Lake salmon | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Actinopterygii |
Order: | Cypriniformes |
Family: | Cyprinidae |
Subfamily: | Danioninae |
Genus: | Opsaridium |
Species: | O. microlepis |
Binomial name | |
Opsaridium microlepis (Günther, 1864) | |
Synonyms | |
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The lake salmon or mpasa (Opsaridium microlepis) is an African species of freshwater fish, endemic to Lake Malawi, in the family Cyprinidae found in Malawi, Mozambique, and Tanzania. Its natural habitats are rivers and freshwater lakes. [1] [2]
It is a silvery fish which resembles trout of the family Salmonidae [3] and lacks the pink or orange coloured fins of many of its congeners. They can grow to up to 4 kg (8.8 lb) in weight [4] and 47 cm (19 in) in total length [2] The larger adults are plain coloured while the juveniles have vertical dark bars along the body which they lose as they grow. [5]
The lake salmon occurs in the pelagic zone of Lake Malawi, over sandy substrates. The juvenile fish stay close inshore near the mouths of the tributary rivers. The adults feed on small pelagic fishes, especially Engraulicypris sardella , [2] while the juveniles feed on plankton, insects and other small organic matter. During the rainy season the adult fish migrate up the tributary rivers from the lake to spawn, this mainly takes place at night in shallow, well-oxygenated, flowing waters over gravel substrates with no silt. there is an extended spawning period which starts with the onset of the rains and continues after the rains, [1] from May to October. The young remain in the rivers until they have grown somewhat and are able to return to the lake. [5]
The lake salmon is threatened by overfishing and there are very high mortality rates in adult fish during the spawning season as the rivers are often totally blocked with weirs and with gill nets which prevent the fish from running upstream, especially during years of low rainfall. Other threats include deliberate poisoning and the deterioration of the spawning grounds due to siltation from soil erosion caused by deforestation and agriculture, which also causes habitat deterioration as water is abstracted from the breeding streams for irrigation and this makes it difficult for the juveniles to return to the lake from the spawning areas. [1] It is caught using ring nets and by angling. [2]
The Bua River runs through the Nkhotakota Wildlife Reserve in central Malawi and this is the only river where the spawning grounds are protected because the surrounding woodlands are protected from clearing. The headwaters of another spawning river, the North Rukuru, are protected within the Nyika National Park but there is increasing deforestation between the park and the spawning grounds. The Linthipe River is a major spawning river and it is unprotected being polluted with untreated sewage from the city of Lilongwe. The condition of the spawning rivers in Tanzania and Mozambique is not known. [1]
Malawi is a landlocked country in southeast Africa. It is wholly within the tropics; from about 9°30S at its northernmost point to about 17°S at the southernmost tip. The country occupies a thin strip of land between Zambia and Mozambique, extending southwards into Mozambique along the valley of the Shire River. In the north and north east it also shares a border with Tanzania. Malawi is connected by rail to the Mozambican ports of Nacala and Beira. It lies between latitudes 9° and 18°S, and longitudes 32° and 36°E.
Lake Malawi, also known as Lake Nyasa in Tanzania and Lago Niassa in Mozambique, is an African Great Lake and the southernmost lake in the East African Rift system, located between Malawi, Mozambique and Tanzania.
Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres. Such migrations are usually done for better feeding or to reproduce, but in other cases the reasons are unclear.
The snail darter is a small species of freshwater ray-finned fish, a darter from the subfamily Etheostomatinae, part of the family Percidae, which also contains the perches, ruffes and pikeperches. It is found in East Tennessee freshwater in the United States and in small portions of northern Alabama and Georgia. First recorded in 1973, the snail darter was listed as endangered under the U.S. Endangered Species Act of 1973 by 1975. The species was at the center of a major environmental law controversy that involved a lawsuit seeking to halt the completion of Tellico Dam, which posed a risk of extinction for the snail darter by blocking its migratory route. The case was eventually appealed to the U.S. Supreme Court, which ruled on it in its 1978 decision Tennessee Valley Authority v. Hill.
Steelhead, or occasionally steelhead trout, is the common name of the anadromous form of the coastal rainbow trout (Oncorhynchus mykiss irideus) or Columbia River redband trout. Steelhead are native to cold-water tributaries of the Pacific basin in Northeast Asia and North America. Like other sea-run (anadromous) trout and salmon, steelhead spawn in freshwater, smolts migrate to the ocean to forage for several years and adults return to their natal streams to spawn. Steelhead are iteroparous, although survival is approximately 10–20%.
The sockeye salmon, also called red salmon, kokanee salmon, blueback salmon, or simply sockeye, is an anadromous species of salmon found in the Northern Pacific Ocean and rivers discharging into it. This species is a Pacific salmon that is primarily red in hue during spawning. They can grow up to 84 cm in length and weigh 2.3 to 7 kg (5–15 lb). Juveniles remain in freshwater until they are ready to migrate to the ocean, over distances of up to 1,600 km (1,000 mi). Their diet consists primarily of zooplankton. Sockeye salmon are semelparous, dying after they spawn. Some populations, referred to as kokanee, do not migrate to the ocean and live their entire lives in fresh water.
The lake sturgeon, also known as the rock sturgeon, is a North American temperate freshwater fish, one of about 25 species of sturgeon. Like other sturgeons, this species is a bottom feeder and has a partly cartilaginous skeleton, an overall streamlined shape, and skin bearing rows of bony plates on the sides and back.
