Digestion, Nutrition, and Growth
Cod and haddock normally feed daily. In fact, feeding is the most frequent of all voluntary activities. Feeding activities vary through the seasons, cycles of migration, reproductive status, and even age and size affect feeding habits. Unlike warm-blooded animals, a fish's metabolism is under the direct control of the water temperature. The metabolism decreases with decreasing temperatures, meaning less feeding is needed during the winter months. Feeding takes less time for carnivorous fish than it does for herbivorous fish. This is due to the fact that carnivores can obtain all necessary components of their diet (proteins, lipids, calories, etc.) without consuming all the bulk associated with eating plant material. Small fish consume a greater percentage of their body during feeding than larger fish do.
Sight, olfaction, taste, and other receptors play a large role in locating prey and feeding. The ear and lateral line are important sensory organs in finding prey. These two organs are often considered together, because they are similar in structure, although they do differ slightly in function. The ear responds to sounds and displacement of the head, while the lateral line responds to movements of the water. Olfaction (smelling) is important in finding and orienting prey organisms. Taste receptors are found not only in the oral cavity, but also on the lips, branchial cavity, and the chin barbel.
The food enters the mouth and is lubricated with mucus, produced by the mouth, pharynx, and esophagus. Food is swallowed, and passes through the esophagus. The esophagus is short and distensible, allowing the fish to swallow relatively large objects. From the esophagus, the food bolus enters the stomach, where digestion begins. The muscular stomach secretes protective mucus, pepsin (a protease), and hydrochloric acid, which maintains a stomach pH of about two. The flow of these gastric juices is stimulated by the act of feeding. The stomach stores food and initiates digestion through the mixing of food with gastric juices. The length of the intestine is dependent upon the type of diet. Herbivorous fish often have intestines twenty times longer than their body length. Carnivorous fish, such as the cod, have an intestine length about equal to their body length. Digestion continues in the intestine, which is neutral or slightly alkaline. Enzymes produced by the pancreas, liver and intestinal mucosa aid in digestion. The pyloric caeca is a series of blind sacs located between the stomach and intestine. The pyloric caeca aids in absorption by increasing the surface area of the gut.. The liver, which is located around the stomach, secretes bile and emulsifiers. These compounds are carried to the intestine, where they aid in fat digestion. The pancreas tissue is diffused in and around the liver. The pancreatic tissue secretes trypsin, an important protease in fish digestion. Absorption of food materials occurs in the pyloric caeca and along the length of the intestine. Solid waste products exit the digestive system through the rectum and anus. The rate of digestion and absorption is dependent upon the size of the fish, the type and amount of food, and environmental factors, such as temperature.
No fat or carbohydrate digestion occurs in the stomach. Digested nutrients are absorbed into the blood by a combination of passive diffusion, active transport, pinocytosis, and are carried to the liver by a portal vein. 10-20% of ingested food is indigestible and is excreted as feces. 10-15% of calories ingested are used for digestive processes. Oxygen consumption increases by 50% or more with digestion. Fish are usually not fed for 24 hours prior to handling or transportation. This decreases the amount of oxygen needed, because no digestion is occurring. Since stressed fish require more oxygen, the decrease of oxygen consumption from lack of digestion helps to ensure that there will be enough oxygen during stress. Also, the decrease in feces, carbon dioxide, and ammonia excretion helps the fish in stressful situations.
Fish, like all other animals, require some necessary components in their diets. These include proteins, carbohydrates, fats, minerals, vitamins, and water. The quality of the protein is important; the proteins consumed should contain ten essential amino acids (argenine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophane, and valine). These are essential for the proper growth of the fish and must be provided in the diet. There are also a great number of vitamins and minerals necessary for proper growth which must be supplied via the diet. Health problems and disformities may occur if the diet is lacking any of these necessary components.
Growth and growth rates are determined by several factors, including the genetics of the animal, the quality and quantity of food available, as well as environmental conditions. Growth is usually greater in warm weather conditions. Growth is regulated by hormones produced by the endocrine system; growth hormones produced by the pituitary are the most important. The growth of wild populations may be difficult to measure. One method of measurement is to catch fish season to season. The age of the fish can be estimated by studying the marks of the scales. Weights and measures are taken. The average size of certain age groups of fish can then be determined. After a few years of doing this, relative growth rates can be measured. Another method to measure growth would be to catch fish, measure and then tag them. After tagging, the fish would be released and hopefully recaught later. If recaught, new measurements would be taken, so that changes in weight and length could be directly determined.
