1,720,973 research outputs found
Effects of electro-fishing on galvano-taxis and carcass quality characteristics in sea bass (Dicentrarchus labrax)
No full textWe evaluated the feasibility of an electro-fishing system using numerical simulations for laboratory tanks
and the open sea. A non-homogeneous bi-dimensional electric-field model for water and fish based on discrete
formulation of electro-magnetic field equations was developed using GAME (geometric approach for
Maxwell equations) software. Current densities (μA/cm2) and voltage differences (V/m) were calculated
for a fixed shape and spatial geometry of electrodes (one circular anode central to two symmetric linear
cathodes 10 m distant from each other). Voltage gradients inside the fish and close to the body (head–tail
potential difference and mean, maximum and minimum field modules) were determined. Tank and open
sea environments were numerically described for single fish 10 cm or 30 cm long and for groups of 30
fish 10 cm long. In the open sea, a tension of 90 V at the electrodes and a water conductibility of 5 S/m
resulted in an area of fish attraction (voltage gradient >10 V/m) of about 30 m2. Fish in the open sea and
in groups had greater internal voltage differences than did fish in tanks and single fish
Quality changes of culrtured sea bass (Dicentrarchus labrax) after an electro-fishing treatment
No full textNumerical simulation of electro-fishing in seawater
No full textWe evaluated the feasibility of an electro-fishing system using numerical simulations for laboratory tanks and the open sea. A non-homogeneous bi-dimensional electric-field model for water and fish based on discrete formulation of electro-magnetic field equations was developed using GAME (geometric approach for Maxwell equations) software. Current densities (μA/cm2) and voltage differences (V/m) were calculated for a fixed shape and spatial geometry of electrodes (one circular anode central to two symmetric linear cathodes 10 m distant from each other). Voltage gradients inside the fish and close to the body (head–tail potential difference and mean, maximum and minimum field modules) were determined. Tank and open sea environments were numerically described for single fish 10 cm or 30 cm long and for groups of 30 fish 10 cm long. In the open sea, a tension of 90 V at the electrodes and a water conductibility of 5 S/m resulted in an area of fish attraction (voltage gradient >10 V/m) of about 30 m2. Fish in the open sea and in groups had greater internal voltage differences than did fish in tanks and single fish
New species for freshwater aquaculture: preliminary results on small cyprinids rearing.
No full textItalian freshwater fish farming is dominated by the production of salmonids, in particular rainbow trout. During the last decade trout production in Italy declined steadily for various reasons and trout farmers might be interested in the domestication of new species. Diversification is well studied for Mediterranean marine fish farming but not yet for freshwater one. In this scenario, it may be possible to establish new cold water adapted species for a niche market. The key aspects to be considered for introduction of new species are economical (production costs and market demand) and biological (easy adaptation to rearing conditions, endemic species, etc.).
Vairone Telestes muticellus (Bonaparte 1837) and bleak Alburnus alburnus alborella (De Filippi 1844) are two small cyprinids that seem to be potential candidates for diversification in North Italian fish farms. Their feeding and social habits, being not strictly predators and showing strong gregariousness, can facilitate the adaptation to captive rearing and domestication processes, too. Moreover, they are reophilic, moderately cold freshwater fish and autochthonous in the Po valley basin. Market potentials may be both consumption as food and as live bait for anglers.
The aim of this study was a preliminary evaluation of the adaptability of vairone and bleak to captive rearing conditions and to an artificial diet.
After two months of adaptation to experimental conditions, 95 specimens of vairone and 39 bleaks (mean body weight 0.52 g and 0.63 g, respectively) caught from the wild were stabulated in two 1m x 1m, 150 l tanks, supplied with well water (Temperature: 11.5±2.0°C; Dissolved oxygen: 10.8±0.5 mg/l; pH: 8.04±0.12; TAN: 0.02±0.01 mg/l; NO2: <0.02 mg/l)
A practical diet was formulated for both species according to carp nutrient requirements (dry matter 93.6%, crude protein 38.5%, crude lipid 12.0%, crude fiber 0.3%, ash 7.4%). To make the feed suitable to all fish sizes, the dry pellets were crumbled and sieved in particles size range of 0.5-2.0 mm. Experimental diet was offered in a single daily meal to apparent satiety.
Both fish species showed good adaptation to captive conditions over 91 days of rearing. Observed mortality was low for a wild species kept in captivity (5.3% for vairones and 7.7% for bleaks). The artificial diet was well accepted by both species and the final mean weight was 0.57g for vairone and 0.73 g for bleak (weigh gain 11.9% for both species).
Preliminary results point out a positive reaction to captivity and good tolerance to artificial diet. The observed performance stimulates further investigations on specific diets and rearing conditions in order to achieve optimal growth
Comportamento di marcatura in cattività della lince eurasiatica (Lynx lynx) dopo stimolazione ed implicazioni sul monitoraggio in natura.
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