Yes those are aquatic sow bugs (Isopoda - Asellidae)the counterpart of land based sow bugs. There are around 130 species of aquatic Isopoda in the US. To my knowledge they do not thrive in ponds with normal populations of sport fish due to their vulnerability to predation. They are considered little value to the diet of fish. They are secretive and live mostly under rocks, vegetation and debris. There are species of stream and pond dwellers; some species live in caves. If anyone has them common in a pond with panfish it would be very good information to have available as to what pond conditions favor them. Note that Hoosierguy collected his from a creek.
FYI the Ascellus aquaticus is not reported from the US according to my reference (Freshwater Isopoda (Asellidae) of North America.
Ascellus aquaticus is common in Europe. I think Wikpedia has this incorrect on their page for
https://en.wikipedia.org/wiki/Asellus_aquaticus
