[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

RE: Harvesting brine shrimp

As one of the few individuals on the opposite end of the spectrum in
hatching brine shrimp cysts I need again to pass on a few observations I
have made.  My normal hatch amount is usually between 1/10 to 1/4 th of a
cup of brine shrimp cysts per day.  A one pound can lasts me between 3 and 4
weeks.  Luckily I realized years ago that I must always maintain a reserve
of "eggs" because of price and supply fluctuations and usually try to keep
at least a year's supply of "eggs" in reserve which causes one to
"scharf-up" any bargains on eggs whenever the situation arrives.
Occasionally you get one bad can per dozen, but most often all cans are good
and maintain quality for several years.  From my experience, only opened
cans deteriorate after a couple of months exposed to warm temperatures and
humidity.  Even those cans marked "short shelf life" still produce good
hatches after 3 years unopened.

For years I have harvested shrimp much the same way and used a 1 liter glass
separatory funnel to assist in the process.  I hatch my shrimp in one gallon
"pickle" jars bubbled with an open air tube on the floor of my fishroom.
(Note:  no lighting, no extra heating)  Under those conditions (temperatures
between 65 and 70F) it takes a full 3 days to hatch the shrimp.  I usually
have 6 jars in various stages of hatching at any one time.  After 60 hours
you have a significant hatch, but separation of casings and unhatched cysts
is a lot of work.  Most jars will have a good live hatch at 84 hours and at
96 hours you are near the end of the lifetime of the hatch without
significant processing.  In hatching the shrimp I have used a commercial
feed salt for years, buying it in 80 pound bags and never recycling the
water.  80 pounds of salt costs $8 and lasts me nearly a year.

I almost always process a whole hatch jar and pour its contents through a 4
inch brine shrimp net and rinse with approximately a half gallon of fresh
water and transfer the rinsed contents of the net back to a "suspension" of
fresh water and pour this into my separatory funnel.  By now, 5-20 minutes
may have elapsed since I first pulled the air.  When you have a good hatch,
casings are at the top and shrimp are at the bottom.  You can't let this sit
too long because the shrimp will pack in the funnel at the bottom and
suffocate each other by their accumulated mass if you go too long.  Most
often I have at least a full cup of concentrated shrimp per jar to feed to
my fish.

Since a new glass separatory funnel costs at least $100, you can substitute
a plastic soda bottle instead with one of those nozzle tops (the tops slide
open to use as a squirt bottle).  In any case, you need something to control
the flow with an immediate cutoff.  If your separation is not clean, i.e.,
usually the result of an incomplete or bad hatch, you can add salt back into
the separatory funnel (soda bottle adaptation) until the specific gravity of
the solution is sufficient to separate the shrimp (raising to the top) from
the unhatched cysts (going to the bottom).  Then you can rinse again with
fresh water to separate the casings from the shrimp.

Another couple of notes:  I mention repeatedly that I rinse with fresh
water.  My hatching medium contains only salt, sodium chloride.  I try to
minimize the amount of sodium I am transferring into each container of fish
and rinse away as much sodium as possible with each rinse.  According to
Rosario LaCorte, too much sodium carried (usually with brine shrimp) leads
to a bloating-like, goiter condition in fish.  I attribute this to a
degrading water condition caused by the build up of minerals in the water.
Since I have devoted more effort to cleaning shrimp, I see very little of
this effect in younger fish.

I also don't use an airstone.  According to the Plankton Culture Manual, the
fine bubbles produced can block the gut or appendages of newly hatched
shrimp and increase mortality.  It should also be noted that upon hatching,
newly hatched shrimp do not feed for 12 hours.  You can interpret that many
ways including that there is a fairly large window in which to harvest live
newly hatched shrimp or that newly hatched shrimp immediately start losing
mass and food value.

Shrimp not fed during a feeding are usually returned to a fresh solution of
salt water.  Originally I would double the salinity but lately I have found
that duplicating the hatch conditions will allow most shrimp to survive for
approximately an additional 24 hours.  For culturing shrimp to adults, it is
recommended that the salinity be dropped back to 1/5 that of normal sea
water.

Joe Bulterman just reported a good harvest at the Great Salt Lake which is
welcomed news.  I suspect prices will drop but only after a "backlog" is
cleared out.  I would also suspect bargains like I got 3 years ago will take
2-3 years to return.  Those bargain occur after a really good harvest and
suppliers need/want to reduce their inventories of previous year's supply.
I had been led to believe in the past that some suppliers only sold off what
they had on hand from the harvest 2 years earlier (sometimes 3) and that the
sale of processed harvest from the collecting season didn't hit the market
for almost a year after collected.  Current supply and demand may have
changed that.  However, my purchase of "old" Grade A cysts at approximately
this time of year could usually be had for about $8-12 a can.  So, if we are
fortunate to have 2 more good years of harvest, file away and save a cash
reserve to buy these newly canned 2-year old eggs in November of 2002 at
maybe half or less of the price the eggs will be marketed for this summer.

I also wanted to add a comment to Brian Watters' note on fairy shrimp.
Almost 30 years ago I contacted the former curator of the Bombay Aquarium
(India) who had written an article for one of the aquarium magazines on an
attempt to commercially produce fresh water shrimp eggs.  Apparently they
had access to a number of lakes that produced very large quantities of fairy
shrimp and noted the shrimp released resting eggs in captivity.  From the
communication and other information I have read on fairy shrimp over the
years is that contrary to brine shrimp where the egg/cyst floats, fairy
shrimp cysts do not float and are very difficult to separate from the mulm
and detritus (a common problem in attempting to rear/sustain most copeods).
I think if one wants to pursue anything with fairy shrimp as a food source,
they need to find a species that behaves like daphnia and under the right
conditions produces live young instead of resting eggs.  As Brian mentioned,
culturing brine shrimp seems like a waste of time and space even though
literature like the Plankton Culture Manual cites a 7 fold increase in food
mass in a two week period of rearing.  As with any small crustacean culture,
you have better success with a food source of live material.  Unfortunately
there is an art to culturing marine algae or marine plankton as food for the
brine shrimp.  We are much better at dealing with fresh water "bugs" which
we usually have going to feed our fry. 

Dave Koran
---------------
See http://www.aka.org/AKA/subkillietalk.html to unsubscribe