Are all animals equal?

Every year in Australia, scientists use more than a million marine animals for research and teaching. Untangling the ethics of their use is a slippery business.

 Illustration by Arpita Choudhury

Illustration by Arpita Choudhury

From nutrition to tourism to scientific research, marine animals play a huge role in all our lives. There is a growing body of evidence indicating that these creatures possess far greater cognitive ability than we previously believed and can likely feel pain and distress. So why are fish and other aquatic species so often not afforded the same protections under the law as terrestrial animals? Are our animal welfare regulations rooted in evidence or prejudice?

The definition of a ‘person’ and what rights a person is entitled to have been amended and expanded innumerable times throughout history, with contributions from scientists, philosophers, clergy, and lawmakers alike. When it comes to the concept of animalhood, you would perhaps think that finding a definition would be simpler.

The scientific definition of an animal is broad, encompassing organisms from chimpanzees to barnacles to the 20-micrometre-long parasitic myxozoans. However, the legal definition of an animal is a much trickier concept that varies significantly between jurisdictions, with little regard to the opinions of taxonomists. Legally defining an animal is a far-reaching decision, as it effectively defines the category of species that are protected by animal welfare legislation.

So how do we determine what species require our protection? The United Kingdom is often cited as having some of the strictest animal welfare legislation in the world and has a long history of extending protections to new species. A far cry from the original Cruel Treatment of Cattle Act 1822, which protected only cattle, ox, and sheep, the more modern Animal Welfare Act 2006 defines an animal as any vertebrate species — that is, any creature with a spine, including mammals, birds, reptiles, amphibians and fish.

  Zebrafish are among the most widely used aquatic organisms in scientific research.   Understanding Animal Research/Flickr  (CC BY 2.0)

Zebrafish are among the most widely used aquatic organisms in scientific research. Understanding Animal Research/Flickr (CC BY 2.0)


Alternatively, in the United States, the Animal Welfare Act of 1966 defines an animal as any land-dwelling warm-blooded vertebrate, effectively only assigning protections to mammals. Turning their sights to the ocean, the US also signed the Marine Mammal Protection Act into law, extending these protections to sea-dwelling mammals such as dolphins, whales and seals.

Federal Canadian animal welfare laws fall under the Criminal Code for Wilful and Forbidden Acts in Respect of Certain Property, and fail to provide a clear definition of an animal. Instead, the definition varies by province. Nova Scotia, for example, defines an animal as any vertebrate in captivity, with no provisions for wild animals. Prince Edward Island only extends protection to companion animals such as cats and dogs. The majority of provinces also afford exemptions to farming and scientific research sectors from these laws and from duty of care.

In Australia, animal welfare laws are determined by each state government and mostly come to the same conclusion as the UK: that animals are defined as vertebrates. However, Western Australia and South Australia explicitly exclude fish from protection, despite their status as a vertebrate species.

The rationales behind these highly variable definitions of animals are hard to pin down, and rarely align with scientific classifications. In many cases, it can be argued that certain species are denied protection to safeguard the commercial interests of particular industries. Both the US and Canada set out specific exceptions for farming and research industries, despite their classification system. It is also likely no coincidence that the two Australian states that exclude fish from welfare legislation collectively produce a disproportionate 41% of the country’s seafood products.

  In many jurisdictions, animal welfare laws have specific exceptions for farming and scientific use.   Dana McMahan/Flickr  (CC BY-NC 2.0)

In many jurisdictions, animal welfare laws have specific exceptions for farming and scientific use. Dana McMahan/Flickr (CC BY-NC 2.0)


Fish and invertebrates are traditionally excluded from animal welfare debates. In part, this is likely because people find it far easier to empathise with animals that exhibit ‘human-like’ traits. Often dubbed ‘charismatic species’, large anthropomorphic animals elicit responses from people far more easily than more abstract animals like amphibians or insects. While this is often used effectively in ad campaigns from welfare groups to promote empathy toward farmed animals, it can also have negative effects on the protection of important but less relatable species.

A modern example of this is the disproportionate level of public attention on panda conservation, while mass extinction of more ecologically significant species is left understudied and underfunded. Due to fishes’ lack of endearing facial features or expressions, and our limited interaction with life beneath the waves, we are far less likely to intuitively relate to these species.

Biases aside, the question that is danced around here is simple: Are fish and marine invertebrates unfeeling amino-acid driven machines, or are they sentient beings capable of experience? Being able to detect painful stimuli and react accordingly is not necessarily evidence of sentience. The sea slug Aplysia is a commonly studied organism due to its incredibly simplistic nervous system. Touching the Aplysia’s siphon triggers a gill withdrawal reflex, which is greater if stimulus is also applied to its tail. While this may appear as the conscious effort of an intelligent creature to escape danger, the biology behind this phenomenon is, in fact, so simple that we can draw a circuit diagram that requires no higher-order cognition.

