Identity
Seriola dumerili Risso, 1810 [Carangidae]
FAO Names: En – Greater amberjack, Fr – Sériole couronnée, Es – Pez de limón
Biological features The morphology of Seriola dumerili changes considerably from juveniles to adults. Body elongated, fusiform, moderate height, somewhat compressed laterally and covered with small cycloid scales. The total number of gill rakers decreases with size, from 15–22 at 2–7 cm in length, to 11–19 at sizes greater than 20 cm in length. Two dorsal fins, the first with seven hard spines and the second with one hard spine and multiple soft rays (29–35). Colour yellow-green in juveniles and blue-olive laterally and silver ventrally in adults. Black lateral band from eye to anterior base of dorsal fin, excluding the neck. The juveniles show 5 vertical, dark body bands and a sixth band at the end of the caudal peduncle.
Images gallery
Broodstock greater amberjack samplingBroodstock greater amberjack sampling Fertilized eggsFertilized eggs
Profile
Historical background
The greater amberjack is an important commercial fish, as well as a popular game species, in Europe and North America. It has been an important basis for many coastal communities where it is highly appreciated because of the high quality meat and commercial value. The total worldwide catch of Seriola dumerili has increased tenfold since 1990, reaching 3 287 tonnes in 2009 , of which about 17 percent was taken by United State of America and around 80 percent was fished in the Mediterranean and Black Sea by European (Greece, Italy and Spain), African (Algeria and Tunisia) and Asiatic countries (Cyprus, Israel and Syria).
Japan is the largest producer of greater amberjack (called Kanpachi) where its production has increased quickly in the last decades. Although there is a lack of data on Japan’s aquaculture production, this accounted about 30 percent (46 000 tonnes) of all Japanese amberjack (Seriola quinqueradiata) production in 2002, and reached about 72 000 tonnes as estimated by World Wildlife Fund (WWF) in 2009 . This increase has been a result of its better flesh quality, higher market prices and demand compared to other Seriola species. Moreover, the growth of greater amberjack is faster and it has a better feed conversion rate than Japanese amberjack when cultured at temperatures above 17 ºC.
The farming of S. dumerili has a long history in the Mediterranean. In the 1980s aquaculture of this species started with the fattening (grow-out) of wild caught juveniles (starting at about 100 g) using fish aggregating devices and subsequently cultured in tanks and cages in Italy and Spain. These experiments were able to produce the first commercial production and established the basis for the development of the greater amberjack culture. However, following pathological difficulties with disease and a lack in reliable seed supply the farming activities stopped. As with many other marine species, juvenile production has been the major biological bottleneck. However, recent progress made in reproduction techniques (natural and hormonal induced spawning) has allowed a number of advances in hatchery production of researchers to juveniles.
These advances have encouraged investment in greater amberjack aquaculture enterprises, both in hatcheries and ongrowing farms. In recent years, S. dumerili has garnered significant interest in the Mediterranean, and is now considered as one of the most important species to diversify the commercial production of fish in countries around the Mediterranean and in North and South America. Malta, Spain, Greece, Italy, Croatia and Turkey have ongoing research and development programmes to further develop aquaculture of this species. Malta already has a small production (estimated at 500 tonnes) coming from the small research hatchery in collaboration with a local fish farming company. Saudi Arabia’s National Prawn Company is currently developing commercial production of new/emerging finfish species, with a great potential for the expansion. Moreover, a 7th Framework EU funded research project DIVERSIFY has identified a number of new/emerging finfish species, with a great potential for the expansion of the EU aquaculture industry, one of which is S. dumerili.
Main producer countries
In addition to the countries indicated in the map, referred to a pool of “amberjacks” species (Japanese amberjack -plus- grater amberjack -plus- amberjacks unidentified), production activities of greater amberjack have also been reported in several Mediterranean countries (Malta, Greece, Spain and Italy), the Near East (Saudi Arabia) and the Americas (United States of America and Mexico).
Main producer countries of Seriola dumerili (FAO Fishery Statistics, 2013)
Habitat and biology
S. dumerili has a wide distribution in tropical and subtropical (45°N–28°S) areas of the Atlantic and Indo-Pacific Oceans. It is common in the Mediterranean Sea, and is also present from Senegal to the Gulf of Biscay, and rare along the coast of the United Kingdom. Greater amberjack can be found from Nova Scotia to Brazil in the western Atlantic, and South Africa, Persian Gulf, Australia, Japan and Hawaii in the Pacific.
