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Between the June 15 and June 30 settlement dates, the short interest increased in all but one of the six most heavily shorted stocks traded on the Nasdaq. Short sellers moved most notably on BlackBerry and Intel during the period, while again shying away from MannKind. Frontier Communications held on to its spot at the top of the list for the second period in a row.

Note that the six most shorted Nasdaq stocks all had more than 100,000 shares short by the end of June.

After jumping more than 32% in the previous period, the short interest in Frontier Communications Corp. (NASDAQ: FTR) added another 6.3% late in the month to more than 170.42 million shares, or 14.9% of the telecom’s float. That was the greatest number of shares short since last August. The days to cover jumped to more than seven as the average daily volume shrank in the period. Some analysts see big upside in Frontier. The stock ended the short interest period more than 1% higher, compared to an almost 1% decline for the Nasdaq. Frontier is more than 26% lower year to date. Shares closed Friday at $4.90, within a 52-week trading range of $4.79 to $8.46.

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After a marginal slip in the previous period, the number of Sirius XM Holdings Inc. (NASDAQ: SIRI) shares short crept up less than 2% to more than 141.93 million late last month. That was 6.2% of the total float. At the current average daily volume, it would take a little more than five days to cover all short positions. Apple Music’s debut is the latest change in the streaming music landscape. Short sellers watched the share price pull back about 1% during the two weeks between settlement dates, but it is now up more than 6% year to date. Shares ended last week at $3.73, in a 52-week trading range of $3.14 to $4.04.

A 7.9% bump in short interest brought Intel Corp. (NASDAQ: INTC) to about 138.42 million shares short at the end of the period. That totaled 2.9% of the company’s float. The number of shares short has been growing since mid-April. The days to cover has ticked up to more than four. We recently took a look at Intel’s cybersecurity efforts. Shares retreated about 3% in the short interest period. The stock is now down more than 19% year to date and closed most recently at $29.17. Shares have traded between $28.82 and $37.90 in the past year.

By the end of the month, Advanced Micro Devices Inc. (NASDAQ: AMD) had more than 117.70 million shares short, up less than 1% from mid-June. The most recent reading totaled 18.6% of the company’s float. The days to cover dropped to more than four as the average daily volume surged to its highest level since early in the year. One analyst recently called for AMD stock to double, though others have been cautious. The share price ended the two weeks more than 5% higher than where it began, though at one point it was up more than 15%. The stock closed at $1.96 on Friday, and the 52-week range is $1.93 to $4.80.

MannKind Corp.’s (NASDAQ: MNKD) short interest, at around 115.08 million shares as of June 30, was down 4.4% from the previous period. Note that it was 44.9% of the total float, and the days to cover jumped from about eight to more than 21. Peak short interest year to date was more than 131 million shares, back in May. MannKind’s inhaled insulin drug Afrezza has yet to find any real demand. Shares ended last Friday at $5.38, in a 52-week range of $3.46 to $10.18. The stock saw a share price decrease of more than 6% in late June, and it has pulled back an additional 4% or so since.

ALSO READ: Short Interest in Apple Jumps

BlackBerry Ltd. (NASDAQ: BBRY) saw the largest surge in short interest among those featured here. The more than 101.69 million shares as of the end of June was 11.9% higher than in the previous period, as well as 20.7% of the total float. It would take more than seven days to cover all short positions. The number of shares short was last above 100 million back in January. BlackBerry’s recent earnings report failed to excite, and shares retreated more than 13% in the two-week period. Shares closed Friday at $7.69, in a 52-week range of $7.61 to $12.63. The stock is now down about 30% year to date.

Rounding out the top 10 were Express Scripts Holding Co. (NASDAQ: ESRX), Groupon Inc. (NASDAQ: GRPN), Microsoft Corp. (NASDAQ: MSFT) and Apple Inc. (NASDAQ: AAPL), which rejoined the top 10, replacing Micron Technology Inc. (NASDAQ: MU).