Green fish , also called game fish or bait fish , is a small pelagic fish that is preyed on by larger predators for food. Predators include other larger fish, seabirds and marine mammals. Typical marine ornamental fish feed near the base of the food chain in plankton, often by filtering food. They include mainly fish from the Clupeidae family (herring, sardines, shad, hilsa, menhaden, anchovies and sprats), but also other small fish, including halfbeaks, silversides, smelt like capelin, and fusilier gold band depicted on the right.
The forage fish compensates for its small size by forming a school. Some swim in the grid that is synchronized with the mouth open so they can efficiently filter out the plankton. These schools can become large herds that move along the shoreline and migrate in the open ocean. Beting is a concentrated fuel resource for large marine predators. Predators focus heavily on the shelf, very conscious of their numbers and existence, and create their own migrations that can reach thousands of miles to connect, or stay in touch, with them.
The main producers of the oceans, especially those contained in plankton, produce food energy from the sun and are the raw fuel for seafood nets. Feed Foods transfer this energy by eating plankton and becoming food for top predators. In this way, forage fish occupies a central position in the sea food and lake nets.
The fishing industry catches fish feed primarily to feed the livestock. Some fisheries scientists have expressed concern that this will affect populations of predatory fish that depend on it.
Video Forage fish
In the ocean
Typical marine ornamental fish are small fish, silver-silver schools like herring, anchovy and menhaden, and other small fish baits, such as capelin, smelts, sand spears, halfbeaks, pollocks, butterfish, and juvenile rockfish. Herring is a superior forage fish, often marketed as sardines or pilchards.
The term "forage fish" is a term used in fisheries, and is applied also to find species that are not true fish, but play an important role as predators prey. So invertebrates such as squid and shrimp are also referred to as "forage fish". Even small creatures such as shrimp called krill, small enough to be eaten by other forage fish, but large enough to eat the same zooplankton as forage, are often classified as "forage fish".
Forage fish utilize copepod, mysids and krill biomass in the pelagic zone to become the dominant converter of the huge production of oceans of zooplankton. They are, in turn, the main prey item for a higher trophic level. Forage fish may have reached their dominance because of the way they live in very large schools, and often very quickly.
Although forage fish are abundant, there are relatively few species. There are more species of primary producers and predators peak in the sea than forage fish.
Seafood web
Forage fish occupies a central position in the seafood nets. The position occupied by fish in the food web is called trophic level (Greek trof? = food). The organisms they eat are at a lower trophic level, and the organisms that eat them are at higher trophic levels. Forage fish occupy the middle level in the food web, serving as the dominant prey for higher level fish, seabirds and mammals.
The ecological pyramid is a graphical representation, along the line of diagrams on the right, which shows how the biomass changes or productivity at each trophic level within an ecosystem. The first or bottom levels are occupied by major producers or autotrophs (Greek autos = self and trophe = food). This is the name given to organisms that do not feed on other organisms, but produces biomass from inorganic compounds, mostly by the process of photosynthesis.
In the oceans, most of the primary production is done by algae. This contrasts with the soil, where most of the primary production is done by vascular plants. Algae range from single floating cells to inherent seaweed, while vascular plants are represented at sea by groups such as seagrass. Larger producers, such as seagrass and seaweed, are largely confined to the littoral zones and shallow waters, where they adhere to the underlying substrate and are still inside the photon zone. Much of the primary production in the ocean is done by microscopic organisms, phytoplankton.
Thus, in marine environments, the first lower trophic level is occupied primarily by phytoplankton, a microscopic drift organism, mostly single-celled algae, floating in the ocean. Most phytoplankton are too small to be seen individually with the naked eye. They can appear as a green change of water when they are present in a high enough amount. Because they increase their biomass largely through photosynthesis they live in a sun-lined surface (euphotic zone) of the ocean.
The most important phytoplankton groups include diatoms and dinoflagellates. Diatoms are very important in the oceans, where they are estimated to contribute up to 45% of the total main production of the oceans. Diatoms are usually microscopic, although some species can reach up to 2 millimeters in length.
