Harmonizing Animal Health and Welfare in Modern Aquaculture: Innovative Practices for a Sustainable Seafood Industry

Abstract

A critical distinction often overlooked, yet rudimentary to the sustainable infrastructure of a complex and generative industry, is the fundamental difference between animal health and welfare in aquaculture. While these terms are frequently used interchangeably by producers, advocates, and policymakers, understanding how they both correlate and deviate from one another in commercial farming practices is an essential element of sustainable development with animal welfare as a priority, rather than a mere formality. This review represents a turn of the tide where we aggregate effective examples of actionable blueprints the seafood industry can use to elevate and replicate responsible practices in modern aquaculture. These practices must be designed to respect the interests of all stakeholders, including the animals farmed, and ensure that their quality of life in captivity is not just maintained but enhanced. The importance of incorporating animal welfare into decision-making processes, as it is closely tied to public health and environmental sustainability, has garnered attention in recent years with no indication of fleeting interest. Articulating the observed benefits in farming operations that have adopted positive welfare processes can expose a more sustainable, harmonious relationship between producers and animals in the seafood industry and help facilitate meaningful progress with collective buy-in.

1. Introduction

The Organization for Economic Co-operation and Development (OECD) Guidelines for Multinational Enterprises on Responsible Business Conduct states, “Enterprises should respect animal welfare standards that are aligned with the World Organization for Animal Health (WOAH). An animal experiences good welfare if the animal is healthy, comfortable, well nourished, safe, is not suffering from unpleasant states such as pain, fear and distress, and is able to express behaviors that are important for its physical and mental state. Good animal welfare requires disease prevention and appropriate veterinary care, shelter, management and nutrition, a stimulating and safe environment, humane handling and humane slaughter or killing” [1]. The fifth United Nations Environment Assembly (UNEA 5.2) [2], which concluded in 2022, resulted in the adoption of 14 resolutions aimed at addressing the escalating triple planetary crisis. These resolutions seek to enhance efforts for environmental protection and to achieve the Sustainable Development Goals (SDGs) by 2030. The initial resolution calls for the assembly of partners and stakeholders to collaborate in identifying the connections between animal health and welfare, sustainable development, environmental issues, and human health and well-being. This Animal Welfare, Environment, and Sustainable Development Nexus [3] requires the United Nations Environment Program, the Food and Agriculture Organization of the United Nations, and the World Health Organization to present a report acknowledging that animal welfare can contribute to addressing environmental challenges; the health and welfare of animals, sustainable development, and the environment are linked to human health and well-being, highlighting the necessity of addressing these connections through a One Health approach, based on a strong body of science supporting animal welfare. These are both prime examples of how entities must consider animal welfare in their decision-making processes by underscoring the importance of proactively incorporating animal welfare into decision-making processes, as it is closely tied to public health and environmental sustainability. In this pivotal moment of industry transition in aquaculture, it is critical to identify, establish, and enhance best welfare practices that affect trillions of aquatic animals produced and slaughtered for human consumption each year. There is an ongoing desire to bridge gaps in understanding and practice within the aquatic animal welfare space, ensuring that positive, sustainable, and feasible welfare protocols can continue to be implemented and recognized as beneficial for both producers and the animals they farm. By operating in alignment with the latest scientific findings and technological advancements, stakeholders can conceptualize a new approach to adopting improved welfare protocols that are rigorous, mutually beneficial, and widely accepted.

Good health is necessary for good welfare. However, it alone does not sufficiently demonstrate a high level of welfare without taking into account the psychological needs of the animals, whether that be behavioral needs, feelings, or what the animal wants [4]. Welfare assessment frameworks and measurements utilized by the aquaculture sector have traditionally focused only on the physical or health-based aspects of welfare. “Positive” welfare in aquaculture can be analyzed according to species-specific, science-based measurements and assessment protocols. The most widely accepted framework accounting for positive experiences is the Five Domains Model [5]. This structure uses significant developments in animal welfare science, such as the emerging interactions between the physiological (biological health) and psychological (subjective experience) aspects of animal welfare and the critical importance of promoting opportunities for positive interactions while concurrently reducing preventable pain and suffering in captive conditions.

As aquaculture production rises as a result of the growing push for “Blue Foods” (“food derived from aquatic animals, plants, or algae that are caught or cultivated in freshwater and marine environments”) [6], it will become increasingly necessary to develop more efficient production systems. However, efficiency should not exclusively rely on intensification. Coordinated and universal efforts must be considered, such as the 4R Approach to Seafood System Reform employed by Aquatic Life Institute (ALI) [7]. Through strategic streams of activity throughout the supply chain, ALI’s advocacy pursuits are identified and executed according to one or more of the following principles: reduce the number of animals in, or remove animals from, the seafood system and its supply chain; refine the conditions in which animals are currently kept or captured in the seafood system and its supply chain; replace animal products with sustainable plant-based or cell-based alternatives to the extent possible in the seafood system and its supply chain; reject the introduction of additional animals into the seafood system and its supply chain. In accordance with the “refine” principal, ALI collaborates with stakeholders to initiate modifications and procedures that minimize pain and distress while positively enhancing the lives and welfare of aquatic animals to the extent possible. In order to encourage realistic refinement, we must first retrieve knowledge and information related to what is currently in practice. By integrating progressive research with existing practice, the results serve as modern examples of improvements that may be replicated or adapted in various farming scenarios but can also provide valuable guidance to producers, policymakers, researchers, and invested stakeholders, enabling them to improve animal welfare, productivity, sustainability, and environmental stewardship in aquaculture. “Best practices” refer to guidelines, procedures, and methods that signify the most effective and reasonable approach to take in a specific situation. These industry protocols and activities should be designed to foster economical and responsible aquaculture production and expansion with respect to final product quality, safety, and environmental sustainability. The primary objective of this article is to showcase some of the “best” practices already utilized in aquaculture that demonstrate tangible benefits both in animal production (health) and quality of life (welfare). This study aims to identify, consolidate, and evaluate innovative on-farm practices that simultaneously improve animal welfare and production efficiency in aquaculture. These innovative practices are expected to demonstrate measurable improvements in health, welfare, and environmental outcomes compared to conventional practices.

