What makes week-old anchovies riskier than fresh ones
Decomposition creates multiple hazards beyond visible mold—bacterial toxins and rancid oils irritate the stomach lining within hours. Your Shih Tzu's small size means even trace amounts hit harder; 8 kg dogs can't dilute toxins as effectively as larger breeds. The real danger often comes from what you didn't see him eat.
Check between floorboards and under appliances for oily residues where more rotten fish might hide. Dogs often return to contaminated spots for second helpings. Use a flashlight to inspect—what looks like ordinary dirt could be decaying fish particles stuck in grout lines.
Neurological signs that demand same-day vet care
Mycotoxins from certain molds disrupt nerve function, sometimes causing delayed symptoms like leg tremors or exaggerated blinking. These may appear 4-8 hours post-ingestion as the toxins reach peak bloodstream concentration. Don't mistake initial calm for safety—some dogs show no early signs before neurological issues emerge.
If his walk seems 'drunk' or he bumps into walls, that's an emergency regardless of when you notice it. Time matters with mold toxins—the sooner treatment begins, the better the outcome. Record video of any odd movements to show the vet, as symptoms may come and go.
Hidden salt in spoiled fish products
Even if the anchovy was packed in oil rather than brine, decomposition concentrates whatever salt was originally present. Your dog's kidneys will work overtime processing this while simultaneously handling mold toxins—a double burden on his system. Small breeds like Shih Tzus already have higher kidney disease risks.
Monitor for 'salt poisoning' clues like circling behavior or exaggerated thirst. These differ from mold reactions but can appear together. If he laps up water frantically then immediately vomits clear liquid, that's a classic sodium imbalance red flag worth mentioning to your vet.
Why you might find more evidence tomorrow
Dogs often hide illness instinctively, so tomorrow's first bowel movement could reveal undigested fish bits or oily residue you didn't know he ate. Save any unusual stool samples in a sealed bag for potential vet analysis. Dark tarry stools or bright red streaks both indicate gastrointestinal irritation.
His appetite over the next 24 hours tells you more than his energy level—many dogs act normally while refusing food after ingesting toxins. Offer plain boiled rice and chicken only if he seems hungry, but don't push food if he shows disinterest. Dehydration becomes the priority now.
The full verdict, portion guidance and serving notes are collected on the Anchovy food facts page.