Crustaceans form a large group of arthropods
usually treated as a subphylum
It include Crabs, Lobsters, Cray fish, Shrimps, Krill, and
The study of that because more than 10million
crustacean produced annually for human consumption.
They have many ecological and phylogenetic
significance also. The study of crustaceans mainly
through specimen analysis.
The collection and preservation of specimen through
The collection mainly through hand picking or using nets
The specimens are well documented and preserved for
1. HAND PICKING
This is one of the common technique
use to collect crustaceans. Gloves
are permitted for this.
2. SPANNER CRAB NET
It is a net attached to a rigid
rectangular frame not exceeding 1.6
meters in length and 1 meter in width
net capable of extending more than
0.1 meter beneath the frame is
suspended in a horizontal position.
There are many regulations for the
use of spanner crab net .
BOX CRAB TRAP
•It is made from strong non
•It’s advantage is ones crab enters
searching for bait, it can’t escape.
•The down side of this trap is storing
and transporting it since it collapse.
•PYRAMID CRAB TRAP
These are flat when lying on the
bottom of sea floor, but when raised
to the surface they form the shape of
This is similar to ring crab trap
because ,no wall or prevents to resist
the escape of crab from trap.
Benefit from ring trap is that, it is slightly sturdier and
so used in waters with strong currents.
RING CRAB TRAP
•These are very popular
•Primarily used in river mouths and protected
bays, but it is also use in open shoreline.
•It is a sample piece of equipment that
contains two wire rings that form the top and
bottom of a collapsible basket.
•The lower ring is smaller than the upper ring
and connected by a strong netting that forms
REGULATIONS FOR USING
CRAB TRAP AND CRAB NET
• Not more than 1 trap or net to be used (or in
possession) by any person at any one time.
• Maximum dimensions - 1.2 meters (length) x 1 meter
(width) x 0.5 meter (depth) or has a diameter not
exceeding 1.6 meters at the top or bottom for crab traps.
• The float/ buoy must measure not less than 100mm in all
dimensions, which show the details about, type of net , name
and address of the crabber.
THE MARYLAND CRAB POT
• It is a cubic structure
,generally 2 cubic feet and
weight of 15 pounds after
• It is an enclosed framework
of wire with four opening.
• These openings are
constructed four entering the
crab to the trap
•The crab doesn’t leave back on the same way they entering.
•Crabs swim upward and go through the opening of the inner
portion ,crabs become permanently trapped..
•A floating buoy attached to the crab pot to locate the
TECHNIQUES OF CRABS
Crabs can be preserved wet in 6-10% formalin neutralized
with Hexamine i.e., 100 gm per 1000ml formalin.
To avoid limb-shedding the unique phenomena of
autotomy alive crabs may be narcotized first with few
menthol crystals or by adding few drops of chloroform.
Then preserved in spirit or formalinated spirit for a day or
two, to make the autotomizing muscles as well their
After fixing,crabs can be preserved in 6-10% formalin for
the laboratory studies.
The colour retension in crabs is now experimented with
5% aqueous Solution of sodium arsenite to preserve red
and related colours
COLLECTION OF LOBSTERS
•A lobster trap or lobster pot is a portable trap that traps
Lobsters or crayfish.
•. Lobster traps are constructed of wire and wood. An
opening permits the lobster to enter a tunnel of netting.
•. Pots are usually constructed in two parts, called the
"chamber" or “kitchen”, where there is bait, and exits into
the “parlour”, where it is trapped from escape.
•Lobster pots are usually dropped to the sea floor about a
dozen at a time, and are marked by a buoy so they can be
picked up later
COLLECTION OF PRAWNS
HAND HAULD NET
•Maximum length of 6 meters.
•Mesh size between 30mm-36mm
measured across the diagonal.
•Must not be staked or set, or joined
or placed with any other net.
•Must be continuously and manually
pulled through the water and not used
as a stationary net.
•Hauling lines of up to a maximum of
2 metres in length may be used.
