Final answer:
Alarm signals released by fish in response to a predator can be chemical, which allows these signals to circulate and cause an alarm response in fish located in a separate tank through shared water systems.
Step-by-step explanation:
The question deals with the behavior of fish in a tank responding to the presence of a predator. When a predator fish was introduced into one of the tanks, the fish in that tank began to release alarm signals. These signals are indicative of stress or danger and are a form of communication among fish. What's particularly interesting is that the alarm signals were able to influence fish in a separate tank. This response was due to the alarm signals being in a chemical form that circulated through the tanks' shared water system, thereby reaching and affecting the fish in the other tank. This is an example of how fish can communicate potential threats to one another even without direct visibility or physical interaction.