The greater amberjack is a pelagic and epibenthic fish that inhabits both nearshore reef habitats as well as the open sea, usually found between 18 and 360 m depth. Juveniles exhibit a strong aggregation behavior around floating objects.
It is an opportunistic species that feeds on a wide range of prey which varies during the life history. Young individuals less than 8 cm in length feed mainly on zooplankton. When they are between 8 and 12 cm in length they enter a transitional phase, progressively increasing their predation on larger benthic and nektonic organisms. Once greater than 12 cm in length, they begin to feed exclusively nectobenthics, finally changing to a piscivorous diet by the time they reach 20 cm, when they leave the open sea to approach the coast. Adults feed on pelagic fish and cephalopods.
S. dumerili grow rapidly, reaching a maximum length of 180–190 cm and 80 kg of weight. In the Mediterranean, fish born in the spring will reach about 800 g and 40 cm of weight and length, respectively, one year later, tripling the length at four years of age (93–106 cm). In the Atlantic stock, the growth rates vary between 17 and 24 cm per year in the young and 0.7 cm per year in older fish.
This species is gonochoric, meaning separate males and females, and there is no sexual dimorphism. Sexual differentiation occurs at 24–26 cm in length (4–5 month of age), and reach sexual maturity at 4 and 5 years of age (about 109 and 113 cm in length) in males and females, respectively, in the Mediterranean. In the western Atlantic stock, males and females mature at 3 and 4 years of age (80 and 83 cm in length), respectively.
The spawning period varies among different areas. In the Mediterranean, the adults spawn from May to July. In the western Atlantic they spawn from March to May, in the eastern Atlantic from April to September, and in the Pacific from February to June. The females have a synchronic ovary with at least two groups of oocyte development. It is a multiple spawner, releasing pelagic eggs several times during the same spawning period. The ratio of females to males is 1:1 in the Mediterranean stock, and 1.2:1 in the Atlantic.
Egg size is around 1.1 mm and fecundity is accordingly high, though dependent on the specific stock (15–50 million eggs per female in the Atlantic, 4–9 million in the Mediterranean and 1–4 million in the Pacific).
Production
Production cycle
Production cycle of Seriola dumerili
Production systems
Seed supply Although the majority of greater amberjack aquaculture production currently comes from Japan, most of the detailed information about reproduction, larval rearing and grow-out methods are reported from other producer countries. This is because Japanese production has been based largely on wild juveniles and imported juveniles from neighboring countries because the number of hatchery produced juveniles is not sufficient to meet the demand, and they are of poorer quality and show deformities and low growth. Therefore, little work has been carried out on the hatchery rearing in Japan and thus there are no established methods of juvenile production.
However, juvenile production has been studied more intensely in Europe in recent years, and juvenile production is increasing in Spain, Greece and Malta. In the European, Asian and American countries the hatcheries of greater amberjack keep their own broodstock in tanks or cages, fed with bait fish and supplemented with vitamins, to obtain fertilized eggs. Thus, these countries have developed larval rearing techniques to ensure adequate supply of juveniles.
In Japan the seed is caught from the wild but there are increasing hatcheries producing juveniles for grow-out in other Asian countries. Greater amberjack juveniles are being produced on a small scale in Europe and there is increasing interest from a number of countries, namely Spain, Greece, Malta and Italy.
The wild juveniles farmed in Japan are mostly caught in nearby waters, but some are captured and imported from other Asian countries. The number of juveniles imported from China and Viet Nam was about 20 million in 2000.
Hatchery production
S. dumerili spawn from spring to early fall, although this spawning period varies with latitude. The females release eggs with a periodicity higher that other species (about once weekly). Natural spawns have been observed in captivity. However, reproductive failure often occurs in captivity, and hormonal therapies to induce spawning are applied to females and males maintained in tanks or cages. The fertilized eggs float and are spherical (about 1 mm in diameter and 1 oil droplet of 0.2 mm of diameter) and can be collected by a mesh net. The number of eggs obtained varies between 4 000 and 30 000 eggs per kg in induced spawns and approximately 100 000 eggs per kg in natural spawning. These fertilized eggs are floated in incubators (100–500 eggs per litre) and hatch within 30–45 hours. The incubator tanks are supplied continuously with filtered seawater and gentle aeration to prevent clogging of the outlet sieves.