The second trophic level (primary consumer) is occupied by the zooplankton feeding phytoplankton. Together with phytoplankton, they form a food pyramid base that supports most of the world's fishing areas. Zooplankton are small animals found with phytoplankton in sea-surface waters, and include small crustaceans, and fish and seed larvae (newly hatched fish). Most zooplankton are filter feeders, and they use a complement to filter phytoplankton in water. Some of the larger zooplankton also eat smaller zooplankton. Some zooplankton can jump a little to avoid predators, but they can not really swim. Like phytoplankton, they float with currents, tides and wind instead. Zooplankton can multiply rapidly, their population can increase up to thirty percent a day under favorable conditions. Many live a short and productive life and reach maturity quickly.
The most important groups of zooplankton are copepods and krill. This is not shown in the picture above, but discussed in more detail later. Copepoda is a group of small crustaceans found in marine and freshwater habitats. They are the largest source of protein in the ocean, and are important prey for fish feed. Krill is the next largest source of protein. Krills are large zooplankton predators that feed on smaller zooplankton. This means they actually belong to a third trophic level, secondary consumers, along with forage fish.
Together, phytoplankton and zooplankton are mostly planktons in the ocean. Plankton is a term used for small organisms that float in the sea (Greek planktos = nomad or drifter). By definition, organisms classified as plankton can not swim against ocean currents; they can not withstand ambient currents and control their position. In marine environments, the first two trophic levels are occupied mainly by plankton. Plankton is divided into producers and consumers. The producers are phytoplankton (phyton = Greek) and the consumer, who eats phytoplankton, is zooplankton (Greek zoon = animal).
Diet
Feed fish feed in plankton. When they are eaten by larger predators, they transfer this energy from the bottom of the food chain upward and in this way is the central connection between the trophic level.
Fish feeds are usually filter feeders, which means that they feed by filtering suspended matter and food particles from water. They usually travel in large, slow-moving, crowded schools with open mouths. They are usually omnivores. Their diet is usually based primarily on zooplankton, though, because they are omnivorous, they also pick up some phytoplankton.
Young forage fish, like herring, mostly eat phytoplankton and as they mature they start consuming larger organisms. Older herring fish feed on zooplankton, small animals found at sea level, and larvae of fish and fried fish (newly hatched fish). Copepods and other small crustaceans are common zooplankton eaten by forage fish. During the daytime, many forage fish stay in deep water security, eating on the surface only at night when there is less possibility of predation. They swim with their mouths open, filtering plankton out of the water as it passes through their gills.
Sea halfbeak are omnivores that feed on algae, plankton, sea plants such as seagrass, invertebrates such as pteropods and crustaceans and smaller fish. Some tropical species eat animals during the day and plants at night, while others alternate summer carnivores with winter herbivores. They are in turn eaten by billfish, mackerel, and sharks.
Predator
Fish forage is a food that sustains larger predators above them in the seafood chain. The luxury they present in their school makes them the ideal source of food for top predator fish such as tuna, striped sea fish, cod fish, salmon, barracuda and swordfish, and sharks, whales, dolphins, sea dolphins, seals, sea lions , and seabirds.
Schooling
The forage fish compensates for its small size by forming a school. These sometimes enormous meetings move the seafood network. Most forage fish are pelagic fish, which means they form their school in open waters, and not at the bottom (benthic fish) or near the bottom (benthopelagic fish). They were short-lived, and mostly ignored by humans, regardless of the occasional supporting role in a documentary about a great sea predator. While we may not be paying much attention to them, the big sea predators are very focused on them, very aware of their number and whereabouts, and make migrations that can reach thousands of miles to connect with them. After all, forage fish is their food.
