Shrimps
are common in the tidal pools on Chek Jawa. However, they are difficult
to spot as hide in burrows or just beneath the sand. Even those in
plain sight disappear from view as many are nearly transparent. They
are adapted for bottom dwelling.
Shrimp Food: Larger shrimps are
mostly scavengers or eat small plants and animals. Smaller ones feed
on plankton and algae.
Backward Getaway: Unlike crabs
which have stiff shells to protect their abdomen, a shrimp has a thin,
flexible shell over a long abdomen that ends in a broad fan-like tail.
A quick contraction of the muscular abdomens propels the shrimp backwards.
To swim slowly, the shrimp paddles with the small swimmeretes under
the abdomen.
Mating prawns: Shrimps have separate
genders. To mate, a male inserts his sperm packet into a special receptacle
in the female. Fertilisation, however, is external. The female releases
the sperms from the packet together with her eggs. A female prawn
produces a huge number of eggs, as much as one million in one spawning!
Some may carry their eggs under their tails.
Prawn babies: Like many marine
creatures, shrimps undergo metamorphosis. That is, they change their
shape as they develop through their life cycle. Most adult shrimps
migrate to deeper waters to breed and release their eggs. Eggs usually
hatch quickly, within a day or so. After hatching from the egg, the
larvae look nothing like the adults! These larvae drift with the plankton,
changing shape as they develop further. Eventually, they look more
shrimp-like and migrate back to shallow waters. Here they develop
into mature adults before starting the cycle all over again.
Role in the habitat: Shrimps are
numerous and eaten by a wide variety of larger creatures. In coral
reefs, some species of shrimps act as cleaners, picking parasites
and dead skin off fishes. The fish 'clients' allow the cleaner shrimps
to do their job without eating them. These cleaners are often brightly
marked.
Human uses: Shrimps and prawns
are relished by people everywhere. In Asia, shrimps are eaten in many
ways. Besides the usual dishes made from whole shrimps, they may also
be dried, or made into paste ('belachan') or mixtures ('cincaluk').
Tiny shrimps are used as condiments, and shrimps flavour crackers,
balls and other delicacies.
The large prawns that we eat often come from prawn farms or are harvested
from the wild by trawling or traps.
Status and threats: While traditional
farming and harvesting methods are sustainable, large-scale commercial
prawn farms and prawn trawling are more destructive and unsustainable.
Commercial
prawn farming often involves:
- Destroying
large tracks of mangroves and other intertidal habitats to create
the farms;
- Harvesting
egg-bearing adults from the wild to provide stock for the farms;
- Introducing
non-native prawns which could upset the natural balance if they
escape;
- Adding chemicals
to the water to prevent diseases or boost growth. These affect
surrounding wildlife;
- Releasing
large amounts of waste water from the farms that poison the surrounding
habitats; and
- Saltwater
from the ponds eventually seep into groundwater and affects supplies
of freshwater to humans and wildlife in surrounding areas.
Large-scale
trawling often involves:
- Dragging
large heavy nets repeatedly over shallow areas. This damages everything
on the sea bottom. Recovery of the habitat can take 1-20 years.
- An enormous
waste: commercially valuable prawns often make up only 10% of
what is caught, the rest is thrown back often dead.
|
|
| Prawns
or Shrimps? The words ‘prawn’
and ‘shrimp’ are interchangeable. Small prawns are often called
shrimps. |
Prawn
metamorphosis
Larva just after
hatching from the egg
First stage after
the larval stage
Adult prawn |