2. Materials and Methods

Results are a compilation of details and information regarding advanced practices in aquaculture as they relate to the more “positive” aspects of animal welfare. Insights, methodologies, innovative techniques, and illustrations currently employed by industry experts, researchers, or practitioners in the aquaculture sector were gathered and analyzed according to publicly available information. Through consultations with a distinguished network of scientific colleagues and researchers, the verification of “best” welfare practices according to novel studies and evidence was achieved. Previous research related to aquatic animal welfare recommendations was referred to as a foundation for development and evaluation [8]. The primary pillars of welfare that were considered include water quality optimization, total space requirements and ideal stocking densities, environmental enrichment strategies, sustainable feeding or feed composition, and humane stunning and slaughter.

Commonly farmed species that were searched during this review include Atlantic salmon (Salmo salar), rainbow trout (Oncorhynchus mykiss), common carp (Cyprinus carpio), grass carp (Ctenopharyngodon idella), Nile tilapia (Oreochromis niloticus), European sea bass (Dicentrarchus labrax), gilthead sea bream (Sparus aurata), pangasius (Pangasianodon hypophthalmus), turbot (Scophthalmus maximus), and Pacific whiteleg shrimp (Litopenaeus vannamei). These specific species were chosen for further consideration and evaluation of best practices due to their relevance within the global seafood industry. It is important to highlight that not all species were covered equivalently in this analysis due to the availability and accessibility of information. However, those who engage in farming activities of the species listed above, in addition to others not mentioned, are encouraged to reach out with adequate details regarding their practices should they wish to be featured in future reports on this subject matter.

Aquatic animal welfare assessments considered physiological, psychological, behavioral, and relational parameters. In practice, ensuring that captive animals have a “life worth living” requires implementing suitable husbandry practices. This includes maintaining optimal environmental conditions, offering a nutritionally balanced diet to all individuals, and ensuring appropriate healthcare and monitoring. Additionally, it is essential to create opportunities for positive experiences by allowing animals to exercise choices, such as access to varied environments and species-specific enrichment. Furthermore, housing animals in social groups that reflect their natural behaviors can help minimize aggression and encourage healthy social interaction. Together, these interventions should aim to provide animals with a significantly higher quality of life than that previously experienced in captivity. Voluntary details were not easily obtained from producers; therefore, we turned to publicly available information in order to identify some of the practices currently in use or in development that could provide positive on-farm welfare opportunities for aquatic animals while affording aspects of improved efficiency for those involved in production. Given the absence of universally agreed-upon definitions of “positive welfare” for aquatic animals, this article adopts a multi-faceted, integrative approach to identifying and evaluating advanced aquaculture practices.

A comprehensive review of peer-reviewed articles, industry reports, and white papers was conducted to identify practices with potential benefits to both production efficiency and animal welfare. Specific focus was given to identifying practices explicitly described as reducing stress, enhancing natural behaviors, or improving overall health outcomes. Input from stakeholders, including aquaculture practitioners, animal welfare scientists, and industry experts, was sought to validate the practical application and perceived welfare benefits of the practices identified. This consultation process aimed to ensure the relevance and feasibility of the practices described.

Practices were included based on their alignment with recognized welfare principles (e.g., the Five Freedoms) and their evidence-supported contributions to health and welfare outcomes. Practices with conflicting evidence or lacking clear welfare implications were excluded or highlighted for further research. When available, specific case studies and real-world applications were incorporated to provide additional context and support for the practices discussed.

By employing these methods, this article seeks to provide a foundational reference point for future evaluations of on-farm practices, offering a springboard for the development of standardized definitions and more rigorous methodologies. While this flexible approach reflects the current state of the field, it lays the groundwork for continued collaboration and refinement in defining and achieving positive welfare outcomes in aquaculture.

3. Results

The following results are listed according to the welfare pillar deemed primarily applicable to the specific practice identified during evaluation. However, as each pillar of welfare is highly interrelated, practices can also be attributed to increased welfare in several different areas. A brief summary of the welfare consideration is provided, followed by innovative farming methods, details, and their accompanying graphics and illustrations.

3.1. Water Quality

Aquaculture sites should be carefully chosen or designed so as to ensure the adequate flow of clean water of suitable quality according to species’ requirements. Water quality parameters must be regularly monitored at various depths and maintained in an optimal range for the species. The water quality risk assessment must be coupled with an action plan once poor water quality is detected. Producers must maintain accurate records of water quality parameters and publish data periodically and centrally. Water quality (at least turbidity, total dissolved solids, oxygen, ammonia, carbon dioxide, temperature, pH, salinity, and, in the freshwater context, nitrate) must be monitored regularly using an appropriate technical device for each parameter, with a frequency appropriate for both the species and the system in order to avoid deleterious impacts on welfare. Poor water quality needs to be addressed promptly. Facilities must be designed and installed to avoid or minimize impacts on resources. Facilities must ensure an adequate supply of clean water according to the characteristics of the farming system and species’ requirements [9,10].