Herring is one of the most spectacular school fish. They gather together in large numbers. The schools have measured more than four cubic kilometers, containing about four billion fish. These schools move along the coastline and across the open ocean. The Herring School in general has a very precise setting that allows schools to maintain a relatively constant cruising speed. Herrings have very good hearing, and their school reacts very quickly to predators. The herring keeps a certain distance from a moving scuba divers or a cruising predator like a killer whale, forming a vacuole that can look like a donut from a reconnaissance plane. The subtleties of the school are far from fully understood, especially those that swim and eat energetics. Many hypotheses that explain the functioning of schools have been suggested, such as better orientation, synchronized hunting, predator confusion and reduced risk are found. Schools also have disadvantages, such as the buildup of excretion in the respiratory and oxygen media as well as the depletion of food. The way the array of fish in schools might provide energy saving benefits, though this is controversial.
On quiet days, anchovies schools can be detected on the surface a mile away by the small waves they form, or from a few meters at night when they trigger bioluminescence around the plankton. Underwater footage shows herring constantly sailing at high speeds of up to 108 cm per second, with much higher escape speeds.
They are a fragile fish, and because of their adaptation to school behavior they are rarely displayed in an aquarium. Even with the best facilities the aquarium can offer them to be sluggish compared to their vibrating energy in the wild schools.
Copepod hunting
Copepoda is a group of small crustaceans found in marine and freshwater habitats. Many species are planktonic (floating in seawater), while others are benthic (living on the seafloor). Copepods are usually one millimeter (0.04 inches) long to two millimeters (0.08 in) long, with teardrop shaped bodies. Like other crustaceans, they have steel-coated outer frames, but they are so small that these armor, and the whole body, are usually transparent.
Copepods are usually dominant zooplankton. Some scientists say they form the largest animal biomass on the planet. Another challenger is the Antarctic krill. But copepods are smaller than krill, with faster growth rates, and they are more evenly distributed across the ocean. This means that copepods almost certainly contribute more secondary production to the world's oceans than krill, and perhaps more than all other groups of marine organisms together. They are the main items on the menu of forage fish.
Copepoda is very alert and evasive. They have a large antenna. As they spread their antennae, they can feel pressure waves from the approaching fish and jump at high speed for several centimeters.
The herring is a pelagic feeder. Their prey consists of a wide spectrum of phytoplankton and zooplankton, among which copepods are the dominant prey. Young herring usually catches small copepods by hunting them individually - they approach them from below. The (half speed) video loop on the left shows the teenage herring eating on copepods. At the center of the picture copepoda successfully escaped to the left. The opercula (a hard bone flap covering the gills) is widespread to offset the pressure waves that will alert the copepods to trigger the jump.
If the concentration of prey reaches a very high level, the herring adopts a method called "ram feeding". They swam with their mouths wide open and their opercula flourished. Every few feet, they close and clear their gill filter for several milliseconds (filter the food). In the photo on the right, ram herring feed at copepoda school. All fish open their mouths and wide opercula at the same time (visible red gills - click to enlarge). Fish swim in the grid where the distance between them equals their long jump of prey, as shown in the animation below.
In animation, teenage herring hunts copepods in sync: Copepoda senses with their antenna pressure waves from approaching herring and reacts with a quick jump jump. The jump length is fairly constant. Fish align themselves on the grid with this distinctive long jump. Copepoda can be raced about 80 times before the tire comes off. After the jump, it takes 60 milliseconds to spread the antenna again, and this time delay becomes its destruction, because the almost unlimited current of the herring allows the herring to finally break the copepod. A single teenage herring can never catch a large copepod.
Migration
Forage fish often make large migrations between spawning, feeding and feeding them. Schools of a particular stock usually travel in a triangle between these basics. For example, one stock of a herring has spawning spots in southern Norway, where they eat in Iceland, and their nursery in northern Norway. Such broad triangular journeys may be important because forage fish, while feeding, can not distinguish their own offspring.
A lush dining place for fish feed is provided by marine upwellings. Oceanic gyre is a large-scale ocean currents caused by the Coriolis effect. Wind-driven surface currents interact with these gyres and underwater topography, such as seafloor and continental shelf edges, to produce downwellings and upwellings. It can transport nutrients that grow in plankton. The result can be a rich eating place appealing to forage fish for plankton. In turn, the forage fish itself becomes a feeding place for larger predatory fish. Most upwellings are beaches, and many of them support some of the most productive fisheries in the world. The leading upwelling areas include coastal Peru, Chile, the Arabian Sea, western part of South Africa, New Zealand east and coast of California.
