May 15 (Reuters) - A handful of hedge funds, including

Millennium Management LLC, and other asset managers are among

the institutions that acquired stakes in the recently launched

U.S. exchange-traded funds (ETFs) tied to the price of bitcoin

in the first quarter, according to recent regulatory filings.

New York-based Millenium revealed it had $2 billion invested

in several of the new ETFs as of March 31. That included

positions in BlackRock's ( BLK ) iShares Bitcoin Trust, the

Grayscale Bitcoin Trust, and funds launched by issuers

such as Bitwise Investments and ARK Investment Management.

Other purchasers included Boston-based hedge fund manager

Bracebridge Capital, which owned $262 million of shares in the

ARK 21Shares Bitcoin ETF as of the end of the first

quarter and $81 million in the BlackRock ( BLK ) product.

Bracebridge, which did not return calls seeking comment, has

among its clients a group of institutional investors such as the

endowments of Yale University and Princeton University.

A filing from the state of Wisconsin's investment board,

which manages $156 billion in assets for the Wisconsin

Retirement System, disclosed purchases of BlackRock's ( BLK ) iShares

Bitcoin Trust worth more than $99 million as of the end of

March. It also disclosed holding of more than $63 million in

shares in the Grayscale Bitcoin Trust.

The State of Wisconsin Investment Board declined to comment.

Other hedge funds with positions in the bitcoin ETFs

included some that had already invested in bitcoin before the

U.S. Securities and Exchange Commission finally approved the

spot bitcoin ETFs in January.

New York-based Hunting Hill Global Capital said it owned

$29.1 million in the Fidelity Wise Origin Bitcoin ETF

and $21.3 million in the Grayscale Bitcoin Trust.

Adam Guren, founder and CEO of Hunting Hill, said the firm

had been investing in Grayscale's bitcoin trust for a year or

more as bitcoin's price and the value of its stake increased

ahead of the ETF approval.

Investors have poured some $29 billion into the bitcoin ETFs

since January, Morningstar Direct data showed.

The filings appear to confirm that while a handful of

hedge funds have taken large positions, retail investors -

including investment advisors - remain the largest category of

purchasers by number. Hightower Advisors, one of the largest

advisory firms in the country, disclosed holdings of about $68

million in the bitcoin ETFs, but declined to comment on

portfolio decisions.

The quarterly disclosures, known as 13-F filings, are made

to the Securities and Exchange Commission around 45 days after

the end of each quarter and may not reflect current positions.

Matt Hougan, chief investment officer of Bitwise, noted

in a memo to clients posted on the social media platform X that

he expected that by the time all the filings are processed, they

will show that as many as 700 institutions own $5 billion or

more in the new ETFs. Until these filings appeared, it has been

difficult to determine which investors have been behind the

buying in the products, which has greatly exceeded even the most

bullish estimates and helped drive the price of bitcoin itself

to new highs this year.