Hi, Seafood Safety 2008
The procedures for the scenarios you mention will be the same as you would use for quality or food safety issues.
1. What would you do if your supplier delivered decomposed fish or if you found bad fish in your cooler? Follow the same procedure if the product is found to be mislabeled or from a non-certified source.
2. Follow your product recall procedure. Although this is not a regulatory recall for food safety, you would follow the same procedures. Just add some details to your recall plan to show that you will notify affected customers and arrange for appropriate corrective measures to be taken (return, relabeling, or whatever)- you will probably want to call it a "retrieval" or "withdrawal" rather than a recall, though, since it will not involve the government. You will also need to notify your MSC/ASC certification body.
3. Basically, the Chain of Custody certification is all about traceability and proving that the product is certified at all stages if you are going to represent it to your customer as being certified. Make sure you are properly labeling the product in storage, particularly if there is a possibility that it could be confused with non-certified product. You can use your traceability SOP or create a similar one that is specific to MSC/ASC.
If you are subcontracting any of the processing, make sure that your subcontractor has their own certificate or is added to yours, and if you know you will be selling the product as certified, then let them know before they start processing it.
It looks a lot scarier than it really is, as long as you have good traceability procedures in place.
Good luck!