Louisiana Crawfish: 5 Steps to Minimize Impacts of White Spot Syndrome Virus

Crawfish ponds. Photo: LSU AgCenter

1. Avoid unnecessary stocking of existing ponds:

Research has shown that population density, management of water quality and forage crops has roughly 20 times as much influence on crawfish size as genetics do.

Although many producers have the idea that adding new stock to their permanent ponds will somehow improve the size and yield of their crawfish through some genetic mechanism, this is not the case.

The good thing about this finding is that if a pond has an established, healthy population, there is no need for supplemental stocking and the risk of introducing WSSV can be avoided entirely.

2. Obtain healthy stock:

If you MUST stock a new pond or a pond in a rice-crawfish rotation, make every effort to obtain stock from healthy ponds.  These ponds should have no unusual death loss – in traps, in sacks, or in the open ponds. If possible, inspect the ponds from which your stock will be acquired.

Do not use crawfish from ponds showing any suspicious signs such as dead crawfish in traps, dead crawfish on the pond bottom or floating at the surface, or with any noticeable slow, and lethargic crawfish inside or outside of the traps.

The same goes for ponds that had these problems earlier in the season. Wild-caught stock may potentially carry the virus but it is not possible to observe them as it would be in a pond.

Because of this, it is important to thoroughly inspect wild-caught animals for signs of weakness or slow, uncoordinated movements prior to making a decision to use them for stocking.

3. Other stocking considerations:

Although the most up-to-date recommendations encourage crawfish producers to obtain stock from several sources to improve the chances of good burrowing survival and reproduction, this approach multiplies the possibility of encountering and stocking infected animals.

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If a single source of healthy crawfish can be identified, it may be best to use that source as a sole supplier for stocking.  However, it is still very important to follow recommendations for evaluating whether animals have the potential for good survival and reproduction.

Things to look for include bright yellow fat reserves, a good ratio of females to males (preferably 50-50 or better), healthy and active behavior, and the presence of few or no white river crawfish.

As always, care should be taken to minimize stress during handling by keeping crawfish wet, in the shade, and not too hot or too cold (do not use crawfish that have been stored in a cooler overnight).

4. Water sources:

WSSV can be transmitted in water. Water drained from an infected pond can transport the virus some distance in drainage canals and bayous. It is also possible that wild crawfish and aquatic insects living in the waterways are infected or carry WSSV.

Using surface water to flood your pond could potentially be a source of infection. WSSV has not been found in well water right out of the ground.

5. Equipment:

Do not move traps, boats or other equipment from farm to farm (or even pond to pond within your own farm, if a problem is suspected) without taking measures to prevent the spread of WSSV.

Ideally, boats should be power washed to remove all mud and debris, and then allowed to dry in the sun for a minimum of one week.  Traps can simply be cleaned of mud and debris and then dried thoroughly in the sun.

Alternately, boats and traps can be power washed and then sprayed or scrubbed with a 5% bleach solution.

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