1. Longevity for most bony fish species is unknown. Most species probably live no longer than about 12 to 20 years.
2. In aquariums, some species of bony fishes have lived more than 50 years. Koi (Cyprinus carpio), have been known to live as long as 100 years, and large groupers at Sea World of California have lived in park aquariums for 25 years and are estimated to be about 30 years old.
3. Large species generally have a longer lifespan than smaller species.
1 . Growth rings are periodically deposited on the scales, vertebrae, and earstones of many species of bony fishes. Experts can stain these hard body parts, examine them for growth rings, and estimate the age of the fish.
2. Examining the scales, vertebrae, or earstones of known-age fishes after their death enables researchers to compare the estimated age (based on growth rings) with the fish's known age.
3. In some species, tagging and releasing fish can help produce information about growth rates. A tagged fish can be measured again when it is recaptured. Researchers correlate the measurements with the number of years since recapture and calculate a yearly growth rate.
1. Depending on the species, bony fishes have a wide variety of predators, including other fishes, birds, reptiles, amphibians, mammals, and various invertebrates.
2. Small bony fishes have a large variety of predators. Large bony fishes have fewer predators.
3. Many bony fishes will eat members of their own species.
1. Commercial fishing.
a. More than I 00 million metric tons of bony fishes are harvested every year for human consumption. In some countries, bony fishes may provide up to 50% of all animal protein consumed (Bond, 1977).
b. Bony fishes are also used to feed livestock, make fertilizer, and produce fish oil. Metallic paints, leather, glue, and medicines all are made from bony fishes or bony fish byproducts.
c. Some commercial fishing operations catch large numbers of non-targeted species, which are discarded. Non-targeted catch is called bycatch.
2. Recreational fishing.
Various species of marine and freshwater bony fishes are targeted for small scale fishing for food and recreation.
3. Habitat destruction.
a. Damming, channelization, stream diversion, and silting (a result of deforestation or agriculture) alters aquatic habitats. Sometimes fish populations cannot survive the habitat changes.
b. The loss of coastal wetlands threatens fish populations, as estuaries are important nursery grounds for many species of ocean fishes.
4. Pollution.
Chemicals that are used on land can eventually end up in freshwater systems and oceans. Such chemical contaminants can enter the food chain and become concentrated in the bodies of fishes.
a. Pesticides may enter waterways through agricultural runoff. Household and garden pesticides can enter waterways, too-through sewers and storm drains.
b. Small amounts of heavy metals occur naturally in the ocean, but industrial pollution has increased the amount of heavy metals in many aquatic environments. Heavy metals may also enter waterways when people empty household chemicals such as paints into sewers and storm drains.
(1) The effects of heavy metals on fishes is not well known, but we do know that more than minute amounts of heavy metals are poisonous to humans. The best known heavy metal poisoning is from mercury. The U.S. Department of Agriculture (USDA) has set a maximum acceptable level for mercury in fish. Any fish with more than 0.5 ppm (parts per million) mercury may not be sold as food.
(2) Heavy metals accumulate in the tissues of organisms that ingest them and are passed up the food chain. Thus, large carnivorous fishes are most susceptible to high levels of heavy metals.
c. Acid rain results when the emissions of fossil fuels combine with moisture in the atmosphere to form droplets of sulfuric or nitric acids. The droplets fall as rain or snow and can reduce the pH level in lakes and streams to the point where the pH is inhospitable to native species.
d. Oil spills are harmful for fish populations.
e. The rainbow trout (Salmo gairdneri) is sensitive to degradations in water quality and has been used to study the effects of various pesticides and waste products on aquatic life (Bond, 1979).
5. Introduced species. A non-native fish species introduced into a habitat can alter the ecology of that habitat and may have devastating results on native species. One species native to Southeast Africa, the tilapia Oreochromis mossambica has been introduced to tropical lakes and streams all over the world, virtually eliminating many native species.
6. Aquarium collection. Some fishes sold in pet stores are collected using chemicals that kill many of the fishes exposed to them and destroy other marine life as well. Sea World encourages aquarium enthusiasts to purchase "hand-caught" or captive-bred fishes.
1. As in any animal population, a variety of diseases can be responsible for bony fish deaths. These include bacterial, viral, and fungal infections and tumors.
2. Many types of internal and external parasites are common to bony fishes. They include cestodes, nematodes, trematodes, protozoans, and copepods.
SeaWorld/Busch Gardens Animal Information Database
www.seaworld.org / www.buschgardens.org
©2002 SeaWorld, Inc.
All Rights Reserved.