“I don’t think the fish ‘understand’ that the cats are potentially dangerous”. This is a sentence written by a visitor on a forum about home aquariums.
If visitors to this page are looking for information about keeping a cat and aquarium fish in the same home, I hope it helps. It is quite an interesting topic and quite a complicated one; the main reason being that although we understand the domestic cat quite well because of the proliferation of millions of websites about the domestic cat over the preceding 5 years, scientists are still learning about fish.
The aspect of fish which scientists are learning about is their level of intelligence and whether they have emotions and feel pain etc. which very much dictates how we relate to them. People tend to relate to animals in a hierarchical system meaning people tend to rank, for example, the domestic dog higher than a fish in an aquarium with respect to intelligence and rights. That may be misguided.
The question I have is whether it is sensible or reasonable to keep both cats and fish in the same home. It is certainly relatively easy to keep cats away from an aquarium. A lot of people use squirt bottles to scare the cat away from the fish which I’m afraid to say is unfair and wrong because it is a form of negative reinforcement which is what we call “punishment”.
However, despite that people use the squirt bottle against their cat to stop them going near the aquarium. Right away you can see a negative aspect in respect of keeping cats and fish in the same place.
The aquarium should be covered to protect the fish but I suppose some people don’t cover their aquarium. We know that sometimes cats, being fascinated by the fish inside an aquarium, try to hook them out with their claws (if they still have their claws because many in America are declawed). It may be the case in fact that some people who keep fish and cats declaw their cats in part because they wish to protect their fish. If that is the case then it is another negative impact in keeping cats and fish in the same place.
What about the fish? The question I have is this: even though a person can successfully protect the fish from the cat, fish are a prey item to the cat. Fish are not a primary prey item to the domestic cat, far from it, but given the opportunity fish could be a prey item. This probably comes from the wild cat ancestor which will feed on rodents primarily but living near watercourses might on occasions and where appropriate, prey on fish.
If fish are a prey item for the cat (or an interesting ‘object’ to catch) this begs the question whether fish recognise the domestic cat or any cat as a predator. Most fish have very well-developed sense organs. They have excellent eyesight. They also have good hearing. Hearing is an important sensory system for most species of fish.
Certain fish have a strong sense of smell. Experiments provide evidence that fish can feel pain and have fear responses – although, this is a developing area and more work is required. In aquatic environments, in this instance I am referring to the wild, fish are able to call upon information about the predation risk where they are from environmental cues gathered from visual, olfactory and mechanical senses.
A research paper says that “predator identity can be learned through socially transmitted information, direct encounters with predators or indirectly by associating a predator’s odour with an alarm cue”, which is a chemical released by damage to the skin after having been attacked by a predator.
It would seem to me that if a cat had on one occasion grabbed fish out of an aquarium and the fish had survived then the fish would probably be fearful of the presence of the cat in the future. The big question is whether fish inherently have a hardwired fear of the domestic cat. If that is the case then the presence of a cat around the aquarium would stress the fish and be a disincentive to keep both cats and fish in the same home if one wants to be fair to the fish and if one is concerned about their welfare.
However, the fish aquarium websites indicate to me that fish are not bothered by the presence of a cat. A cat may have a habit of resting on top of an aquarium because it is warm. The reports I read on the aquarium websites indicate that this does not upset the fish but the information is anecdotal and there is no hard information about this.
I have to speculate in coming to a conclusion, which is this: there is a potential, at least, for fish in an aquarium, in a person’s home, to become stressed by the presence of a domestic cat in the vicinity of the aquarium but there is nothing to support that suggestion other than the fact that, as mentioned, fish have highly developed sensory systems and are predator-aware.
Part source: Plos One