The octopus, an intelligent and fascinating cephalopod, has captured the human imagination for centuries. However, its role on the consumer’s table is relatively new. Octopus farming, an emerging but booming practice, is opening up new possibilities for aquaculture but also generating controversy.
According to the European Commission’s Directorate-General for Maritime Affairs and Fisheries (2020), global octopus catches reached 450 thousand tons in 2017. The leading octopus-producing countries are China, Morocco, Mauritania, Japan, and the EU28.
Octopus biology exhibits a series of characteristics that make them suitable candidates for large-scale cultivation: a short life cycle, very high growth rate, high nutritional value profile, good adaptation to captive conditions, and high fecundity (García-Fernández, 2022). However, the interest in promoting octopus farming has sparked discussions about the ethical viability of their cultivation, as octopuses are considered among the most intelligent animals in the animal kingdom (Quero, 2021).
Octopuses are considered intelligent animals because they can solve problems, mimic their surroundings, differentiate between humans, and hunt (Jacquet et al., 2019). Additionally, a report from the London School of Economics (LSE) found solid evidence that cephalopods are sentient beings.
In this article, we aim to provide an overview of the main characteristics of octopuses, their reproduction, feeding, and aquaculture experiences.
Characteristics of Octopuses
Octopuses, also known as octopods, are invertebrates belonging to the order Octopoda, class Cephalopoda, and phylum Mollusca.
Several studies have shown that octopuses can be trained and develop memory skills. According to Quero (2021) and Vega (2022), the characteristics of these aquatic animals continue to surprise scientists: they can taste with their tentacles or dream, and their neural network includes their tentacles, suckers, and skin.
Octopods can adapt their color and body surface to match their surroundings.
Furthermore, various studies report that based on the color of the octopus’s body, you can recognize its “mood”; blue when nervous, pale when scared, or reddish when angry.
Anatomy of Octopuses
Octopuses are bilaterally symmetrical, with the mouth and beak located at the central point of their eight limbs or tentacles. Each tentacle has two rows of suckers that help them catch their prey.
The largest species of octopus in the world is the “giant octopus” (Enteroctopus dofleini), with adults reaching weights of 15 kg and tentacles up to 4.3 m long.
In contrast, the smallest species of octopus in the world is O. wolfi, measuring around 2.5 cm and weighing less than 1 gram.
Octopuses have three hearts.
Octopus Habitat
Octopods are nocturnal animals and are benthic (living on the bottom).
They inhabit various regions of the ocean. Different octopus species are found in habitats including complex coral reefs (Sung et al 2022).
Anderson (1997) reports that in the case of the octopus O. tetricus, which inhabits the northeast of New Zealand, it prefers to live in coral reefs during the breeding season, while the rest of its life is spent in habitats with soft sediments.
It is important to note that octopus farming has been experimented with in land tanks or marine cages containing tubes for octopuses to hide in; we will report some experiences of octopus aquaculture later on.
Octopus Reproduction
All cephalopods are gonochoric; octopuses have a single gonad located in the posterior part of the visceral mass and are associated with the coelom.
In the adult stage, octopuses exhibit clear sexual dimorphism; in males (smaller than females), one of the arms transforms into a hectocotylus at its distal end, which acts as a copulatory organ.
During reproduction, the male octopus uses a specially adapted arm to deposit a packet of sperm directly into the female’s mantle cavity, after which rapid senescence occurs, and it dies.
Casalini et al. (2020) analyzed the reproductive performance of O. vulgaris breeders fed with two different diets (mixed fish or mixed crustaceans) using a recirculating aquaculture experimental system. Rey-Méndez (2015) and Castellanos (?) report that octopuses have high fertility (100,000 – 500,000 eggs). The female deposits the fertilized eggs in a burrow and cares for them until they hatch, after which she also dies.
What Do Octopuses Eat?
Almost all octopus species are predators.
Paralarvae
Octopus paralarvae feed on copepods, arthropod larvae, and other zooplankton species. Reis et al. (2021) recommend that in the cultivation of O. vulgaris paralarvae, it is necessary to find a live prey, easy to obtain and maintain in the laboratory, that satisfies the nutritional requirements of octopus paralarvae and adapts to their predatory behavior, and they used the zoea of Grapsus adscensionis achieving good results compared to Artemia. Ortiz et al. (2021) recommend that for the breeding of O. americanus paralarvae up to 10 days old, the following prey densities should be provided: 80 copepods per liter, 160 Artemia nauplii per liter, and 80 Artemia zoea per liter.
On the other hand, Gómez (2017) determined that a diet containing 80% blue crab meat (Callinectes sapidus), 11% mussel (Mytilus galloprovincialis), 5% tuna eye oil, and 4% gelatin provides the best results in the cultivation of juvenile O. bimaculoides.
Juveniles
In the case of O. maya juveniles, Gallardo et al. (2020) recommend diets with a proportion of 70% squid and 30% crab to meet their nutritional needs; however, the researchers warn that a 30% crab proportion has a direct impact on costs and profitability.
On the other hand, Iraba et al. (2023) investigated the growth and survival rates of O. cyanea using natural and formulated diets; they determined that specific growth rates (SGR) and survival were higher in octopuses fed in treatment A (natural diet of frozen crabs Scylla serrata) and lower in treatment D (0% crab content).
Adults
In their adult stage, octopuses feed mainly on crustaceans, polychaete worms, snails, clams, shrimp, fish, and other octopuses.
García (2016) experimented with the development of a commercial diet for O. vulgaris. She evaluated the effect of prey such as squid (Loligo gahi), crayfish (Procambarus clarkii), and hake (Merluccius gayi) on the growth, survival, and energy balance of O. vulgaris, determining that squid is the best prey for octopus cultivation in the fattening stage.
