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~Understanding Your Fish~
July 24, 2009

Understanding Your Fish

Welcome to the 47 new subscribers.

Understanding the fish in your pond, what makes them thrive, what stresses them, and how they grow and breed not only adds to the enjoyment of keeping them, but also increases the chances of maintaining a healthy stock.

Fish have evolved over many years to suit their particular environments. For example, fat-bodied fish will not be at home in fast moving streams. Many fish have down turned mouths that help them as they search for food at the bottom of rivers and ponds. Fish that inhabit muddy environments often have barbels around the mouth in order to detect their food.

Most fish have a buoyancy device called a swim bladder. This is an adjustable airbag that allows fish to remain at various depths in the pond.

The gills are located just behind the head and are protected by a gill cover plate called the operculum. The gills allow the fish to expel waste products, such as ammonia and carbon dioxide. This process is similar to breathing and works by passing water from the mouth through the gill filaments and out through the operculum. As water passes through the gills, it comes into contact with the tiny blood vessels that absorb the oxygen from the water and then expel the toxins. Damage to the gills is extremely serious, although fairly easy to detect.

Fins are used for both stability and propulsion. In addition, many fish species use them during courtship and to fan their eggs. Most fish have seven fins, although some species have evolved different fin structures to suit their own habitats. The Caudal fin (or tail) is mainly used for propulsion, while the Dorsal and Anal fins act as stabilizers, almost like the keel on a boat. Two pairs of fins-the pelvic and pectoral- are used for directional control and adjusting the position of the fish in the water. The fish use these fins for turning and stopping.

It is important to check the finnage of fish in your pond regularly, as the soft tissue can be easily damaged and infected during squabbling or courtship behavior.

The Scales of a Koi are covered in a protective layer of mucus that helps keep the fish free from infection. The scales themselves grow constantly and protect the soft tissue beneath.

Fish rely on the same five senses that humans possess. The main difference is that fish use their nostrils only for smelling or detecting food, not for breathing. In addition to being able to hear, fish have an extra sensory faculty that detects underwater vibrations. This is known as the Lateral Line and is visible on most species as a small row of holes along the body of the fish.

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