In the shrimp farming industry, disease tops farmers’ list of concerns. But disease is often a downstream consequence of other welfare threats, like environmental stressors.
Among other things, oxidative stress from air exposure kills farmed shrimp who are discarded before slaughter. To determine whether this threat qualifies as serious enough to invoke the Animal Sentience Precautionary Principle, we interviewed experts in shrimp aquaculture and caridina lava tigers.
The Problem
Shrimp are a diverse group of species, with stunning forms and colors. They come from all over the world, but only three groups have managed to find their way into aquaria: dwarf ornamental shrimp, fan shrimp and long-arm shrimp. The latter have enjoyed a boom in aquaristics in recent years and can be seen in many aquaria around the US.
Shrimp face numerous welfare challenges, from cannibalism to toxic levels of ammonia to suffocation. In the case of farmed shrimp, these issues may be particularly serious since they are often so numerous. Farmed shrimp are also vulnerable to pathogens and environmental contaminants such as metals and sulfides. While it is unclear whether shrimp are sentient, these risks lead to a strong case for applying the Animal Sentience Precautionary Principle to farmed shrimp (Waldhorn & Autric, 2023).
In addition to these potential harms, there are other ways that shrimp may be harmed in the course of their farming:
Farming ponds are often lined with plastic or concrete, preventing shrimp from burrowing or hiding. The absence of shelters may also deprive shrimp of a sense of safety from predators, which can cause them to experience high levels of stress (Aparicio-Simon et al., 2010).
Intensive and super-intensive farms often raise their shrimp indoors, shielding them from weather-mediated salinity changes. However, the use of low-salinity water in these systems can be detrimental to shrimp, resulting in slower growth and reduced immunity against diseases such as white spot syndrome (Boopathy et al., 2007).
Shrimp are a common food source for larger fish and invertebrates, making them susceptible to disease from pathogens. In addition, water pollution may reduce their immune responses and prevent them from absorbing the nutrients they need from their feed.
In the event of an outbreak of pathogens or water contamination, farmers may have to destroy all the shrimp in a pond to prevent a spread of disease to other tanks and other areas of their farm. While this approach is necessary to ensure biosecurity, it can be extremely stressful for shrimp. During this period, shrimp may be chased through nets, scooped up in bags and moved into new containers that expose them to air for prolonged periods of time. This exposure is likely to cause oxidative stress, leading to death (Luong & Guan, 2015).
The Solution
Shrimp have a very complex and delicate water chemistry. They are also highly susceptible to a variety of diseases and parasites. This is why it is important to quarantine new shrimp before they are added to the aquarium, ensuring that they are free of pathogens. Regular weekly water changes and a controlled diet are key to reducing stress levels in the fish tank, as well as keeping water values stable and healthy for the shrimp.
Annually, viral infections are responsible for significant losses in tropical shrimp aquaculture. These problems are primarily a downstream consequence of other issues, such as poor water quality (Anderson et al., 2016a; 2017; 2018; 2019; HATCH, 2023b).
In addition to water quality issues, many farmed shrimp are subjected to a range of other welfare threats. Some of these issues affect all shrimp throughout their lives, such as a lack of substrate, while others are more specific to certain subpopulations.
Farmed shrimp are also exposed to numerous forms of physical damage. This includes the potential to be crushed by other shrimp during harvesting, as well as oxidative stress during transport and slaughter. Additionally, it is not uncommon for farms to subject shrimp to partial harvesting, in which a percentage of the population is killed during the farming cycle in order to improve cash flow and create more space for larger shrimp to grow (Estrada-Perez et al., 2016; Yu et al., 2009).
Finally, some farmers use slave labor to harvest and process shrimp. This is especially common in Bangladesh, where impoverished families are recruited by traffickers to work in shrimp factories. The global shrimp industry is notoriously opaque, and it is difficult to know where most farmed shrimp originate or who labored to bring them to market.