How Do Octopuses Breathe?
Breathing in octopuses involves introducing water into the mantle cavity through an opening, passing it through the gills, and expelling it through the siphon.
The structure of the gill lamellae allows for high oxygen absorption.
Octopus Farming
Currently, octopus farming is being experimented with in Mexico (Santillán, 2019), Japan, Spain (Rey-Méndez, 2015), Chile (Zuñiga, 2011), Peru, among other countries; however, commercial cultivation is not yet a reality.
In recent years, due to the high market value of O. maya and O. mimus, these species have been identified as strong candidates for marine aquaculture in ponds and tanks (Gallardo et al., 2017).
In Mexico, as reported by Santillán (2019), they have been studying the physiology, digestive system, and reproductive system of O. maya.
Castellanos (?) indicates that octopus juveniles and adults can easily adapt to captivity, grow at water temperatures between 17 and 22°C, have very high growth rates (6-7% in weight/day), and a short lifespan (1-2 years).
In 2018, the Spanish Institute of Oceanography reported that after 20 years, they successfully reproduced octopuses (O. vulgaris) in captivity, marking a milestone for the commercial exploitation of the species through aquaculture.
Recently, Powell (2022) published an article describing advances in octopus aquaculture and the challenges it presents.
Octopus Egg Incubation
Spreitzenbarth and Jeffs (2020) developed an incubation system for O. tetricus eggs and achieved hatching rates exceeding 90% in upwelling incubation systems with additional aeration for the three broods, compared to 10-40% in upwelling systems without aeration; demonstrating that O. tetricus egg incubation can be achieved in the absence of maternal care.
Most octopus species hatch as paralarvae and are planktonic for weeks or months, depending on the species and water temperature. According to Castellanos (?), the main milestones of the life cycle, at a water temperature of 25°C, are:
- Embryonic development: 20-25 days
- Hatching (paralarva < 3 mm): 33 – 40 days.
- Settlement (juveniles – average weight 0.1-0.25 g): 30 – 60 days.
Cultivation of Octopus Paralarvae
During the larval period, the octopus’s lifestyle is planktonic (García-Fernández, 2022). Castellano (?) reports the following conditions for the cultivation of paralarvae of the species O. vulgaris:
- Tanks of 100-500 liters (dark interior)
- Water filtration
- Photoperiod 12:12, 150-200 lux, 21°C
- Density: 3-5 individuals/L
- Aeration: moderate
Spreitzenbarth et al. (2021) evaluated the behavior of O. tetricus paralarvae aged 0-5 dph (days after hatching) under different experimental conditions and determined that the paralarvae exhibited better feeding behavior (attacks on live food) in dark tanks.
Recently, Uriarte et al. (2024) studied aspects of feeding and temperature management in breeders, egg incubation, paralarvae rearing, and early juvenile growth of the Patagonian red octopus (Enteroctopus megalocyathus).
Fattening of the Octopus
The initial experiences of commercial octopus farming were based on capturing sub-adult specimens and fattening them in captivity. However, this farming system is highly vulnerable as it relies on the availability of wild organisms.
Rey-Mendez (2015) describes experiences conducted in Galicia (Spain), where specimens weighing less than 1 kg are captured and introduced into a net bag containing a PVC tube (20 cm in length and 15 cm in diameter).
Under these conditions, Rey-Mendez (2020) states that the octopus fattening process lasts for 3 to 4 months, resulting in a final size of 2.5 to 3 kg. Additionally, it is noted that daily feeding ranges between 5-10% of the total weight of the octopuses.
On the other hand, García (2016) reports that the maximum sustainable density for octopus fattening in tanks should not exceed 20 kg/m3 for a maximum period of two months. However, it is important to consider the introduction of shelters. Suzumura et al. (2022) suggest that shelters for octopuses constructed from square vertical plates spaced with suitable gap widths for Octopus sinensis are a useful addition to maximize the number of octopuses that can be maintained under farming conditions.
Casalini et al. (2023) evaluated how different environmental conditions (Basic vs. Enriched) affect subadults of O. vulgaris maintained in recirculation systems; they reported that octopuses kept in enriched environments displayed various body patterns and gained significantly more weight than those kept in basic environments. These findings are supported by Hu et al. (2024), who report that placing shelters in rearing containers is an environmental enrichment method that can effectively improve the welfare of aquatic animals; they studied a set of standard specifications for shelter use in the artificial cultivation of Amphioctopus fangsiao.
Ethics in Octopus Aquaculture
The intelligence and sensitivity of octopuses raise serious ethical concerns about their captivity farming. Living conditions on farms, loneliness, and stress experienced by these animals are subjects of debate. Sacrifice practices are also controversial, as there is no universally accepted method considered humane. This has led some international certifiers to exclude octopus farming from their standards.
In this context, Gestal et al. (2023) have identified specific octopus welfare markers defined as Operational Welfare Indicators (OWI) to measure and integrate them into octopus aquaculture good practice monitoring plans, which can help alleviate ethical concerns. Similarly, Sequeiro (2023) determined that farmed and wild octopuses generally present similar microbiota diversity and abundance, supporting the notion that rearing conditions in aquaculture are similar to those in nature.
Conclusions
Technological advancements and the prospects of implementing the first commercial octopus farms have fueled discussions about the ethical viability of this aquaculture practice. However, the aquaculture industry has been responding by establishing animal welfare indicators.
Although “bottlenecks” (larval survival, artificial diet, etc.) persist for octopus farming at a commercial level, scientific advancements suggest that this activity could become a reality in the coming years.
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