Marine scientist Rima Jabado has spent the last three years visiting docks around the United Arab Emirates and the fish markets of Dubai, chatting with fishermen and asking them about sharks. What she hears from all of them, she says, is that shark stocks have dropped drastically in the warm waters offshore in the Gulf.

The cause: China’s vast and growing appetite for shark fins as an ingredient in soup. Estimates vary, but the global trade in shark fins totals hundreds of millions of dollars a year, and tens of millions of sharks around the world may be caught every year for their fins. Some experts estimate that stocks of some shark species in inshore reef systems around the world have fallen by up to 90 percent.

Dubai has become a major global supplier of fins, the UN says. The fifth-largest exporter in the world, it is the auction point for fins not only from its own waters but also from Oman and other Middle Eastern and African nations that send sharks and fins to Dubai for sale. Dubai exports an estimated 500 metric tons of shark fins and other shark products a year to Hong Kong, to which roughly half the world’s shark fin production is shipped.

The trade is legal, though efforts are being made to ban the practice of “finning” — hacking the fins off of sharks and throwing the rest overboard, often when they are still alive. Four years ago, under international pressure, the UAE joined the growing number of countries banning the practice.

But Jabado says more needs to be done. Tracking the effect on shark populations is difficult — which is why Jabado is trying to collect hard data on the size and makeup of the population in the Gulf and to quantify the trade in the fins. On the docks, the Canadian researcher interviews fishermen on the size of their catches and where they caught them. She collects data and DNA samples from each shark they catch. She also tags sharks off the UAE to track their movements.

Only if there’s accurate figures showing there is a decrease in some shark species, she says, will the government start to act.