Exploring the Nutritional Benefits of Amphipods for Optimal Growth in Commercial and Ornamental Fish

July 6, 2023
Marine Science
Reef Aquariums

Feeding aquarium fish often involves using artificial feeds made from marine ingredients like fishmeal and fish oil. These ingredients are very nutritious for most saltwater fish. However, they are expensive and becoming scarcer worldwide. As a result, fish foods often include cheaper and more easily available ingredients from land, such as soy flour, lentils, and vegetable oils. But these ingredients are not a natural food source for marine species, which makes it hard for fish to accept, eat, and digest them. This is the main reason why aquarium inhabitants often have slow growth, diseases, changes in color, deformities, low or no reproduction, laziness, and frequent death. Most marine fish and other ornamental organisms such as corals, anemones, and shrimps usually eat in the wild a variety of small marine organisms found on the seabed (benthic organisms) and in the water column (planktonic organisms). These organisms are the ideal food for aquarium species, but aquarists rarely have access to them, which makes it difficult to provide this type of food to their pets.

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The Importance of Sustainable Food Production for Ornamental Marine Species

The challenge of finding suitable natural foods is a big problem for both aquarium enthusiasts and the aquaculture industry that focuses on producing ornamental marine organisms like fish, corals, shrimps, and macroalgae in a sustainable way. This industry aims to reduce the strain on wild populations caused by fishing. Approximately 90% of marine fish for aquariums are caught from the wild and unfortunately, for every marine fish that makes it to our aquariums, many others die during the long journey from the fishing site to our homes. That's why there is a lot of hope placed in scientific advancements that can generate new techniques and production methods for aquarium organisms.

Currently, scientific research is focusing on the search for and development of new foods that allow for the sustainable production of ornamental marine species. Brine shrimp and rotifers are commonly used today as live food for fish and invertebrates. These small crustaceans are the most commonly used organisms also for large-scale fish production, especially in freshwater. This is mainly due to their simple and affordable industrial cultivation methods, but most importantly because fish love them. However, for the production of saltwater fish, the use of these organisms as food is inadequate because they are not of marine origin; they originate from freshwater or saline environments. Therefore, they do not provide a suitable nutritional profile for most marine species.

For this reason, marine amphipods, which are small shrimp-like crustaceans ranging from 1 to 10 mm in size, have recently caught the attention of researchers, hobbyists, and those involved in aquaculture.These creatures are a natural food source for many commercial and ornamental interest species. Moreover, they naturally possess all the necessary nutrients for optimal growth. Marine amphipods can be found in various environments, such as submerged rocks, seagrasses, and even on the beach. What makes this group of organisms remarkable is that many species engage in parental care. This means that the female, male, or both parents take care of their offspring for a significant period, protecting them from predators and providing the necessary food for their growth and survival.

male and female amphipods

Amphipods: A Key Source of Nutrition for Marine Species

Among the more than ten thousand amphipod species living today, with each one of them with unique characteristics, there are a few that stand out as especially interesting for aquarium enthusiasts. One of them is the species Paryhale hawaiensis. Paryhale is an abundant species and is found in all tropical and subtropical seas of the world. It is a fast-growing animal that lives in large colonies of organisms, with more than seven thousand individuals per square meter. It feeds on all kinds of organic matter, both animal and vegetable, and even decomposing materials. It is a species that can withstand high and low temperatures, as well as highly degraded and hostile environments. That is why researchers have found that its cultivation can be extremely simple and easy, ensuring large productions suitable for use in the aquarium and aquaculture industry. Paryhale is so interesting that it has been used in hundreds, perhaps thousands, of scientific studies to decipher various aspects that go beyond aquarism, such as limb regeneration, evolution, and embryonic development. Scientists have amassed an immense amount of information about Paryhale, and in fact, its entire genome has been sequenced, meaning all of its genetic information has been identified. Therefore, there are many molecular tools that researchers can use to decipher all sorts of biological mysteries.

In the Multidisciplinary Teaching and Research Unit (UMDI) of the National Autonomous University of Mexico (UNAM), located in Yucatan state, we have recognized the significant potential of Parhyale for worldwide aquaculture development. Consequently, we have conducted both basic and applied scientific research to gain a deeper understanding of Parhyale's biological aspects, which form the foundation for its large-scale and sustainable breeding in captivity. Within our research group, the Marine Ornamental Species Ecology and Culture Research Program (PIECEMO, Programa de Investigaciones en Ecología y Cultivo de Especies Marinas de Ornato), in collaboration with other laboratories, we not only investigate and reproduce Parhyale, but also strive to enhance the cultivation of various marine species used for ornamental purposes, such as seahorses (Hippocampus erectus), marine polychaetes (Bispirabrunnea), different types of cleaner shrimp, snapping shrimp, giant anemones (Condylactis gigantea), and various coral species.

