As a reefkeeping
enthusiast I have delighted in coral propagation for the last
several years and my hobby led me to become Invertebrate Director
at our city's largest aquarium store. There I have had a chance
to enrich my hobby in many ways. Surrounded by an array of
aquarium products, livestock, and literature I have been able
to move on to the "next level" of aquaculture, breeding a
true marine ornamental, the familiar Peppermint Shrimp. Thanks
to a particularly inspiring article by Matthew Wittenrich
in the summer 2002 Seascope newsletter profiling his successes
breeding these shrimp, I decided that this was something I
had to try. One of the challenges I've faced being in charge
of the shrimp we sell at the store is understanding their
behavioral interactions and this experience has given me a
keener understanding of how to keep and breed these fascinating
arthropods.
In this article
I hope to not only add to the present body of literature on
the topic of peppermint and Lysmata shrimp breeding
in general but to focus a greater emphasis on behavioral interactions
of the shrimp communities in broodstock and growout scenarios.
Also I will explain some unique techniques I've developed
that have contributed to my success.
Click
for larger view
Hatchery
layout: broodstock and larval tanks
I began my project
last year by creating a 55 gallon broodstock tank for the
adult shrimp and placed as many as 28 individuals in there
at first. I was not surprised to witness progressive cannibalism
amongst them over time which has confirmed my strong belief
that you can only house just so many shrimp within a given
amount of tank space. Today my conclusion drawn from this
is that just under ten adult peppermint shrimp can be successfully
housed in a tank of this size. It is during molting episodes
when cannibalism most often occurs and this is also when mating
occurs as well so there seems to be a fine line between sex
and murder in the shrimp world depending on the density of
individuals in a given captive environment. Naturally hunger
is also a strong factor and underfed shrimps are certainly
more prone to cannibalistic behavior. Feeding the adult shrimps
daily with quality feeds, vitamin and lipid enriched, is a
big part of success with large hatches and healthy larvae.
Proud
sponsor of this column
Perhaps the most
fascinating thing I've been able to witness is the actual
reproductive process in front of my eyes at night in the tank.
Since there are no other fish or organisms of any kind in
the broodstock tank the shrimp are free to exhibit uninhibited
sexual behavior without fear of predation. When an adult starts
to hatch larvae from the swollen mature eggs attached to its
pleopods (swimmerets), it is chased around the tank by the
other shrimp no doubt in hopes of capturing a tasty larval
meal as well as the phenomenal attraction of mating with that
shrimp after its subsequent molt. All the shrimp exhibit a
very high activity level, swimming in a racetrack manner around
the tank. Once hatching is complete the "mother" shrimp will
exit its exoskeleton even as another shrimp is right on top
of it waiting for its chance to mate by grabbing the soft-bodied
"female phase" shrimp and contacting it crossways from underneath.
As simultaneous hermaphrodites, these very same two shrimp
may have their male/female roles reversed within so many days
to a week as the eggs reach maturity on the adult that had
previously enacted the fertilizing male role!
Exciting as all
this was, only until I could isolate the larvae, known as
zoeae by biologists, would I really be in business to raise
them. Inevitably after such evenings of observation it became
obvious when a hatch was imminent or in progress. I managed
to collect my first batches of larvae by the simple, albeit
tedious method of cutting off all pumps in the tank and concentrating
them at a spot under a light to which their phototrophic nature
attracted them and then dipping them out with a cup to transfer
to their larval rearing tank. It became quite apparent that
a more efficient method of larval collection would be necessary
so I constructed a device for this purpose designed after
Joyce Wilkerson's "Larval Snagger" detailed in her book on
raising clownfish. Another book I was reading at this
time, "How to Raise and Train Your Peppermint Shrimp" by April
Kirkendoll. It described the use of a larval collection device
as well. This acrylic box sprouting siphon tubes, a fine mesh
strainer, a small powerhead, and a nightlight for larval attraction
seemed bizarre if not questionable for the purpose it was
intended. When even after the very first night it was installed
I discovered it full of tiny zoeae, I was overjoyed and have
come to firmly believe in the need to employ a larval collection
device if one is going to regularly raise these shrimp. Although
the Wittenrich article describes an alternate method of adult
transfer to a rearing tank for larval collection, I tend to
agree more with Kirkendoll's recommendation of broodstock
tank larval collection to minimize undue stress to the adult
and frankly it seems far more practical than trying to capture
a specific adult from the main tank.