Once or twice a day the seawater circulation and aeration are stopped so that any non-floating or dead eggs are removed to maintain optimal water conditions. The newly hatched larvae (about 3.5 mm in length) have a yolk-sac (0.1 mm3 of volume) lasting for about 1 week, though feeding is started upon mouth-opening before the yolk-sac is exhausted. For best results, newly hatched larvae are reared in large, circular tanks with a volume greater than 20 m3 at low densities (5–10 larvae per litre). However, higher densities and lower volumes have been tested but this technology is not fully developed. Over 80 000 juveniles were produced in Malta from ten 2.5 m3 (total volume 25 m3) circular fiberglass tanks in 2012 with a stocking density of 60 larvae per litre.
Normally the larvae are supplied with live feed. Enriched rotifers, Brachionus plicatilis, are used during the first three to four weeks, often in combination with algae (either freshly produced or concentrated). Artemia nauplii are added at 12–16 days post hatching (dph) and Artemia metanauplii from 20–25 to 40–50 dph. At 25–30 dph formulated feed is supplied and the size particles are increased according to the age and size of larvae. The growth is enhanced by raising the rearing temperature above 22 ºC, and the water flow is increased gradually.
During larval rearing there are often two mortality spikes. The first is related to the start of feeding when the larvae open their mouths and the eyes become pigmented between 3–4 dph. The swim bladder inflation occurs at 5–9 dph. This mortality peak can be a result of inappropriate prey size or inadequate conditions for first feeding. The second mortality event occurs at 20 dph, coinciding with the onset of aggressive behavior or cannibalism. Aggregation against individuals smaller as well as the beginning of aggregation behavior occurs before 20 dph but this is also dependent on the rearing conditions, especially water temperature. The growth rate, lower during the first 20 days, increases significantly thereafter. However, larval survival rates remain low, so the development of mass culture techniques is necessary. Larvae reach 4 cm in length and 0.5 g at 40 days of age with a survivorship of 3.5 percent.
Nursery
The production systems of greater amberjack in Japan are similar to those used for S. quinqueradiata and consist of three well differentiated stages: collection of fry (2.5–5 cm) that are dewormed using freshwater baths and classified by size to prevent cannibalism, rearing fry to juveniles (5–15 cm), when they are graded by size again, and grow-out of juveniles to commercial size (> 40 cm). Most of the farming systems use floating square structures in coastal protected regions. It is important to use high quality feed and maintain correct stocking density to maintain high survival and growth.
In the Mediterranean, with regards to the capture based aquaculture, the juveniles obtained can be stocked in sea cages at about 4 cm, but are very often kept in tanks until they reach a larger size before transfer to the ongrowing facility, depending on the country. Grow-out operations in cages appear less problematic, although fish are prone to infestations of monogenean parasites, while in tanks the fish are prone to cryptocaryonosis.
Ongrowing techniques
Under standard farming conditions greater amberjack show rapid growth in sea cage facilities. However, stocking density requires special attention because it varies with the type of facility, grow-out stage of the fish and environmental conditions at each aquaculture site. Adequate mesh size improves the water exchange rates and dissolved oxygen, and the stocking density will be a result of these combined variables together with water temperature. Growth reduction in greater amberjack occurs at temperatures lower than 21 ºC and dramatically below 17 °C. In Japan, the fish cultured under these conditions reach 6.0 kg after 2.5 years. In the Mediterranean, ongrowing at 20–22 °C yields 1 kg after 1 year, 3 kg after 2 years and 6 kg after 3 years with 90 percent survival. In addition to these positive growth results, greater amberjack show good feed conversion.