The Ethical Dilemma
Shrimp are popular all over the world: they’re stuffed into sandwiches in the UK; hung onto glass rims to make cocktails in America; and added to national dishes like paella in Spain, noodle soup in Vietnam, and Pad Thai in Thailand. But if you’re thinking about treating yourself to a prawn cocktail or a shrimp sashimi sandwich, consider this: shrimp farming has some major ethical baggage: It causes environmental damage; its workers are often subjected to severe forms of human rights abuse and horrific acts of animal cruelty; and its production has been linked to bacterial outbreaks in supermarkets (read our analysis on the links between shrimp and salmonella here).
From breeding to slaughter, farmed shrimp face a number of welfare threats. Some of these concerns are diseases that afflict all shrimp for most of their lives, while others affect specific subpopulations, such as female breeders. They’re also vulnerable during harvest and slaughter, enduring oxidative stress that can lead to neuronal degeneration.
As for environmental damage, the intensive farms that house these crustaceans have been linked to environmental degradation, including the destruction of natural habitats and the slashing of mangroves. Additionally, shrimp are more sensitive to water pollution than other livestock species; high density shrimp farming contributes to the spread of disease within farms, and certain water contaminants — such as ammonia and cyanide — can cause molting delays, weakened immune responses, and even death by asphyxiation.
The handling process itself can also be distressing for shrimp, as shrimp can experience physical damage and/or behavioral changes from being held too firmly or experiencing environmental shocks. In addition, chasing and air exposure both induce primary stress responses in shrimp, and this stress may have lasting effects on their health.
Despite these welfare risks, the vast majority of farmers use a method called partial harvesting to improve cash flow and to give larger shrimp more room in ponds. In some cases, farmers even slaughter whole ponds of shrimp at the end of the production cycle.
Consequently, there’s an argument that these kinds of practices should be banned in order to protect shrimp’s welfare. However, it’s important to note that the evidence supporting shrimp sentience is still very sparse. As such, it’s important that we apply the Animal Sentience Precautionary Principle to farmed shrimp until further research can support a more definitive moral position on their status.
The Future
Shrimp are sentient creatures that are vulnerable to several welfare threats. Some of these threats are systemic and persist throughout the shrimp farming industry, such as disease outbreaks and bacterial contamination. Others are more individualized, such as the lack of substrate to hide on and the heightened vulnerability to oxidative stress during harvest and slaughter.
Regardless of the specific issue, these threats can all be reduced or eliminated through proactive and effective practices. For example, implementing strict biosecurity measures can help to mitigate disease outbreaks, and selecting for disease resistance can lead to stronger shrimp immune response. However, the problem is that these measures can be costly for farmers and their clients.
Another common threat that can be addressed through proactive measures is water quality. Farms can improve water quality by reducing contaminants, using better filters, and by introducing more natural substrate. Similarly, avoiding the use of unnatural chemicals like antibiotics and disinfectants can improve water quality by reducing bacteria levels.
As far as addressing more individualized welfare issues, freshwater enthusiasts can support reputable breeders and stores that prioritize the well-being and ecological impact of their practices. Choosing only to purchase shrimp that are clearly labeled as their particular species can also minimize the risk of accidentally hybridizing or muddling genetics.
Ultimately, the future of breeding specialized shrimp variants is dependent upon research in areas such as genomics. Advances in this field can allow us to increase and accelerate the rate of genetic progress for shrimp, and this will enable breeders to produce a greater variety of healthy and attractive strains. This may include strains with enhanced colors, delineation of their pattern, and other physical traits that can be manipulated. In addition, understanding the genetic factors that contribute to varying levels of disease tolerance and resistance between different strains can help breeders to improve their breeding programs by enhancing shrimp immune response. For instance, identifying and studying the evolutionary history of the immune genes C-type lectin and HMGB can be used to estimate their divergence time and select for beneficial alterations in shrimp immunity.