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Digestion, Nutrition, and Growth
Cod and haddock normally feed daily. In fact, feeding is the most frequent of all voluntary activities. Feeding activities vary through the seasons, cycles of migration, reproductive status, and even age and size affect feeding habits. Unlike warm-blooded animals, a fish's metabolism is under the direct control of the water temperature. The metabolism decreases with decreasing temperatures, meaning less feeding is needed during the winter months. Feeding takes less time for carnivorous fish than it does for herbivorous fish. This is due to the fact that carnivores can obtain all necessary components of their diet (proteins, lipids, calories, etc.) without consuming all the bulk associated with eating plant material. Small fish consume a greater percentage of their body during feeding than larger fish do.
Sight, olfaction, taste, and other receptors play a large role in locating prey and feeding. The ear and lateral line are important sensory organs in finding prey. These two organs are often considered together, because they are similar in structure, although they do differ slightly in function. The ear responds to sounds and displacement of the head, while the lateral line responds to movements of the water. Olfaction (smelling) is important in finding and orienting prey organisms. Taste receptors are found not only in the oral cavity, but also on the lips, branchial cavity, and the chin barbel.
The food enters the mouth and is lubricated with mucus, produced by the mouth, pharynx, and esophagus. Food is swallowed, and passes through the esophagus. The esophagus is short and distensible, allowing the fish to swallow relatively large objects. From the esophagus, the food bolus enters the stomach, where digestion begins. The muscular stomach secretes protective mucus, pepsin (a protease), and hydrochloric acid, which maintains a stomach pH of about two. The flow of these gastric juices is stimulated by the act of feeding. The stomach stores food and initiates digestion through the mixing of food with gastric juices. The length of the intestine is dependent upon the type of diet. Herbivorous fish often have intestines twenty times longer than their body length. Carnivorous fish, such as the cod, have an intestine length about equal to their body length. Digestion continues in the intestine, which is neutral or slightly alkaline. Enzymes produced by the pancreas, liver and intestinal mucosa aid in digestion. The pyloric caeca is a series of blind sacs located between the stomach and intestine. The pyloric caeca aids in absorption by increasing the surface area of the gut.. The liver, which is located around the stomach, secretes bile and emulsifiers. These compounds are carried to the intestine, where they aid in fat digestion. The pancreas tissue is diffused in and around the liver. The pancreatic tissue secretes trypsin, an important protease in fish digestion. Absorption of food materials occurs in the pyloric caeca and along the length of the intestine. Solid waste products exit the digestive system through the rectum and anus. The rate of digestion and absorption is dependent upon the size of the fish, the type and amount of food, and environmental factors, such as temperature.
No fat or carbohydrate digestion occurs in the stomach. Digested nutrients are absorbed into the blood by a combination of passive diffusion, active transport, pinocytosis, and are carried to the liver by a portal vein. 10-20% of ingested food is indigestible and is excreted as feces. 10-15% of calories ingested are used for digestive processes. Oxygen consumption increases by 50% or more with digestion. Fish are usually not fed for 24 hours prior to handling or transportation. This decreases the amount of oxygen needed, because no digestion is occurring. Since stressed fish require more oxygen, the decrease of oxygen consumption from lack of digestion helps to ensure that there will be enough oxygen during stress. Also, the decrease in feces, carbon dioxide, and ammonia excretion helps the fish in stressful situations.
Fish, like all other animals, require some necessary components in their diets. These include proteins, carbohydrates, fats, minerals, vitamins, and water. The quality of the protein is important; the proteins consumed should contain ten essential amino acids (argenine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophane, and valine). These are essential for the proper growth of the fish and must be provided in the diet. There are also a great number of vitamins and minerals necessary for proper growth which must be supplied via the diet. Health problems and disformities may occur if the diet is lacking any of these necessary components.
Growth and growth rates are determined by several factors, including the genetics of the animal, the quality and quantity of food available, as well as environmental conditions. Growth is usually greater in warm weather conditions. Growth is regulated by hormones produced by the endocrine system; growth hormones produced by the pituitary are the most important. The growth of wild populations may be difficult to measure. One method of measurement is to catch fish season to season. The age of the fish can be estimated by studying the marks of the scales. Weights and measures are taken. The average size of certain age groups of fish can then be determined. After a few years of doing this, relative growth rates can be measured. Another method to measure growth would be to catch fish, measure and then tag them. After tagging, the fish would be released and hopefully recaught later. If recaught, new measurements would be taken, so that changes in weight and length could be directly determined.
Back to Anatomy and Physiology Menu
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