Copadichromis borleyi is a species of haplochromine cichlid fish endemic to Lake Malawi in East Africa. The species is popular in the fishkeeping hobby where it is frequently kept in aquariums. The species has numerous common names, including redfin hap and goldfin hap.
Labeobarbus johnstonii is a species of cyprinid fish. It has long been placed in Barbus, the "wastebin genus" for barbs, by default, and this is still being done by the IUCN. However, the species is increasingly being restored to related yellowfish genus Labeobarbus which seems a much more appropriate placement. It is presumably hexaploid like the other yellowfish. The supposed subspecies latirostris of its relative L. intermedius is actually misidentified L. johnstonii.
Enteromius litamba is a ray-finned fish species in the family Cyprinidae. It has long been placed in Barbus, the "wastebin genus" for barbs, by default, and this is still being done by the IUCN. However, the species is increasingly being restored by some taxonomists to the related yellowfish genus Labeobarbus, others place it in the genus Enteromius. It is presumably hexaploid like the other yellowfish.
Opsaridium microcephalum is a species of ray-finned fish in the family Cyprinidae found in Malawi, Mozambique, and Tanzania. Its natural habitats are rivers and freshwater lakes.
The brook stickleback is a small freshwater fish that is distributed across the US and Canada. It grows to a length of about 2 inches. It occupies the northern part of the eastern United States, as well as the southern half of Canada. Small populations are scattered throughout the Mississippi-Great Lakes basin extending to Colorado, New Mexico, Kentucky, Tennessee, etc., though some of these areas are not native to the species. This small fish inhabits clear, cool streams and lakes. They eat small invertebrates, algae, insect larvae, and occasionally their own eggs. They are also preyed upon by smallmouth bass and northern pike. Feedin time is usually dawn and sunset. The brook stickleback does have active competition mostly from minnows, but feeding times are different, along with diet. Spawning occurs in midsummer. Males secure a territory, build a nest, and mate with females. Males provide protection for the eggs, ward off predators, and usually die later in the season. This is considered an annual species. The nests are built out of aquatic grasses. Though the brook stickleback is not considered a threatened species, deforesting and changing waters are altering ecosystems of the species. Harvesting of trees around riparian environments is having a large effect of the stream ecosystem where the brook stickleback resides.
The giant cichlid, also known as the emperor cichlid, is a species of fish in the family Cichlidae, endemic to Lake Tanganyika in Africa. It is the only member of its genus Boulengerochromis and tribe Boulengerochromini.
Buccochromis rhoadesii is a species of haplochromine cichlid. It is endemic to Lake Malawi, Lake Malombe and the upper Shire River in the countries of Malawi, Mozambique, and Tanzania.
Copadichromis geertsi is a species of haplochromine cichlid which is endemic to Lake Malawi.
Spawn is the eggs and sperm released or deposited into water by aquatic animals. As a verb, to spawn refers to the process of freely releasing eggs and sperm into a body of water ; the physical act is known as spawning. The vast majority of non-mammalian, non-avian and non-reptilian aquatic and/or amphibious lifeforms reproduce through this process, including the:
The warpaint shiner is a species of freshwater fish found in North America. It is common in the upper Tennessee River basin as well as in the Savannah River, the Santee River, and the New River in North Carolina. Adults have a mean length of 9 centimetres (3.5 in) and can reach a maximum length of 14 centimetres (5.5 in). The maximum age reported for this species is 4 years.
Tilapia sparrmanii, the banded tilapia, or vlei kurper, is a widespread and adaptable cichlid fish that is found in warmer freshwater habitats of southern Africa. They prefer water with ample plant cover, and occur naturally as far north as DR Congo and Tanzania. They have been introduced locally in the northern hemisphere. Younger banded tilapia feed on crustaceans and insect larvae, while the adults feed on terrestrial and aquatic plants and other debris. They undertake local migrations and may shoal before and during spawning time. They guard their own eggs, and although they may move eggs or fry in the mouth, they are not known to be actual mouthbrooders like several other tilapia species. This species can reach a length of 23.5 centimetres (9.3 in) TL and is an important foodfish.
Hucho bleekeri, the Sichuan taimen, is a species of freshwater fish in the salmon family (Salmonidae), endemic to the Yangtze basin in China. Their typical habitat includes mountain streams and small rivers, typically being found in the catchment areas of the Dadu River in Sichuan and Qinghai Provinces, as well as the Hanjiang River and its tributaries in southern Shaanxi province. This particular fish population is largely threatened by habitat loss and illegal fishing, resulting in a "critically endangered" conservation status from the International Union for Conservation of Nature.
Fish go through various life stages between fertilization and adulthood. The life of a fish start as spawned eggs which hatch into immotile larvae. These larval hatchlings are not yet capable of feeding themselves and carry a yolk sac which provides stored nutrition. Before the yolk sac completely disappears, the young fish must mature enough to be able to forage independently. When they have developed to the point where they are capable of feeding by themselves, the fish are called fry. When, in addition, they have developed scales and working fins, the transition to a juvenile fish is complete and it is called a fingerling, so called as they are typically about the size of human fingers. The juvenile stage lasts until the fish is fully grown, sexually mature and interacting with other adult fish.