1 . As a group, bony fishes have a diverse range of food preferences.
a. Bony fishes may be herbivores (plant-eaters), carnivores (meat-eaters), omnivores (plant- and meat-eaters), or detritivores (animals that eat decomposing plants and animals).
b. As a group, bony fishes can eat all sizes of plants and animals, from the smallest of microscopic plant plankton to some of the largest marine animals.
c. Some of the animals common in the diets of bony fishes include annelid worms, marine snails, mussels, clams, squids, crustaceans, insects, birds, amphibians, small mammals, and other fishes.
2. Many bony fish species are semi-selective eaters, eating some foods more than others.
1 . The amount of food a bony fish eats is directly related to its size, its metabolic rate, and the temperature of its environment.
a. Smaller fishes generally have a higher metabolic rate than large fishes of the same species. Thus, small fishes generally eat more relative to their body size.
b. Fishes are "cold-blooded": their body temperature is determined by the temperature of their environment. Warm-water fishes generally have higher metabolic rates and require more food than cold-water species of the same size.
2. Some bony fishes can go long periods without eating. Some freshwater eels (Anguilla spp.) can survive more than a year without food (Lagler, 1962.)
3. Some researchers have calculated food intake.
a. In one study, bluegill (Lepomis macrochirus), a small freshwater fish, ate between 1 % and 35% of their body weight in food per week, depending on water temperature (Lagler, 1962).
b. Studies on anchovies (family Engraulidae) during the summer showed a food intake of about 8% to 1 0% of body weight per day (Lagler, 1962).
1 . Many bony fishes, such as mackerels and tunas (family Scombridae), seabasses (family Serranidae), and others are active predators. Predatory fishes prey most often on weak members of an animal population. They select weak, ill, injured, or dying prey because it is easier to catch.
2. Some bony fishes, such as anchovies (family Engraulidae) are filter feeders. They strain plankton from the water with gill rakers.
3. Many bony fishes, including catfishes (family Ictaluridae) are adapted for bottom feeding.
4. Some bony fishes are quite specialized for feeding.
a. Bilifishes (family Istiophoridae) use their long bills to stun prey.
b. Archerfish (Toxotesjaculatrix) shoot water "bullets" at insects as high as 1.8 m (6 tt.) above the water, knocking them to the water's surface.
c. Lying at the bottom of the ocean and looking more like a rock than a fish, the stonefish (Synanceja spp.) waits for prey to come to it. When an unsuspecting animal swims by, the stonefish swiftly gulps it.
d. The 91 -cm (3-ft.) arawana (Osteoglossum bicirrhosum), a freshwater fish of South America, can leap entirely out of the water to seize small birds.
An arawana (Osteoglossum bicirrhosum) can leap entirely out ot the water to seize small birds.
e. Some fishes produce strong electric current to stun prey. The electric catfish (Malapterurus electricus) can produce 350 volts of electricity. The South American electric eel (Electrophorus electricus) can produce up to 650 volts of electricity.
f. Some species of bony fishes, notably the cleaner wrasse (Labroides dimidiatus), are "cleaners" that pick debris and parasites from larger fishes.
5. A species'particular mouth shape and teeth are adapted to accommodate a particular diet.
a. The wolf eel (family Anarrhichadidae) has large canine teeth to grasp its shelled prey and blunt molars for crushing the shells.
b. The blue sucker (Cycleptus elongatus) has thick, nubby lips that help it suck plants from rocks.
c. Parrotfishes (family Scaridae) use chisel-like teeth in a beaklike mouth to nibble on reef-building corals. These fish are herbivores that eat the algae within the coral. In the process, they grind the coral's hard exoskeleton and defecate sand.
The gulf grouper (Mycteropercajordani) is an active predator that gulps its prey whole.
1 . Bony fishes have been used to control undesirable organisms.
2. The western mosquitofish (Gambusia affinis) feeds on aquatic mosquito larva. It is commonly introduced to non-native areas to control mosquito populations.
3. The grass carp (Ctenopharyngodon idella) and various species of tilapia (Oreochromis spp.) have been introduced in some areas to control aquatic plant growth. Tilapia are used for weed control throughout the southern United States because they feed on algae and soft vascular plants.
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