Cobia Fish: an Alternative for Tropical Marine Aquaculture

The cobia fish (Rachycentron canadum), also known as lemonfish or bijupirá (Brazil), is a large migratory marine fish that has captivated the attention of seafood enthusiasts worldwide. Renowned for its succulent white flesh and thrilling fight, the cobia has earned a reputation as a culinary gem and a prized catch among sport fishermen. Native to warm waters around the globe, the cobia typically inhabits coastal areas and ventures into deeper waters during warmer months.

Moreover, cobia is a fish with easy reproduction, robustness, and rapid growth, characteristics that make it an ideal species with great potential for development through aquaculture. Cobia farming was established in the early 1990s (Benetti et al., 2021), and currently, it is cultivated in several countries, with the main producers being China, Panama, Taiwan, and Vietnam.

Taxonomy of the Cobia Fish

The scientific name of the cobia is Rachycentron canadum (Linnaeus, 1766), derived from two Greek words: rachis (spine) and kentron (sharp point), referring to the 7-9 extremely sharp and retractable dorsal spines. This species is the sole representative of the Rachycentridae family and the order Perciformes. The taxonomic classification is:

Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Carangiformes
Family: Rachycentridae
Genus: Rachycentron
Species: Rachycentron canadum (Linnaeus, 1766)
Common name in Spanish: Cobia, pez limón
Common name in English: Cobia, Crabeater, Sergeantfish, Ling, Cabio, Cubby yew, Lemonfish, black kingfish, black salmon, prodigal son, codfish, and black bonito.

Biological Characteristics of the Cobia fish

The cobia fish is a fast-growing fish that can reach lengths of up to 2 meters (6.5 feet) and weigh up to 68 kilograms (150 pounds). These fish can live up to 12 years.

Cobia fish have an elongated fusiform body and are dark brown with a single dorsal fin; while juveniles have a distinct coloration with alternating white and black horizontal stripes and bronze, orange, and green spots.

These fish have large pectoral fins typically held horizontally, which may help the fish achieve a shark-like profile. The first dorsal fin has six to nine independent, short, robust, and sharp spines. The fish lacks a swim bladder.

Where is the Cobia Fish Caught?: Global Distribution

The cobia is found in tropical and temperate waters worldwide, inhabiting coastal areas and venturing into deeper offshore waters during warmer months. Its global distribution extends across the Atlantic, Pacific, and Indian Oceans, with notable populations in:

• Western Atlantic: From Canada to Argentina, including the Caribbean Sea and the Gulf of Mexico

• Eastern Atlantic: From Morocco to South Africa, including the Mediterranean Sea

• Western Pacific: From Japan to Australia

Cobia can be found near structures in the water (buoys, debris, shipwrecks, and artificial reefs) or around large animals (sharks, turtles, and rays). Adult cobia travel alone or in small groups.

Feeding of Cobia Fish

Cobia are strong and aggressive predators that primarily feed on crustaceans but also consume fish and squid in their natural habitat.

In aquaculture conditions, feeds have been designed to meet the nutritional needs of cobia, including plant-based protein; however, Benetti et al. (2021) highlight that one of the major challenges remains the development of practical commercial feeds that are ecologically and economically efficient, as feed conversion ratios remain high, ranging between 2.0 and 3.0:1.

Feeding Frequency

Zhang et al. (2021) studied the feeding habits of cobia larvae and juveniles and concluded the following:

• Early Feeding Ability: Cobia fish larvae show good feeding capability, starting to feed as early as 3 days after hatching with a 70% feeding incidence. This increases to 100% in juveniles.

• Relationship Between Feeding and Growth: Food consumption increases with body mass in both larvae and juveniles, following a predictable pattern described by a binomial equation.

• Digestive Efficiency: Cobia fish larvae and juveniles have a relatively fast digestive system, with intestinal fullness fluctuating between 0.1% and 1.0%, and satiety occurring within 1 hour. Digestion time ranges from 0.5 to 3 hours, depending on age and prey type.

• Feeding Rate: The study provides daily feeding rates for cobia larvae and juveniles (ranging from 24.85% to 61.38% of body weight), which can be used as a reference for feeding practices in aquaculture.

• Feeding Rhythm: Cobia fish larvae and juveniles exhibit a circadian feeding pattern, being more active during the day.

On the other hand, Motta et al. (2023) observed that a feeding frequency of eight meals per day, along with an ad libitum feeding regimen, is most suitable during the juvenile phase of cobia.