• It is a seasonal gear, particularly used on
high salinity and high turbidity conditions
• Made up with conical nylon monofilament
• Maximum diameter of hoop or ring 0.6
• Minimum mesh size 20mm measured
across the diagonal.
• It is used for fishing in areas with seagrass
meadows ,particularly in the outer channel
• Scoop net with small handle is normally
used to collect crabs from hand line and
•It is cotton net variable in size 12mto 30 m long with
mesh size of 1or 2 cm.
•Commonly used at time of tide ,
•SINGLE HOOK HANDLINE
•It is commonly used in outer channel sectors of lakes
•It is a single nylon filament with a hook attached on
Different methods are used for preservation of
crustaceans.The preservation include different steps
A fixative actually "fixes" a specimen by stabilizing
(cross-linking) the proteins within its tissues such that
long afterwards, the tissues will still retain a semblance
of their appearance in life.
The most common fixative for crustaceans historically
has been formalin. "), this is a 37%-40% aqueous
solution of the gas formaldehyde.
To overcome the brittleness of specimen add softening
agents like propylene phenoxytol , glycerol.
The DNA denaturation property of formalin ,we use
95% ethyl alcohol.
A preservative, in contrast to a fixative, is a
solution in which the specimen can be stored and
maintained without further degradation.
far the most common preservative in regard to
storage of crustaceans is ethyl alcohol, usually in a
concentration of 70 to 75%.
As with the fixatives, occasionally propylene glycol
or glycerol are added in small amounts to maintain
flexibility of the appendages and to slow down the
desiccation of the specimen,
RELAXATION OF SPECIMEN
Crustaceans, like some other arthropods, can throw off
(autotomize) a limb when alarmed, and this behavior is
often seen when the animal is exposed to a fixative or
"Relaxing" the specimen by adding some kind of
narcotizing agent (e.g. clove oil, magnesium chlorate,
chloral hydrate, Epsom salts, CO2 gas, menthol, or
other chemicals, ) to the water in which it is being held
prior to fixation is helpful for avoiding autotomy.
. Limb autotomy also can be avoided by chilling the live
specimen (immersing it in ice water for a few hours) and
then transferring it to the desired fixative or
COLLECTION OF CLADOCERANS
Cladocerans are small crustacean ,zooplanktons like
daphnia, larval nauplius etc..are coming under this
It is easy to collect cladocerans in small habitats where a
boat is not necessary.
A small dip net on a long handle (at least 2 m long,
telescopic), or a throwing net with a line about 10 m long,
both of them of 0.1 mm mesh size and with a mouth
diameter of 15 to 20 cm,
It is important to collect enough material, always a large
population has to be examined in order to get reliable
There are two routine ways to preserve zooplankton for
further identification and treatment.
Either 40 % formaldehyde solution is added to the total
volume of the sample to get a final dilution of about 4 %
formaldehyde, or the zooplankton is filtered out and
transferred to 70 % ethyl alcohol (ethanol).
It is preferable to transfer material preserved in formalin to 70%
alcohol since long storage in the former preservative makes the
. The addition of 10% by volume of glycerol or propylene glycol
to each ethanol sample is a good precaution against drying.
At first specimens picked out from the sample should be
transferred to a small volume of 70 % alcohol to which several
drops of lignin pink and chlorazol black E have been added.
After staining cladoceran specimens should be transferred
either to a mixture of ethanol and glycerol (3:1), and then
possibly dissected and mounted in any water miscible medium,
or whole specimens, Canada balsam, as a traditional medium,
or synthetic resins are recommended.
The crabs, lobsters, cladocerans, shrimps.etc are
coming under the group of crustaceans.
They are collected by using many techniques
Crabs collected by hand picking, using crab net ,crab
Lobsters are collected by lobster trap.
Prawns are collected through hand hauled net, scoop
net, stake net and also by hook hand line.
The collected specimens are fixed by using formalin,
and preserved in 70-75% ethyl alcohol.
Some crabs and lobsters are preserved by dry