Fish migration - AbsoluteAstronomy.com

Many types of fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

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. Fish usually migrate because of diet or reproductive needs, although in some cases the reason for migration remains unknown.

Classification

Classifications can be either fundamental (like biological classification that rests on a phylogenetic basis), or are merely heuristic typologies (as here, about migrations) to assist communication about complex issues. Classifications are judged according to their fundamental accuracy, whether they are convenient or not. Typologies in contrast are essentially arbitrary and their effectiveness is to be judged solely by the problems they solve or create. Secor and Kerr (2009) for example show several typologies that encapsulate various aspects of fish life history.

Migration is a word used in multiple senses. It is important to distinguish "true" migration, i.e. a life-history-structured or at least patterned activity such as seen in anadromous species like salmons, from mere movement or wandering as may happen, say, with euryhaline species that easily move between fresh and salt water but not necessarily or with regularity. "Vertical migration", for example, the phenomenon of plankton and fishes regularly changing their depth throughout the 24h day, is a special usage unlike migrations of (e.g.) salmons that range over distances in migrations that may cover river, lake, and sea, or the great migrations of game through Africa's Serengeti.

Anadromous and catadromous are words that have been commonly used for centuries. They are slightly more narrowly used in the following classification of [truly] migrating fish by Myers 1949:

"Diadromous. Truly migratory fishes which migrate between the sea and fresh water. There has been no English term by which one can refer collectively and briefly to anadromous, catadromous and other fishes which truly migrate between fresh and salt water, and this new term is now proposed ... . Like the two well known ones, this adjective is formed from classical Greek ([dia], through; and [dromous], running). ...

Anadromous. Diadromous fishes which spend most of their lives in the sea and migrate to fresh water to breed (From [ana], up ...). ... [This narrowed the previous usage which could apply to fish never crossing the freswater/sea boundary but simply moving upstream to spawn, for example in some fishes of the Rift Lakes]

Catadromous. Diadromous fishes which spend most of their lives in fresh water and migrate to the sea to breed. (From [cata], down ...). ... [This narrowed the previous usage which could apply to fish never reaching the sea but moving downstream to spawn]

Amphidromous. Diadromous fishes whose migration from fresh water to the seas, or vice versa, is not for the purpose of breeding, but occurs regularly at some other stage of the life cycle. (From [amphi], around, on both sides ...) ... [The elements "vice versa" and "purpose" are troublesome however]

Potamodromous. Truly migratory fishes whose migrations occur wholly within freshwater. (From [potamos], river ... ) ... [Rarely used. This term and oceanodromous received the fishes excluded by the narrowing of anadromous and catadromous]

Oceanodromous. Truly migratory fishes which live and migrate wholly in the sea. (From [oceanos], the ocean ... ) ... [Rarely used. This term and potamodromous received the fishes excluded by the narrowing of anadromous and catadromous] ”

The "-ous" endings are for the adjectival form of the terms; nouns are obtained by replacing that ending with "-y", e.g. anadromy.

The terms anadromous and catadromous were of long standing (and similar but not identical usage); the other terms were coined by Myers. Myers was hesitant about introducing new terms however, saying:

"The writer's strong aversion to the infliction of new scientific terms upon the scientific public has, however, caused him to proceed with great circumspection. ... Finally, the writer has ventured to propose new terms only because he feels that certain new terms will be of distinct advantage in some specialized types of ichthyological work, and that the general biologist and fishery worker will seldom or never have to bother his head about them. Catadromous and anadromous will almost certainly always remain the most important and probably the only widely used terms of their class."(emphasis added)

Myers' term diadromous has proved useful as an inclusive term. But his prediction was otherwise accurate: anadromous and catadromous, are indeed the main widely understood terms. Secor and Kerr (2009) found only one paper that used oceanodromous, 18 using potamodromous, and 122 using amphidromous compared to 985 times for anadromous, 143 times for diadromous, 71 times for catadromous. Obviously the amount of work done on a group is one source of this variation, but another source is the perceived utility and standing of the term itself.

