Black Spot Problem In Shrimp

INTRODUCTION

Shrimp are considered as the second largest export sector in our country. But black spot problem is great problem which reduced the shrimp production. Black spot is a disease. Black spot disease is one of the most common diseases. First the crustacean shell will get damaged, followed by crustaceans and detritus decomposing bacteria invade. Finally a deadly invasion of freshwater algae-like bacteria, spread and attack, causing shrimp mortality. (Happens when the immunity system is down).

WHAT IS BLACK SPOT DISEASE

The disease is caused by Benekea sp which attack main component of the cell walls of the exoskeletons of arthropods

The early stages, lesions are small brown spots, ulcers after lesions gradually become black. Bacterial will destroyed muscle tissues under the shell. The most common bacterial infected area is the gill, abdominal muscle belly, tail section and gastropods. Seriously infected will just lie on its side, only gastropods and gills in motion.

Black spot disease is one of the most common diseases. First the crustacean shell will get damaged, followed by crustaceans and detritus decomposing bacteria invade. Finally a deadly invasion of freshwater algae-like bacteria, spread and attack, causing shrimp mortality. (Happens when the immunity system is down).

RESEANS ON HOW THIS DISEASE OCCURR

There are many reasons on how this disease might occur.

1. Bad water conditions
2. Unhealthy shrimps
3. Too much NO
4. Hormones imbalance (during mating and molting)
5. Soil bed turned bad (Usually happens after long usage of soil 1-2 years)

PREVENTION OF BLACK SPOT DISEASE

Blackspot in shrimp has traditionally been prevented and controlled by the use of sodium sulfites, known as dip or powder. When used correctly at the proper dip solution and soak time and on the vessel soon after harvest and rinsing, sulfites are very effective in preventing blackspot from forming during storage. An issue of concern with using sulfite dip is that a small percentage of consumers are allergic to sulfites. To control this potential food safety hazard, the FDA requires that labels on sulfited and packaged shrimp products include a statement that the product contains sulfites. This statement will alert the sensitive consumer of the health risk of eating the shrimp that contains sulfites. This same statement to the direct sales customer will provide similar protection for sulfite-sensitive people. Another risk to the fisherman is the abuse, or overuse, of sulfites on shrimp that then are improperly chilled and stored or frozen, and spoil in the hold.

This situation can then produce hydrogen sulfide gas, which is very poisonous, and presents a serious health risk for people entering the hold for unloading. Alternative enzyme-based products, with trade names such as Everfresh or Prawn Fresh, have been developed in recent years that do not contain sulfites to control blackspot on shrimp. This allows for producing “sulfite free” shrimp without blackspot, which do not then require a sulfite statement on the package label. These and potentially other alternative products allow marketing shrimp to customers who want shrimp that do not contain sulfites. These alternative products have been developed in shrimp fisheries other than in southern Louisiana and the Gulf of Mexico. Their label use directions (solution concentration and soak time) may need to be adjusted or increased to effectively control blackspot during storage and distribution.

REMEDY OF THIS PROBLEM

1. Isolate the infected shrimps – Best to isolate them in another tank to prevent any spreading.
2. “Wash” the soil bed. – Use siphon to clean the soil, there might be left over food or dead shrimps under the soil leading to bad water conditions.
3. Change the soil bed – If possible，Changing soil is better than washing the soil as it will be more effective.
4. Water change – Water change is necessary, at most 1/3 of the water as the shrimps are very sensitive to water changes! It is advised to change more if the situation is bad.
5. Add in Beneficial bacteria – Restart the Beneficial bacteria colony in the tank.
6. Remove all the items in the tank – remove all items in the tank. (e. g. drift wood, breeding box etc. ) This is to ensure that we are able to spot dead shrimps and remove them immediately.
7. Increase the supply of oxygen - think by increasing the supply of oxygen, after the disease, it can help to prolong the life of shrimp, for more treatment time. Best to put the air driven sponge filter.
8. Increase flow rate – Increase flow rate by adding another canister filter. Avoid direct flow on the shrimps by adding a rainbar. Introduce more mosses so the shrimps won’t be swept away.
9. Add salt for aquarium. – in anyways is should be effective but not too much.
10. Add in plants with roots. – this is to absorb all the excess nutrients in the soil.

CONCLUSION

Black spot disease is common disease in shrimp culture. Blackspot, or melanosis, in shrimp is a harmless but objectionable discoloration or darkening, occurring primarily along the swimmerets, head, tail and nearby shell areas, before spreading further along shell edges and through the body. Blackspot is caused by a system of enzymes that are naturally present in the shrimp. These enzymes, in the presence of air, can chemically transform colorless compounds in the shrimp into complex brown pigments near the shrimp surfaces and shell. If you want reduced this problem we have to control the algae bloom in water. Keep soil quality good and keep our water environment neat and clean. By this we can reduced this problem.