Short Report: Fluence Energy short interest at record high

Welcome to this week’s installment of “The Short Interest Report” – The Fly’s weekly recap of short interest trends among some of the most widely followed high-short-float stocks. Using the data from our partner Ortex.com, which utilizes the latest information from stock lenders to estimate short interest changes for thousands of publicly traded companies, this report will screen for some of biggest changes in short interest as a percentage of free float and days-to-cover ratios while also considering the short interest data on some of the more volatile and heavier-traded names of the week. Based on the availability of data from Ortex, the report tracks the trading period that covers prior Friday through Thursday of this week, excluding holidays. As a basis of comparison for stocks discussed below, the S&P 500 index was down 1.6%, the Nasdaq Composite was down 2.0%, the Russell 2000 index was up 3.8%, the Russell 2000 Growth ETF (IWO) was up 0.3%, and the Russell 2000 Value ETF (IWN) was down 0.5% in the five-day trading session range through October 16.

SHORT INTEREST GAINERS

• Ortex-reported short interest in Fluence Energy (FLNC) had troughed at 2025 lows of around 22% in the final week of September, though with the stock having propelled higher in October, bears are willing to try and fade the rally. Short interest as a percentage of free float jumped from 35.5% a record high of 52.6%, even as days-to-cover on the name is sinking from 5.2 to 4.9 due to a surge in trading volume over the past month. Meanwhile, the stock of the energy storage solutions was up 31% in the five-day period covered. Fluence also has now nearly tripled from early September lows, while its year-to-date gains amount to 20%.
• Ortex-reported short interest in Core Scientific (CORZ) hit a two-month low around 19% early last week but has since bounced notably higher, reaching 23.7% this Thursday – within a percentage point of 2025 highs seen in late August. The spike in bearish positioning is also a counter-trend to prevailing overall bullish sentiment on the stock, with shares of the HPC host/crypto-miner having hit record highs this Wednesday. In the five-day period covered through Thursday, Core Scientific traded up 9%, and year-to-date, the stock is up 31%, though Friday’s 6% decline at the time of writing tracks the broader selling in the crypto space.
• Ortex-reported short interest in Nano Nuclear Energy (NNE) has seen a gradual uptrend for much of the year, though this week, the increase in bearish positioning was especially pronounced. Shorts as a percentage of free float jumped from last week’s base of about 25% to over 34% even as days-to-cover on the name barely budged from 4.1 to 4.2 due to the uplift in trading volume. The stock also hit record highs last week, having gained 86% this year on the upswing in the nuclear energy investment theme, though shares are now down 23% from that peak, including today’s 5% drop. In the five-day period covered, Nano Nuclear was still up 2.1% through Thursday.

SHORT INTEREST DECLINERS

• Ortex-reported short interest in Apogee Therapeutics (APGE) was down from 23.7% to 19.3% – a 2025 low – while the stock was up 3% this week and has now gained 35% since last week. Traders are responding positively after the company’s $300M raise announced last week and intended to “fund preclinical studies, clinical trials, manufacturing, and commercial readiness activities in support of its antibody programs”, with bears taking notice by fleeing for the exits rather than fading the rally. Year-to-date, Apogee is still down 47%.
• Ortex-reported short interest on Grindr (GRND) is down sharply this week, falling from 112% all the way to 37%, with days to cover rising however from 2.1 to 2.9 amid a substantial increase in trading volume. The stock has been among the most heavily shorted names within our screen, though after a 50% decline in share price over just the past three months and reports of large shareholders looking to take the company private, bears are booking profits. The stock was still up 3.1% in the five-day period through Thursday, though year-to-date, shares are now down 25%.