What happened

What a difference a month makes!

Barely a month ago, shares of dry bulk shipping stock Castor Maritime (CTRM 0.29%) turned sharply higher on news that the Baltic Exchange Dry Index (BDI) was continuing to set new highs. The good news continued through the month of March, culminating in the BDI surpassing 2,300 on March 22.

But now the BDI is slumping, and Castor Maritime is slumping, too, down 8.8% as of 3:35 p.m. EDT today.

Simple red arrow declining stock chart on a white checked background

Image source: Getty Images.

So what

The BDI tracks the rates shippers like Castor Maritime can get for hauling dry bulk goods (e.g., coal, iron pellets, and grain) across the ocean. The problem is, over the last three weeks, the BDI has shed 10% of its value.

This is bad news for Castor Maritime stock, which has lost about 50% of its own value over the past three weeks.

Now what

Will things get better for Castor Maritime, or worse? Referring to the BDI's chart, I cannot help but notice that, while certainly down over the past three weeks, at Friday's closing price of $2,085, the BDI is still valued about where it was on March 17, back when Castor Maritime stock cost nearly $0.99 a share -- or more than twice where it trades today.

This would seem to imply that investors are overreacting to the decline in the BDI, and selling Castor Maritime shares too soon. Then again, if the BDI resumes its downtrend (it's kind of leveled off over the past week or so), then all bets are off, and I would expect to see Castor Maritime sink right along with it.

Sadly, that seems to be exactly what today's sellers are predicting will happen.