Will a catfish carcass have poison or bacteria in it?

Likely yes.: Degenerating / rotting animal flesh (such as a fish carcass) would almost certainly have some bacteria within it. The environmental conditions in which the dead fish was found would be important. A healthy fish that was caught and cleaned and quickly cooked or frozen would have a low likelihood of harboring bacteria, while a carcass on the ground in the sun for several days would putrify.

A.W Dr. Sturgis.: Many catfish also contain toxic venom. 'the venom of catfish is a complex composition of hemolytic, dermonecrotic, oedema-producing, and vasospastic factors and contains several amino acids, 5ht, 5-nucleotidase, and phosphodiesterase.' http://www.Ncbi.Nlm.Nih.Gov/pmc/articles/pmc3634300/.