Amphidromy is rarely understood by the wider fish biology audience, or alternatively "There seems to be some reluctance to use the term amphidromy". Myers' definition's ambiguity ("or vice versa") and teleology ("for the purpose of") is one part of that problem. Its meaning/usage has been adjusted (but two such adjustments were found zero times by Secor and Kerr (2009)), and recently it has been stated as differing from anadromy simply because return to fresh water occurs at a juvenile or immature stage; other differences have been claimed (such as where most growth occurs) but they are necessary consequences of the stage at return and therefore are not independent. Some authors have therefore eschewed amphidromy in favour of the more widely understood terms: either anadromy, with or without a remark that return to rivers occurs at an earlier stage (e.g. "juvenile-return anadromy" ), or diadromy which discards information that would be conveyed by anadromy with or without remark.

It has to be borne in mind that any typological system has heuristic value as a convenience for description, and need not reflect phylogeny: each category (term) may include representatives of many distantly related taxa, each of which may well have close relatives that are in another category (term) or that are not migratory and thus fall completely outside the typology. These terms are therefore of limited safety when used alone to screen data to be considered for an analysis, or to decide which species should be read about to explore a phenomenon or possible comparison.

The limitations of typologies were clearly stated by Myers himself. Each may be useful in one context, for one purpose, but not another. I.e. they may categorise along different axes (see Secor and Kerr (2009)). For example, Myers in the same year devised another interesting set of terms, also directed at fishes, but on the basis of their salt-tolerance.

As a footnote it is interesting to note that George S. Myers had previously been one of the degree supervisors for Porfirio Manacop, whose ground-breaking Master's work (in 1941, later published 1953) on a Sicyopterus species overturned the prevailing notion that it was catadromous. It is likely that Myers was impressed by this, and used Sicydium as the "type" genus for amphidromous.

And, as a contrary footnote showing how science fails: regrettably, Manacop's work seems to have been as locally unpopular as it was innovative, because over 20 years later the group he worked on was still being referred to by a colleague in the Philippines who would certainly have known of his work, incorrectly and without evidence, as catadromous.

And although these systems were originated for fishes, they are in principle applicable to any organism.

Forage fish

Forage fish, also called prey fish or bait fish, are small fish which are preyed on by larger predators for food. Predators include other larger fish, seabirds and marine mammals. Typical ocean forage fish feed near the base of the food chain on plankton, often by filter feeding...

often make great migrations between their spawning, feeding and nursery grounds. Schools of a particular stock usually travel in a triangle between these grounds. For example, one stock of herrings have their spawning ground in southern Norway

Norway

Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

, their feeding ground in Iceland

Iceland

Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...

, and their nursery ground in northern Norway. Wide triangular journeys such as these may be important because forage fish, when feeding, cannot distinguish their own offspring.

Capelin

Capelin

The capelin or caplin, Mallotus villosus, is a small forage fish of the smelt family found in the Atlantic and Arctic oceans. In summer, it grazes on dense swarms of plankton at the edge of the ice shelf. Larger capelin also eat a great deal of krill and other crustaceans...

are a forage fish of the smelt family found in the Atlantic

Atlantic Ocean

The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

and Arctic

Arctic Ocean

The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest and shallowest of the world's five major oceanic divisions...

oceans. In summer, they graze on dense swarms of plankton

Plankton

Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...

at the edge of the ice shelf. Larger capelin also eat krill

Krill

Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...

and other crustacean

Crustacean

Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s. The capelin move inshore in large schools to spawn and migrate in spring and summer to feed in plankton rich areas between Iceland

Iceland

, Greenland

Greenland

Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...

, and Jan Mayen

Jan Mayen

Jan Mayen Island is a volcanic island in the Arctic Ocean and part of the Kingdom of Norway. It is long and 373 km2 in area, partly covered by glaciers . It has two parts: larger northeast Nord-Jan and smaller Sør-Jan, linked by an isthmus wide...