The subjective experience of other species is something we can only hope to glimpse, but there are indications that fish do, indeed, experience pain. Fish physiology and behaviour are adversely affected by exposure to painful stimuli, resulting in significantly increased ventilation rate and abnormal rocking behaviours. A study found that goldfish and trout learn to avoid areas where they receive mild electric shocks, but will brave these areas if accompanied by a member of their own species, indicating that their response to pain is not wholly reflexive. Food-deprived goldfish are more likely to risk pain for nourishment, and acid-injected zebrafish will choose to swim in a brightly lit barren tank with analgesic dissolved in the water, rather than a more comfortable enriched tank. Fish have also been shown to have high degrees of social intelligence, associative memory and learning, and even the formation of social traditions and rules.

  We may be underestimating the cognition and sentience of fish.   Benson Kua/Flickr  (CC BY-SA 2.0)

We may be underestimating the cognition and sentience of fish. Benson Kua/Flickr (CC BY-SA 2.0)


There is also significant scientific evidence that invertebrate cephalopods such as octopuses, squid and nautili can experience pain, suffering, and lasting harm. These creatures also exhibit complex behavioural and learning capability. These findings have given rise to the term “exceptional invertebrates” in scientific literature, to refer to invertebrates that possess highly sophisticated nervous systems.

This is not to say that the debate on fish sentience does not continue to be waged in the scientific community. Some researchers argue that our interpretation of fish behaviour is coloured by our propensity to anthropomorphise animals, and that fish and invertebrates lack the requisite brain structures to experience pain or fear as we do. Opponents to this viewpoint argue that as our understanding of fish neurobiology is limited, and that, because fish have met many of our criteria for consciousness, taking a precautionary stance is the more ethical option. Symptomatic of the larger reproducibility crisis affecting all of science, many related studies on fish pain and sentience provide conflicting evidence for both sides of the argument.

In 2016, a total of 1,130,620 marine animals were used for research or teaching in Australia, making up 16% of the total animals used. Researchers are held to a slightly higher degree of animal welfare expectation than other industries in Australia. To secure a licence to use animals in research, and to be eligible for funding from government bodies, researchers must comply with the Australian Code of Care for the Use of Animals in Research.

Unlike welfare legislation, the Code of Care promotes consideration of the wellbeing of all vertebrates and cephalopods. However, the Code does not outline what constitutes harm on a species-by-species basis, and delegates these decisions to the independently organised Animal Ethics Committees (AECs) set up by universities and medical research institutions. Audits are carried out to verify that AECs are upholding the principles of the code, that experiments are conducted accordingly, and that researchers are sufficiently trained to deliver the required level of care.

Similar frameworks exists in a number of forms in other countries, represented in such documents as the United States’ Institutional Animal Care and Use Committee Guidebook and European Union Directive on the protection of animals used for scientific purpose.

  In some animal ethics frameworks, protection is extended beyond vertebrates to include squid, octopuses and cuttlefish.   Martin Cathrae/Flickr  (CC BY-SA 2.0)

In some animal ethics frameworks, protection is extended beyond vertebrates to include squid, octopuses and cuttlefish. Martin Cathrae/Flickr (CC BY-SA 2.0)


While certainly a step above welfare legislation for other sectors, these Codes are far from perfect. The lack of a clear regulatory framework on what constitutes unnecessary suffering, coupled with the autonomous and consensus-based nature of AECs, can expose these important decisions to interpretation and bias. Zebrafish, despite their vertebrate status, are found to be one of the least evaluated species by AECs. A review of European studies found that, despite their inclusion in the EU Directive, fish and cephalopods were often kept in sub-optimal environmental conditions for their species.

Ignoring the welfare of animals in research is not only an ethical issue, but also detrimental to the quality of experimental data. Pain and distress have a profound impact on the behaviour and physiology of animals and introduces a significant confounder into an experiment. Unmanaged pain can impact an animal’s ability to heal, cause significant hormonal imbalance, and result in neurological impairment. Fin clipping, a common experimental practice often carried out for genomic screening of zebrafish, causes changes in fish behaviour and reduces their activity. The use of pain-relieving drugs, however, ameliorates these adverse effects. Recognising animal distress and designing ethical experiments are crucial to ensuring the integrity of the findings, and, therefore, has significant scientific value, benefiting both the subject and the researcher.

Despite a growing body of data indicating higher cognitive function and potential for suffering, legislation and public perception of marine life have been slow to catch up. Recognising our inherent biases and developing a more evidence-based perspective on sentience and suffering is important if we are to have fair and informed debate on our animal welfare laws. Animal welfare and protection has far-reaching implications on our economy, environment, and quality of scientific research. As such, it is important to address this growing disconnect between the evidence and our laws.

Edited by Andrew Katsis