Already in the 19th century Sabaneev (1960) reported that piscivorous visually guided zanders, Stizostedion lucioperca, which eat only live food can nonetheless be caught on dead fish cut into stripes with the skin and silver scale. Like other visually guided predatory fish, namely pike, Esox lucius, and perch, Perca fluviatilis, zanders never eat decaying fish. According to the modern knowledge, zanders could respond in addition to visual cues to alarm pheromone that released in the water from the injured skin of fish or from dead fish without injuring their skin (Malyukina et al., 1980).

Indeed, dead fish in trolling and other rigs may be used to fish big pike and zander (Sabaneev, 1960).

In the undirect winter experiments carried out in the USA by Wisenden & Thiel (2001), predatory fish active in cold season such as pike, E. lucius, walleye, S. vitreum, largemouth bass, Micropterus salmoides, and yellow perch, P. flavescens, colud be attracted by the skin extract of fathead minnow, Pimephales promelas (Cyprinidae).

In the direct field experiments (Dnipro river in Ukraine, in June) described below, we found that S. lucioperca could be attracted by alarm pheromone of roach, Rutilus ruitlus.

Chemical stimulus of one type was prepared by squashing 30 g of roach skin together with the scale in the rough clay mortar and diluted with the 0,3 liter of river water, without further filtration. Chemical stimulus of another type was prepared of 30 g of roach flesh without skin in the foregoing way (according to Malyukina et al., 1980, standard extract of fish skin contains 1g of skin per 1 liter of water).

To compare both chemical stimuli, artificial soft lures made of high quality white foam rubber were used. Lures were in the form of stripes (0,5 x 0,5 x 5,0 cm) attached at one end to the single hooks (VMC live bait hooks #1/0, short shank). For more buoyancy, one white styrofoam olive was dressed similar to sabiki on the line leader in front of each lure.

In the field, two units of the typical feeder rods with reels, main lines, simple sinkers and two line leaders, 30 and 40 cm length, with the attached lures were used. In one rig, lures attached to 30 and 40 cm leaders was soaked with the skin and flesh extracts, respectively, vice versa in another rig.

Lures of both types were compared in the typical zander location with the depth of 2,0- 2,5 m at the distance of 15-20 meters from the shore, with the middle flow. Tests were carried out during two nights from 10⁰⁰ of evening until 12⁰⁰ of midnight, skin and flesh extracts in rubber bodies of lures were resoaked every thirty minutes.

In total, within two nights 21 bites were obtained. Potential predators, in addition to zander, were large individuals of chub, Leuciscus cephalus, ide, L. idus, and wels catfish, Silurus glanis, all with the nocturnal type of feeding activity. Among potential predators, 9 individuals of zander (from 0,8 to 1,2 kg) were caugh, all for lures soaked with the skin extract (sign test, n = 9, z = 9, p < 0,01). Also, single 3 kg wels was caught for the same lure.

These data show the preference of zanders to alarm pheromone of cyprinid fish. According to Valentinčič (2004), for wild zanders an odor of the fish flech extract must be indifferent.

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Perch

Freshwater percid (Percidae) fish can be divided into the two groups depending on type of their activity and sensory equipment. European perch, Perca fluviatilis, American yellow perch, Perca flavescens, and numerous American darters (Etheostoma) demonstrate the day type of activity (first of all of the feeding activity), are visually guided fish and, thus, may be included in the first group.

In laboratory and natural conditions, both perches usually do not eat immobile as well as dead food and demonstrate relatively weak responses to food odors or their absence. According to Mirza et al. (2003), an aqueous brine shrimp (Artemia spp.) extract (5 g of frozen shrimp in 150 ml of distilled water for 1 hour) induces searching movements in P. flavescens. Both perches, however, do not go practically into the minnow traps baited with the animal lures (in contrast to cyprinid, cobitid and other fish).

In aquarium, blinded P. fluviatilis may find the pieces of earthworms using olfactory and gustatory systems (Wunder, 1927). But convergence of perch with brown trout, Salmo trutta, on sensory system utilization is incorrect.

Skin of percid fish contains alarm pheromone that is documented in yellow perch P. flevescens, common ruffe Gymnochephalus cernuus and other species. Releasing in the water, this pheromone induces in small (planktivorous) perch an avoidance behaviour, whereas large (piscivorous) perch display feeding behaviour (Mirza et al., 2003; Harvey & Brown, 2004).

Zander

Another group is formed by percids with the twilight or nocturnal type of feeding activity with the morphologically developed chemosensory and lateral line systems. Three Europen zanders or pikeperches, Stizostedion lucioperca , S. volgensis and estuarine pikeperch S. marinus, both North American zanders, walleye S. vitreus and sauger S. canadensis, all species of Gymnocephalus genus (such as common ruffe G. cernuus, Donets ruffe G. acerina, striped ruffe G. schraetser and other), all species of Zingel genus (such as Z. zingel, Z. streber, Z. balcanicus and other) and sculpin-perch Romanichthys valsanicola (single species of Romanichthys genus) belong to this group. Three last genera are represented in temperate Europe, except common ruffes which occupy mainly boreal areas around the world being active intruders in America.

Underyearling walleyes are mainly visually guided fish with the olfactory system that can detect individual chemicals and artificial food odors (Rottiers & Lemm, 1985). In particular, fish are attracted by amino acids (arginine), betaine, washings from live Daphnia and Artemia but reject many other chemicals (cysteine, glycine, glycine-betaine).

According to Valentinčič (2004), walleyes and some other fish occupy an exclusive niche of visually guided predators with the secondary role of chemosensory system in feeding behaviour. Electrophysiological dara indicate that olfactory system of walleyes is broadly tuned while gustatory system of them is tuned very narrowly. On the other hand, behaviuoral data for wild walleyes show that over 90 % of fish do not use chemical senses to release feeding excitatory state. In addition, walleyes which are not conditioned to eat nonliving foods during their early life do not use olfactory and taste systems to control feeding bahaviour (Valentinčič, 2004).

The olfactory sensitivity of nocturnal percid fish to foo ... Read more »