. The migration is affected by ocean current

Ocean current

An ocean current is a continuous, directed movement of ocean water generated by the forces acting upon this mean flow, such as breaking waves, wind, Coriolis effect, cabbeling, temperature and salinity differences and tides caused by the gravitational pull of the Moon and the Sun...

s. Around Iceland maturing capelin make large northward feeding migrations in spring and summer. The return migration takes place in September to November. The spawning migration starts north of Iceland in December or January.

The diagram on the right shows the main spawning

Spawn (biology)

Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...

grounds and larval drift routes. Capelin on the way to feeding grounds is coloured green, capelin on the way back is blue, and the breeding grounds are red.

Highly migratory species

The term highly migratory species (HMS) has its origins in Article 64 of the United Nations Convention on the Law of the Sea

United Nations Convention on the Law of the Sea

The United Nations Convention on the Law of the Sea , also called the Law of the Sea Convention or the Law of the Sea treaty, is the international agreement that resulted from the third United Nations Conference on the Law of the Sea , which took place from 1973 through 1982...

(UNCLOS). The Convention does not provide an operational definition of the term, but in an annex (UNCLOS Annex 1) lists the species considered highly migratory by parties to the Convention. The list includes: tuna

Tuna

Tuna is a salt water fish from the family Scombridae, mostly in the genus Thunnus. Tuna are fast swimmers, and some species are capable of speeds of . Unlike most fish, which have white flesh, the muscle tissue of tuna ranges from pink to dark red. The red coloration derives from myoglobin, an...

and tuna-like species (albacore, bluefin, bigeye tuna

Bigeye tuna

The bigeye tuna, Thunnus obesus, is an important food fish and prized recreational game fish. It is a true tuna of the genus Thunnus, belonging to the wider mackerel family Scombridae....

, skipjack

Skipjack tuna

The skipjack tuna, Katsuwonus pelamis, is a medium-sized perciform fish in the tuna family, Scombridae. It is otherwise known as the aku, arctic bonito, mushmouth, oceanic bonito, striped tuna, or victor fish...

, yellowfin

Yellowfin tuna

The yellowfin tuna is a species of tuna found in pelagic waters of tropical and subtropical oceans worldwide.Yellowfin is often marketed as ahi, from its Hawaiian name ahi although the name ahi in Hawaiian also refers to the closely related bigeye tuna. The species name, albacares can lead to...

, blackfin

Blackfin tuna

Blackfin tuna is the smallest tuna species in the Thunnus genus, generally growing to a maximum of in length and weighing 21 kg . Blackfin have oval shaped bodies, black backs with a slight yellow on the finlets, and have yellow on the sides of their body...

, little tunny, southern bluefin

Southern bluefin tuna

The southern bluefin tuna, Thunnus maccoyii, is a tuna of the family Scombridae found in open southern hemisphere waters of all the world's oceans mainly between 30°S and 50°S, to nearly 60°S...

and bullet), pomfret, marlin

Marlin

Marlin, family Istiophoridae, are fish with an elongated body, a spear-like snout or bill, and a long rigid dorsal fin, which extends forward to form a crest. Its common name is thought to derive from its resemblance to a sailor's marlinspike...

, sailfish

Sailfish

'Sailfish' are two species of fish in the genus Istiophorus, living in warmer sections of all the oceans of the world. They are predominately blue to gray in color and have a characteristic erectile dorsal fin known as a sail, which often stretches the entire length of the back...

, swordfish

Swordfish

Swordfish , also known as broadbill in some countries, are large, highly migratory, predatory fish characterized by a long, flat bill. They are a popular sport fish of the billfish category, though elusive. Swordfish are elongated, round-bodied, and lose all teeth and scales by adulthood...

