Sea lice are copepods which parasitise fish. Copepods are a group of small Crustaceans found in the sea and nearly every freshwater habitat and they constitute the biggest source of protein in the oceans Parasitism is a type of symbiotic relationship between Organisms of different Species. There are two species of sea lice commonly found on cultured salmonids, Caligus elongatus, a species of parasite that infests over fifty different species of marine fish, and Lepeophtheirus salmonis, which infests only salmon and closely related species such as rainbow trout (but current research indicates it may be spread via the three-spined stickleback). Fish farming is the principal form of Aquaculture, while other methods may fall under Mariculture. Salmonidae is a family of Ray-finned fish, the only living family of the order Salmoniformes. Parasitism is a type of symbiotic relationship between Organisms of different Species. Fish are aquatic Vertebrate animals that are typically ectothermic (previously Cold-blooded) covered with scales, and equipped with two Salmon is the common name for several species of Fish of the family Salmonidae. The rainbow trout ( Oncorhynchus mykiss) is a species of Salmonid native to tributaries of the Pacific Ocean in Asia and North America The three-spined stickleback, Gasterosteus aculeatus, is a Fish native to much of northern Europe, northern Asia and North America Both species are also found on wild salmon.

There is reported concern that sea lice flourishing on salmon farms can spread to nearby wild juvenile salmon and devastate these populations. Fish farming is the principal form of Aquaculture, while other methods may fall under Mariculture. ^[1] Sea trout populations in recent years have seriously declined due to infestation by sea lice from salmon farms. The brown trout ( Salmo trutta morpha fario and S trutta morpha lacustris) and the sea trout ( S ^[2]

As sea lice develop from eggs to adults, they shed their exoskeletons in a series of moults. An exoskeleton is an external Skeleton that supports and protects an animal's body in contrast to the internal Endoskeleton of for example a Human. Ecdysis is the Molting of the Cuticula in Arthropods and related groups ( Ecdysozoa) This creates a number of identifiable life stages. Sea lice in the first two stages are called nauplii. A nauplius (plural nauplii) is the first Larva of animals classified as Crustaceans (subphylum of Arthropoda) Nauplii can neither feed nor attach themselves to fish. In the next, copepodid, stage, the lice can attach themselves to fish. They then moult through four chalimus stages during which they are anchored to a host fish. As pre-adults (two stages) and adults (one, final stage), they can crawl about the host fish. It appears that they are most damaging to the host fish in these final, motile stages.

Sea lice have always been relatively common on adult salmon as they return to spawn. However, sea lice cannot tolerate fresh water, and drop off the fish as they encounter reduced salinities. Freshwater is a word that refers to bodies of water such as Ponds lakes rivers and streams containing low concentrations of dissolved Salts and other Total dissolved Salinity is the Saltiness or dissolved salt content of a body of Water. Natural infection dynamics on wild salmon are not well understood. However, lice are typically very rare on juvenile salmon in areas far from fish farms.

By contrast, relatively high abundances have repeatedly been reported on juvenile salmon that have migrated past fish farms. Evidence collected in both the Atlantic and Pacific Oceans indicates that these infestation levels can often be lethal. The Pacific Ocean is the largest of the Earth 's Oceanic divisions Smaller host fish appear to be particularly vulnerable. Hence, pink salmon (Oncorhynchus gorbuscha), which migrate out to sea immediately upon emergence from spawning gravel, are particularly at risk. Pink salmon or humpback salmon, Oncorhynchus gorbuscha, (from a Russian name for this species gorbuscha--горбуша is a Species of anadromous Nonetheless, larger species, specifically including wild Atlantic salmon (Salmo salar) have been found to have lethal lice loads near fish farms. Atlantic salmon, known scientifically as Salmo salar, is a species of Fish in the family Salmonidae, which is found in the northern Sea lice are also economically damaging to the fish farms themselves; in one recent year, sea lice cost salmon farmers more than US$100 million for treatment and lost production, which represents about 20% of their total costs. The United States dollar ( sign: $; code: USD) is the unit of Currency of the United States; it has also been

Currently, fish farmers rely heavily on the chemical emamectin benzoate (SLICE) for controlling sea louse infestation rates. Many governments now impose limits on sea louse infestation levels on fish farms. The adequacy of existing regulations, and the environmental impacts of the use of SLICE are highly controversial. Public opinion is particularly polarized in the northeast Pacific where a moratorium on expansion has been lifted by the British Columbia government while the Alaska government is maintaining a total ban on salmon farming in its waters. British Columbia (ˌbrɪtɨʃ kəˈlʌmbiə ( BC) ( (la Colombie-Britannique C Alaska ( Аляска Alyaska) is a state in the United States of America, in the northwest of the North American continent

References

1. ^ Martin Krkosek, Jennifer S. Ford, Alexandra Morton, Subhash Lele, Ransom A. Myers, and Mark A. Lewis Declining Wild Salmon Populations in Relation to Parasites from Farm Salmon. (14 December 2007) Science 318 (5857), 1772.
2. ^ Clover, Charles (2004). The End of the Line: How overfishing is changing the world and what we eat. Ebury Press, London. Random House Inc is the world's largest English-language general trade book publisher ISBN 0-09-189780-7.  

• "Study provides first direct evidence sea lice kill young wild salmon", Simon Fraser University. Simon Fraser University ( SFU) is a public university in British Columbia with its main campus on Burnaby Mountain in Burnaby and satellite campuses in  
• Wild salmon and sea lice. Simon Fraser University. Simon Fraser University ( SFU) is a public university in British Columbia with its main campus on Burnaby Mountain in Burnaby and satellite campuses in
• Watershed Watch: an organisation that promotes salmon protection in British Columbia