Capelin is a forage fish of the smelly family found in the Atlantic and Arctic Oceans. In the summer, they graze on a bunch of planktons on the edge of the ice shelf. Larger capelin also feeds on other krill and crustaceans. The Capelin are moving on the beach in large schools to lay eggs and migrate in spring and summer to feed in plankton-rich regions between Iceland, Greenland and Jan Mayen. Migration is influenced by ocean currents. Around Iceland matures capelin makes a great feeding migration to the north in spring and summer. Migration resumes from September to November. Spawning migration begins in northern Iceland in December or January.
The diagram on the right shows the main spawning sites and the drift larvae route. Capelin on the way to the green eater, the capelin on the way back is blue, and the breeding grounds are red. In a paper published in 2009, researchers from Iceland described the application of particle models that interacted with capelin stocks around Iceland, which successfully predicted spawning migratory routes for 2008.
Predator attack
School forage fish is subject to constant attacks by predators. An example is the attack that occurred during the run of African sardines. The African sardine run is a spectacular migration by millions of silvery sardines along the southern coastline of Africa. In terms of biomass, sardine operations can rival East Africa's largest reindeer migration.
Sardines have a short life cycle, live only two or three years. Adult sardines, about two years old, the mass at Bank Agulhas where they lay their eggs during spring and summer, release tens of thousands of eggs into the water. Adult sardines then enter hundreds of shoals into the sub-tropical waters of the Indian Ocean. A larger one may be 7 kilometers (4.3 miles) long, 1.5 kilometers (0.93 mi) wide and 30 meters (98 feet) deep. A large number of sharks, dolphins, tuna, sailfish, seals Cape, and even killer whales swarm and follow the shoals, creating madness along the shoreline.
When threatened, the sardines instinctively group together and make a large bait ball. The bait ball can be up to 20 meters (66 feet) in diameter. They are short-lived, rarely last more than 20 minutes. A total of 18,000 dolphins, behaving like shepherd dogs, circling sardines into these bait balls, or herding them into shallow waters where they are more easily captured. Once captured, the dolphins and other predators take turns hijacking the bait ball, gobbling up the fish as they sweep. Seabirds also attack them from above, swarm gannets, cormorants, terns and gulls. Some of these sea birds fall from a height of 30 meters (98 feet), plunging through the water leaving a trail like steam in the back like a fighter.
Eggs, left in Agulhas Banks, drifted northwest with currents into the waters off the west coast, where the larvae develop into teenage fish. When they are old enough, they converge into dense groups and migrate south, back to Agulhas banks to restart the cycle.
Maps Forage fish
Forage fishery
History
Herring has been known as a staple food source since 3000 BC. In Roman times, anchovy was a base for a fermented fish sauce called garum. This staple dish is produced in industrial quantities and transported over long distances.
Fishing for sardella or sardine ( Sardina pilchardus ) is an ongoing activity on the Adriatic coast of Croatia Dalmatia and Istria. It traces its roots back thousands of years. The area is largely Venetian territory, part of the Roman Empire. This area is always sustained through fishing, especially sardines. Throughout the coastal cities still promote the traditional practice of fishing by sailboats for tourism and festivals.
The capture and processing of Pilchards grew rapidly in Cornwall between 1750 and 1880, after which stocks declined almost in the terminal. Recently (2007) the stock has improved. The industry has been featured in many works of art, including Stanhope Forbes and other Newlyn School artists.
Contemporary
Traditional commercial fisheries are directed at high-value marine predators such as cod, rockfish and tuna, rather than forage fish. As technology evolves, fisheries become highly effective in locating and catching many predatory fish from collapsing stocks. Industry is compensated by switching to lower species in the food chain.
In the past, forage fish is more difficult to lure profitable, and is a small part of global marine fisheries. But modern industrial fishery technology has enabled the removal of increased numbers. Industrial scale shark fisheries require large-scale fish landing to recover profits. They are dominated by a small number of fishing companies and processing companies.
