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

Microsmatic fish are represented by numerous freshwater and marine species in which the well developed visual system provides most of the behavioural responses in comparison with the less developed chemosensory system. Visually guided diurnal or twilight predators as well as visually guided bentivorous and planktivorous species form this group of fish. The chemosensory system of microsmatic fish is active in providing their reproductive behaviour, social behaviour, spatial migration, partially anti-predator behaviour and is weak or indifferent in providing feeding responses.

Here, we consider esociform fish.

Esocidae

5 species: Esox americanus, E. lucius, E. masquinongy, E. niger, E. reicherti

Fresh waters of boreal Eurasia and Northern America

Northern pike, E. lucius, and other representatives of Esox genus, including Amur pike, E. reicherti, and some North American species, are apexpredators with the well developed vision and lateral line system.

According to data received by Devitsyna & Malyukina (1977) in the electrophysiological experiments, the olfactory system of pike, E. lucius, responds only to conspecific sexual pheromones (gonad extracts), but does not respond to conspecific odors, pure water and feeding substances like fish blood or tissue extracts. In feeding behaviour, musky, E. masquinongy, use vision and seismosensory system (New et al., 2001).

Pike larvae decrease the frequency of their attacks on zooplankters and show other anti-predator responses to chemical cues of Eurasian perch, Perca fluviatilis (Lehtiniemi, 2005; Lehtiniemi et al., 2005). It is also shown that pike are attracted by alarm pheromone of fathead minnow, Pimephales promelas (Mathis et al., 1995; Chivers et al., 1996; indirect data by Wisenden & Thiel, 2001).

Dalliidae

3 species: Dallia admirabilis, D. delicatissima, D. pectoralis

Fresh waters of Bering Sea basin

Blackfish primarily feed on crustacens (ostracods, cladocerans, copepods) and insect larvae (ephemeropterans, hemipterans, dipterans, odonates), with the occasional cannibalism and consumption of juvenile pike, E. lucius (Chlupach 1975).

However, leading sensory systems in feeding and reproductive behaviours of blackfish are unknown.

In winter with the oxygen lack, blackfish concentrate in the vicinity of holes in the ice, being easy to capture with the simple funnel-shaped traps made from strips of tamarack or spruce (Andersen et al., 2004). In spring and fall, blackfish are also easily caught while migrating to and from their summer habitats by placing the traps in narrow channels, it is appear these traps are not baited.

Umbridae

4 species: Novumbra hubbsi and Umbra krameri, U. limi, U. pygmaea

Fresh waters of Europe and Northern America

According to rare observations, feeding behaviour of mudminnows is rather provided by vision. For example, European mudminnow, U. krameri, eat in an aquarium only living and moving invertebrates such as cladocerans, copepods, Chaoborus larvae, chironomid larvae, culicid larvae, mayflay larvae, Acellus aquaticus and tubificid worms (Kováč, 1997). Cannibalism and hunting on juvenile fish in the nature are occasionally observed. However, Glasgow & Hallock (2009) report that Olimpic mudminnows, Novumbra hubbsi, are caught by the minnow traps baited with the chironomid larvae baits (15 g of chironomid larvae per one funnel-shaped trap). So, the problem of sensory providing of feeding behaviour in mudminnows is currently unclear.

On the other hand, chemical cues may play an important role in social and anti-predator behaviours of mudminnows. Indeed, central mudminnows, U. limi, demonstrate anti-predator behaviour in response to conspecific chemical alarm cues (Wisenden et al., 2007). Yet, mudminnows display comlex reproductive behaviour, from territory guarding to parental care (Hagen et al., 1972; Bohlen, 1995; Kováč, 199 ... Read more »