We Need Better Measures For Fish Welfare

In their underwater world so radically removed from our own, fishes seem to fall out of sight, and out of mind. However, it’s important to keep in mind the scale of their existence: there are more species of teleost fish (a class of bony fish) than of all other vertebrates combined. And with different species needing different conditions, ensuring good welfare for fish in captivity is no easy task. In this article, the authors bring together research on the key issues surrounding fish welfare to understand the gaps and suggest a path forward.

The article starts with a brief look at the legislation. A 2010 E.U. Directive aims to protect the welfare of all vertebrates, including teleost fish. Unfortunately, although it suggests parameters, the diversity among species of fish and the difficulty of understanding what fish welfare means have hampered this attempt to protect them: we simply don’t know enough.

Good welfare means being both physically and mentally healthy. But what does this look like in fishes? Going beyond invasive methods like blood and tissue sampling, the authors describe how to use physical and behavioral cues to tell how a fish is doing. Physically, signs like color changes and bitten fins can indicate that a fish is suffering, for example; behaviorally, aggression and changes to swimming patterns similarly offer clues.

The environment that a fish lives in affects his or her welfare. Environmental factors range from the temperature, pH, and salinity of their water, to the levels of light, noise, and environmental complexity. Even color may play a role – research suggests that blue may reduce aggression, for example.

There are a lot of variables to get right here, and a lot that changes depending on the species. To add another layer of difficulty, the relationship between environment and welfare is not always straightforward. For example, more complex environments better reflect a fish’s natural habitat, and improve their cognitive skills. But they can also increase competition and stress among fishes. As such, the authors emphasize the importance of great care and thoughtful research in figuring out welfare-friendly environments for captive fishes.

The number of fishes in a given space, as well as how they are fed both strongly affect social interactions among them. As with other aspects, foraging behavior and acceptable density vary by species. But as a rule, the authors suggest that the best option is to use self-feeding systems, which allow fishes to choose when and how much to eat. They also highlight the importance of further research into swimming activity, to help us better understand how the number of fishes in a space affects their welfare.

In addition to conditions within the aquarium, what goes on above water is important: having well-trained staff and good protocols can help to protect fish welfare. Staff should be able to recognize the signs of poor welfare. And since (contrary to their reputation!) fishes have good memories and learning abilities, it’s important to standardize procedures. Although cleaning equipment might at first scare fishes, for instance, research shows that they quickly get used it.

The common thread running through this article is that we need more research into fishes and their welfare. It’s also really important to improve practices in reporting conditions. Many research papers that the authors looked at did not even include information required by the 2010 E.U. directive – which is itself lacking due to its generalizations. Of 84 total papers, not one mentioned noise, even though it’s something that is known to harm fish welfare, and only a few described the complexity of the environment as a factor. With information so thin on the ground (or rather, in the water), it’s hard to accurately assess the welfare of these fishes. Given how much work needs to be done here, it’s vital that, as animal advocates, we help put fishes in the spotlight.