Determination of physical behaviour of feed pellets in Mediterranean water

Type Article
Date 2006-02
Language English
Author(s) Vassallo P1, Doglioli Andrea2, 3, 4, Rinaldi F2, Beiso I1
Affiliation(s) 1 : Univ Genoa, DIPTERIS, Dept Study Terr & Its Resources, Genoa, Italy.
2 : Univ Genoa, Dept Phys, DIFI, Genoa, Italy.
3 : UFR Sci & Tech, Lab Phys Oceans, CNRS, UMR 6523,IFREMER,UBO, F-29238 Brest 3, France.
Source Aquaculture Research (1355-557X) (Blackwell science), 2006-02 , Vol. 37 , N. 2 , P. 119-126
DOI 10.1111/j.1365-2109.2005.01403.x
WOS© Times Cited 18
Keyword(s) Waste dispersion, Mediterranean, Feed pellets, Water adsorption, Floating time, Settling velocity
Abstract Settled uneaten feed causes the most intense impact under sea cages, and settling velocity of the feed pellets represents a key parameter for waste dispersion models. Even if some data about physical properties of feed pellets have been published in the framework of salmonid rearing, there is a complete lack of information related to the Mediterranean Sea, as regards typical values of temperature, salinity and feed composition for Gilthead Sea Bream (Sparus aurata L.) and Sea Bass (Dicentrarchus labrax L.). In this study we try to fill this lack, determining dimensions, water adsorption properties, floating times and settling velocities of a typical growing sequence of pellets for the species mentioned above, under defined laboratory conditions reproducing Mediterranean Sea water. The settling velocity increases with pellet size from 0.087, for the smallest pellet (3 mm), to 0.144 m s(-1), for the 5 mm pellet. The biggest extruded pellet (6 mm) falls slower (0.088 m s(-1)). The floating time before pellet's fall is found to be a critical parameter in determining settling velocity. The latter depends on pellet's size, water temperature and salinity. The examined pellets reach a 42% of weight increase after 10 min of immersion, while no appreciable dimension change is observed. Our results are in part different from previous ones and could play a role in evaluating and modelling Mediterranean aquaculture environmental impact.
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