Click
for larger view
Click
for larger view
Larval
collector, top and front views.
Notice intake siphon with nightlight and cage preventing
adult access.
Larval
rearing tank
Brine
shrimp
Proud
sponsor of this column
A tall, bare 15
gallon tank wrapped in black plastic trash bag material (to
shield it from side lighting) filled with saltwater and an
air stone serves as the larval tank. At first I created a
siphon design to transfer water to and from the broodstock
tank in hopes that the biological stability of the adults'
system would prevent ammonia and nitrite from poisoning the
larvae. A fine mesh strainer kept the larvae from being siphoned
back through. Well intentioned as this may have been, this
piggy-backing system design turned out to be deadly to my
adults as the heavy feeding of the larval tank polluted the
broodstock tank so much that I ended up losing all my adults
to disease! This was my first major setback, but nevertheless
I successfully managed to bring 76 larval shrimp to metamorphosis
in this first trial. I now follow the so-called hobbyist method
of larval tank rearing as advocated by both Wilkerson and
Kirkendoll where the larval tank is an independent entity
receiving daily bottom siphonings and water change to insure
water quality. In the future I plan to design a dedicated
larval filtration system to enhance their life support and
environmental stability. I also would like to design a multi-tank
larval system utilizing the "planktonkreisel" concept of conical
larval tanks with upwelling water movement used in advanced
aquaculture laboratories.
Whether the larval
tank has its own filter or not, frequent bottom siphonings
will be necessary especially when dead foods are offered.
Cloudy water is also a familiar situation that further indicates
need for additional water change. Virtually every single day
I am changing some percentage of larval tank water. If ammonia
or nitrite is an issue an ammonia detoxifying conditioner
can be added.
A battery-powered
airpump check valved into the airline will save the lives
of larvae if the power goes out. Larvae can only last so long
without the gentle rolling of the water that the airlift creates.
Without this they will eventually settle to the bottom and
die. The type of airpump that automatically kicks on when
sensing power loss is the one that is required.
Although for a
brief time I was culturing rotifers and phytoplankton in the
thought that this would be a necessary part of the process,
the Kirkendoll book confirmed that this was not needed and
that the zoeae are started on new hatch artemia from
day one. That has proven to be a boon as phytoplankton culture
seemed particularly tedious and prone to culture crashes.
Brine shrimp are easy to hatch but it is important to always
have a newly hatched batch of artemia nauplii the morning
following a peppermint shrimp hatch. When I am collecting
larvae I force myself to start a new hatch of brine shrimp
as a daily morning ritual so that the batch from the day before
is ready to feed to my shrimp larvae. Brine shrimp nauplii
that may be ready for feeding before larvae are obtained can
be fed to my reef systems otherwise. Since the peppermint
shrimp breed so regularly hatches can be obtained every few
days. Collected larvae can be added to the same larval tank
for up to a month and although there may be some cannibalism
of the smaller younger zoeae, if food items are supplied in
daily abundance this doesn't seem to constitute much of a
problem.
Kirkendoll's recommendation
of a fine bubble diffuser in the corner of the tank works
well for my larvae and I use a limewood air block for that
purpose. A gentle air output seems to be best for these little
guys which can be increased somewhat as they mature, but not
so strong as to batter them against the sides of the tank.
One of the great things about peppermint shrimp larvae is
their willingness to grab onto and eat various dead foods
which are easily offered. During my first batch of larvae
that I raised I used as many as three airstones with vigorous
output in order to keep certain frozen foods suspended which
the larvae did actively feed on but in retrospect this was
surely far too turbulent for them. Without this vigorous output
the frozen foods just settled on the bottom. I was somewhat
disappointed with flakes too. Although they would float for
a while which was good they too would eventually sink to the
bottom unavailable to the larvae. Then I had an inspiration.
Since they obviously enjoyed flake foods and the challenge
was to have a continuous presence of such in the tank, why
not utilize an automatic flake feeding device as used for
freshwater fish? I used a rotary flake feeder that I modified
so that every compartment on the dial would dispense flakes
continuously all day long into the larval tank. It was a resounding
success! The only drawback to this was the absolute necessity
of a nightly bottom vacuuming as a thick layer of flakes quickly
built up. As long as the nightly siphoning was performed I
never had any problems with larvae getting tangled up in it
or mortality due to excess pollution.
