The scuds I bought look like the ones in this series of pictures (bottom picture of the 4 in the post by Bill D about 3/4 of the way down the page in this link shows them fairly well)
The body of your critters seems to be broad all the way to the back, so it may be a cousin to the ones I/Bill D have?
I bet they are closely enough related that if they were found natively in waters in your area that they probably are invertebrates in that same family. The fish probably love to snack on them
A better close up picture would help. And it always pays to be cautious before introducing a new critter in the pond.
Did they come from your pond already? Where was the minnow trap if you are planning to move them to your pond?
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
Last edited by Bill Cody; 03/30/1602:42 PM.
aka Pond Doctor & Dr. Perca Read Pond Boss Magazine - America's Journal of Pond Management