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Fish ignore odors and taste of alien foods

As shown by trade catalogs, many of national manufacturers use products of marine origin to produce baits, groundbaits and attractants for freshwater fish. Marine polychaetes, molluscs, cephalopods, crustaceans and fish are among these products. These products are readily available in the world markets and have relatively low cost. Generally, baits, groundbaits and attractants with marine ingredients are usually positioned as instantaneous and attractive for freshwater fish.

Really, the results of field experiments described below show that statements of this kind are untrue. The first typical response both of freshwater and saltwater fish to odors, alien for their environments, is aversion to these odors.

Brief aversion of fish to novel foods, with their odors and taste, is called neophobia while an additional persistent wariness to novel foods is called dietary conservatism (DC) (Thomas et al., 2010). However, there are some part of adventurous consumers (AC) which eat novel foods overcoming their neophobia (specifically, in threespined stickleback, Gasterosteus aculeatus). Generally (Thomas et al., 2010), the presence of AC and DC patterns in natural fish populations allows these populations to develop adaptive foraging strategies in the changing environments.

freshwater feeding organisms

saltwater feeding organisms

sludgeworms, Tubifex tubifex

ragworms, Nereis diversicolor

sludgeworms, Tubifex tubifex

mudworms, Tubificoides benedii
zebra mussel, Dreissena polymorpha

Black Sea mussel,
Mytilus galloprovincialis

pearl mussel, Unio pictorum

long-finned squid, Loligo vulgaris
river sideswimmers, Gammarus pulex

Caspian sideswimmers,
Pontogammarus maeoticus

narrow-clawd crayfish,
Astacus leptodactylus

brown shrimp, Crangon crangon

weatherfish, Misgurnus anguillicaudatus (flesh)

flathead mullet, Mugil cephalus

Note, weatherfish and mullet had distinct "swamp" and "seaweed" odors, respectively

We have tested an attractiveness for freshwater fish odors of feeding organisms of freshwater and saltwater origin. Compared feeding organisms are enumerated in the Tab.1, freshwater feeding organisms were familiar for freshwater fish. Marine organisms, except squids, were delivered in ice from Odesa region, the Black Sea, in Kyiv by car. Raw fresh frozen squids were purchased in an international commercial supplier and identified to species.

Selected feeding organisms were crushed and stored in the refrigerator in conditions of deep freezing. Before testing, they were thawed and mixed with the pure clay of grey color in proportion 10 gr food per 100 gr clay. Open thin wall cylindrical feeders (4 cm diameter, 1 cm height) made of stainless steel were used. Directly in the field, feeders were filled with slide with the visually similar compared clay and food mixes.

Abundant wild common roach, Rutilus rutilus, (4-9 cm total length) were used as model fish.

Experiments were carried out on the sandy shallows of 20-30 cm depth in still water with good visibility of fish through the polarized glasses. Moving along the shore, fish faced with the left or the right wall of the guided corridor set perpendicular to the shore, avoided the walls and entered the corridor. The walls of the corridor (40 cm width) made of fine meshed net (30 cm height, 120 cm length) with small floats and lead weights were installed with the help of four stainless steel pins. Entering the corridor, fish moved along the walls and faced near the shore with the two feeders placed at the distance of 25 cm between their centers and attached to the bottom with the two stainless steel pins. Approaching, fish selected one of the two feeders with the compared mixes and usually bitten clay, if the odor and taste of the corresponding mix were attractive.

About 85% of roach preferred in all tests familiar odors over unfamiliar ones and bitten clay with the matched taste (240 tests in total, clay first touch, sign test, p < 0.01).

Note, roach actively feed on blue mussels, Mytilus edulis, in coastal eutrophicated areas of the Black Sea (Lappalainen et al., 2004). However, for roach in inland waters marine Mytilus are alien foods.

One test session was carried out in the same manner with the Black Sea red mullet, Mullus barbatus ponticus (with the well developed chemosensory system: Andriyashev, 1944) in the natural sea conditions. As expected, mullets preferred familiar odors of saltwater M. galloprovincialis and Ostrea edulis over an unfamiliar odor of freshwater U. pictorum (mussels were crushed without shells and mixed with the pure clay).

Basic References

Andriyashev A.P. 1944. The methods of food searching in the mullet (Mullus barbatus ponticus Essipov). Journal of General Biology 5, 193-195

Lappalainen A., Westerbom M., Vesala S. 2004. Blue mussels (Mytilus edulis) in the diet of roach (Rutilus rutilus) in outer archipelago areas of the western Gulf of Finland, Baltic Sea. Hydrobiologia 514, 87-92

Thomas R.J., King T.A., Forshaw H.E., Marples N.M., Speed M.P., Cable J. 2010. The response of fish to novel prey: evidence that dietary conservatism is not restricted to birds. Behavioral Ecology 21, 669-675

Category: Baits | Views: 866 | Added by: nickyurchenko | Rating: 0.0/0





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