On iNaturalist, I think a lot of river eels (Anguillidae) are ID’d through location. That’s probably fine for most wild eels, especially in Europe and America (though location-based IDs always make it a lot harder to get accidental releases or vagrants properly ID’d), but a lot of market eels are caught far in the ocean as larva, raised in captivity, then sold around the world. These eels can’t be ID’d by location. So, is there any way to physically tell them apart? Is it possible to ID the market fish to species?