Masaló Llorà, Ingrid

Oca Baradad, Joan

Reig Puig, Lourdes

English

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460ACOUSTIC DOPPLER VELOCIMETRY ALLOWS DETERMINING DAILY SWIMMING ACTIVITY OF SEA BASS Dicentrarchus labrax L. Joan Oca*, Ingrid Masalo and Lourdes Reig  Departament d’Enginyeria Agroalimentària i Biotecnologia Universitat Politècnica de Catalunya  Urgell 187 08036 Barcelona, Spain joan.oca@upc.esAcoustic Doppler Velocimeter (ADV) has been used for the measurement of turbulence produced by ﬁsh swimming activity (Masaló et al, 2004) supplying a quantitative measure, which can be related with both environmental conditions and daily behaviour. The knowledge of ﬁsh activity is an important tool, not only for the study of ﬁsh behaviour but also to assess its inﬂuence in the homogeneity of water quality and in the sediment dynamics into the tank. Traditionally, behavioural studies of activity in ﬁshes have been developed using video-tracking methods, ultrasonic pressure transmitters, infrared sensors or through indirect measures as oxygen consumption. The present study was conducted in an on-growing farm and tries to determine the daily swimming activity of European Sea Bass (Dicentrarchus labrax, L.), using ADV.Experiments were made in a 46 m3 tank, with octagonal shape, 167 cm of water depth and circular ﬂow pattern. The body weight of ﬁsh averaged 48 g and growing density was 35.5 kg m-3. Measurement of velocity was made at a 95 cm depth point, for a period of 40 h, registering 20 seconds every 5 minutes with a 25 Hz frequency. Water salinity and temperature were 15 ‰ and 15 ºC respectively, and ﬁsh were exposed to an artiﬁcial photoperiod (8:00 to 23:30 hours lighting). During the experiment, ﬁsh weren’t fed.Data processing was made, according to Masaló et al (2004), applying three ﬁlters: COR (>70), SNR (>5) and Phase-space threshold despiking ﬁlter. The Root Mean Square (RMS) of velocities, in every axis and in velocity magnitude, was the parameter used to measure ﬂow turbulence, which is mainly due to ﬁsh swimming activity.The results obtained showed an increase of turbulence in the measurement point during the light period, which can be related with an increase in ﬁsh activity (Figure 1). RMS averages of light and dark periods are presented in table 1. Accordingly, ADV seems to be a reliable tool to detect changes in ﬁsh activity. FIGURE 1: Evolution of RMS-magnitude during the experiment. Dark horizontal bars represent the dark-period.TABLE 1: RMS average of light and dark period during the experiment. 

Acoustic doppler velocimetry allows determining daily swimming activity of sea bass (dicentrarchus labrax, I)

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Acoustic doppler velocimetry allows determining daily swimming activity of sea bass (dicentrarchus labrax, I)

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