Proud
sponsor of this column
Ideally the prescribed
methodology for the maturation of Lysmata wurdemanni
(or L. rathbunae) zoeae through live foods entails
feeding progressively mature artemia as the shrimp
larvae mature and that the culturist would have successful
artemia cultures in growout for this purpose. Good
as this would be, it's not a necessity either especially if
you are feeding other foodstuffs as described above. I feed
new hatch artemia daily for the first four weeks (or
longer if there are new larvae still being added to the tank)
in combination with the flakes. After the fourth week the
zoeae are usually big enough to handle adult brine shrimp
which then can be offered. Raising brine shrimp to adulthood
is a challenge even for advanced aquarists due to the fouling
of culture water and I must admit that this has still proven
to be a stumbling block. Fortunately, working at an aquarium
store where live adult brine shrimp are available every week
has simplified this issue for me. When the peppermint larvae
are old enough for adult brine I just switch them over to
that while feeding the flakes all along and they do just fine
with that. Having access to live adult brine shrimp is obviously
going to be a big advantage if one is trying to raise peppermint
shrimp. The adult brine should be fortified with HUFA-enriched
feeds and phytoplankton.
The larval tank
should be shielded with dark or black material throughout
the shrimps' larval stages, but it is okay to pull the front
cover aside for temporary viewing. Biofilms will noticeably
build up on the front glass after a week and zoeae can become
coated in this material as they swim against the front glass
due to side lighting while viewing. A quick easy cleaning
of the front glass with an algae magnet I have found to be
a great way to improve visibility as well as minimize biofilms
that can coat and harm larvae during viewing. Algal growths
of any length should also be scraped off the sides of the
tank to keep newly hatched larvae from getting tangled.
Typically my shrimp
larvae will metamorphose (the final of many series of molts)
into tiny little shrimp along the sides of the tank after
their fifth week. I wait until all the shrimp have metamorphosed
before they are transferred to their growout environment.
Removing post larval shrimp will be problematic if there are
still zoeal stage larvae floating around the tank.
Click
for larger view
Growout
trough array
Click
for larger view
Juvenile
shrimp are eager to "clean" your hand.
Here I assert
the importance of a dedicated site for growout of the shrimp.
All the work put into raising the larvae will surely be for
nothing if they are added too soon to a typical aquarium.
Often they will just disappear never to be seen again. This
I learned the hard way. Also you cannot expect to house fifty
of them in a ten gallon tank either as the same issues with
cannibalism will be played out until you are down to your
last shrimp! I toyed with different ideas of keeping each
shrimp in a separate cubicle but this wasn't very practical.
I ended up creating an array of growout troughs, shallow plastic
trays with plenty of space which were plumbed in line to a
reef system and became a baby shrimp sanctuary. I collected
rocks from the side of the road and laid these and numerous
lengths of scrap vinyl hoses around in the troughs for the
little shrimp to hide in and it has worked out very well.
They just need a dedicated space of sufficient size proportions
to allow them to grow to a marketable size to go into a regular
aquarium. These subadult juveniles need to be fed every day
to optimize growth and deter cannibalism.
The 2nd batch
of shrimp I raised in 2003 occurred in the fall when I had
a new population of adults and had perfected a more streamlined
system of brine culture, larval collection, and better larval
survival with the auto feeder. With this batch I brought a
sizeable 220 shrimp to metamorphosis.
Another experiment
I tried involved adding 11 juvenile shrimp back into the adult
broodstock tank to see how they would interact. At first they
coexisted in seemingly peaceful groups but after a few weeks
it became apparent that the larger adult shrimp were attacking
the younger juveniles, a spectacle I bore witness to during
a night viewing session. Eventually all the juveniles disappeared.
The lesson one can draw from this is the need for shrimp communities
to be composed of individuals of comparable size for optimum
survivability.
The raising of
these shrimp over the past year has simply been one of the
most rewarding things I have ever done. As each component
in the process developed the excitement heightened until ultimate
success and the creation of a systematic methodology became
reality. Now I am looking forward to future attempts at other
marine ornamental species.
References
Kirkendoll,
April, 2001. How to Raise and Train Your Peppermint Shrimp.
Riley, C.M.,
1994. Captive Spawning and Rearing of the Peppermint
Shrimp (Lysmata wurdemanni). Seascope, Summer.
Wittenrich,
Matthew, 2002. Metamorphosis in 19 Days (Breeding Lysmata
rathbunae Shrimp). Seascope, Summer.
Wilkerson,
Joyce D., 2001. Clownfishes (A Guide to Their Captive
Care, Breeding & Natural History).