3.1.1. Example of Current Industry Technology for Monitoring Water Quality—Tidal by X in Collaboration with Cognizant at Mowi Farms [11,12]

• Practice/Technique: Figure S1 from an Energy Theory article [13] shows their advanced underwater sensing and software analysis platform that gathers intelligence on real-time growth, weight distribution, feeding control, and automatic lice counting for salmon. By leveraging advanced camera technology alongside machine learning and perception, Tidal’s system can effectively monitor and analyze fish behavior, environmental conditions, and the health of salmon over time.
• Species/Farming Method: Atlantic salmon (Salmo salar), in open sea cages (Norway).
• Indicators and Measurements: The equipment, shown in Figure S2, continuously collects and interprets images of fish to understand how the fish are growing, identify disease, and monitor behaviors such as feeding. It collects a mix of environmental data such as temperature and salinity to identify patterns between fish health and the environment, illustrated in Figure S3.
• Observed Production Benefits: This technology can improve business outcomes and lower the carbon footprint of aquaculture operations by significantly minimizing feed wastage, a significant source of carbon emissions in aquaculture, by using machine perception tools and artificial intelligence to automate feeding time according to fish hunger levels. This system can also minimize costs associated with inefficient treatment of disease and product loss from disease-related mortality prior to harvest.
• Observed Welfare Benefits: The system provides continuous, real-time data on the health of salmon, enabling early detection of diseases and conditions that could compromise their welfare. Early intervention can prevent suffering and improve overall fish health. By monitoring growth and weight distribution, the system ensures that fish are developing properly. This helps in maintaining optimal feeding practices, reducing overfeeding or underfeeding, which can stress the fish and affect their health. Automated feeding control ensures that salmon receive the right amount of food at the right times. This reduces competition and aggression among fish, leading to a more stable and stress-free environment. The ability to count lice automatically allows for quick and accurate detection of parasitic infestations. Catered treatments can be administered, reducing the physical discomfort and health risks posed by lice. By tracking fish behaviors, the system can identify signs of stress, aggression, or abnormal activity, allowing for timely interventions to address welfare issues. Tracking environmental factors such as water temperature, oxygen levels, and pH ensures that the habitat remains within optimal ranges for salmon health, preventing environmental stressors. Advanced machine learning algorithms can predict and model potential welfare issues before they become severe, allowing for proactive management practices that enhance the overall well-being of the fish. Over time, the system can build comprehensive health models for the salmon, providing valuable insights into long-term welfare trends and enabling continuous improvements in husbandry practices. Automated systems reduce the need for frequent human intervention, minimizing the stress associated with handling and disturbances and ensuring a more natural and less intrusive environment for the fish. The data gathered can be used to develop and refine welfare standards and practices, promoting better overall conditions for farmed salmon and setting benchmarks for the aquaculture industry.

3.1.2. Example of Current Industry Practice for Improving Water Quality—Folla Alger, Cermaq, and SINTEF Ocean [14,15]

• Practice/Technique: Integrated Multi-Trophic Aquaculture (IMTA) [16] uses a minimum of two aquatic species from different trophic levels (e.g., salmon and kelp) that are farmed in a coordinated approach to enhance efficiency, minimize waste, and deliver ecosystem services. Lower trophic level species, such as kelp, utilize the waste nutrients produced from co-cultured fed species, like salmon.
• Species/Farming Method: AURORA IMTA is an ongoing initiative to develop an industrial solution for integrated aquaculture that combines Atlantic salmon and kelp farming in Northern Norway. The sea-based facility features eight salmon net pens and four sizable kelp frames within a modified frame mooring system. The salmon net pens are organized into two clusters of four, situated at either end of the facility shown in Figure S4. Meanwhile, the kelp frames are positioned in between these two groups of salmon net pens.
• Indicators and Measurements: SINTEF (Trondheim, Norway) utilizes their own hydrodynamic model system, SINMOD, to estimate the water contact between aquaculture sites, dispersal of lice and viruses, dispersal and sedimentation of dissolved particulate waste, current conditions for planning of maritime installations, etc. SINMOD modules analyze the physical and marine biological processes, including primary production and the dynamics of zooplankton populations and their growth potential for extractive aquaculture, in addition to the effects of climate change on primary and secondary production in the ocean. Current SINMOD simulations indicate that the kelp facility will not negatively affect the oxygen saturation in and around the salmon facility to any great extent and that the allocated salmon biomass will make a measurable contribution of nutrient salts for kelp production. As this farm is still in a trial phase (2022–2026), samples have been taken of both kelp, grown on ropes in Figure S5, and salmon to see if the species affect each other’s microbiota, which will later be expanded to include the effect of feed containing kelp ingredients on salmon in the facility.
• Observed Production Benefits: IMTA ultimately produces valuable low trophic biomass based on nutrient resources that would otherwise be lost or wasted from aquatic animal biomass already being reared. Combined operations can contribute to increasing value creation. This setup allows the nutrients released by the salmon to be used in a sensible way to produce kelp, which can in turn be used as a raw material in new feed. The research manager with SINTEF Ocean states that 50% better kelp growth can be achieved by cultivating it together with farmed fish and will continue to explore the additional advantages of combined operation.
• Observed Welfare Benefits: Various benefits could be realized in this multi-trophic rearing system in terms of improved welfare implications for both farmed animals as well as those typically caught and reduced to fishmeal and fish oil ingredients for aquafeed. Seaweeds are considered a plant protein that can be used to replace marine ingredients in aquafeed. They contain [17] components of essential minerals, vitamins, pigments, compounds, fatty acids, and amino acids required for feed ingredients. Studies [18] have shown that replacing fishmeal with seaweed to a certain extent can improve growth, feed utilization, body composition, and disease resistance in fish. Exploring the optimization and efficiency potential of kelp as a feed ingredient is an objective of this project. While prioritizing plant-based ingredients is an important consideration for the seafood industry, it is crucial to note that this should not be utilized as a means to amplify intensive seafood production as a result of increased resource efficiency. Kelp has been extensively studied for its carbon sequestration potential. Co-production of salmon and kelp also reduces the ecological impact of dissolved nitrogen and phosphorus released into the ocean at a typical salmon farm and may serve as a vital resource for mitigating or eliminating surplus nutrients and metals from the water column, especially around coastal [19] areas susceptible to the negative externalities of urban sewage, domestic runoff, fisheries’ waste disposal, etc. As a result, water quality could be greatly improved for all aquatic animals within the vicinity.

