Reply To: Genetically Engineered Animals and Kashrus

Fish from different species cannot reproduce together. The ability to reproduce together and produce fertile offspring is actually what defines animals as belonging to the same species. Different species that are very similar have produced sterile offspring together, e.g. the liger,a cross-breed of the lion and tiger, but I highly doubt that any species so dissimilar that one has fins and scales and one does not could accomplish this.