, saury

Saury

Sauries are fish of the family Scomberesocidae. There are two genera, each containing two species. The name Scomberesocidae is derived from the Greek, skombros = tuna/mackerel, and esox = nursery of salmon....

and ocean going shark

Shark

Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s, dolphin

Dolphin

Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...

s and other cetaceans.

These high trophic

Trophic level

The trophic level of an organism is the position it occupies in a food chain. The word trophic derives from the Greek τροφή referring to food or feeding. A food chain represents a succession of organisms that eat another organism and are, in turn, eaten themselves. The number of steps an organism...

oceanodromous species undertake migrations of significant but variable distances across oceans for feeding, often on forage fish, or reproduction, and also have wide geographic distributions. Thus, these species are found both inside the 200 mile exclusive economic zone

Exclusive Economic Zone

Under the law of the sea, an exclusive economic zone is a seazone over which a state has special rights over the exploration and use of marine resources, including production of energy from water and wind. It stretches from the seaward edge of the state's territorial sea out to 200 nautical...

s and in the high seas outside these zones. They are pelagic

Pelagic fish

Pelagic fish live near the surface or in the water column of coastal, ocean and lake waters, but not on the bottom of the sea or the lake. They can be contrasted with demersal fish, which do live on or near the bottom, and reef fish which are associated with coral reefs.The marine pelagic...

species, which means they mostly live in the open ocean and do not live near the sea floor, although they may spend part of their life cycle in nearshore waters.

Highly migratory species can be compared with straddling stock and transboundary stock. Straddling stock range both within an EEZ as well as in the high seas. Transboundary stock range in the EEZs of at least two countries. A stock can be both transboundary and straddling.

Other examples

Some of the best-known anadromous fish are the six species of Pacific salmon, which are Chinook (King), Coho (Silver), Sockeye (Red), Chum (Dog), Pink (Humpback), and Cherry. The salmon hatch in small freshwater streams. From there they migrate to the sea to mature, living there for two to six years. When mature, the salmon return to the same streams where they were hatched to spawn. Salmon are capable of going hundreds of kilometers upriver, and humans must install fish ladder

Fish ladder

A fish ladder, also known as a fishway, fish pass or fish steps, is a structure on or around artificial barriers to facilitate diadromous fishes' natural migration. Most fishways enable fish to pass around the barriers by swimming and leaping up a series of relatively low steps into the waters on...

s in dam

Dam

A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

s to enable the salmon to get past. Other examples of anadromous fishes are sea trout, three-spined stickleback

Three-spined stickleback

The three-spined stickleback, Gasterosteus aculeatus, is a fish native to much of northern Europe, northern Asia and North America. It has been introduced into parts of southern and central Europe.-Distribution and morphological variation:...

, and shad

Shad

The shads or river herrings comprise the genus Alosa, fish related to herring in the family Clupeidae. They are distinct from others in that family by having a deeper body and spawning in rivers. The several species frequent different areas on both sides of the Atlantic Ocean, Mediterranean Sea....

The most remarkable catadromous fishes are freshwater eel

Eel

Eels are an order of fish, which consists of four suborders, 20 families, 111 genera and approximately 800 species. Most eels are predators...

s of genus Anguilla, whose larvae drift from swawning grounds in the Sargasso sea, sometimes for months or years, before entering freshwater river and streams as glass eels or elvers (see eel life history
Eel life history
The eel is a long, thin bony fish of the order Anguilliformes. Because fishermen never caught anything they recognized as young eels, the life cycle of the eel was a mystery for a very long period of scientific history...

).

An example of a euryhaline species is the Bull shark

Bull shark

The bull shark, Carcharhinus leucas, also known as Zambezi shark or unofficially known as Zambi in Africa and Nicaragua shark in Nicaragua, is a shark common worldwide in warm, shallow waters along coasts and in rivers...

