The problem of providing live food for their fish beset aquarists until about 1947. It was then discovered in the USA that brine shrimp eggs will remain viable (alive) for at least 10 years when stored in a dry and fairly cool place and will hatch in salty water. This discovery led to the brine shrimp eggs being collected in quantity in their natural environment and marketed on a commercial basis throughout the world as a source of constant live food for aquarium fishes. The eggs cannot be used as fish food because fish cannot digest the tough shells. However the newly hatched shrimp, which the fish relish, do not have a firm shell and can be readily torn to bits by almost all small fish. Live shrimp are caught in San Francisco Bay salt ponts and frozen for shipment to pet shops all over North America.
Brine shrimp are custraceans of the genus Artemia, subclass Branchiopoda, and order Anostraca. They occur throughout the world, living and reproducing only in water of high salinity in natural salt lakes and also ponds where sea water is evaporated to obtain salt. Although they may have descended from ancient fresh-water form, they cannot live long in fresh water.
The Taxonomic status of Artemia has long been controversial, especially in Europe where Artima varies more than it does in the United States. The present consensus is that there is a single world wide species – Artima salina, which has many varieties.
In the United States brine shrimp are best know from the Great Salt Lake, Utah, where the salanity of the water in 1950 was about 25 percent, and in San Francisco Bay, California, primarily in the salt-evaporation ponds. Sometimes these brineshrimp congregate to form ribbon like patterns on the surface of the Great Salt lake nearly half a mile wide and extending for miles out into the lake. They are often so abundant that the water looks red.
Great Salt Lake is the remains of a fresh water lake called lake Bonneville which trained into the Pacific Ocean by way of the Columbia and Snake Rivers. Beause of decreased rainfall and a drop in level, its outflow stopped. Evaporation by the sun then became greater than inflow of freshwater from the Jordan River and the Bear River, and Salt concentration increased. In recent times the lake area has varied according to fluctuations in the lake level, ranging from 2200 square miles in 1873 to 1500 square miles in 1940.
The ancestors of the Great Salt Lake brine shrimp may have lieved in Lake Benneville when it was fresh water and gradually adapted to the increasing saltiness of the lake.
Brineshrimp life history
Adult brine shrimp are about one third of an inch long. The males are smaller, but stronger and more active than females. They have 112 pairs of swimming legs and 2 stalked compound eyes. Disclike gills occur about midway down the legs. The brine shrimps variation in color from pale yellow-green to blood red is caused by the chemical nature of the salts in solution in ponds and lakes where they live.
The adult brine shrimp in Great Salt Lake and in San Francisco Bay die when the water temperature falls below 6C
Brine shrimp eat the free floating algae and other microscopic organisms that occur in brine ponds and salt lakes.
Brine shrimp reach sexual maturity within 18 to 21 days after hatching and reproduce in two ways. If no males are present the females have embryos that develop from an unfertilized eggs. This phenomenon is called parthenogenesis. When mature females and males are present, the male fertilizes the eggs within the reproductive tract of the female. The eggs remain within the body of the female until a touch shell has formed around each one. Then the eggs, which resemble fine brown sand, are deposited in the water where they will hatch if conditions are favorable. If the female deposits her eggs in seawater which has a specific gravity of 1.09 or higher, they will float on the surface and will not hatch but may be blown by the wind or be carried by water currents to beaches – where they remain until it rains and they are washed back into the water. Rain tends to dilute the surface of the water – and when the eggs come into contact with it they hatch because the specific gravity is less than 1.09 and the temperature is higher than 9C.
In many instances the eggs hatch within the ovisac of the female, and the embryos develop to nauplii (larvae) before they are born. Movements of the muscles surrounding the ovisca keep the young brine shrimp in motion. Just before birth occurs, some nauplii are suddenly released from the others and moved towards a funnel shaped aperture ni the ovisac. After a few convulsive movements of the funnel muscles the aperture opens and the nauplii are forcefully ejected into the water.
The natural environment determines whether a female will bear living young or lay eggs. Some shrimp along the coast are washed into a tidepool and left as the tide retreats. If the pool is above the normal high tide line, several weeks may elapse before the sea again reaches the pool. Meanwhile the water in the pool evaporates, and the salinity increases. The brine shrimp at this time bear living young. Evaporation may continue, and the salt percentage rise. More shrimp and less water mean less food and the population may start to decline. Responding to this changed enviroment, the females stop bearing living young and begin laying eggs. When the tide reaches the place where the tidepool was, the eggs are washed out to sea. Though they had lain on the shore for weeks, they now hatch.
The eggs, which are not harmed by low temperatures, hatch in nature in great numbers in the spring. Baby shrimp are born with a single eye and one main set of legs. During growth, they acquire a shell which they shed a number of times during their life time. Changes occur in the body at each molt until, in the adult, there are 2 eyes and 11 pairs of legs and in the case of males, 12 penises.
There are several kinds of fresh water fairy shrimp are closely related to brine shrimp. Water fleas are more distant relatives.
The brine shrimp main enemy in nature are salt water fly larvae, birds and human collectors. So far as known, brine shrimp do not have harmful parasites. An abundance of brine shrimp in some areas may result from a lack of enemies.
How to use brine shrimp
Brine shrimp are valuable. They are excellent as zoological teaching material for classroom laboratories, for the development from egg to larva may be obseved under a microscope in a short period of time.
Brine shrimp are superior for testing insecticides. This crustacean demonstrates a high sensitivity against a broad range of compounds.
Baby brine shrimp have become in recent years one of the standard foodsfor young tropical aquarium fishes, after the fiches have passed the stage where they need microscopic organisms as food. Adult brine shrimp also form an excellent food for larger fish.
Fish hatcheries also use brine shrimp for feeding fish. The Utah Fish and Game Department collected brine shrimp in the Great Salt Lake for use as an experimental trout food. The Department found that growth and mortality of newly hatched rainbow trout fed brine shrimp diet were approximately the same as when the trout were fed a turkeyblood and live diet or dry feed, Kokanee salmon fed brine shrimp made excellent growth, while those fed blood and liver or dry food lost weight.
Brine shrimp also aid salt production. They precipitate insoluble calcium carbonate and calcium sulfate impurities from ponds. The shrimp strain these impurities out of the water along with their microscopic food. The calcium carbonate and calcium sulfate particles are not absorbed in the intestine but become incorporated in the fecal pellets which drop to the bottom of the pools. This precipitation occurs before the salt is crystallized in the final stage of solar production.
Brine shrimp buy online are not commonly used for human food because they are too small. However they were so numerous at times in the past that indians inhabiting the Great Salt Lake region dried them for use as food.
Collecting and processing brine shrimp eggs
Brine shrimp eggs in their natural enviroment are found floating on the top of the water or on the shore where wind deposits them. They are netted from shallow water or scooped from the shore, along with mud and sand and placed in buckets.
Processing the eggs without damaging the tender embryos or starting them to hatch is an exacting technique. The mud is washed using a high-pressure spray through a fine screen. This separates out the dead shrimp, parts of dead sigh and birds and other large impurities. Eggs and water then pass through a sluice box which picks up sand. Since wet, fertile brine shrimp eggs since in fresh water, the overflow removes dead eggs, shells and dust, leaving behind the viable eggs and lettle else.
The eggs are then spread out on a thin layer to dry in the guy. When dried they are cleaned once more in a blower, which removes dust left over from the water and any lighters, dead, eggs.
A small sample of the eggs is weighted and then allowed to hatch. The larvae are weighed to assure a high quality yield when the eggs each the aquarist. The eggs are vacuum packed in cans for shipment to dealers, labs and schools as well as commercial fish hatcheries.