Activity
Some species of fish, such as tunas, swim continually.
Many species spend most of their time lying on the ocean bottom. Bottom-dwellers include stonefishes (Synanceja spp.), flatfishes (order Pleuronectiformes), and blennies (family Blennidae).
Certain species have peak activity times during a day.
- Morays (family Muraenidae) are an example of fish that are more active at night.
- Butterflyfishes (family Chaetodontidae), parrotfishes (family Scaridae) and others are most active during the daytime.
- Some bony fish species are most active at dawn and dusk.
Schooling
Many species of small bony fishes swim together in a coordinated fashion, called schooling.
- Schooling is an adaptation for avoiding predators: An individual fish has a lesser chance of being eaten by a predator when in a school than when alone. A school of small fish may give the impression of a large animal, discouraging predators.
- Schooling poses a hydrodynamic advantage and increases reproductive success. It also may facilitate locating food sources.
Spawning aggregations develop for the purpose of reproduction. These schools consist mainly of reproductively mature individuals. Cod (family Gadidae) often form spawning schools.
Migrating schools form along migration routes of bony fishes. Migrating schools often form into other types of schools, such as spawning schools. Salmon (family Salmonidae) form migrating schools as they travel upstream to spawn.
Feeding schools develop in the feeding grounds. Feeding schools form primarily due to the concentration of food organisms. Feeding schools can be comprised of many different species of bony fishes at different developmental stages.
Wintering schools originate in the wintering grounds of bony fishes. Various species of bony fishes may congregate into areas with the appropriate environmental conditions for survival during the winter months. These schools often disband after the winter season.
Territorial Behavior
Various species of bony fishes have sharply contrasting territorial behavior. Although damselfishes (family Pomacentridae) are relatively small, they are fearless in defending a territory. However, most large groupers (family Serranidae) will retreat from their territory if approached by another animal.
Swimming
Most species of bony fishes propel themselves with the caudal fin, but many species use other fins for propulsion.
Among the slowest-swimming bony fishes are the eels.
The Guinness World Records lists the fastest bony fish as the sailfish Istiophorus platypterus, which has been clocked at 109 km per hour (68 mph).
Sound Production
Many bony fishes produce sound, sometimes in association with reproductive, social, territorial, or aggressive behavior.
Depending on the species, a bony fish can produce sound by rubbing its teeth together, vibrating its swim bladder, or by flexing and contracting muscles.
Most sounds produced by bony fishes are below 10,000 Hz.
Symbiotic Relationships
Several species of small bony fishes, such as the cleaner wrasse (Labroides dimidiatus), are "cleaners" that eat debris and parasites from the skin and scales of larger fishes.
Remoras (family Echeneidae) commonly attach themselves to sharks or other large fishes, whales, and sea turtles using a modified dorsal fin. They eat scraps left over from the meals of their hosts. They may eat parasites as well.
Some bony fishes have symbiotic relationships with nonfish species. Clownfishes (family Pomacentridae) live unharmed among the venomous tentacles of sea anemones, which protect the clownfish from potential predators.
Bony Fish Attacks
The great barracuda (Sphyraena barracuda) has been known to attack divers. Barracuda may confuse shiny objects with the shiny scales of their prey.
Piranhas (Serrasalmus spp.) can be voracious predators - they're quick swimmers with razor-sharp teeth. Piranhas inhabit freshwater river systems in South America. During periods of low rainfall, streams and rivers recede, and schools of piranhas can become trapped in shallow ponds. Here their usual prey - smaller fish - are soon consumed. A school of starving piranhas can consume large animals in minutes. Under these circumstances, piranhas have been known to attack humans. They are not a threat to humans when water levels are high and food is abundant.
Morays (family Muraenidae) inhabit tropical and warm-temperature waters of the world. Most species can be found in coral reefs and rocky areas taking shelter in cracks and crevices. Divers tormenting them, feeding them, or invading their areas have provoked nonfatal attacks.
Non-Schooling Social Behavior
Bony fish species show great diversity in social behavior and social organization. For example, in many wrasse species, social structure includes a large dominant male and many smaller, subordinate females. In contrast, most large predatory bony fishes such as groupers (family Serranidae) are mostly asocial except during breeding seasons.
