Circle Trade, the trading operation of Circle, has increased its minimum ticket size on bitcoin trades to $500,000 from $250,000.

The move comes during a trading lull in the market for digital currencies across crypto exchange venues.

Chief executive Jeremy Allaire told Business Insider the size of block trades has grown significantly since the beginning of the year.

Trading activity at one of the largest cryptocurrency trading shops is picking up despite a lull across exchanges that trade crypto.

In an interview with Business Insider, Circle chief executive Jeremy Allaire said the size of block trades made by Circle Trade, the firm's over-the-counter trading desk, has grown since the beginning of the year. The firm has also doubled the size of its minimum crypto trades from $250,000 to $500,000, according to Allaire.

That's despite a sharp decline in cryptocurrency trading volumes across retail exchanges. Per data from CoinMarketCap, 24-hour trading volumes are down to about $20 billion a day from all-time highs near $70 billion at the beginning of the year.

But "the market is robust" for Circle.

"The minimum ticket size has moved up to $500,000 with an average of $1 million," Allaire said.

Some transactions, according to Allaire, are larger than $100 million.

"That watermark will continue to rise," Allaire said.

OTC trading occurs off exchange venues, such as Coinbase's GDAX or Kraken, for instance. The point of such desks is to provide a platform for high-net-worth crypto-holders and institutions to make large trades without impacting the broader market.

As an alternative to crypto exchanges, they typically have deeper liquidity to support such transactions. One industry insider told Business Insider that deeper liquidity in OTC markets has played into the growth of a number of trading shops.

"If I have $5 million, I can't do that trade on GDAX," the person said.

OTC desks can also provide a more secure alternative to crypto exchanges, which are known for hacks and outages.

Circle, which counts investment bank Goldman Sachs as a a strategic backer, trades more than $2 billion in cyptocurency a month. It recently expanded its operations in Asia, Bloomberg reported.

Recently, Circle announced it acquired Poloniex, a cryptocurrency exchange. It plans to scale the business by bringing it to new markets, adding the number of coins on its platform, and enabling fiat-to-crypto transactions.

Elsewhere in the cypto OTC market, DRW's Cumberland operates a trading desk. Kraken, as Business Insider first reported, recently launched their own, too.

A person familiar with operations at Genesis, another cryptocurrency trading shop, told Business Insider its average trade size has increased to about $300,000. The company trades $1 to $2 billion a month, the person said.