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.