Page 288 - Agriculture_Form_Three

Agriculture for Secondary Schools

Management of fish health
To monitor fish health, farmers should be familiar with common clinical signs, signs
of stress and unusual behaviour. Changes in behaviour may be the first sign that fish
are being stressed. Physical changes may become apparent such as abnormal growth,
lesions or discoloration on the body surface, loss of some scales, cloudiness of eyes,
eroded fins and clogged gills. In case a disease occurs, a quick and effective response
is necessary. The pond in which the disease is observed should be quarantined and
management should be adjusted. Chemicals or veterinary drugs may be used for
disease treatment under guidance of veterinarian. As such, the following aspects
have to be adhered to as general management of fish health.

(a) Avoid stress of fish
Stress can be minimised by using the right stocking density, regularly feeding the
fish, careful handling only when necessary and maintaining good water quality.
(b) Regular sampling of fish

Fish should be sampled for growth and health once or twice a month. This can
also be used to estimate biomass in the pond and calculate the feed to be offered.
Sampling should be done in the morning. The fish should be weighed as soon as they
are caught then released to the pond again. Around 20 - 40 fish should be weighed.
Fish should not be fed prior to sampling.
(c) Regular fish observation
The farmer should regularly check the fish for signs of diseases. This can be unusual
behaviour, physical damages, spots, swelling, etc. A healthy fish has a good appetite
and is an active swimmer.

(d) In case of disease outbreak or high mortalities inform the authorities
If farmers encounter unusual high mortalities or observes signs of diseases, they
should notify an extension worker or veterinary expert as soon as possible.
(e) In case of a disease outbreak, quarantine the pond
Make sure no people enter the pond area except authorised persons, if necessary. Do
not move equipment out of the pond area.

(f) Proper use of veterinary drugs and chemicals
In case veterinary drugs are used to treat a disease, they should be administered
according to the instructions of the manufacturer and should be administered by
an authorised personnel only. Fish should not be harvested before the end of the
withdrawal period (the time in which residue may be found in the edible parts of the
fish) of the product, which can be found on the label of the medicine.

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