"trade in shark fins" is correct, "shark-fin trade" would be too; "trade with shark fins" would be weird. Compare the frequencies for a more common commodity: h

"trade in shark fins" is correct, "shark-fin trade" would be too; "trade with shark fins" would be weird. Compare the frequencies for a more common commodity: https://books.google.com/ngrams/graph?content=trade+in+wheat%2Ctrade+of+wheat%2Cwheat+trade%2Ctrade+with+wheat&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Ctrade%20in%20wheat%3B%2Cc0%3B.t1%3B%2Ctrade%20of%20wheat%3B%2Cc0%3B.t1%3B%2Cwheat%20trade%3B%2Cc0 https://books.google.com/ngrams/graph?content=trade+in+wheat...