Brine shrimp harvest boom on
Great Salt Lake
Utah’s brine shrimp industry collected a bumper harvest of Artemia cysts from Great Salt Lake this season, a welcome relief after three devastating years when the resource appeared to have all but vanished.
Breaking all previous records, the 2000 harvest
measured 19.3 million pounds of raw, wet eggs in a seven-week season that
began Oct. 11 and closed Nov. 27. The boom was attributed to fluke weather
conditions.
“Several weather factors – an unseasonably dry
and warm winter with a dry spring and late fall last year – meant that
there was a third generation of adults bearing eggs,” said Don Leonard,
president of the Utah Artemia Association.
Harvesters have suffered record lows since the
1997-98 season, when the numbers settled at 6.1 million pounds, then dropped
to 4.6 million pounds in 1998-1999, and fell again to 2.6 million pounds
last year.
“I’d like to be able to say that the resource has
turned around”, said Leonard, “and that we could count on a harvest like
this from now on. But in actuality, weather predictions indicate that this
is more likely a one-year fluke”.
In 1994, the Utah Division of Wildlife Resources
(DWR) and Utah State University began monitoring brine shrimp populations in
Great Salt Lake. A sampling protocol was established to determine when the
population of Artemia is high enough to begin an annual harvest. Then, when
monitoring records indicate a certain level of depletion, the harvesting
season is closed to allow the remaining cysts to perpetuate the next
year’s population.
The egg harvest is carried on as a commercial fishery
requiring a DWR-issued permit, called a Certificate of Registration (COR),
to participate. In a management move to control the harvest effort, DWR
placed a limit on entrants to the fishery in 1996. Thirty-two harvesting
companies are issued a maximum total of 79 permits for the season. The brine
shrimp industry supports the DWR management efforts, and pays $10,000 each
year to obtain each COR.
The quality of eggs, and therefore their value, is
determined by their hatch rate. Top quality cysts have a hatch rate of over
90%, though a mid quality 80%-90% is still acceptable to processors.
Processors dry and can the raw eggs, or use them as an ingredient in feed
formulations.
Wholesale prices for raw eggs have ranged from $5 to
$25 per pound since the mid-1990s, though $9-$10 is a typical price.
It will take up to two months for the industry to
know what the actual numbers are in terms of a yield weight for the 2000
harvest, but Leonard suspects that the quality of his year’s catch will
prove high – certainly higher than recent past years.
“We’ve had several dismal years,” he said,
referring both to the volume and quality of recent harvests.
Nauplii, baby brine shrimp that hatch from the eggs,
are used to feed the early life stages of farm-raised shrimp.
There is a worldwide demand for the product and the Great Salt Lake
is the dominant source of brine shrimp eggs.
The product harvested this year will not necessarily
be sold this year. The processed eggs are stored, and the industry comes up
with an inventory management plan that helps supply hatcheries through the
lean harvest years.
“I have to say, though, that we had gotten in a
situation where the cupboards were pretty bare,” admitted Leonard, citing
the region’s three previous years of poor harvests.
The live cycle of brine shrimp in the Great Salt Lake
includes a late fall production of eggs. Since food is scarce and
temperatures have started to drop, the females produce eggs with hard-walled
cysts that will stay dormant until the following spring, hatching when
conditions are improved.
Cysts produced by females late in the season float on
the lake, often as large reddish-brown streaks. These are the eggs that are
harvested, with 5% to 20% left to produce a new generation of brine shrimp
the following spring.
Great Salt Lake is divided into a north and south arm
by a railroad causeway constructed in 1959. The north arm gets little inflow
of fresh water and therefore has a high salinity level ranging between 22%
and 26 %, too high for brine shrimp success.
The south arm of the lake, where the bulk of
harvesting occurs, suffered from low saline levels for a few years,
resulting in the growth of a type of algae that brine shrimp won’t eat.
Saline levels this year increased to about 8%, one of the components for
this year’s generous harvest.
Issues of low salinity and insufficient algae are
ongoing for the region’s harvesters. As with any weather-dependent crop,
the forces of nature make it a nickel toss as to whether it will be boom or
bust.
“Weather predictions are not favourable that this
is a trend,” said Leonard.
“We’ve already had a colder, earlier start to
this winter.”
(article by Zoë Alexis Scott in Fish Farming News,
Nov/Dec 2000)