Macrobranchium Unit of African Regional Aquaculture centre (ARAC)
deal with the culture of prawns. The prawn comes from the new Calabar river
where they are caught with a trap know as The Non Return Value: The water comes
and goes 6hourly. Due to tidal movement in the river, the non return value trap
is set when the tide is low and can only be harvested when it is low.
There are
different ponds in Macrobranchium unit. The area where the ponds are located is known to be European
Economic community (EEC) pond and water flows in the pond through the sluice
gate. The major challenges i encountered in the ECC pond is “Snake” which flow
with the water in EEC pond.
Species of Macrobranchium in ARAC.
There are two species
of Macrobrachion found in ARAC
1. Macrobrancium macrobrachion
2. Macrobranchim vollenvonile
The macrobranchium vollenvonile
has pale blue coloration at the tip of the leg while Macrobranchium
macrobranchion has legs with yellow coloration at the leg. The female
has an opening under then.
Scientific classification 1
kingdom Animalia
1. Sub kingdom - Arthropoda
2. Class - Crustacea
3 Order - Decapoda
4. Suborder - Natantia
5. Family - palaemonidae
6 Genus - macrobrachium
7. Species - macrobrachium macrobrachion macro
brachium vollenhovenii
SETTING OF TRAPS
Early in the morning before the tide comes, we set
traps for the prawns using the non return valve traps with palm fruits as bait.
There traps were set in opposite direction to the inward flow of water so that
the macrobrachium species will be trapped when the water is flowing back. The
traps were pinned to the ground using a bamboo stick that is sharpened at one
edge. The screen in the sluice gate prevent predator like snake and carnivores
fishes from the wild from entering the pond.
The traps were checked the next day
and the caught prawns were collected and various measurements were taken. The
measurement include the carapace total length, post orbital total length, post
orbital carapace length, sex, weight and specie
MEASUREMENT OF PRAWNS:
The measurement is carried out to monitor the growth
of the prawn and it is done with ruler, exercise book and biro for recording
purposes.
1. Total
length (TL) this is measured from the tip of the rostrums to the end of telson.
(ii) Post
total length (SL) this is from the mouth of the prawn and before the tail fin.
(iii) Post orbital total length: It is the
length from the bark of the stalked eye and the end of the telson.
(iv) Carapace
length: This is the length from the tip of the rostrum of the prawn to the
first segment and the carapace margin just before the first abdominal segment.
(v) Post
orbital carapace length-This is measured from the sack of stalked eye to
the first segment.
The measured prawns are transferred
into a net-long cage and put in the culture pond and are fed twice daily. Some
aquatic macrophyte like water lily, water hyacinthy is found in the pond.
Life cycle and natural Reproduction
Members of genus macrobrachium have
their life cycle spanning between fresh and brackish water habitats
environment.
Age of maturity of prawn is five
months. Adults breed in fresh water and mating occurs between a mature male
and matured female. The genital opening is located ventrally at the base of
third pair of legs in female and fifth pair of legs in the male. There is a
“gap” the seminal receptacle in females at the base between fourth and fifth
pair of the walking legs.
Spawning
occurs a few hours after mating and the female carry the egg in their abdomen.
The female can lay up to 5,000 to 30,000 eggs depending on the size of female
MEASUREMENT TABLE
|
S/N
|
SPP
|
T.L
|
PTL
|
CL
|
PLC
|
WT
|
SEX
|
|
1
|
MM
|
4.9cm
|
3.9cm
|
2.0
cm
|
1.2cm
|
3.0g
|
male
|
|
2
|
MM
|
4.3cm
|
3.5cm
|
1.9
cm
|
1.1
cm
|
2.6g
|
Male
|
|
3
|
MV
|
4.5cm
|
3.6
cm
|
2.0
cm
|
1.0
cm
|
2.4g
|
Male
|
|
4
|
MV
|
6.2cm
|
5.2
cm
|
2.5
cm
|
1.6
cm
|
4.0g
|
male
|
|
5
|
MM
|
5.2cm
|
4.2
cm
|
2.3
cm
|
1.2
cm
|
3.8g
|
male
|
|
6
|
MM
|
5.2cm
|
4.2
cm
|
2.2
cm
|
1.3
cm
|
3.9g
|
male
|
|
7
|
MM
|
5.0cm
|
3.9
cm
|
2.3
cm
|
1.3
cm
|
3.9g
|
Male
|
|
8
|
MM
|
5.6cm
|
4.5
cm
|
2.3
cm
|
1.4
cm
|
4.2g
|
Male
|
|
9
|
MM
|
5.1cm
|
4.2
cm
|
2.2
cm
|
1.2
cm
|
2.7g
|
Female
|
|
10
|
Mm
|
5.5cm
|
4.5
cm
|
2.4
cm
|
1.2
cm
|
2.5g
|
Female
|
Activities carried
out in the unit
Early morning at about 6am. I went
to the unit by then the tidal movement is high at about 12am the tidal is low I
check and remove the traps collected, the caught prawns and other species like
crabs and fishes (Snake head) I took various measurement of the prawns and took
them to the culture tank. I reset the traps for another catch.