They probably were sniffing for drugs, in customs. I'm not sure how lucrative smuggling mollusks a few at a time would be. (This dog was used to search fishing vessels and check out large cargo containers.) Although, I am but young in the ways of mollusk-smuggling.
"John is convinced that Tammy's amazing abalone detection abilities will pave the way for teams of future 'ecodogs' to protect South Africa's rich, exotic biodiversity. In 1996, after months of training in finding hidden fresh, frozen, and rotten abalone in plastic pipes, his little dog became the world's first canine to be accredited for endangered mollusk protection.... With forty-five successful finds and no misses in her accreditation test, Tammy impressed even the most skeptical police officers."
—Merrily Weisbord and Kim Kachanoff, Dogs with Jobs: Working Dogs Around the World (NY and London: Pocket Books, 2000), 245