Feed supply
During the grow-out of greater amberjack, optimal environmental culture conditions and proper feeding are very important for growth, health and survival. Wild caught juveniles and early aquaculture used trash fish as feed, but in 1990s producers developed the wet, semi-moist and dry feeds. Although some significant advances have been seen in formulated feed related to nutrient and energy requirements in the last years, juveniles are fed with extruded feeds developed for sparids and/or turbot in Mediterranean and raw fish for larger amberjacks in Japan and when water temperature decreases. In the Mediterranean region, only broodstock fish are fed on raw fish, supplemented with vitamin premix and cephalopods near the spawning period. As a result, food conversion rates vary considerably between grow-out methods developed in Japan and Mediterranean countries. Greater amberjack need a high protein content (greater than 53 percent in young and greater than 40 percent in adults), and different diets between summer and winter. The fat content should be greater than 20 percent with high highly unsaturated fatty acids (HUFA) levels and high caloric content and the feed. Feeds are based mainly on marine protein (fishmeal), although plant proteins and oil can replace some of the marine ingredients, use alternative sources of protein and lipid to reduce expense.
Feeding strategies, such as frequency and ration, also affect the profitability of such operations. The feeding frequency ranges from more than 5 times a day to 3 times a week, depending on body weight, growing stage and seawater temperature. Generally, a feeding regime slightly lower than satiety (80 percent) shows best results.
Under farming conditions some males born in captivity will be sexually mature at three years of age and between 4 and 10 kg, while some naturally spawned eggs (though scarce and non-fertilized) have been obtained from females after four years. However, there is currently no significant closed-cycle production of greater amberjack anywhere in the world.
Harvesting techniques
The market size for greater amberjack is usually 3–5 kg and is achieved 24–36 months after hatching. The size at harvest and the length of the grow-out period vary according to the mean annual water temperature and also on the preferred market size in relation with flesh quality.
In the Mediterranean countries the grow-out facility of greater amberjack uses similar cages to those used for other marine finfish and thus the harvest techniques are quite similar. In order to maintain high product quality, fish are starved for several days before harvesting so as to evacuate the stomach and intestinal tract and thereby delay the deterioration in meat quality. As for other species, the fish are crowded into a relatively small area so that the animals can be harvested with dipnets, graded, and placed into a chilled container.
Handling and processing
Farmed greater amberjack is used mainly for sushi and sashimi in Japan and for immediate consumption in Europe. Consequently they are exclusively sold fresh, though some is sold frozen at a higher price achieved on the market. The flesh quality decreases significantly after a few days, depending on rearing conditions, harvest and post-harvest treatments. To maintain their excellent meat quality, the fish are slaughtered instantly after harvest, bled and chilled before whole fish or fillets are packed in ice. It is possible that new value-added products can be developed in the future.
Production costs
Production costs vary considerably, depending on the culture system, geographical area and the level of technology applied. Information for this species is minimal due to the lack of closed cycle production, but as in other cultured finfish, fry and feed represents the major portions of the total production costs. Inadequate culture conditions (mainly low temperature) can increase the length of the production cycle and hence the production costs. Negative incidences of diseases can also contribute to the relatively high production costs.
In Spain, hatchery produced seed costs around 3.3 USD/fish and the feed costs 2.3 USD per kg. Because the feeding pellet is the same used for other finfish cultured species and it is about 0.8 € per kg (0.88 USD per kg). Data provided are based on 2015 data assessment.
Given that the greater amberjack farming is relatively new it is likely that production costs will decrease significantly within a few years once fry production and diets have been be improved.
Diseases and control measures
Both farmed and wild S dumerili are susceptible to a variety of diseases caused by viruses, bacteria and parasites. These diseases have significant effects on production, sustainability and economic profitability. Although there are diseases caused by viruses and bacteria, the main mass mortalities are a result of certain parasites. Several disinfectants and chemotherapeutic products, as well as diverse treatments protocols, have been used with varying degrees of success. Diseases normally break out under suboptimal culture conditions, after handling or in periods with suboptimal environmental conditions.
The major disease problems affecting greater amberjack are included in the table below.
In some cases antibiotics and other pharmaceuticals have been used in treatment but their inclusion in this table does not imply an FAO recommendation.