3.1.3. Example of Current Industry Technology for Improving On-Farm Water Quality—Moleaer’s Nanobubble Solutions [20]

• Practice/Technique: Moleaer’s system, shown in Figure S6, operates in line with water flow, employing gas-to-liquid injection technology. It transforms bulk oxygen into nanobubbles, enriching water with high concentrations of dissolved oxygen. These negatively charged bubbles, around 100 nanometers in diameter and exhibiting neutral buoyancy, remain suspended in the water column for extended durations, acting as an oxygen buffer to stabilize dissolved oxygen concentrations. The generator in Figure S7, engineered for continuous use, features no moving parts and can be easily integrated either directly into the flow line or in a side stream to boost oxygen levels in any given process.
• Species/Farming Method: Case studies are listed specifically for Coho salmon in a Chilean flow-through hatchery and delousing vessels for Atlantic salmon in Norway. Optimal water oxygenation is a universal necessity across all species and systems. Therefore, we can reasonably conclude that this solution could be beneficial for a variety of species and systems; however, it is important to consider critical factors that may vary. Moleaer states that the nanobubble systems are compatible for use in both saltwater and freshwater, allowing for horizontal or vertical installation. They can be utilized in wellboats and land-based aquaculture systems for sea lice treatments, oxygenation of net pens, and seabed remediation.
• Indicators and Measurements: Appropriate water quality and adequate levels of dissolved oxygen are critical for survival during all phases of aquaculture production, regardless of species being reared. Various water quality parameters, positive or negative interactions with one another, in addition to the dynamic interplay between water quality and other husbandry aspects such as stocking density, for example, must be carefully and continuously monitored by the producer. Behavioral changes, growth, mortality rates, etc., must all be closely evaluated when factors are being introduced to the farming environment. In case studies assessing the advantages of this technology, producers also evaluated pathogen control, biofilm removal, and fish health while avoiding the use of chemicals.
• Observed Production Benefits: During a Chilean hatchery case study [21], Moleaer reported that over the course of the evaluation, the Trinity nanobubble generator data results showed monthly savings of around USD 1025, a 41% reduction in operational costs accounting for oxygen and energy consumption. Total oxygen consumption decreased from 5.4 m³/h with original equipment to 3.6 m³/h with the Trinity generator. Energy consumption was reduced from 15 kW/h to 7.5 kW/h, a 50% reduction in cost. Water consumption was also reduced by 114 m³/h or 4.5% of the total flow by eliminating a pump from the operation. Results also indicate that the system’s ability to maintain consistent and optimal dissolved oxygen levels had a positive impact on fish growth. Nanobubbles contribute to minimizing the environmental consequences of pharmaceuticals, ensuring the maintenance of high-quality water, decreasing the reliance on chemicals for managing micro-organisms and biofilm, and ultimately enhancing product quality.
• Observed Welfare Benefits: Beyond the clear health advantages linked to optimal water quality that enhance overall welfare, a recent study [22] explored the effects of bubbles as a form of physical, occupational, and sensory enrichment for rainbow trout. The researchers observed a reduction in aggressive and abnormal behaviors in fish raised with bubble diffusions. Additionally, these repeated bubble diffusions decreased fearfulness and enhanced learning capabilities in the fish. There were no significant differences in growth parameters across the treatments. The study concluded that bubble enrichment positively influenced the long-term behavior of farmed rainbow trout, enabling the incorporation of “positive welfare” concepts into existing fish farming practices while ensuring ease of technical maintenance. Another study [23] investigated the effect of nanobubble aerators on microbial communities in a whiteleg shrimp aquaculture pond. The results indicated that the nano-aerator significantly increased microbial community diversity and beneficial species abundance in the pond. Their findings suggest that nanobubble technology could promote beneficial bacteria in these aquaculture ecosystems, thereby regulating water quality and reducing incidence of disease in shrimp ponds.

3.1.4. Example of Current Industry Farming Location for Improving Water Quality—Chicoa Fish Farm [24]

• Practice/Technique: The farm has developed innovative offshore breeding as the cornerstone of the production process, eliminating the need for expensive capital investment in onshore concrete ponds. This enables the entire production process to function independently of large electrical grids.
• Species/Farming Method: Chicoa Fish Farm is a large-scale, cage-based tilapia farm in Mozambique that raises Nile tilapia in Lake Cahora Bassa. Chicoa’s furthest production cages are only 500 m from shore. Maintenance, husbandry, feeding, and harvesting are all conducted much more efficiently due to the location.
• Indicators and Measurements: By utilizing offshore breeding, precise genetic selection, and sustainable farming practices, the farm showcases one of the lowest feed conversion ratios for tilapia globally. Chicoa’s fish feed is composed of vitamins, minerals, essential proteins, and oils to strengthen the immune system of each farmed fish. The fish have adapted to the surrounding natural environment and benefit from the appropriate temperatures, large water exchange, and high oxygen levels. The farm’s methods are designed to be cost-efficient, environmentally sustainable, and to have a low carbon footprint.
• Observed Production Benefits: Small-scale farmers need access to high-quality fingerlings, readily available feed, and ongoing training. As an anchor farm, Chicoa delivers these three essential components to the small-scale aquaculture sector in Mozambique by means of vertical integration. Chicoa partners with the Department of Fisheries and strategically aligned Development Finance Institutions to train and equip small-scale tilapia farmers throughout Mozambique. Chicoa aims to grow its business through an out-grower model, with the goal of incorporating 450 smallholder farmers by 2025. This initiative is designed to generate job opportunities and promote sustainable development in the area. To support these out-growers, Chicoa will offer services including loans, agricultural inputs, and training to enhance the establishment of local sustainable fish farms.
• Observed Welfare Benefits: Farm location provides fish with appropriate water quality conditions, eliminating the risk of system failure associated with resource-intensive land operations that could result in mass mortalities. The water quality management window is relatively small with many land-based systems, relying heavily on backup protocols in place. Traditional tilapia pond production has been observed in this region; however, ponds can undergo faster water quality deterioration due to excess fertilizer or feeding practices. Ponds are also more exposed to natural destruction such as increased instances of predation or flooding, which could destroy ponds for future use and lead to mass escapes. Cage farming could reduce pressure on land use and improve fish welfare where there is natural exchange of water.