, which lives in Lake Nicaragua

Lake Nicaragua

Lake Nicaragua or Cocibolca or Granada or is a vast freshwater lake in Nicaragua of tectonic origin. With an area of , it is the largest lake in Central America, the 19th largest lake in the world and the 9th largest in the Americas. It is slightly smaller than Lake Titicaca. With an elevation...

of Central America and the Zambezi River

Zambezi

The Zambezi is the fourth-longest river in Africa, and the largest flowing into the Indian Ocean from Africa. The area of its basin is , slightly less than half that of the Nile...

of Africa. Both these habitats are fresh water, yet Bull sharks will also migrate to and from the ocean. Specifically, Lake Nicaragua Bull sharks migrate to the Atlantic Ocean

Atlantic Ocean

The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

and Zambezi Bull sharks migrate to the Indian Ocean

Indian Ocean

The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...

.

Diel vertical migration

Diel vertical migration

Diel vertical migration, also known as diurnal vertical migration, is a pattern of movement that some organisms living in the ocean and in lakes undertake each day. Usually organisms move up to the epipelagic zone at night and return to the mesopelagic zone of the oceans or to the hypolimnion zone...

is a common behavior; many marine species move to the surface at night to feed, then return to the depths during daytime.

A number of large marine fishes, such as the tuna

Tuna

, migrate north and south annually, following temperature variations in the ocean. These are of great importance to fisheries

Fishery

Generally, a fishery is an entity engaged in raising or harvesting fish which is determined by some authority to be a fishery. According to the FAO, a fishery is typically defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of boats,...

.

Freshwater fish migrations are usually shorter, typically from lake to stream or vice versa, for spawning purposes. However, potamodromous migrations of Colorado pikeminnow of the Colorado River system can be extensive. Migrations to natal spawning grounds easily be 100 km, with maximum distances of 300 km reported from radiotagging studies.

Historic exploitation

Since prehistoric times humans have exploited certain anadromous fishes during their migrations into freshwater streams, when they are more vulnerable to capture. Societies dating to the Millingstone Horizon

Millingstone Horizon

Millingstone Horizon is an archaeological period of Native American dominance denoting a period in California, USA involving extensive use of manos and other grinding technology. The interval is a subset of the Archaic Period; specifically Millingstone is usually applied to the period 6500 to...

are known which exploited the anadromous fishery of Morro Creek

Morro Creek

Morro Creek is a coastal stream in San Luis Obispo County, California, USA. This watercourse discharges to the Pacific Ocean at the city of Morro Bay.-Natural history:...

and other Pacific coast

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

estuaries

Estuary

An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....

. In Nevada

Nevada

Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...

the Paiute

Paiute

Paiute refers to three closely related groups of Native Americans — the Northern Paiute of California, Idaho, Nevada and Oregon; the Owens Valley Paiute of California and Nevada; and the Southern Paiute of Arizona, southeastern California and Nevada, and Utah.-Origin of name:The origin of...

tribe has harvested migrating Lahontan cutthroat trout along the Truckee River

Truckee River

The Truckee River is a stream in the U.S. states of California and Nevada. The river is about long. Its endorheic drainage basin is about , of which about are in Nevada. The Truckee is the sole outlet of Lake Tahoe and drains part of the high Sierra Nevada, emptying into Pyramid Lake in the Great...

since prehistoric times. This fishing practice continues to current times, and the U.S. Environmental Protection Agency‎ has supported research to assure the water quality in the Truckee can support suitable populations of the Lahontan cutthroat trout.

Modelling fish migration

In a paper published in 2009, researchers from Iceland recount their application of an interacting particle model to the capelin stock around Iceland, successfully predicting the spawning migration route for 2008.

External links

United Nations
United Nations
The United Nations is an international organization whose stated aims are facilitating cooperation in international law, international security, economic development, social progress, human rights, and achievement of world peace...

: Introduction to the Convention on Migratory Species
Living North Sea – International project on tackling fish migration problems in the North Sea Region
Fish Migration Network – Worldwide network of specialist working on the theme fish migration

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.