Fishes of Maine / W. Harry Everhart.

Abstract

the eels and others have become flattened from side to side as the basses and are known as compressed. Fishes of Maine are either rounded or compressed in body form. Covering the fish externally is a layer of mucus secreted by the glands of the skin. This mucus protects fish from external infection. Fishermen have long been cautioned to wet their hands before handling fish which they intend to return to the water. Handling with dry hands would remove a large amount of this protective covering and leave the fish exposed to fungus and bacterial invasions. Immediately under the mucus lies the epidermis and under the epidermis are embedded the scales. The scales are laid down shortly after the fish is hatched and reflect changes which may occur in the life history of the fish. Age of fish can be determined from the number of year marks, and periods of good growth and poor growth can be detected from the spacing of the growth rings on the scale. Ages of fishes in this book refer to the number of completed year marks on the scale and conform to the manner in which we ordinarily report the age of a human. Among fishes of Maine the lamprey eel, hornpout, and freshwater sculpin are without scales. Scales of Maine fishes may be divided into the cycloid type and the ctenoid type. Cycloid scales are usually small, and embedded deeply in the skin. Trout and salmon are examples of fish with cycloid scales. Ctenoid scales have several rows of spines along their posterior or exposed edge. These spines, or ctenii, give the fish a rough or spiny feeling. Bass and white perch are examples of fish having ctenoid scales. Fins of fishes are thin folds of skin supported by rays, spines, or both. Fish are frequently classified either as "soft-rayed" fish such as trout, or as "spiny-rayed" fish such as bass. Rays are finely segmented and often branched while spines are unsegmented, unbranched, and usually hard. Counts of rays and spines, since their number is reasonably constant, are frequently of value in identification of closely allied forms. Paired fins include the pectorals located behind the gill openings and the ventral or pelvic fins located on the lower side of the body. Fish are frequently classified as to whether the fins are positioned posteriorly or anteriorly on the ventral side or belly of the fish. Most "advanced" fishes have the ventral fins placed under, or nearly under, the pectoral fins when the location is described as thoracic. If the ventral fins are in front of the pectoral fins then the location of the ventral fins is described as jugular. When the ventral fins are posterior their position is considered abdominal. Unpaired fins include the dorsal, adipose, caudal or tail fin, and the anal fin. Although a fish swims primarily by muscular movements of its body it depends on the caudal fin lending power to the movements, on the dorsal and anal fins for stabilizing the movement, and on the pectoral and ventral fins for steering and maneuvering. Fish obtain their oxygen from water passing over the gills. Closing the g...

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