DISEASE AGENT TYPE SYNDROME MEASURES
Iridovirus infection Viral Splenic Virus Virus Abnormally hypertrophic cells in spleen, kidney, heart, intestine and gill Exclude potentially infected fish
Viral Nervous Necrosis Virus Lethargy; pale coloration and loss of appetite Exclude potentially infected fish
Vibriosis Vibrio anguillarum Bacteria Reddening of fins and skin; skin ulceration; muscular necrosis; haemorrhaging; lethargy Oral administration of sulfa drugs or antibiotics; limiting densities in cages; daily surveillance; good quality feed
Pseudotuberculosis Photobacterium damselae subsp. piscicida Bacteria White nodes on spleen and kidney Oral administration of antibiotics; administer prophylactic doses
Streptococcosis Streptococcus sp. Bacteria Bleeding inside the gills; sores on the fins; ulcers on the base of the tail Oral administration of antibiotics; limiting densities in cages; good quality feed; not over-feeding; removal of infected fish
Epitheliocystis Chlamydia-related organisms Reduced growth; branchial; respiratory distress Major pathological problem at early stages; minor problems in juveniles and adults; hygiene and disinfection of the culture environment is recommended
Fungal infection Ichthyophonus hoferi Fungi Affects circulation system and other organs of the fish; clinical signs seen only when infection is well established; colour change; deformity; emaciation; loss of balance No effective treatment, although a combination of oral and in-water medication with 2-phenoxyethanol has been recommended; prompt removal of infected fish; stop feeding raw fish or raw fish based products
Cryptocaryonosis; marine white spot Cryptocaryon irritans External protozoan ciliate White foci visible on skin; interconnected larger masses of whitish spots; darkened body; lethargy Prolonged copper immersion; freshwater dips; formalin bath; salinity reduced to 20 ‰; or less; decrease system temperature to < 20 ºC
Kudoosis amami Kudoa amamiensis Myxosporidian parasite Affecting the muscle; accelerate degeneration and post mortem myoliquefaction; effects on product quality No treatment available
Beko disease Microsporidium seriolae Microsporidian parasite Affecting the trunk muscles; after cyst’s degeneration the neighboring muscle tissue shows necrosis; concave body surface Vaccination; oral antibiotic treatment
Flatworm infection Benedenia seriolae; Neobenedenia melleni (syn. Girellae) Trematode Attaches to skin; feeding on mucus and epithelial cells; secretion of viscous fluid; darkened body; erratic swimming; lethargy; loss of appetite; itching; rubbing against culture surface site; develop sores and skin peels; exposed flesh Prevented by dipping in freshwater, periodic baths with hydrogen peroxide (500 ppm); praziquantel or formaldehyde has been recommended; handling material disinfection is recommended
Zeuxaptosis; Flatworm infection Zeuxapta seriolae Trematode Attaches to one or two lamellae of the gills by the haptor hooks feeding on blood which may cause a fatal anaemia; gill mucus secretion; normal skin colour and weight; slow swimming Formaldehyde baths (300 ppm for 1 hour) every 15–30 days seem effective. Baths (alone or combined) with 300 ppm hydrogen peroxide; fresh water; copper sulphate; clove oil; praziquantel (or oral administration) has been recommended; Handling material disinfection is recommended
Sanguinicolosis Paradeontacylix sp. Trematode Affects circulation system and other organs of the fish; accumulation of eggs in the gills blood vessels; multiple lesions and microhaemorrhages; anaemia No effective treatment; regular cleaning and disinfection of nets and handling materials could reduce the risk of the parasite transmission
Statistics
Production statistics
Of the total production reported to FAO, Spain was the only producer from 1992 to 1997, while in 2006 and 2007 Taiwan Province of China was the largest producer. Significant greater amberjack production occurs in Japan, but the reported statistics include all species of Seriola together. Even so, it is estimated that the Japanese production of greater amberjack is more than 30 percent of the total Seriola species cultured. The total value of the global production of this species was 808 051 USD in 2007.
Market and trade
Greater amberjack is a valuable food fish that sells well in the traditional fish markets as well as having potential for value-added products. Farmed fish can be sold at different sizes (whole or slices) depending on the country. The preference in sizes affects market prices. In Malta small sizes reach 15–20 USD per kg while larger fish fetch lower market prices, typically 10-15 USD per kg, because large fish are only suitable for steaks. However, prices in Italy and Spain for the largest fish are similar or even higher the smaller fish in Malta.
