Conversation with Doctor Lynne Sneddon of University of Liverpool

Doctor Lynne Sneddon is the Director of bioveterinary science at the University of Liverpool. She spoke with ACE Researcher Kieran Greig on February 22, 2018. This is a summary of their conversation.

How is farmed fish welfare usually measured? How accurate are these methods, and how could they be improved?

Production measures are often used, and typically these include measuring growth, feed conversion efficiency, and lack of disease. Of course good water quality is crucial for fish welfare so farms closely monitor this. More contemporary methods include movement detection systems such as echolocation or camera-based monitoring. These combined with water quality measurements can provide a very useful means of assessing wellbeing. Most producers can easily measure parameters such as pH, temperature, and oxygenation along with other factors that can pose a risk to fish health. Measuring water quality and growth rates or other production measures is prevalent in aquaculture as these metrics provide reliable information on the health, which is likely associated with welfare. The measurement of pH, ammonia, nitrite, nitrate, and other measurements of water quality can easily be done on farms with sample kits or with the help of digital sensor systems. However, measuring water quality alone may fail to catch some crucial considerations for welfare such as possible malnutrition, injury, or disease. Here, it’s necessary to inspect the fish in order to closely monitor the condition of the animals.

Disadvantages to water quality and growth measurements are that they do not indicate pain, fear, or boredom. I would recommend a combination of water quality measurements, production trait measures, and behavioral measures of some individuals. However, it is important to choose the individuals well—sometimes the most dominant members of a group are doing well while the subordinate individuals are under tremendous stress. This is especially true with more aggressive species such as salmon, trout, and catfish. A solution could be the separation of larger, more dominant individuals from the subordinates. Regular size-grading, where larger individuals are removed from groups, is currently a routine practice on some farms.

Many studies demonstrate that fish stress response is very much like our own, with the production of cortisol being an endpoint. Measuring cortisol has been proposed as a means of gauging stress and welfare. This approach is very successful under carefully controlled conditions (for example, in laboratory studies). However, measuring cortisol is problematic in real world situations, such as on fish farms, and is not generally considered a reliable indicator of welfare in the fish farming industry. The conclusions that can be drawn from it depend largely on other empirical contingencies. Cortisol is known to fluctuate across the day as it does in humans, so measurements must consistently be made at the same time of day. With fish, cortisol does increase when the animal perceives a stressor, but fish also show elevated cortisol in response to positive events such as anticipating food. Therefore, it is important to consider many factors before we can use cortisol as an indicator of overall welfare.

The accuracy of compressing multiple measurements into one is a tricky question. On the one hand, there might be a situation where many metrics score well while one area needs improvement. Still, in the end, the Researchers have to make judgment calls based on multiple factors to make any fully informed decisions about fish welfare.

The accuracy and quality of measurements is currently better than it’s ever been, but there are many neglected species in research. European Researchers are probably more invested in researching their own domestically grown species, particularly salmon and trout, because there is so much more legislation controlling their farming industry and these species are economically important in that region. Husbandry procedures such as environmental enrichment could be improved such that the animals can control or anticipate potentially stress-inducing situations.

Fish are an incredibly diverse group and each species has its own water quality requirements and life history, so we need more research on a variety of farmed fish species to truly make progress in this area. It is not a one-size-fits-all scenario—each species should be investigated to fully understand how to improve their welfare. There are still many issues in aquaculture that require further research despite progress. These include slaughter, vaccination, and transportation.

What is the timeline for understanding fish welfare? How much funding is required to make progress in this field?

Major improvements in understanding and modeling welfare could be done within the next five to ten years, assuming adequate funds are made available to Researchers. It’s difficult to estimate required funding. A typical three-year grant in the U.K. is about £500,000. If subject to Full Economic Costing, approximately half of this may go to the institution. You need engagement and agreement from the farmers and the industry in order to conduct research on farms, or you have to do isolated laboratory studies (although some universities also have large aquaria or research-led farms). Getting industry involvement is vital to make a real impact in improving fish welfare. While highly desirable, anecdotal evidence suggests that working with the industry presents specific challenges—for instance, publication of data can be delayed while awaiting approval from the industry. I have no direct experience with the possible publication bias or vested interest in research funding.

What are the different welfare indicators to consider across species?

Water quality, growth, and reproduction measurements apply rather universally across species—providing appropriate conditions for each species should help to maintain welfare. For salmon and trout, fin condition has been investigated as a welfare indicator. Fin damage due to biting during social interactions is specific for these species, too. In contrast, for catfish, lesions and lumps are a specific problem. Research is still ongoing and for some species like carp, relatively little is known.

