Freshwater fish should not be fed to fish-eating species of marine birds because

• A. Because freshwater fish have low nutritional value
• B. Because exposure to new parasites is possible
• C. Because they are difficult to digest
• D. Because they are typically contaminated with salt

Answer: (B)

Freshwater fish carry parasites that marine birds may not have previously encountered, so feeding them introduces a chance of cross-species parasite transmission. Parasites often have specific host ranges, but new prey items from different ecosystems can bring in organisms the birds’ immune systems aren’t prepared to handle, leading illness or spreading disease in rehab or wild populations. Keeping their diet aligned with marine-origin prey minimizes this parasite exposure risk, which is the main safety concern. The other ideas—nutritional value, digestion, or salt contamination—don’t capture this cross-species parasite risk as the primary reason.