The forage populations are particularly vulnerable when faced with modern fishing equipment. They swim near the surface in compacted schools, so they are relatively easy to find on the surface with sophisticated electronic fishfinders and from above with reconnaissance planes. Once there, they are scooped out of the water using highly efficient nets, like purse nets, which move most schools.
The spawning pattern of forage fish is very predictable. Some fisheries use the knowledge of these patterns to harvest the forage species as they come together to spawn, remove the fish before they actually lay their eggs. Fishing during spawning periods or at other times when fish feeding in large quantities can also be a blow to predators. Many predators, such as whales, tuna, and sharks, have evolved to migrate long distances to specific locations to feed and breed. Their survival depends on their findings at the feed school on their eating grounds. The great sea predators found that, no matter how they adapted for speed, size, endurance or stealth, they were on the losing side when faced with contemporary industry fishing machines.
Overall, forage fish covers 37 percent (31.5 million tons) of all fish taken from the world's oceans each year. However, since there are fewer species of forage fish compared to predatory fish, forage fish feed is the largest in the world. Seven of the top ten fish target fish feed. Total catches of the world herring, sardines and anchovy alone in 2005 were 22.4 million tonnes, 24 percent of the total world catch.
The Peruvian anchoveta fishery is now the largest in the world (10.7 million tons in 2004), while the Alaskan pollock fisheries in the Bering Sea are the world's largest single species fisheries (3 million tons). Pollock Alaska is said to be the largest source of single species of fish in the world. However, pollock biomass has declined in recent years, possibly posing a problem for both the Bering Sea ecosystem and the commercial fisheries it supports. The NOAA acoustic survey shows that pollock 2008 population is almost 50 percent lower than last year's survey rate. Some scientists think this decline in Alaska pollock could repeat the collapse experienced by the Atlantic cod, which could have negative consequences for the entire Bering Sea ecosystem. Salmon, halibut, Steller's endangered sea lions, fur seals, humpback whales feed pollock and rely on healthy populations to defend themselves.
Use as animal feed
Eighty percent of the sharks caught are given to animals, in large part due to the high content of long-chain omega-3 fatty acids useful in their flesh. Ninety percent is processed into fishmeal and fish oil. Of this amount, 46 percent were fed to aquaculture, 24 percent for pigs, and 22 percent for poultry (2002). Six times the weight of forage fish is fed to pigs and poultry rather than the consumption of seafood throughout the US market. One of the most promising alternatives to fish oil as a source of long chain fatty acids omega-3 and certain amino acids is algae oil from microalgae, the original source of these fatty acids in fish feed.
According to Turchini and De Silva (2008), 2.5 million tons of annual forage catch are consumed by the global cat food industry. In Australia, pet cats eat 13.7 kilograms of fish per year compared to 11 kilograms eaten by the average Australian. The pet food industry is increasingly marketing premium and super-premium products, when different raw materials, such as by-products from the fish filleting industry, can be used instead.
Environmental issues
In 2008, the Sea Around Us Project completed a nine-year study of forage fish led by fisheries scientist Jacqueline Alder and Daniel Pauly. They concluded that...
By 2015 sardine populations fall along the west coast of the United States, causing fisheries to close early and remain closed during the 2015-2016 season. The main reason for population accidents, is overfishing because of the demand for fish food and fish oil used in feed for cultivation and for human nutritional supplements. In an effort to provide relief from the pressures placed on forage fish populations, the World Bank along with the University of Arizona, the Monterey Bay Aquarium and the New England Aquarium have sponsored a competition called the F3 Challenge (Free Fish-Free), which will award $ 200,000 to producers the most successful fish feed that develops aquaculture bait that is not made from fish.
