The appearance of artificial, seminatural and modified natural fishing baits can be dismatched with their taste. In the laboratory experiments described below, we have tested the responses of model fish to baits of this kind.

Juvenile induviduals of wild common roach, Rutilus rutilus, tench, Tinca tinca, crucian, Carassius carassius, and home goldfish, Carassus auratus, of about 5,0-5,5 cm standard length, were used in the experiments. Each fish were trained individually to eat seminatural sideswimmers, Gammarus lacustris, of calibrated 6,0-6,1 mm length, within 10 days in order to form an acquired search image, visual and gustatory, in respect of this food. Then modified sideswimmers, with the taste of white worms, Enchytraeus albidus, earthworms, Lumbricus terrestris, molluscs, Unio pictorum, and grey meat-fly larvae, Sarcophaga carnaria, were offered for comparison.

Seminatural sideswimmers were prepared of natural amphipods by soaking them in pure alcohol, within 12 hours, and subsequent rinsing in pure flowing water, within 2 hours. Then soaking prey were placed into the mess of crushed natural amphipods for 12 hours, to return them the (semi)natural taste. In other four cases, soaking amphipods were gustificated for the same 12 hours in the mess of white worms, earthworms, molluscs and grey meat-fly larvae, respectively.

Note, seminatural and modified amphipods had the same pale color.

Fish were trained to eat seminatural amphipods which were offered one by one through the transparent glass tube in the aquarium cover. Fish noticed the sinking amphipod and fell behind it. When the sinking amphipod appeared out of the tube, fish grabbed it, tested some time, spitting and grabbing, and ate or ignored.

After 10 day training, fish usually ate each seminatural amphipod immediately, without test spittings, or after no more than 1-2 spittings. However, when an amphipod with an unfamiliar taste was offered, this picture changed. The number of spittings increased dramatically, up to 12-16 and more during the first familiarization. Fish mostly rejected an unusual amphipod, then returned to it to test again and so on. In general, about 10 days of training were needed in order to return the number of test spittings to the minimum, that is to 0-2 spittings.

No differences were observed between natural amphipods and amphipods with the restored taste.

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Earthworms, Eisenia foetida, are widely used as an accessible bait for many fish. Fishing practice shows, however, that these worms are not as attractive to fish as it is commonly believed.

The scientific term foetida references the well known fact that these worms use the yelowish stinky secretion for self-defense. If the worms are handled roughly, they emit an unpleasure odor designed to drive away predators. This stinky secretion can also be used to distinguish E. foetida from some close relative worms that look in the similar ways.

In addition, there are problems with the palatability and nutritive value of these worms as food for fish in aquaculture in comparison with other earthworm species (Stafford & Tacon, 1985; Reinecke et al., 1991; Ortega et al., 1996; Kostecka & Pączka, 2006). The aim of the foregoing research was to find the strong arguments advocating an idea to use these worms as an available protein source to fish.

Fishing Practice

In the field experiments, we compared the attractivities of an odor of squashed live earthworms, E. foetida, that may be unfamiliar food to fish, and an odor of natural food. Spined loach, Cobitis taenia, were selected as an model fish due to their abundance in the research area, small size (usable for minnow traps) and the night type of feeding activity (Robotman, 1977; Marszał et al., 2003). Squashed live bloodworms, Chironomus plumosus, were used in the capacity of food that is closer to the natural diets of spined loach in the different habitats than terrestrial earthworms.

Spined loach, Cobitis taenia (powered by Lubomir Hlasek)

Experiments were carried out in the upper part of Kaniv’s reservoir, below Kyiv, in the summer season.

Fish were caught in the narrow ducts of 20-40 cm depth with the slightly muddy sandy bottom and few macrophytes like pondweeds. Because spined loach were small (4-6 cm), that is mean length for this species, simple minnow traps made of 6 liters transparent plastic bottles were used. When setting at the bottom, the necks of the traps were located at the distance of 20 cm from each other and submerged by half into the sand. After final trap setting, feeders with 3gr of squashed earthworms and, correspondingly, 3gr of squashed bloodworms were fell through the top holes in the pair traps. Traps were ... Read more »