| Various species of Mysid shrimp,
also known as opossum shrimp, have been collected or cultured
as a live food for aquatic animals which prefer living foods,
such as seadragons, seahorses and pipefish. Many other species
of fish relish the addition of Mysids to their diet, but difficulty
in producing these crustaceans in sufficient quantity generally
relegates their use to only the most critical cases. The method
described can produce over 2000 Mysidopsis bahia
per week with a time investment of less than 45 minutes per
day. Equipment cost is minimal, and the only operational cost
of note for this system is the substantial use of Artemia
nauplii as a food source.
Culture Area:
Using a rearing area with 80 - 100 square feet of floor
space, establish three 30 gallon aquariums and ten 10 gallon
tanks with synthetic seawater (at a salinity of 21 to 22 ppt)
and air-driven biological filters. It helps to pre-establish
the bacteria in the filters by running them in the sump of
another marine system for three to four weeks prior to this
time. An Artemia system capable of hatching from 8 to 10 grams
of cysts (dry weight) per day is also required.
Beginning the Mysid Culture:
A starter culture of around 200 captive raised young adult
Mysids is added to one of the 30 gallon brood aquariums. These
are fed newly hatched Artemia nauplii "at liberty"
twice a day. When they become sexually mature, their young
are removed twice a day, just prior to each feeding. The young
Mysids are housed in the ten gallon rearing aquariums at a
density of between 1200 and 1300 per tank. A new rearing tank
is started when the last one reaches that density. When all
ten rearing tanks are filled, room for new baby Mysids is
created by harvesting the oldest rearing tank and utilizing
it as fish food. When the first tank of collected young Mysids
reach 4 to 5 weeks of age, about 200 of them are used to set
up the second 30 gallon brood aquarium. Continue collecting
young from both brood tanks and then after another month or
so, select another 200 young adult Mysids and use them to
set up the third brood tank. The culture should now be at
peak production. At some point, productivity in the first
brood tank will start to decline as the Mysids reach old age.
At that time, the old adult Mysids are removed, the brood
tank cleaned and 200 young adults are selected from one of
the rearing tanks and set up in the first brood tank. In this
way, a fairly constant, highly productive culture can be maintained.
Husbandry:
Despite their widespread use as pollution bio-assay organisms,
Mysids are not too demanding in terms of water quality (as
long as the values remain within a reasonable range). No unusual
mortality was noticed in tanks even when the ammonia concentration
approached 1 ppm.
Average water quality for mysid culture tanks:
Temperature = 75°F
Salinity = 20–22ppt
pH = 8.2
Light = 75 foot-candles
Ammonia = 0.1 mg/l
Nitrite = 0.01 mg/l
Artemia Culture:
Prior to being fed to fish, Mysids should be fed Artemia
which has first been fortified with Super Selco. Fortified
Artemia can be fed to the Mysids at every feeding, but since
this is a very time consuming and expensive process, routine
Mysid feedings can be done with "bulk Artemia" as
follows:
- Using an inverted, clear two litre soda bottle (with a
cap) with a 1" hole cut in the bottom, add 6–8
grams of Artemia cysts, four tablespoons of sea salt and
fill with tap water. Add an airline and harvest after 28
hours by removing the air line, letting the bottle settle,
and slightly loosening the cap over another container. Let
the settled nauplii run into the container, and tighten
the cap back on before any of the empty cysts flow out.
Strain the nauplii through a brine shrimp net, rinse with
clean seawater and feed out immediately.
Hints and Tricks:
- Three models of sponge filter were tested: All became
clogged with Artemia naupulii, and needed to be rinsed out
in seawater every week or so. Eventually, the sponges became
too clogged to be easily cleaned. Bio-filters were constructed
using plastic deli cups, 1" rigid tubing and bio-media
(figure 1) which did not clog as readily.
- Various hydroids and other "pests" can show
up, (mainly in the brood aquariums) and need to be removed
by stripping down that tank. At the very least, these hydroids
compete with the Mysids for food, and at the worst, they
may actually consume juvenile Mysids.
- When productivity is low, start up a new rearing tank
after seven days, even if the target level of 1200 baby
Mysids has not yet been met. The reasoning is that if there
is more than a one week age difference, the older Mysids
will prey upon the newly added ones.
- Surplus adult Mysids can be frozen for later feeding,
or added live to a large holding aquarium, as sort of a
"rainy day fund".
