Explain why the chemical released from the injured fish may not cause an alarm response in other fish species

There is an evolutionary reason why such mechanisms would only work within species: Fish would get an advantage (as a population) from warning their co-specifics, but not from warning other species. So they would (through the process of evolution) tweak their signals to be only readable by the same species. 

The answer would be cstep by step explanation: all of the other animals developed their features while the salamander was born with them