The Great Potential Of Amphipods

Paryhale is a topic of great interest to us. We want to understand its nutritional profile and how it can be changed or improved depending on its food source. Our recent findings show that Paryhale has a good amount of fats and lipids that are suitable for most marine species, even when it is fed with low-quality sources of these nutrients. This is possible because Paryhale has the necessary tools in its genes to produce enzymes that can make polyunsaturated fatty acids (also known as omega-3 long chain fatty acids) from more simple lipids found in materials from the land, which are typically lacking in these fatty acids. These discoveries are significant not only for aquariums but also for human nutrition and medicine. These nutrients are highly recommended in people's diets to enhance vision and brain development, as well as to reduce heart problems.

We firmly believe that marine amphipods like Paryhalewill be used as dietary supplements for humans in the future. To confirm the excellent nutritional profile of Paryhale, we conducted several tests in the laboratory using the lined seahorse (Hippocampus erectus). This species is commonly found in aquariums, is of high commercial value, and is threatened by pollution and habitat loss. The seahorses showed significant improvements in their growth and survival when fed with Paryhale compare to when they were given Artemia as livefood. Not only did the seahorses perform better, but we also observed that they consumed more food (the double compared with Artemia) and much faster (in ten minutes compared with more than an hour with Artemia). This is no surprise because the size, shape, and swimming behavior of the amphipods are appealing to the seahorses. It is worth noting that amphipods are one of the most important components of the seahorses' natural diet.

The use of marine amphipods has many benefits.These small creatures are not only suitable for seahorses, but they also make excellent food for juveniles of Octopus maya according to our observations in the lab. Amphipods are nutritious and their behavior makes it easier for the octopuses to catch them. They are also a good option for feeding other fish and invertebrates that struggle with eating artificial food, like Mandarin fish and Moorish Idols. Amphipods can even help aquarium fish grow and reproduce better. Many wild species struggle to eat commercial foods, which leads to high mortality rates. Amphipods can assist these species during this difficult transition and also help reduce the occurrence of diseases.

Our scientific research has allowed us to develop techniques for the industrial production of amphipods. We have success fully reproduced Paryhale, using Biofloc systems. Biofloc systems are highly productive and low-cost culture systems that promote an overwhelming growth of a community of microorganisms, including bacteria, microalgae, protozoa and a diversity of all types of micro invertebrates, which consume dissolved nutrients and waste contributing to improving water quality and serve as primary food for the species that are cultivated there. Due to the high density of microorganisms in these systems, the water in the ponds looks brown and cloudy, apparently dirty, but the species that manage to withstand these conditions are favored by an immense amount and diversity of food. These systems, in addition, are considered more sustainable than the traditional ones, since they require minimal amounts of fresh water, with no water replacements, only the necessary to compensate for evaporation. Biofloc systems are commonly used for robust species such as white shrimp and Nile tilapia but may not be suitable for all organisms. Thus, we consider the raising of amphipods in biofloc a great achievement with the potential of sustainably producing large amounts of fish food of great quality.  

Again, Paryhale is a species that we find particularly interesting. We are currently using it as a model to study the negative effects of climate change and pollution on marine organisms. It is versatile and easy to manipulate and reproduce in the laboratory. This allows us to conduct numerous experiments and biochemical analyses to gain new knowledge.

So, if you get the chance to see these little creatures in your aquarium, know that they help keep the aquarium healthy by eating leftover food and annoying stringy algae. They also make a great snack for your fish, so if you can, try separating and breeding them for food. It's an easy job that will definitely make your fish happy and healthy.

About the author:
Jorge Arturo Vargas-Abúndez

Arturo is a passionate biologist and researcher specialized in ornamental species aquaculture. He obtained his PhD in Life and Environmental Sciences from Università Politecnica delle Marche (Italy). He is currently working in the development of the aquarium industry in Mexico and assessing the effects of climate change and pollution in aquatic animals.

About the Author
Jorge Arturo Vargas-Abúndez

Arturo is a passionate biologist and researcher specialized in ornamental species aquaculture. He obtained his PhD in Life and Environmental Sciences from Università Politecnica delle Marche (Italy). He is currently working in the development of the aquarium industry in Mexico and assessing the effects of climate change and pollution in aquatic animals.