3.2. Space Requirements and Stocking Density

Aquatic animals should have adequate space and a suitable volume of water to display their natural behaviors, such as foraging and nesting. Aquatic animals should be stocked at a density no higher than the level which is shown to produce the lowest stress, lowest maladaptive behaviors, and lowest conspecific aggression. This will be determined based on the most reliable evidence available, taking into account species, life stage, and rearing system. Producers must keep records of both density and total space available to individual animals, monitoring their behaviors and making any necessary adjustments to assure social hierarchies/interactions are appropriate for the species being farmed [25,26,27].

Example of Current Industry Technology for Monitoring On-Farm Biomass and Movement—CageEye [28]

• Practice/Technique: Echo sounders measure fish location by emitting sound and listening for the echo. CageEye’s echo sounder technology uses software to track acoustic data in a fish cage while relying on machine learning to measure and analyze biomass movements, as shown in Figure S8.
• Species/Farming Method: This technology is currently in use by several Atlantic salmon commercial sea-cage farms in Norway, in addition to a Chilean salmon farm, with expansion projected throughout 2024. The technology has been tested to monitor fish behavior in various offshore, funnel, and shallow cages as well. In its current form, the system would not be applicable for tanks or ponds where solid surfaces, ambient sounds, bubbles, etc., require modifications. However, in the next 3–5 years, this company is expected to expand to other salmon markets and perhaps explore reconfigurations for additional species.
• Indicators and Measurements: Echo sounders can map the position of every fish in large volumes of water, every few seconds, using sonar. Echograms record and track movement in the cage. Machine learning algorithms that accompany the acoustic technology deliver immediate behavioral patterns and can indicate early warning signs of disease and other significant events.
• Observed Production Benefits: Figure S9 shows that for feeding regimes, if the majority of the population are swimming near the surface, this indicates anticipatory behavior and producers should feed, while if most of the fish are swimming lower, it is time to reduce the amount of feed distributed to reduce waste and costs. Case studies have demonstrated this technology’s ability to detect pancreas disease [29] indicators over a month prior to detection using standard procedures. Other significant events could include instances of predation. Abnormal behavior [30] was visible using CageEye positioning data 3 days before site personnel found a bluefin tuna in one of the cages.
• Observed Welfare Benefits: CageEye signed a contract to develop WelfareShield, a European Union co-funded project, to construct a system that provides 24/7 welfare monitoring for salmon in cages. WelfareShield, still in development, will use AI/deep learning models that combine group swimming behavior with feeding response and environmental parameters and pick out deviations from “normal” behavior according to individual cages, to indicate the overall group welfare status of the fish.

3.3. Environmental Enrichment

Animals must be provided a variety of species-specific positive behavioral opportunities within the enclosure. Specific structures and resources that enable the display of natural species behaviors and enhance psychological well-being through physical activity and mental challenges tailored to specific species’ traits should be implemented and explored further. Immediate surrounding enrichments include enclosure coloration, substrate provision, lighting, water complexity, structures, shelters, feeding systems, etc. More detailed information and accompanying references can be found in ALI’s Industry Shift Towards Environmental Enrichment in Aquaculture [31].

3.3.1. Example of Current Industry Technology for Individual, Animal-Based Farming and Enrichment Implementation—iFarm [32]

• Practice/Technique: BioSort utilizes software to recognize a biometric fingerprint of head features similar to state-of-the-art facial recognition software. The head geometry and spot pattern of individual fish are used to create an ID database. Individual health information is then stored in their respective health journals each time the fish passes the sensor. iFarm systems were integrated within commercial circular open cages that consist of an adapted snorkel cage with a submerged net roof to keep the fish population deep and a snorkel passage the fish must swim through to reach the surface to fill their swim bladders with air. Recognition of individual animals and health records is a unique part of the iFarm technology.
• Species/Farming Method: Cermaq (Oslo, Norway) and BioSort AS (Fornebu, Norway) have development licenses from the Norwegian Directorate of Fisheries to explore a novel production technology that aims to introduce individual-based precision farming to Atlantic salmon, sea-cage aquaculture.
• Indicators and Measurements: Computer vision models run continuously to collect information about every individual fish passing through the system, including lice detection and other parameters related to health, welfare, and growth. The sorting mechanism is connected to a system for transporting sorted fish to a separate surface enclosure for any treatment deemed necessary. Non-sorted fish return via the same openings to the main net enclosure.
• Observed Production Benefits: Individual growth rates, lice prevalence (including early stages of lice), physical wounds or signs of illness, etc., are all recorded in the fish’s health record. Using these data, iFarm separates the fish so that treatment is adapted to the individual’s needs, and producers only treat fish that need it, without additional stress caused by handling or sorting. Cermaq states this will reduce mortality in the marine production phase by 50–75%. iFarm also provides a full overview of fish in the main cage, allowing for more precise feeding regimes that minimize waste. According to current projections, the initial investment cost will be able to be repaid within one production cycle.
• Observed Welfare Benefits: The goal is that iFarm systems installed in 2025 and beyond will provide value creation through lower production costs with less lice treatments and better fish welfare and health, while providing unmatched insight into growth and health in the population, driven by individual health records. And while this demonstration of individual-based farming could mitigate or prevent animals from experiencing many aspects of negative welfare in aquaculture, it also represents a significant shift for the seafood industry in recognizing fish as sentient individuals that require different considerations throughout their lives. Perhaps this concept could be further explored to analyze and evaluate individual behaviors and preferences in farming systems that could be instrumental in the implementation or adjustment of more positive welfare practices such as environmental enrichment, motivations, and interactions.