With regard to water quality, the guidelines for normal oxygen saturation are to maintain oxygenation at 80%–100% (about 5 mg/L) or optimally at 6 mg/L. Carp are very resistant to oxygen deficiency while trout and salmon are very sensitive to it, so the metrics for each species would vary. The European Food Safety Agency has published guidelines for five different species altogether. Oxygenation can be a major problem and it’s well recognized, so farmers are invested in maintaining good aeration.

How do carp differ from other species in terms of welfare indicators?

Carp would need a different welfare measurement system than salmon or trout. Among other differences, carp is a more robust species and resists changes in water quality and lower dissolved oxygen levels to a greater extent than salmonids do. With regard to potential differences between various species of carp, I have done research mainly into the behavior of the common carp. There were two other carp species in the laboratory aquarium and based on my knowledge, the different species can be farmed together and have similar tolerances, life histories, and behaviors. Regarding salmon or trout, there is more variety in their life history since Atlantic salmon are born in rivers, go through a process of smoltification, and migrate to the sea where they live their adult life and return to their natal river to lay eggs. Farmed rainbow trout remain in freshwater their entire lives in land-based farms. These developmental changes in Atlantic salmon affect their tolerances for and preferences regarding water quality in the aquaculture situation.

What is the impact of selective breeding on welfare?

It is possible to selectively breed lines of fish with differing responses to stress by breeding from individuals with the highest and lowest cortisol responses. If breeding is conducted between the largest and most dominant individuals, it would lead to lines of fish that have higher aggression, are more risk-taking, and have other less desirable traits. This may imply inbreeding, too if the same broodstock are used time again and then their offspring are bred together. The industry has had this issue with terrestrial animal farming, for example chickens, where breeding for high muscle growth has led to welfare problems such as heart problems and skeletal deformities. The knowledge about breeding issues is more comprehensive for some species than others, but the impact of breeding practices in aquaculture need more investigation.

Tell me about environmental enrichment and stress tolerance.

The density of fish in some aquaculture systems is typically between 10–30 kg/m². Above that level, welfare can be quite poor and water quality declines due to the ammonia secreted by the fish. The public and welfare organizations are starting to ask whether the fish’s lives are worth living, and whether there could be implementations of behavioural management or stimulation to improve their wellbeing during farming.

Of course, a stress-free life might sound good but there is a theory that a number of small short-lived stressors are actually beneficial for animals in two ways. Firstly, a monotonous environment with no stress may cause boredom and frustration. Secondly, if an animal recovers successfully from a small stressful event, they can cope with the next stressful event better and it helps build their resilience. So, if a fish experiences no stress and is suddenly subject to a long or very challenging stressor (e.g. vaccination or transport), its welfare may be more impaired as it does not have the capacity to deal with this type of event. Ways to enable the fish to experience small doses of stress include netting and tank cleaning. You can also give them ways to learn to avoid stressors by giving them two or more tanks to move into when one is subject to disturbance. It is unclear, however, how fast a fish learns. Rainbow trout, for example, can be fast learners, so teaching them these things might take only a few trials.

There are other ways to reduce stress. For example, a PhD student set up large black plastic fronds (material similar to black bags) as hideouts for the more submissive individuals. Surprisingly and with little effort, this decreased the stress levels of these fish substantially. Pipes can be used in the same manner to provide refuge for the fish but only with caution, as this can be very species-specific.

What is the impact of vaccinations on welfare?

Research should be conducted regarding the impact of vaccinations. Specifically, we need to identify the issues associated with having to take the animals out of water in the process and the effects of the vaccine. On some farms, fish are lifted from the pools or tanks into the air to be vaccinated. The vaccinations reduce mortality somewhat, but the process itself causes stress. To mitigate this, some farms use sedation to ensure the fish are not struggling against the procedure.

What role do transportation and slaughter methods play in improving farmed fish welfare?

Humane slaughter is one of the greatest opportunities to reduce farmed fish suffering.

Ethical concerns surrounding pain and suffering of animals used for food are growing across the globe. For example, in Latin America 75% of respondents to a survey agreed that fish should be included in humane slaughter regulations, and the Farm Animal Welfare Committee accept that fish experience pain.

When animals are killed, pain should be avoided—this can be achieved through pre-slaughter stunning. Stunning is typically applied to animals to induce unconsciousness and insensibility to pain stimuli for long enough to ensure that they do not recover during exsanguination (blood loss). However, fish present specific issues that make the traditional stunning methods that are used for terrestrial animals especially problematic. Many approaches are used to kill fish including concussion using percussive stunners, electrical stunning, and gas stunning. Fish are often crowded then pumped up into pipes and subject to a stunning method. Therefore, the density in which the animals are kept and the stunning machines being used are points of interest.

