From the environment:
* Plastic debris: This is a growing concern in oceans worldwide, and salmon can ingest plastic particles. This can be a hazard to the fish and also potentially contaminate the meat.
* Sand and grit: If salmon are caught in areas with sandy bottoms or if they are handled roughly during processing, sand and grit can get mixed in with the meat.
* Parasites: Some parasites, like anisakis, can be found in salmon and can cause illness if consumed raw or undercooked. These are technically biological contaminants, but they can be considered physical due to their visible nature.
From processing:
* Bones: Salmon bones, especially smaller ones, can sometimes remain in the fillets even after processing.
* Scales: Scales can sometimes detach and remain in the fillets, especially if the fish wasn't properly scaled before processing.
* Metal fragments: Metal fragments can be introduced during processing, for example, if metal equipment is not properly maintained.
It's important to note that the presence of these contaminants is not necessarily a sign of poor quality or safety. However, it's always best to inspect your salmon carefully before preparing it to ensure there are no foreign objects present.
It's also important to remember that most salmon sold in supermarkets and restaurants is commercially caught and processed. This means it has undergone strict quality control measures to minimize the risk of contamination.