3.3.2. Example of Current Industry Technology for Environmental Enrichments—KelpRing—Sustainable Aquaculture Innovation Center [33,34]

• Practice/Technique: The purpose of KelpRing is to replicate cleaner fish’s natural shoreline habitat and transfer it into salmon pens, in the sea lice zone. Creating a natural environment for cleaner fish helps reduce stress and enhances their lifespan, leading to better control of lice. The KelpRing comprises a negatively buoyant, year-round platform on which natural kelp grows, providing habitat enrichment for the cleaner fish. The cleaner fish are sheltered within the natural kelp forest and from there will foray out to feed on lice. The lightweight, rounded, and flexible nature of the KelpRing minimizes damage to the nets.
• Species/Farming Method: KelpRings were deployed in Atlantic salmon sea pens in a practical, industrial-scale sea trial shown in Figure S10, creating a kelp forest in which wrasse cleaner fish could hide and interact with the salmon in a relatively natural setting (in comparison with traditional commercial settings) that more closely aligns with the fish’s experience in the wild. Figure S11 demonstrates the KelpRing being deployed at variable depths which ensure that the cleaner fish remain in an appropriate zone within the water column.
• Indicators and Measurements: Numerous animal behaviors were observed during the trial, such as swimming, resting, and seeking shelter in the KelpRing. These behaviors are indicative of health and welfare benefits for the cleaner fish. Cleaner fish also demonstrated favoring the natural kelp over the artificial hides currently used in the industry.
• Observed Production Benefits: The KelpRing is manufactured from recyclable and reusable materials and reduces the need for medical/chemical lice treatments and their subsequent discharge or residue in the surrounding environment. This product also reduces the carbon footprint of expensive and high-energy treatment methods utilizing generators, pumps, large marine vessels, and transit between sites of vessels employed for lice treatments. Increased productivity and salmon growth rates through the reduction in treatments have been demonstrated, in addition to a decrease in mortality rates for both salmon and cleaner fish during production. Further cost savings and various benefits resulting from the reduction in staff hours currently spent cleaning fake plastic hides, given that kelp is naturally self-cleaning, have also been documented.
• Observed Welfare Benefits: This innovation aims to improve cleaner fish welfare and survival rates by providing them with their own natural kelp forest within salmon pens. A symbiotic relationship exists between the kelp plants and the cleaner fish, as noted by the way wrasse rub themselves against the plants. A previous feasibility study stated [35] that the introduction of natural kelp on salmon farms can have medicinal properties and a calming effect on cleaner fish, boosting their ability to eat sea lice off the salmon. Kelp takes in and flourishes on the nitrates and phosphates found in salmon waste, while also releasing oxygen into the cages through photosynthesis. Additionally, the natural kelp habitats offer an engaging element for the farmed salmon, enriching their environment.

3.4. Feeding and Feed Composition

Animal-based fish feed should be replaced with alternative proteins to the extent that the evidence suggests this will not have a deleterious impact on the health and well-being of the fish and the ecosystem. Alternative feed products, such as algal oils, bio-processed soybean meal, and lima bean flour, should be used in place of fish products, to the extent that they do not impair health and welfare. The most sustainable alternative feed product should be preferred. Fishmeal and fish oil should be identified and quantified by the number of individual animals consumed per individual farmed aquatic animal. The animals used in fishmeal should be recorded by species and geographical sourcing [36,37].