Nutritional Requirements of the cobia fish

The nutritional requirements of cobia fish have been widely studied. The following table summarizes the main findings:

Table: Nutritional requirements of the cobia fish.

Proteins

Pham et al. (2020) report that narrow-leaf lupin seed meal can replace up to 20% (200 g/kg) of fish meal protein in diets without negative effects on the growth of juvenile cobia. Wang et al. (2024) recommend replacing up to 20-30% of fish meal protein with cottonseed meal (CSM) extracted with methanol, supplemented with L-lysine and DL-methionine, for juvenile cobia diets.

Carbohydrates

Cobia appears to utilize carbohydrates more efficiently than lipids for energy, based on better growth performance and lower feed conversion ratios with higher carbohydrate levels in the diet. A lipid-to-carbohydrate ratio of 0.47 results in the best overall growth and survival rate in juvenile cobia fish (Zhao et al., 2020).

Wang et al. (2022) report that diets for juvenile cobia ish with higher dietary carbohydrate levels (up to 22.5%) showed greater final body weight, specific growth rate, feed efficiency, and protein efficiency ratio; however, this also led to higher fat deposition and potentially larger livers and digestive organs.

Probiotics

Garrido-Pereira et al. (2014) recommend using Bacillus spp. as a probiotic in cobia fish larval rearing within recirculating aquaculture systems.

Reinoso et al. (2023) suggest that the yeast strains Candida haemuloni C27 and Debaryomyces hansenii C10 and C28 could be potential probiotic candidates and should be evaluated in cobia fish larvae.

Cobia Reproduction

Male cobia fish reach sexual maturity at around 2 years of age (approximately 52 cm in length), while females mature at 3 years (69.6 cm in length) and can spawn multiple times a year. Cobia fish spawn in open water, releasing their eggs and sperm into the water, making them pelagic spawners.

Researchers have revealed a specific formula for optimal spawning:

• Year-round Spawning: By manipulating water temperature and light cycles, researchers can induce cobia to spawn consistently throughout the year, ensuring a constant supply of eggs.

• Temperature: Optimal water temperature is between 27 and 30°C.

• Advanced Broodstock Management: A specialized diet rich in sardines, squid, shrimp, and specific supplements keeps cobia broodstock healthy and promotes successful egg production.

• Stress-free Spawning Environment: Maintaining an adequate ratio of females to males and providing “cleaning stations” with neon gobies minimizes stress in broodstock, leading to higher quality eggs.

• Sex Ratio: Maintaining a 2:1 ratio of females to males reduces competition among males.

Spawning

The natural spawning season for cobia fish is from April to September, and they can have up to 20 spawnings in a breeding season, with intervals of 1 to 2 weeks. However, in captivity, spontaneous spawning can occur year-round when the temperature is between 23-27°C. Females release between 375,000 and 2 million eggs each time they spawn, with eggs measuring 1.2 mm in diameter.

Hatching and Larval Development of Cobia

Fertilized cobia fish eggs float, making them easy to collect from the surface of the tank. The eggs have an average diameter of 1.2 – 1.3 mm and an incubation period of approximately 21 – 37 hours at temperatures of 31 – 22°C. The newly hatched larvae measure approximately 3 mm.

Kuang et al. (2021) report that under water temperature conditions of 27°C, salinity of 29 ppm, and pH 8.3, cobia eggs hatched approximately 26.5 hours after fertilization, and newly hatched cobia larvae have a total length of approximately 3.25 mm and depend on their yolk sac for initial nutrition.

After three days, the yolk sac is completely consumed, and the larvae require an exogenous food supply. Over the next few weeks, the larvae consume rotifers, artemia, and copepods until they eventually accept dry feed at approximately 20 days post-hatch.

Cobia fry can be raised in outdoor ponds at the hatchery. Juveniles reach 1 g in five to six weeks. Zhang et al. (2021) report an impressive average daily growth rate (35.90% in length and 56.97% in weight) for cobia larvae and juveniles, while Kuang et al. (2021) detail that cobia larvae begin the transition to juveniles around 14 days post-hatch, with fin development as a key marker. At 22 days post-hatch, juveniles reach a length of approximately 41 mm and begin to develop scales on the caudal peduncle. By 46 days post-hatch, juveniles reach a length of approximately 117 mm, their bodies are covered in scales, and their general appearance closely resembles adult cobia.

