User:Waynnee/sandbox

Behavior[edit]

An 1837 watercolor painting of a golden shiner by Jacques Burkhardt. Golden shiners live in large groups (shoals) that roam widely. Several laboratory studies have shown that the movements of a shoal can be determined by a minority of individuals at the front of it. For example, an individual that knows when and where food is available within a large tank can lead many other fish to the right place at the right time of day. If all fish have similar knowledge, there is still a tendency for some individuals to be found always at the front of a moving shoal, possibly because they are intrinsically hungrier and more motivated to find food. Small fish are also found more often at the front of a shoal than larger fish, again possibly because they are more motivated to find food.

Like other minnows, golden shiners are sensitive to the release of an alarm substance, or schreckstoff, contained within special skin cells. If a predator catches and bites into a minnow, the skin is broken, the substance is released, and other minnows in the vicinity can detect the substance and react to it by leaving the area. The substance can also survive intact in the feces of a predator, and minnows can thus detect the presence of a minnow-eating predator through the presence of its feces. In the laboratory, golden shiners were found to react strongly to water that contained feces from snakes that had eaten other golden shiners, but not nearly as much to water laden with feces from snakes that had eaten green swordtails, a fish that does not possess an alarm substance.

Like other fishes, golden shiners have a good daily time sense and can anticipate the arrival of food when this food is made available at the same time of the day or night. They can also do this when there is more than one mealtime a day. This anticipation is expressed as swimming and positioning towards the food source, and other naive individuals can perceive this and join the anticipating fish in the hope of sharing its food.

Golden shiners are also capable of time-place learning (associating different places with different times of day). They can be taught to feed in one part of an aquarium in the morning and a different part in the afternoon; or to feed in one part in the morning, a different part at mid-day, and back to the first part in the afternoon.

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Effects of Mercury in the Environment

Like many other bony fish Golden Shiners are left vulnerable to the accumulation of mercury in its natural habitat. Researchers have found that Golden Shiners when experiencing long-term exposure to methylmercury develop disadvantageous effects involving the function of the nervous reproduction, immune, and endocrine systems as well as shown differences in behavior. Many fish when exposed to the mercury showed higher concentration of the chemical built up within the brain when compared to its entire body. Fish exposed to high amounts of mercury showed signs of delayed shoaling (grouping) after post-exposure to predators up to nearly three times compared to other groups exposed to lower amounts of mercury.