Fish Welfare In Research

Millions of fishes are used in various scientific studies each year, ranging in purpose from conservation research to biomedical, human-oriented research. In this paper, a group of scholars reviewed existing literature, with a focus on identifying and refining common methods used in fish research, to advocate for improved welfare of a range of fish species.

Some countries have issued national legislation or guidance surrounding the use of fishes in scientific research, although there are many where no such guidelines exist. The recommendations typically state that animals should be free from deprivation of food, free from environmental challenges, diseases and injuries, as well as free from functional impairments, behavioral restrictions, and mental and physical suffering. 

Although, globally, many fishes are experimented on each year – more than half a million procedures were carried out on fishes in the U.K. in 2018 alone – animal ethics are often underemphasized in this field. A 2016 survey of the top 250 peer-reviewed journals for fish research discovered that almost half of all papers did not even mention animal ethics in their author guidelines. From those that did, only a fifth ensured adherence to a specific guiding document.

When discussing alternatives, the researchers name several positive examples, including using fish cell lines as a replacement for live fishes when investigating toxicity of various compounds. Partial replacement is also gaining momentum, where vertebrates are replaced with embryonic life-stage vertebrates or invertebrates, operating under the assumption that they are less sentient. This, however, may seem counterintuitive as recent evidence suggests that some larval-stage fishes respond identically to harmful stimuli as do the adults.

Unfortunately, some researchers assert that, at this point in time, there are instances when it is not possible to replace live fishes in experiments, saying it could be due to higher costs or lower reliability of potential alternatives. The main argument for high fish welfare in those cases could be argued by noting that compromised welfare will reflect in behavioral and physiological changes, yielding unreliable experimental data as a result.

There is plenty of empirical evidence suggesting that fish responses can be interpreted as the experience of pain, includes both physiological and behavioral changes in fishes after being exposed to harmful stimuli. From an ethical perspective, then, we should err on the side of caution and try to protect their health and welfare. The research group highlights several key areas, where improvements can be made:

• Anaesthetics – the use of sensation numbing medicine must be assessed on a case-by-case basis as the effects on welfare vary from species to species and depend highly on specific circumstances.
• Analgesics – the use of pain relieving medicine is increasing in fish research. It is vital that we obtain a deep understanding of both potential benefits and adverse effects analgesics may have on fish welfare.
• In field collection and return – even simple tasks such as collecting and handling fishes for tag deployment can be stressful for the animals, in some cases even resulting in performance impairments and exposing the fishes to higher risks of predation. The researchers highlight that although a return to their natural environments may be beneficial for the individual fishes, there is a risk to the ecosystem, thus the individuals must be carefully assessed in advance. Furthermore, in the case of invasive species removal, it should also be remembered that they are no less of a fish, and procedures must be managed as humanely as possible.
• Post experiment rehousing – in some cases it may be possible to rehome fishes after experiments if they are in good health and without any welfare compromising side effects.
• Transport – fishes often face stress and injury during handling and preparation for transport, and deterioration of water quality during transport, resulting in increased disease susceptibility, stress and shock. It’s crucial to ensure that good water quality is maintained at all times. Over short distances, sufficient oxygen levels and appropriate temperatures are the primary and most rapidly deteriorating parameters.
• Fish diets – although some fish food manufacturers take into account the different requirements of particular fish species, most commercially available diets are not suitable for all fish species. What’s more, very little is known about zebrafish (Danio rerio) nutrition, despite them being the most widely used fishes.
• Environmental enrichment – is associated with reduced stress levels and aggression in many species. Despite that, a recent survey revealed that less than 25% of facilities using zebrafish incorporate plants or substrate in their aquaria, most reporting practicality (i.e. high economic and labor costs) as the reason for not doing so.

The paper should help advocates in refining their efforts towards higher fish welfare in scientific contexts. The specific issues highlighted here should enable us to demand more informed and humane treatment of fishes who are to be experimented on. Without scientific rigor related to high fish wellbeing, in labs and the field alike, many non-significant results will continue to go unreported, many studies will fail to publish how the animals were treated, and many fishes will continue to suffer needlessly.