Bitcoin prices are displayed at the Bithumb Lounge in Seoul’s Gangnam District, March 4. Yonhap

The domestic cryptocurrency industry is grappling with mounting concerns over a market downturn as trading activity sharply weakens amid the ongoing stock market boom and as financial authorities move to tighten regulations, industry officials said Sunday.

According to data the Bank of Korea submitted to Rep. Cha Gyu-geun of the minor Rebuilding Korea Party, both domestic investors’ crypto holdings and transaction volumes have fallen by more than half over the past year.

The value of digital assets held by investors at the country’s five cryptocurrency exchanges — Upbit, Bithumb, Korbit, Coinone and Gopax — fell to 60.6 trillion won…