3.4.1. Example of Current Industry Collective for Improving Feed Composition and Usage—F3 Feed Innovation Network [38]

• Practice/Technique: F3 (Future of Fish Feed) is a collaborative effort between NGOs, researchers, and private partnerships to accelerate and support the scaling of innovative, substitute aquaculture feed ingredients such as bacterial meals, plant-based proteins, algae, and yeast to replace wild-caught fish. The F3 Team invites collaboration with governments, NGOs, and businesses to achieve the objective of sustainable animal feeds in both agriculture and aquaculture. The challenge is to develop a fish-free feed for one of three specified categories: salmonid, shrimp, or other carnivorous species. This initiative aims to lessen the aquaculture industry’s reliance on forage fish by promoting alternative feeds for its primary consumers. Prizes were awarded in each of the three categories—salmonid, shrimp, and other carnivorous species—to the competitor who created and sold the most effective “fish-free” feed, which is made without wild-caught fish or any marine-animal ingredients. The prizes were awarded in each of three categories—salmonid, shrimp, and other carnivorous species—to the contestant that produced and sold the most “fish-free” feed made without wild-caught fish or any marine-animal ingredient.
• Species/Farming Method: This feed composition was considered for rainbow trout (Oncorhynchus mykiss), whiteleg shrimp (Litopenaeus vannamei), and other carnivorous species such as largemouth bass (Micropterus salmoides).
• Indicators and Measurements: Producers analyzed the performance of fish-free feeds in comparison with conventional diets of the same/similar nutrient values. Fish growth, rate of gain, and overall health were assessed and yielded favorable results. A variety of tests are performed during the formulation process, including ingredient functionality, palatability, digestibility, solid waste management, weight gain, fecal production, feed conversion ratio, immune response, final product quality, etc.
• Observed Production Benefits: Fish ate more aggressively with F3 diets. Growth rates for some F3 formulations were better than conventional feeds for the particular species. Final filet quality was described as “far superior in smell, texture, appearance, and taste” [39]. The feed is free from off-flavors or unpleasant odors, attributed to the quality of its ingredients. In contrast, conventional feeds often include mercury, PCBs, microplastics, growth hormones, antibiotics, and various other contaminants, leading to significantly greater long-term healthcare expenses.
• Observed Welfare Benefits: The Feed Innovation Network contributes to suffering avoidance for fish used in marine aquafeed ingredients by providing information on experimental protocols, testing facilities, and promising alternative ingredients. They connect ingredient suppliers, aquafeed purchasers, and fish farmers to foster the development of innovative, cost-effective feed ingredients. Additionally, they offer access to specialists in fish nutrition, aquaculture science, and seafood sustainability standards, along with invitations to exclusive meetings and forums for knowledge sharing. The winners of the carnivorous species challenge were the following: U.S.-based Star Milling Co. (Perris, CA, USA) [40] for its non-GMO plant-based feed that contains omega-3 DHA-rich algae and heart-healthy flax oil for rainbow trout; the Ecuadorian company Empagran [41] for its vegetarian recipe using Veramaris’ algal oil rich in EPA and DHA omegas for Pacific white shrimp, see Figure S12; China-based Jiangsu Fuhai Biotech [42], which used its unique Fatide^® (Jiangsu Fuhai Biotechnology Co., Ltd., Hai’an, China) product with dehulled full-fat soybean fermented by microbes and enzymes for its largemouth bass feed; and Japan-based Dainichi Corporation (Uwajima, Japan) [43], which received an honorable mention for their breakthrough feed for red sea bream. Over three million kilograms of feed were sold in all seafood categories during the roughly 16-month contest, and over 95 million forage fish were spared from use in animal. Please refer to the F3 Forage Fish Savings Estimator for additional details [44].

3.4.2. Example of Current Industry Technology for Improving Feeding Practices—Innovasea FlowFeeder [45]

• Practice/Technique: FlowFeeder [46] is a waterborne feeding solution that gently delivers feed to fish below the surface, minimizing pellet damage and loss commonly experienced with air-blown feeding systems.
• Species/Farming Method: FlowFeeder features a proprietary feed dispenser that can be placed at the ideal feeding depth for the specific species being farmed. This system can be used with Innovasea’s submersible fish pens as well as traditional surface pens from other manufacturers.
• Indicators and Measurements: Waterborne delivery reduces damage to feed pellets, which are often fractured when blown through pipes by an air compressor. FlowFeeder is backed by sensors [47] and high-resolution cameras [48], which provide real-time visibility into the following: feed satiation, pellet detection, and biomass data. Anticipatory behavior, feed intake, and motivation should be measured during feeding to inform any necessary feeding regime adjustments according to species and life stage.
• Observed Production Benefits: The waterborne delivery system requires less power than air-blown systems and can reduce energy costs. FlowFeeder delivers the feed at depths where fish prefer to congregate, resulting in less waste and better feed conversion ratios. This system enables farm operators to feed even when there are heavy waves, strong currents, or surface threats such as harmful algal blooms or sea lice, significantly reducing the number of lost feed days. This improves feeding regimens and helps keep growth targets on track.
• Observed Welfare Benefits: Waterborne feeding systems can provide a better way to feed fish by delivering intact pellets to the animals at their preferred depth, ensuring access to feed for the entire farmed population and reducing the discharge of microplastics and other pollutants into the surrounding environment, such as dust and oil residue from feeding hoses. This system not only prevents pellet loss at the surface, but feeding under the sea lice layer in the water column for Atlantic salmon can reduce the need for subsequent treatment and antibiotics, increasing overall fish health. Distributing feed to farmed fish underwater can also minimize instances of predation, from birds for example, that could be attracted to surface disturbances. Minimizing these interactions could not only alleviate any stress that the farmed fish might encounter but could also decrease the risk of any unknown disease or pathogens being transmitted to the farmed animals through avian predators. An interesting additional welfare consideration that should be further investigated is the noise levels associated with waterborne feeding systems in comparison to traditional airborne systems and their impacts on farmed animals.

3.5. Stunning and Slaughter

In order to minimize the risk of consciousness being recovered, the time elapsed between stunning and slaughter must be minimized. Concurrent methods of stunning and slaughter are preferred, such as those that involve electronarcosis directly leading to electrocution. However, approaches that result in death without a substantial risk of consciousness recovery are also considered acceptable. All stunning and slaughter equipment must be calibrated appropriately for the specific animals to be processed (in terms of species, body size, and life stage), in order to achieve immediate and consistent loss of consciousness. CCTV installation is necessary to ensure clear footage of the backup stun procedure [49]. More detailed information can be found in ALI’s Stunning and Slaughter Best Welfare Practices for Animal Welfare in Aquaculture [50].