Cobia Aquaculture

Cobia fish is an important fish for the marine aquaculture industry in tropical and subtropical regions worldwide. According to Benetti et al. (2021), this species exhibits an extraordinary growth rate and can reach between 4 and 8 kg in 1 year, both in recirculating systems and in sea cages, with females growing almost twice as fast and being larger than males. In this regard, a strategy to boost marine aquaculture of cobia is the rearing of monosex female populations; González and Bermúdez (2021) investigated sexual dimorphism and determined that the difference between sexes can be seen in smaller heads and a greater space, as well as a narrower angle between the eyes and the pectoral fin for females.

Benetti et al. (2021) report that despite continuous progress in maturation, spawning, larval rearing, fingerling production, nutrition, health management, genetics, and grow-out technology, the overall production of cobia fish aquaculture worldwide has been slow in the last decade.

Transport of Juvenile Cobia fish

In mariculture, an important activity is the transfer of larvae and juveniles from hatcheries to production centers. Jayakumar et al. (2023) determined that cobia fish juveniles with an average length and weight of 48±12 mm and 3.0±1.0 g, respectively, can be transported for 48 hours at 25°C with 100% survival at a packing density of 2.5 juveniles per liter (L) (7.5± 2.5 g/l).

Cobia Processing

Lu et al. (2022) report the use of calcined oyster shell powder to improve the shelf life of cobia fillets; the compound inhibited acid-producing microorganisms and aerobic bacteria by regulating the pH during refrigerated storage of the fillets.

Tran et al. (2021) evaluated the effects of guava leaf (Psidium guajava) extract at a concentration of 0.03% (w/v) on the quality of cobia (Rachycentron canadum) fillets during ice storage and concluded that the fish fillets showed significantly higher sensory properties, lower peroxide value (PV), and thiobarbituric acid reactive substances (TBAR).

Diseases

Diseases such as Photobacterium, Amyloodinium ocellatus, and Brooklynella hostilis continue to affect cobia aquaculture production worldwide (Benetti et al., 2021).

Warm Water Lactococcosis

Rao et al. (2022) reported that Lactococcus garvieae, which causes “warm water lactococcosis,” can lead to disease outbreaks in cobia cultured in cages. Diseased fish present clinical signs such as bleeding eyes, darkened back, and enlargement of the liver and spleen.

Conclusion

Cobia aquaculture has been growing slowly despite the species’ potential for the development of tropical marine aquaculture. However, there are some aspects to be resolved in cobia fish farming, such as diseases and the design of diets that meet the nutritional requirements of cobia.

References

Benetti, D. D., Suarez, J., Camperio, J., Hoenig, R. H., Tudela, C. E., Daugherty, Z., McGuigan, C. J., Mathur, S., Anchieta, L., Buchalla, Y., Alarcón, J., Marchetti, D., Fiorentino, J., Buchanan, J., Artiles, A., & Stieglitz, J. D. (2021). A review on cobia, Rachycentron canadum, aquaculture. Journal of the World Aquaculture Society, 52(3), 691-709. https://doi.org/10.1111/jwas.12810

Chi, S., He, Y., Zhu, Y., Tan, B., Dong, X., Yang, Q., Liu, H., & Zhang, S. (2020). Dietary methionine affects growth and the expression of key genes involved in hepatic lipogenesis and glucose metabolism in cobia (Rachycentron canadum). Aquaculture Nutrition, 26(1), 123-133. https://doi.org/10.1111/anu.13006

Garrido-Pereira M. Angélica, Schwarz Michael, Delbos Brendan, Rodrigues Ricardo V, Romano Luis, Sampaio Luís. Efectos probióticos sobre las larvas de cobia Rachycentron canadum criadas en un sistema de recirculación de agua. Lat. Am. J. Aquat. Res. [revista en la Internet]. 2014 Nov [citado 2014 Dic 28] ; 42( 5 ): 1169-1174.

González, R., & Bermúdez Tobón, A. (2021). Determinación de dimorfismo sexual usando técnicas morfométricas en Rachycentron canadum (Perciformes: Rachycentridae) cultivados en cautiverio.