On the lake and river
Forage fish also inhabit freshwater habitats, such as lakes and rivers, where they serve as food for larger freshwater predators. Usually smaller than 15 cm (6 inches) in length, these small bait fish form most of the fish found in lakes and rivers. Small fish families, composed of small fish, chubs, shiners and daces, consist of more than fifty species. Other freshwater forages include suckers, killers, shad, bony fish and fish from the family of mola-mola, excluding bass and crappie, and smaller species of carp. There are also anadromous forage fish, such as eulachons.
In any freshwater or saltwater ecosystem, there will always be desirable and undesirable fish, and this varies from country to country, and often from region to region within a country. Sports fishermen share freshwater predators from forage fish into them:
- that has a good fighting ability and is good to eat, is called sport (or game) fish.
- other less desirable fish, called rough fish in North America and rough fish in England
Rough or rough fish usually refers to unusual fish eaten, not sought for sports reasons, or has become an invasive species that reduces the desired fish population. They compete to find forage fish with more popular sport fish. They are often regarded as a nuisance, and are usually not protected by game laws. Forage fish are generally not considered rough or rough fish because of their usefulness as bait.
The term rough fish is used by US state agencies and anglers to describe unwanted predatory fish. In North America, anglers for salmon, trout, bass, spear, catfish, walleye and muskellunge. The smallest fish are called panfish, because they can be accommodated in a standard cooking pot. Some examples are crappies, rock bass, perch, bluegill and sunfish.
The term coarse fish originated in England in the early 19th century. Prior to that time, recreational fishing was a sport of nobles, who cornered trout and salmon they call "game fish". Fish other than hunted fish are underestimated as "rough fish". These days, "game fish" refers to Salmon (other than grayling) - namely salmon, trout and charcoal. Rough fish consist mostly of larger species of Cyprinids (goldfish, roach, bream) as well as spears, catfish, gar and lampreys. Rough fish is no longer underestimated; indeed, rough fishing has become a popular hobby.
Feed and fish feed
Forage fish is sometimes referred to as fish bait or feeder fish . Bait fish is a term used primarily by recreational fishermen, although commercial fishermen also catch fish for longlines and traps. Forage fish is a fishery term, and is used in the context of fisheries. Bait fish, on the other hand, are fish caught by humans to be used as bait for other fish. The term overlaps in the sense that most of the bait fish are also fish fodder, and vice versa. Fish feeder is a term used primarily in the context of aquarium fish. This basically refers to the same concept as forage fish, smaller fish eaten by larger fish, but the term is tailored to the specific requirements of working with fish in an aquarium.
Timeline
- 2006: US National Coalition for Marine Conservation asks US fisheries managers to put "First Livestock Share!". Their campaigns were launched with the publication of their report, Taking Feed: What are the American Fishers Seizing Predators for Their Prayers? , is available at a cost to the US fishing industry, encouraging fisheries managers to protect predators - prey relationships as a first step towards an ecosystem-based approach to fisheries management.
- 2009: The International Lenfest Forage Fish Task Force was set up to develop a workable management plan to tackle the depletion of forage fish.
- 2015: sardine populations fall along the west coast of the United States.
Recent reports
- Pikitch E and the other 12 (2012) Small Fish, Big Impact: Managing Crucial Link on Web Seafood Lenfest Sea Program , Washington, DC. Summary and other materials available on the Lenfest Sea Program website.
See also
- Foraging
- optimal feeding theory
- Blue Planet
Note
References
-
Pauly, D; Christensen, V; Dalsgaard, J; Froese, R; Torres, F (1998). "Capturing a seafood net" (PDF) . Science . 279 (5352): 860-863. doi: 10.1126/science.279.5352.860. PMID 9452385. Archived from the original (PDF) in 2008-02-21.
External links
- Herring Research: Using Acoustics to Count Fish.
- Sanders, Michael (1995) Impact of predator-prey relations on FAO harvesting and management strategies.
- Skjoldal, Hein Rune (2011) "The ecological effect of fisheries on small pelagic" Document background for the CBD Expert meeting, Bergen, 7-9 December 2011.
- Daniel Pauly at Fish Forever - YouTube: Pauly talks about his "epiphany" about eating anchovy directly.
Source of the article : Wikipedia
0 Comments