It is generally known that fermentation of cereal brans improves their numtrient value, in particular through increasing protein content (e.g., Hassan et al., 2008; Silveira & Badiale-Furlong, 2009). In the field experiments described below, we have tested the attractiveness of fermented and unfermented white brans for cyprinid fish.

Wheat bran for human consumption was fermented with 0,2 % of dry baker yeast (Saccharomyces cerevisiae). Fermentation of moistured bran was carried out at 25^o C within 2 days in plastic bags with the leaking lids.

Moist fermented and moistured unfermented brans were mixed with the pure dry grey clay in proportion 1:1 or 1:2, depending on the clay quality. Both mixes were rolled into the balls (3 cm diameter) and dried in air within 12 hours. Then dry balls (that had practically the same color) were strung on the lines ended by the small button like stoppers, with marks to distinguish them.

In the field, lines with the two compared balls were tied (25 cm between centers of the balls) to the cross bar placed above the water with the help of two racks. Narrow channels (40-50 cm width) in the shallows between macrophytes (usually water lily, Nuphar lutea, and pondweeds Potamogeton spp.) were selected. Balls went down to the depth of about 5 cm, to attract roach and other top dwelling fish, or about 30 cm, to attract crucian and other bottom dwelling fish.

In the surface tests, mainly juvenile roach, Rutilus rutilus, rudd, Scardinius erythropthalmus, as well as juvenile and adult river bleak, Alburnus alburnus, were attracted. In lentic waters, lake bleak, Leucaspius delineatus, occured instead of river bleak. In the bottom tests, mainly juvenile crucian, Carassius carassius, tench, Tinca tinca, as well as juvenile and adult bitterling, Rhodeus amarus, (in areas with the sandy bottom) were attracted.

After immersion into the water, clay balls with fermented and unfermented wheat brans were beginning to crumble with bran particles and attract fish. The fish were biting and destroying the balls. So, the first touch of fish to one of the balls and the destruction of the most attractive ball first were used as criteria for statistical estimations.

The following results were obtained in the first session. Fish first touched 12 balls with the fermented wheat bran versus 3 balls with unfermented bran of 15 pairs of both kind balls offered (sign test, n = 15, z (+) =12, p < 0,05). Similarly, fish first destroyed 13 balls with the fermented bran (sign test, n = 15, z (+) =13, p < 0,01) showing in this way the attractiveness (both olfactory and gustatory) of fermented bran. The same preferences were observed in other four sessions.

Basic References

Hassan E.G., Award Alkareem A.M., Mustafa A.M.I. 2008. Effect of fermentation and particle size of wheat bran on the antinutritional factors and bread quality. Pakistan Journal of Nutrition 7, 521-526

Silveira C.M., Badiale-Furlong E. 2009. Sperathe effects of solid-state fermentation in the functional properties of defatted rice bran and wheat bran. Brazilian Archives of Boilogy and Technology 52, 1555-1562