- The best way to remove larval Mysids from the brood tanks
is by siphoning them out using a flame polished glass tube
attached to a length of 3/16" airline tubing. With
practice, an aquarist should be able to siphon out the babies
at a rate of better than 20 per minute. The trick is to
avoid wasting time trying to siphon out three or four day
old babies, they are just too fast. Focus on the smaller
one or two day old ones that are positioned on the glass
of the aquarium. Free-floating babies are able to escape
the siphon in any direction, making them harder to capture.
Mysids crawling along the glass can only escape along a
180 degree plane, away from the siphon.
- Although time consuming, productivity in the brood tanks
can be enhanced by selectively removing most of the male
Mysids. This reduces predation of the larva as well as the
amount of Artemia needed as food for the breeders. With
a small net, capture the majority of the Mysids which do
not show the female's white brood pouch. You may remove
some non-breeding females with this method, but the majority
will be males. Even a 10:1 ratio of pouched to non-pouched
animals will produce well.
Mysids as Food:
Most zooplanktivorous fishes relish live Mysids in their
diet. Once accustomed to capturing the shrimp, most fish seem
to feed on them with much more vigour than they show for other
foods. In one case, two Red backed butterflyfish, (Chaetodon
paucofasciatus) were first offered live adult brine shrimp.
These the pair consumed at a calculated rate of 30 per minute.
When the butterflyfish were then immediately offered live
Mysid shrimp, they consumed these at a rate of 65 per minute.
Some degree of caution may be in order as these butterflyfish
attacked the Mysids with such ferocity that their snouts became
bruised from repeatedly hitting the tank walls and bottom
as they captured the shrimp. It is unknown if this vigorous
feeding response is due to the good "taste" of the
Mysids, or if the shrimp's swimming behaviour more closely
matches that of a zooplanktivore's normal prey.
Although the nutritional profile of Mysidopsis is not known
by the author, anecdotal reports indicate that as a food item,
they are vastly superior to Artemia in both acceptance and
nutritional value. A group of new-born Hippocampus which had
been fed Artemia naupulii for the first six weeks were gradually
wasting away. Mortality ceased once small Mysids were offered
as the sole food. Captive husbandry of seadragons requires
ample supplies of live mysids, with no other substitute seemingly
available (Paula Powell, Dallas World Aquarium — personal
communication).(NOTE: THIS IS NO LONGER
TRUE - Marc)
Brine Shrimp Enrichment With Liquid Selco
1. Add two level tablespoons of salt to one liter of tap
water in blender (This equals a S.G. of 1.020).
2. Shake container of Selco: Fill the 1 gram spoon with
liquid Selco (by pouring the Selco into the spoon, not by
dipping the spoon into the container of Selco).
3. Add the Selco by rinsing the spoon into the water, and
blend for 3–5 minutes.
4. Strain live brine through a plankton strainer, and add
to the Selco enriched water. Add another liter of water
to which two tablespoons of salt has been dissolved. Aerate
for 24 hours, then feed out.
Addendum:
Some public aquariums have developed a different larval
separation technique: Using differential net material. In
most cases, this simply consists of capturing the entire contents
of a brood tank in a standard fine mesh white aquarium net.
This material is then rinsed through a standard green mesh
aquarium net into an empty rearing tank. The adult mysids
remaining in the green net are returned to the original brood
tank, and this process is repeated every few days.
Benefits: Much faster than individually
siphoning out the larval shrimp one at a time.
Drawbacks: No real ability to
keep track of how many larval mysids are being collected.
More stress on the adults due to repeated netting procedures.
A wider age range of larva are collected, meaning that the
older ones will cannibalize the younger, smaller ones in the
rearing tank. In real application, it has been reported that
since the larval separation method is so fast, (just swoop
a net) that aquarists are not spending as much time observing
the colony and noting how many larva each brood tank produces
in a day — and this is the first, and sometimes only
sign of impending colony crashes.
My recommendation is that aquarists first "learn the
ropes" by closely following the original culture method
as outlined above, and then as their experience level warrants,
begin using the net separation technique on some of the brood
tanks (but not all of them).
Suppliers of Mysid Cultures:
Aquatic Research Organisms
Mark Rosenqvist
1-800-927-1650
Chesapeake Cultures
Elizabeth Wilkens
1-804-693-4046
C-K Aquaculture
1-318-797-8636
Aquatic Indicators
Ray Less
1-904-829-2780
(Commercial accounts only)
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