sound duration of about one minute depending of time duration of pellet distribution."

"The sonogram and the narrow-band frequency spectra (Fig. 2) showed that turbot feeding noise is detected over a wide frequency band of up to 10 kHz or more. Between 3 and 9 kHz, the sound level reached 80–90 dB re 1 APa rms and the corresponding signal/noise ratio was between 15 and 20 dB."

"However, acoustic energy produced by fish feeding also concerned higher frequencies (2–10 kHz). Within this higher frequency band, the two feeding strategies analysed (suction (turbot) and suction+ forward swimming (trout)) were easily identifiable."

"For feeding turbot, the maximum signal/noise ratio observed was between 6 and 9 kHz at 15–20 dB and was consistent with our previous results (Lagarde`re and Mallekh, 2000). The comparison between turbot and trout showed that frequency spectra were similar within the frequency band of 2–5 kHz. The 7–9 kHz frequency band seems to be characteristic of feeding turbot and, furthermore of the exclusive suction feeding mode."

Observation Environment Quotes

"Groups of turbot (Scophthalmus maximus (Linnaeus, 1758)) having a body weight of about 450–550 g (ca. 1500 kg biomass) were also recorded. These fish which were reared in concrete tanks (surface area=32 m2 and depth=0.9–1 m), were hand-fed with G 7 Gouessant feed pellets (3830 pellets/kg)."