Huang, J., Li, R., Xie, R., Chen, Y., Zhang, J., Amenyogbe, E., & Chen, G. (2022). Changes in amino acid and fatty acid composition during early development in cobia (Rachycentron canadum). Frontiers in Marine Science, 9, 995616. https://doi.org/10.3389/fmars.2022.995616

Jayakumar, G Tamilmani, M Sakthivel, P Rameshkumar, K K Anikuttan, M Sankar, B Johnson, G H Rao, T Thomas, N Krishnaveni, N Moulitharan, A A Mercy & A K A Nazar. 2023. Optimization of packing and transportation of the fingerlings of the cobia (Rachycentron canadum) and the silver pompano (Trachinotus blochii). Indian Journal of Geo Marine Sciences Vol. 52 (04), April 2023, pp. 198-204 DOI: 10.56042/ijms.v52i04.7661

KUANG Jiehua, CHEN Gang, MA Qian, HUANG Jiansheng, ZHANG Jiandong, SHI Gang, WANG Zhongliang, TANG Baogui. Embryonic development and morphological characteristics of larvae and juveniles of cobia (Rachycentron canadum)[J]. Journal of fisheries of china, 2021, 45(11): 1814-1824. DOI: 10.11964/jfc.20200812389

Lu, C., Chan, J., Chen, J., Mulio, A. T., Wang, C. R., Huang, H., & Li, H. (2022). Using calcined oyster shell powder as a natural preservative for extending the quality of black king fish (Rachycentron canadum) fillets. Journal of Food Processing and Preservation, 46(12), e17262. https://doi.org/10.1111/jfpp.17262

Motta, J. H. S., Souza, A. B., Polese, M. F., Glória, L. S., Bosisio, F., Mendonça, P. P., & Vidal Jr, M. V. (2023). The effect of feeding frequency on the performance of juvenile cobia (Rachycentron canadum). Arquivo Brasileiro de Medicina Veterinária e Zootecnia, 75, 759-764.

Pham, H. D., Siddik, M. A., Fotedar, R., Chaklader, M. R., Foysal, M. J., Nguyen, C. M., & Munilkumar, S. (2020). Substituting fishmeal with lupin Lupinus angustifolius kernel meal in the diets of cobia Rachycentron canadum: Effects on growth performance, nutrient utilization, haemato-physiological response, and intestinal health. Animal Feed Science and Technology, 267, 114556. https://doi.org/10.1016/j.anifeedsci.2020.114556

Rao, S., Pham, T. H., Poudyal, S., Cheng, W., Nazareth, S. C., Wang, C., & Chen, C. (2022). First report on genetic characterization, cell-surface properties and pathogenicity of Lactococcus garvieae, emerging pathogen isolated from cage-cultured cobia (Rachycentron canadum). Transboundary and Emerging Diseases, 69(3), 1197-1211. https://doi.org/10.1111/tbed.14083

Reinoso, S., Gutiérrez, M. S., Sonnenholzner, S., Mardones, C., & Navarrete, P. (2023). Selection of Autochthonous Yeasts Isolated from the Intestinal Tracts of Cobia Fish (Rachycentron canadum) with Probiotic Potential. Journal of Fungi, 9(2), 274. https://doi.org/10.3390/jof9020274

Tran, M. P., Huynh, T. K. D., Nguyen, L. A. D., Nguyen, T. N. H., Nguyen, Q. T., & Tomoaki, H. (2021). The effect of guava (Psidium guajava) leaf extract on the quality of cobia (Rachycentron canadum) fillets during ice storage. CTU Journal of Innovation and Sustainable Development , 13(Special issue: Aquaculture and Fisheries), 52-63. https://doi.org/10.22144/ctu.jen.2021.017

Wang, J., Lan, K., Wu, G., Wang, Y., Zhou, C., Lin, H., & Ma, Z. (2022). Effect of dietary carbohydrate level on growth, feed utilization, energy retention, body composition, and digestive and metabolic enzyme activities of juvenile cobia, Rachycentron canadum. Aquaculture Reports, 25, 101211. https://doi.org/10.1016/j.aqrep.2022.101211

Wang, J., Wu, G., Gatlin, D. M., Lan, K., Wang, Y., Zhou, C., & Ma, Z. (2024). Dietary Fishmeal Replacement by Methanol-Extracted Cottonseed Meal with Amino Acid Supplementation for Juvenile Cobia Rachycentron canadum. Journal of Marine Science and Engineering, 12(2), 235. https://doi.org/10.3390/jmse12020235

Zhang, J., Amenyogbe, E., Yang, E., Wang, Z., Chen, G., & Huang, J. (2021). Feeding habits and growth characteristics of cobia (Rachycentron canadum) larval and juvenile stages. Aquaculture, 539, 736612. https://doi.org/10.1016/j.aquaculture.2021.736612

Zhao, H., Cao, J., Chen, X., Wang, G., Hu, J., & Chen, B. (2020). Effects of dietary lipid-to-carbohydrate ratio on growth and carbohydrate metabolism in juvenile cobia (Rachycentron canadum). Animal Nutrition, 6(1), 80-84. https://doi.org/10.1016/j.aninu.2019.11.010