Example of Current Industry Technology for Improving Stunning, Slaughter, and Use of Aquatic Animal Products Unfit for Human Consumption—Tiny Fish and Ace Aquatec [51,52]

• Practice/Technique: Tiny Fish harvests and finds premium markets for the small fish, shown in Figure S13, that are removed using Ace Aquatec’s Humane Culling System (A-HCS^®) [53], a compact adaptation of the Humane Stunner Universal, tailored for small-scale operations. Juvenile fish are pumped into the entrance chute, shown in Figure S14, where they flow directly into the water of the stun tube. The electric field in the stun tube rapidly causes unconsciousness. The water system transports the fish to the final dewatering grid in about 40 s. Next, the fish drop into a harvest tub, where an integrated water pump recirculates the water. Ice may be added to the harvest tub to keep the fish fresh.
• Species/Farming Method: The focus is currently on freshwater Atlantic salmon and rainbow trout, as these sectors offer viable tonnage of high-quality fish for their discerning customers, but other sectors are also being considered. During salmon’s freshwater phase, a selection of smaller-sized fish may be removed from the population to allow for the “best” animals to be grown-out at sea, reaching a market size of approximately five kilograms. These fish are typically removed using chemical anesthesia and must then be disposed of in a landfill, ensiled, incinerated, or otherwise repurposed. This company is humanely harvesting smaller, juvenile (1.5–500 g) fish to be processed and distributed as high-value products, minimizing waste.
• Indicators and Measurements: Ace Aquatec states that the system has a 100% stun rate and can process three tonnes of fish per hour more humanely and efficiently than any other method. The Smolt & Juvenile Humane Cull System (A-HCS™) is composed of multiple passive and active safety systems to ensure that, in the event of failure or mis-operation, operator safety and fish welfare are preserved. A 2022 study [54] concluded that Ace Aquatec’s in-water electric stunning can deliver instant and lasting unconsciousness for salmonid juveniles and is well suited for culling operations.
• Observed Production Benefits: Killing by anesthetic overdose is, at present, the only recognized humane approach to juvenile culling and incurs the cost of the anesthetic as well as the responsible disposal of the resulting toxic material. By removing the need for chemicals, this system provides a more ethical way of dispatching excess fish at hatchery facilities, as well as producing an omega-rich protein that can be harnessed for new revenue streams. Where culled fish are healthy and have not recently received medication, using the Ace Aquatec Smolt & Juvenile A-HCS™ allows them to be utilized for a wide range of purposes, including protein sources or pet food ingredients in accordance with local regulations.
• Observed Welfare Benefits: The Smolt & Juvenile Humane Cull System utilizes the same technology found in Ace Aqutec’s Humane Stunner Universal (HSU™) that minimizes fish stress by rendering them completely unconscious in under one second while they remain in the water. Tiny Fish prevents small fish—ranging from 5 g to 80 g—from wastefully entering landfills using the Humane Cull System. Fish of this size can also be extremely difficult to handle appropriately and with care, particularly during culling periods of production. By minimizing handling, their welfare is also protected. This system provides a humane way to cull fish deemed unsuitable for grow-out and also minimizes a portion of the pronounced waste in aquaculture production systems by finding supplemental uses for these fish products rather than promoting additional intensification.

4. Discussion

This is a comprehensive review which combined existing animal welfare recommendations such as the Five Domains Model and the 4R Approach to Seafood System Reform with examples of innovative, modern aquaculture industry practices that prioritize animal welfare. The primary pillars of welfare considered were water quality optimization (e.g., turbidity, total dissolved solids, oxygen, ammonia, carbon dioxide, temperature, pH, salinity, and nitrate), total space requirements and ideal stocking densities (to minimize stress, maladaptive behaviors, and conspecific aggression), environmental enrichment strategies (e.g., enclosure coloration, substrate provision, lighting, water complexity, structures, shelters, and feeding systems), sustainable feeding or feed composition (e.g., replacing fish-derived ingredients with alternative ingredients such as algal oils, bio-processed soybean meal, and lima bean flour), and humane stunning and slaughter methods (which improve the life and product traits of both premium animals harvested for market and rejected animals which might otherwise go into low-value products or be wasted). Salmon, trout, carp, tilapia, sea bass, sea bream, turbot, and shrimp were included because they are commonly farmed species with high relevance to the global seafood industry. This review provides an interesting and valuable resource to support a more sustainable seafood industry.

The results are intended to promote better cross-industry collaboration between academic institutions, advocacy organizations, and producers to both inspire future research and highlight those who are currently leading in their respective areas. This review is an initial accumulation of knowledge and technology advancements that promote collaboration among aquaculture stakeholders, facilitating the dissemination of information and fostering innovation in the seafood industry. However, as additional data become available, a more comprehensive reference guide could be created with various specificities based on species, region, farming system, etc. Furthermore, specifying the exact number of farms participating in each practical example presented is essential. Unfortunately, confidently stating a reasonable estimation is impossible at this time given that this detailed information is not disclosed publicly, and companies are reluctant to share privately. Obtaining details such as these will provide a better context for the results and help evaluate the impact of the innovations at different production scales. The absence of statistical analysis in this study reflects its exploratory and foundational nature. The primary objective was to consolidate and evaluate existing innovative aquaculture practices that align with welfare principles, rather than to generate or analyze new experimental data. Given the variability in data quality and type across public sources, a consistent statistical approach was not feasible. Instead, this study provides a qualitative overview, identifying promising practices that serve as a basis for future research. These findings highlight the need for subsequent quantitative studies to validate the effectiveness of these practices under controlled conditions and develop standardized evaluation methods.

While this is a first attempt at presenting such data as beneficial for animals and producers alike, additional linkages between better animal health, welfare, and efficiency in aquaculture production should be identified and expanded upon in order to elicit a collective call to action from the global seafood industry. Sustainable advancements in aquaculture will stem from comparing promising approaches, fostering coordination and buy-in, and striving to be as cost-effective as possible in implementation. The pursuit of “best practices” is inclusive, acknowledging that the ultimate goal is to establish a harmonious balance between people, our natural environment, businesses, and the health and welfare of animals in aquaculture.