I would not go by daily short volumes in order to gauge the shorting activity. A vast majority of "short" volume you see on there is MM's simply making an efficient market. What you want to be looking for is the open short interest, or SI. Those numbers are typically updated every two weeks, and are reported with a one week lag time. I recommend reading this link to get more familiar with what the numbers are really telling you.
“Naked” short selling is not necessarily a violation of the federal securities laws or the Commission’s rules. Indeed, in certain circumstances, “naked” short selling contributes to market liquidity. For example, broker-dealers that make a market in a security generally stand ready to buy and sell the security on a regular and continuous basis at a publicly quoted price, even when there are no other buyers or sellers. Thus, market makers must sell a security to a buyer even when there are temporary shortages of that security available in the market.