Stress management in fish production (e.g tilapia, cat-fish etc.) is one important factor or key that will determine if your fish farm business will be successful. The following are the consequence of fish stress;
- Reduction in fish immunity to disease/environment changes.
- Lack of appetite.
- Increase in cost of feeding caused by lack of appetite/waste of uneaten feed.
- Fish death.
Fish stress can be manage/control through the following:
- Stock at the right rate to avoid overcrowding either in your storage/holding facility or during transportation.
- Feed at the right feeding rate to avoid over-feeding (waste of uneaten feed) or under-feeding (malnutrition).
- Good water quality management.
- Proper fish handling during total/partial harvest, sorting, sampling /grading.
- Fed fish with good feed (uncontaminated feed).
- Avoid exposing fish to toxic substance.
- Right way of changing water
- Minimize sound & or sudden flashing of light around the fish tank/pond.
DISEASE CAUSED BY PARASITES IN FISH
Parasite are small organism which either develop inside the fish (internal fish parasite) or outside the fish body (external fish parasite).
- INTERNAL FISH PARASITE: are very difficult to control but their effects can be easily identified by fisheries consultant like me who have the special skills. some examples of internal fish parasite are: Myxosoma cerebralis, protozoan cyst which cause Whirling disease, larval stages (metacercariae) of sucking worms (trematodes) which cause black-spot disease and blindness in fish, tapeworm (Cestodes) etc
- EXTERNAL FISH PARASITE: are much easier to detect and identify, it is possible to eliminate them with the right approve drugs/chemical treatment. Some example of external fish parasite are: Flukes (Monogenea) are very small worms attached by hook to the fish, like Gyrodactylus (body fluke) and Dactylogyrus (gill fluke). Secondly, Leeches which are large segmented worms attach to the fish body by a sucker on each end, such as Pisciola sp. Thirdly, copepods which have two elongated egg sacs attached such as Lernaea sp (anchor worm) and Ergasilus sp. Fourthly, Fish lice (Crustacea) which have a flate, disk-like body covered by a rounded dorsal carapace such as Argulus sp. Fifthly, is the water fungi (water moulds) are made of filaments that usually grow into a cotton-like mass or mat such as Saprolegnia sp which can also develop in the gills (Brachiomyces sp).
SYMPTOMS OF PARASITIC DISEASES
- Loss in weight/fish become sterile as a result of Tape-worm (e.g Corallobithrium finbriatum) activities.
- Small raised spots over the entire body surface and fine, also heavily infected fish often congregate at the inlet or outlet of the pond/tank. These are mostly caused by Ich or White spot disease.
- Infected fish will flash or rub against tanks/pond due to severe irritation also show red spots. These are mostly cause by fish lice.
- Others include skin cut and pealing, pale coloration of skin, fish restlessness in water, loss of appetite and decrease in growth, excessive slime production on the skin and gills and massive fish death.
Nicholas Izekor is an Aquaculture Trainer at The Ark Shore Konsults (T.A.S.K.). He holds a Bachelor’s degree in Fisheries Management from the University of Benin, Nigeria.