There has been some debate about which is the most humane stunning method. The processes are likely to cause stress, and there are concerns that the use of carbon dioxide for gas stunning and electric shock for electrical stunning may cause the fish pain. What’s more, the percussive stunning machine has to hit the right area on the head to work effectively, and the fish often have to be handled during this process. Where transport of fish is necessary, it’s vital that the water quality be similar to what the fish are used to. It’s also relevant that it’s necessary to withhold food from the fish prior to moving them because feeding would cause waste which would affect the water quality and could taint the taste of the fish. Future research is required to determine the best and most welfare-friendly means of slaughter.

What do you know about Chinese and Indian slaughter and transportation methods?

In areas like China and India where percussive or electrical stunning machinery to slaughter fish is not used, fish are only slaughtered at the marketplace upon purchase. Fish are likely to be very stressed under these conditions, especially in the containment phase from farm to market. These differences are cultural and could possibly be improved through education.

What are some of the main fish welfare certification schemes?

The GLOBALG.A.P. covers all aquaculture species and provides standards for fish health. One advantage is that it provides guidance to farmers who wish to register with it.

The European Food Safety Authority regulations pertain mostly to a 2009 hygiene and public safety recommendation scheme for five species. Some European countries have had disagreements about welfare measurements like water quality—for example, both the U.K. and Norway farm trout but the water quality parameters are different between the two countries.

The Aquaculture Stewardship Council guidelines are not really aimed at welfare, but environmental and social impacts.

The World Organisation for Animal Health has been helpful in setting aquaculture standards in several ways. They provide guidance on fish health and liaise with veterinary services in many countries. Their focus is mainly to assist with animal and public health through the prevention and control of diseases, and to influence policy through veterinary bodies.

The Global Aquaculture Alliance (GAA) is a non-governmental body that engages and upholds stakeholders. Their mission is to support sustainable, socially and environmentally responsible aquaculture. Accreditation is possible and those seeking it must undertake audits to obtain certification from the GAA. A number of criteria are laid out including some regarding fish welfare.

The RSPCA Assured scheme has the scientific and veterinarian community backing it and is more independent. It relies on science and publishes papers rather than receiving backing from the industry. Disadvantages include that it is currently Euro-centric. However, they have very clear guidelines and a robust auditing method.

In what areas is research most needed to minimize uncertainty about possible welfare indicators and interventions?

There have been developments in terms of ways to measure fish welfare in laboratories, like the use of cameras to unobtrusively monitor movements. Similar developments could be expanded to farmed fish. Most fish farms already have underwater cameras to monitor welfare. However, more species-specific information is needed to interpret behavioral changes and how they link to good welfare.

There is a practice to rid fish of lice called thermolicer which involves “purging” the fish in hot water. The process causes scolds, burns, and sometimes death, as even temperatures above 30° fahrenheit can be painful to fish. Alternatives include the use of feeder or cleaner fish such as lumpfish which eat parasites off the farmed fish, although their welfare should also be considered. Some other methods are mechanical such as the hydrolicer which uses a strong jet of water to dislodge the lice from the fish. There is also a chemical treatment with hydrogen peroxide which removes the lice, but the welfare implications of each method is unknown.

Stunning and slaughtering fish less painfully or without pain will be an important point of interest. Some scientists currently suspect that electrical stunning (which involves running an electrical current through the water) is higher-welfare than percussive stunning because it is more immediate and does not involve handling and causing physical damage. However, we should consider that electrical stunning is often conducted dry or semi-dry where the fish is held out of water, or in a very small amount of water.

What are the welfare considerations for cleaner fishes?

About one feeder fish is required to produce 15 salmon, but there should be a way to develop a more ecologically savvy method that does not require the use of another fish species that is essentially discarded at the end. The numbers are astonishing—for instance, to produce 210,000 tonnes of salmon, 8.4 tonnes of cleaner fish are required.

While sea lice are detrimental to fish health and infestations result in large economic losses, conditions need to be improved for cleaner fish to thrive. From a sustainability point of view, the loss of protein is not ideal since these feeder fish have no purpose once the salmon are harvested. Wild fish have historically been used as cleaner fish, but high demand has meant that cleaner fish are now farmed simply for their use as cleaners. We really need rapid action in terms of setting standards for feeder fish aquaculture. We also need research about feeder fish welfare considerations for rearing and transportation.