Ocean Watch

A reader notes that pet shops sell brine shrimp in vinyl bags at a reasonable price.

"The shrimp appear to be hardy, and can be kept alive in the refrigerator," he writes. "I know from experience they're not easy to grow, so how is it they're so readily available?"

The word brine means super-salty water, and brine shrimp are well named. These creatures thrive in an environment lethal to almost all other animals on the planet.

Brine shrimp, however, don't require such hostile conditions to live. These shrimp can survive from 10 percent salt water (sea water is about 3 percent salt) up to a saturated solution, meaning as much salt as the water will hold before it starts falling to the bottom.

Brine shrimp are adaptable in other areas, too. Adults can tolerate brief exposures to extreme temperatures, ranging from zero to 104 degrees Fahrenheit. This explains why the shrimp survive bouts in the refrigerator.

Since brine shrimp are so robust, they are ideal live food for both fresh and saltwater aquarium fish. Researchers who study invertebrates also feed their subjects brine shrimp, and in many aquaculture farms, brine shrimp are a necessity.

Brine shrimp, therefore, are in huge demand.

Growing these shrimp, however, is a challenge. The process usually starts in the wild, such as Utah's Great Salt Lake. In the springtime, female brine shrimp lay their eggs. If water conditions are good and food (algae) is abundant, the eggs hatch soon after leaving the female's body.

In a few hours the newborns begin growing up. After 11 to 15 molts in about eight days, a shrimp reaches maturity. Most brine shrimp are about a quarter-inch long but grow bigger in ideal conditions.

Late in the summer, when food gets scarce and the temperature drops, females still lay eggs, but they don't hatch. These late eggs, called cysts, are hard-walled and remain dormant until conditions are right. Brine shrimp cysts can remain viable for years.

Fifty of these tiny cysts could fit on the head of a pin, yet there's nothing small about the business they create. In the Great Salt Lake, brine shrimp cysts generate tens of millions of dollars in trade each year.

Competition among harvesters is fierce, with some using high-tech equipment, such as night-vision cameras, to find floating mats of cysts.

The problem with this is that the Great Salt Lake's brine shrimp are a valuable food source for 2 to 5 million shorebirds, 1.7 million grebes and hundreds of thousands of waterfowl that stop there during spring and fall migrations.

Since recent evidence shows a serious decline in the lake's brine shrimp population, environmentalists and shrimpers are at odds.

The answer to brine shrimp shortages is to create more self-generating stocks, but this is easier said than done. Conditions must be precise to produce the hard-shelled cysts.

Still, this type of aquaculture is worth pursuing. Success is for the birds as well as the pocketbook.