Astaxanthin in Aquaculture: More Than a Pigment

Astaxanthin is best known for giving salmon, trout, shrimp and other aquatic animals their pink, orange or red colour. In aquaculture, however, it serves a much broader purpose.

Research shows that dietary astaxanthin can support pigmentation, antioxidant defence, immune function, feed utilization, growth and resilience to environmental stress. These combined roles have made it an important ingredient in modern aquafeeds.

Why Farmed Fish Need Dietary Astaxanthin

Most fish and crustaceans cannot produce carotenoids such as astaxanthin on their own. They must obtain them through food.

In natural environments, salmon and other aquatic animals consume algae, plankton, krill and small crustaceans containing carotenoids. Farmed animals may have limited access to these dietary sources, so astaxanthin is commonly added to formulated feed.

Without enough dietary astaxanthin, farmed salmonids can develop pale flesh. Supplementation helps create the colour consumers expect while also contributing to several biological functions.

Pigmentation and Seafood Quality

Pigmentation remains one of the most familiar uses of astaxanthin in aquaculture.

After being consumed, astaxanthin is absorbed and deposited in tissues such as muscle, skin, shells and reproductive organs. It contributes to the pink flesh of salmon and trout, the red colour of cooked shrimp and the appearance of ornamental fish.

Pigmentation results depend on several factors, including:

• Species and life stage

• Astaxanthin source and concentration

• Feed composition

• Digestive absorption

• Feeding duration

• Water temperature

• Overall animal health

Not all consumed astaxanthin is retained. Some is metabolized or excreted, making bioavailability and feed formulation important considerations.

Antioxidant Protection

Astaxanthin is a lipid-soluble carotenoid with antioxidant activity. It can help protect aquatic animals from oxidative stress caused by normal metabolism and difficult farming conditions.

Farmed fish may experience oxidative pressure from rapid growth, high stocking density, temperature changes, handling, transportation and exposure to pathogens. These conditions can increase reactive oxygen species that damage cell membranes, proteins and other biological structures.

Dietary astaxanthin can support the animal’s natural antioxidant defence systems. This can be particularly valuable during periods of intensive growth or environmental stress.

Growth and Feed Utilization

A 2025 meta-analysis examined 64 studies involving 33 aquatic species. The findings associated dietary astaxanthin with improvements in final body weight, weight gain, specific growth rate and feed efficiency.

The analysis also reported improvements in feed conversion ratio and protein efficiency. These results suggest that astaxanthin can help aquatic animals use dietary nutrients more effectively under certain conditions.

Possible explanations include support for intestinal health, nutrient absorption, antioxidant balance and immune function. By helping animals manage physiological stress, astaxanthin can allow more energy to be directed toward growth.

The most effective inclusion level varies. Species, age, feed composition, farming conditions, astaxanthin source and feeding duration can all influence the outcome.

Immune Function and Survival

Astaxanthin has also been studied for its effects on immune performance.

Dietary supplementation can support cellular and humoral immune responses, including immune-cell activity, protective enzymes and other natural defence mechanisms.

Its antioxidant role can also benefit immune balance. Excessive oxidative stress can interfere with normal immune activity, while stronger antioxidant protection can help aquatic animals respond more effectively to biological and environmental challenges.

The 2025 meta-analysis also found positive effects on survival. However, the supplementation level associated with stronger survival outcomes differed from the range connected with maximum growth. This highlights the need to match feed formulations to the species and production goal.

Stress Resilience and Reproduction

Aquatic animals frequently encounter stress during grading, transport, handling, temperature changes and transfers between environments.

Astaxanthin can support resilience by helping protect cells from oxidative damage and contributing to normal immune regulation.

It also plays a role in reproduction. In salmon, astaxanthin can be transferred to eggs, where it helps protect developing tissues. It has been associated with egg quality, embryo development and fry survival.

In adult salmon, astaxanthin contributes to external colouration involved in reproductive signalling. Its importance therefore extends beyond flesh pigmentation.

Natural and Synthetic Sources

Aquaculture feed can contain astaxanthin from chemical synthesis, microalgae or yeast.

Synthetic astaxanthin is widely used because it is consistent, scalable and generally less expensive. Natural astaxanthin is commonly produced from the microalga Haematococcus pluvialis, which accumulates high concentrations of the carotenoid under controlled stress.

Natural algal astaxanthin differs from synthetic material in its esterification and stereoisomer composition. The algal form is primarily esterified, while synthetic astaxanthin is usually unesterified and contains a different mixture of stereoisomers.

These differences can influence stability, absorption, tissue deposition and antioxidant performance. However, results also depend on the species, dosage and overall feed formulation.

Producing Natural Astaxanthin

Natural astaxanthin production begins with cultivating H. pluvialis. The algae first grow in a green vegetative stage. When exposed to controlled stress, such as strong light or nutrient limitation, the cells accumulate red astaxanthin.

The biomass is then harvested, dried and processed. Because the algal cell wall can limit digestibility, cell disruption is important for making the astaxanthin more accessible.

Extraction methods can include solvents, pressurized liquids, ultrasound-assisted processing and supercritical fluid extraction. Since astaxanthin is sensitive to heat, light and oxygen, careful processing and protective formulation are essential.

New delivery approaches are also being explored. One research project combined astaxanthin-rich algae with insect larvae. The larvae consumed the algae and became a source of both natural astaxanthin and protein for aquafeed. Feeding trials indicated potential benefits for growth and pigment deposition in salmon.

Supporting More Sustainable Aquaculture

Astaxanthin can contribute to aquaculture sustainability by supporting feed efficiency, survival and stress resilience.

Natural production through microalgae also provides a renewable alternative to petroleum-derived synthetic pigments. Integrated systems using algae and insect protein could further reduce dependence on fishmeal and conventional agricultural feed ingredients.

Cost remains a challenge because natural astaxanthin is generally more expensive to produce. Continued advances in cultivation, processing and delivery will be important for wider adoption.

A Multifunctional Feed Ingredient

Astaxanthin is much more than a colouring agent. It supports pigmentation, antioxidant protection, immune function, growth, feed utilization, reproduction and stress resilience.

Its effectiveness depends on selecting the right source, dosage and formulation for each species. As aquaculture technology advances, astaxanthin will continue to play an important role in developing healthier, more efficient and more sustainable farming systems.