Hong Kong prices of cultured greater amberjack are slightly lower than the wild fish, but range from 10 to 20 USD per kg, while in Japan the price is higher (20–30 USD per kg) than other cultured Seriola species because of the better texture of its flesh which is firmer and less buttery, and can sometimes reach up to 50 USD per kg.
The price differences in Europe according to the size will vary with the marketing strategy in the future. For now, whilst the production cost of the fry is very high, and because the culture technology is still being developed and refined, this benefit could be utilized. The optimum strategy may be to utilize the fast growth of the fish and sell at a larger size for a wider variety of value added products. Greater amberjack has an existing reputation as a quality ingredient for sushi and sashimi and is very adaptable to a wide variety of prepared products including Asian or American style marinated fillets or pieces. It would therefore be advisable to develop an active marketing strategy alongside any development of production capacity in order to exploit the full potential of this species.
Status and trends
Practices for the ongrowing methods for greater amberjack in the south of Japan is very well-established. However, the production of practice, aquaculture based on hatchery-reared juveniles is a new industry that still has significant challenges in terms of understanding basic biological issues and developing production methods and protocols that ensure a stable and profitable seed supply. Moreover, the production of a large number of artificially propagated juveniles will reduce pressure on wild stocks.
In Europe, the major biological bottleneck in greater amberjack farming is its successful captive reproduction in captivity so that to supply enough high-quality juveniles can be produced to supply commercial farming activity. This depends on the development of appropriate hormonal therapies to induce spawning. Frequent reproductive failures of this species in captivity, not only in the wild broodstock management that will then be replicated to produce offspring from the artificially produced individuals.
Significant progress has been achieved by researchers and commercial producers in the last years however, it is necessary to invest in all the steps required for the commercial production of this species in captivity. Apart from broodstock management and manipulation, grow-out feeds should be developed, and it is important to understand the nutritional requirements in all stages of their culture. Closing the production cycle and refining reproduction protocols, as well as establishing optimal larval rearing conditions, will help ensure an adequate supply of seed and reduce the overall production costs. In addition, developing a better knowledge of diseases will allow the further expansion of aquaculture of this species. The development of efficient vaccines against the major disease is a prerequisite for the further development of greater amberjack aquaculture while the implementation of breeding programs could contribute to higher growth and improved disease resistance.
The grow-out operations, sea cages appear to have fewer problems although fish are prone to infestations of monogenean parasites. Proper feeding strategies with extruded balanced formulated diets and optimal environmental conditions can reduce the risk of disease and improve the profitability of the farming venture. Some research in high density production has been done in Recirculating Aquaculture Systems (RAS) that may have future potential.
Main issues
The main bottleneck of greater amberjack culture is the hatchery production of seed, and still most production is capture-based. Although artificial propagation has been successful because of recent advances in reproduction, improvements are required in larval and juvenile rearing techniques.
The refinement of the reproduction and larval / juvenile rearing technologies may lead to an expansion in greater amberjack farming in the future, decrease pressure on wild stocks and lower the risk of pathogen transmission. In this sense, the development of adequate bio-security can, with associated preventive practices (site, density, management, etc.) reduce the risk of disease. This, together with the development of more environmental friendly treatments and the development of vaccines, will contribute to the reduction of the use of chemotherapeutics to an acceptable level.
Since the greater amberjack is a carnivorous species, its diet requires fish protein and lipid sources so it is necessary to use feed based, in a great portion, on fishmeal and fish oil. Although the specific nutritional requirements can be sourced from alternative sources, in this respect it is imperative to carry out additional research into supplemental or alternative sources of protein meal and oil for use in feeds for a more sustainable industry.
Responsible aquaculture practices
Best management practices should be applied during the entire production process including detailed monitoring of broodstock and production as well as feeding activity using high quality and nutritionally complete extruded dry pellet diets. These efforts will contribute to maintaining optimal environmental conditions and should be performed in addition to frequent sampling and observation of the stocks for disease monitoring. Biosecurity protocols should be implemented in all stages of production cycle.
Responsible aquaculture at the production level should be practiced in accordance with the main principles of environmental and ecological protection – see Article 9 of the FAO Code of Conduct for Responsible Fisheries.
