aquaculture

According to the Aquaculture Center of the Florida Keys, “Not only is cobia a very tasty fish, it also grows very quickly: they reach 6-7kg one year after hatching (three times the growth rate of Atlantic salmon). These characteristics make cobia an appealing aquaculture species. Farmed cobia have a low feed conversion ratio, another plus for an aquaculture species. Although commercial production of cobia has only just begun in the west, it already has a successful history in Asia, most notably in Taiwan where cobia is stocked in around 80% of ocean cages.”

The Aquaculture Center include some very detailed photographs of cobia, their husbandry, and background information.

Le Xan, from the Research Institute for Aquaculture No I, Vietnam; has published (via Simon Wilkinson, at enaca.org) a report entitled Advances in the seed production of Cobia in Vietnam. From the introduction:

Cobia Rachycentron canadum culture is expanding throughout the world, notably in China and Vietnam. Cobia have an extensive natural distribution, grow quickly, and can feed on artificial diets. Under culture conditions, Cobia can reach 3–4 kg in body weight in one year and 8–10 kg in two years. The products from Cobia are exported to the US, Taiwan Province of China and local markets. Market price of one-year farmed Cobia are around US$ 4–6 kg in Vietnam. Research on seed production and grow out culture of cobia in Vietnam began in 1997-1998.

The University of Texas at Austin Marine Science Institute began researching cobia around 1990. The Marine Science Institute reports that, “In April and May of 2001, cobia caught as juveniles two years earlier spawned naturally in a 9,000 gallon recirculating broodstock system at FAML. This is the first reported spawn of cobia raised from sub-adult to sexual maturity in a recirculating tank system using photoperiod and temperature cycles.” A more detailed elaboration of the research and outlines of cobia husbandry is also available.

There are increasing numbers of summaries and reports being published about cobia. Niels Svennevig, Head, of the International Projects Department, SINTEF Fisheries & Aquaculture, N-7465, Trondheim, Norway has published a summary entitled Farming of cobia or black kingfish (Rachycentron canadum). Houng-Yung Chen, from the Institute of Marine Biology, National Sun Yat-sen University, Taiwan, has published a brief summary discussing the use of low fishmeal feeds for cobia.

Research has also been conducted into the impact of cage farming cobia. Nazira Mejia Niño, from the University of Puerto Rico, has published a thesis submitted for a Master in Marine Sciences in Biological Oceanography, entitled Effects of Sustainable Offshore Cage Culture of Rachycentron canadum and Lutjanus analis on water quality and sediments in Puerto Rico. From the abstract:

This work was part of environmental impact study conducted from August 2002 until October 2003 related to two 3000m³-Ocean Spar submerged open-ocean growout cages stocked with Rachycentron canadum and Lutjanus analis south of the island of Culebra, Puerto Rico.

The principal objectives were to determine the local environmental effects of open-ocean submerged cage culture on water and sediment quality, as well as changes over time of some environmental quality parameters, including the feasibility of these operations on tropical marine waters.

Nutrient concentration (ammonia-N, nitrite-N, nitrate-N, and phosphate) were evaluated bimonthly in the column water and interstitial water at fifteen stations around the cage and three depths for the water samples; likewise, several water and sediment quality parameters were analyzed (dissolved oxygen, water temperature, turbidity, chlorophyll- a, salinity and organic matter). Water analyses indicated that, in general, both cages and the control site showed similar nutrients concentrations throughout the months analyzed. Ammonia was the nutrient with the highest concentration; however, these values were relatively low and normal for these waters.

Results of the first year indicate that this operation did not impact the quality of the water column, or the sediments even though large quantities of feed were introduced into the system. This was probably due to the large amounts of water flowing through the cages. The information obtained from this study provides a basis to evaluate the feasibility of this operation, encourages the open-ocean aquaculture industry.

Following on from information about the Southern Flounder; the culture of flounder in Japan and Korea is well documented.

Tetsuo Fujii and Masayuki Noguchi, from the Japan Sea National Fisheries Research Institute, have published a report entitled Interactions Between Released and Wild Japanese Flounder (Paralichthys olivaceus) on a Nursery Ground. The abstract:

The Japanese flounder, Paralichthys olivaceus, is one of the most important fishes in the coastal fisheries of Japan. But recently, overfishing has caused a reduction of the stock size. To enhance the stock, artificial seeds of Japanese flounder have been released. Interactions between released and wild flounder were examined to determine the success of the stocking program.

We performed experimental releases of artificial seeds in the shallow waters off Igarashi-Hama on the northwestern coast of Japan, from 1990 to 1992. The growth rate of wild flounder varied annually depending on the abundance of mysids that are the most important food for the flounder on the nursery ground. When mysids were less abundant, released flounder dispersed rapidly from the release site, ingested small amounts of food, and grew slowly compared with other years.

The feeding habits of released flounder differed from those of wild flounder when mysids were less abundant. Flounder released then ingested less food and also consumed gammarids which the wild flounder never ate. It was assumed that an abundance of mysids was more critical for released than for wild flounder. Further investigations on the carrying capacity of the nursery ground and improvement of the quality of artificial seeds are needed to enhance the stock size of Japanese flounder efficiently.

Nozomi Okada, Masaru Tanaka, and Masatomo Tagawa from the Division of Applied Biosciences, Graduate School of Agriculture,
Kyoto University, have published research entitled Bone development during metamorphosis of the Japanese flounder (Paralichthys olivaceus): differential responses to thyroid hormone. From the abstract:

The larvae of flatfish change their body structure during metamorphosis, including dramatic translocation of one of the eyes from one side of the body to the other. Such metamorphic processes are in general promoted by thyroid hormones (THs). This study focuses on the response of individual tissues to hormones, and morphological characteristics were examined in hormone-deficient larvae of the Japanese flounder (Paralichthys olivaceus).

Osamu Tominaga et al have published research entitled Daily Ration of Hatchery-Reared Japanese Flounder Paralichthys olivaceus as an Indicator of Release Place, Time and Fry Quality. In situ Direct Estimation and Possibility of New Methods by Stable Isotope. From the document:

Japanese flounder Paralichthys olivaceus is one of the most important target species of stock enhancement in Japan. The release size of hatchery-reared flounder is an important factor affecting survival after release. In order to improve the stocking effect of hatchery-reared juveniles, it is necessary to determine the optimum release place and time. Food availability for stocked juveniles is a key factor to evaluate the quality of release tactics. However, it is not easy to estimate the biomass of food organisms in the release area, because of the difficulty in quantitative sampling. Feeding intensity of released juveniles is affected by not only healthy condition of fish (vitality and nutritional status), but also physical, biological, and environmental conditions in the release area. Therefore, daily ration of fish after release becomes the useful tool to evaluate the release place, time and fry quality.

Aqua magazine (Chile) report some $45 million had been invested developing flounder farming in Chile using Japanese technology. The Japanese flounder had been introduced to Chile in 1997 via Hawaii.

Flounder offer some other interesting aspects from an aquaculture perspective. According to a summary of flounder information from the National Oceanic and Atmospheric Administration of the USA,

Flounder are naturally docile and not easily agitated. As a result, they subject themselves to little stress under farming conditions and, therefore, do better than more excitable species. They also like crowding together, though, as flatfish, they do not fully use the water column as do round fish such as large yellow croakers. In fact, stocking densities for flounder are usually expressed in terms of kilograms per square metre, rather than kilograms per cubic metre as they are for round fish. Optimum stocking density for flounder varies from 20 to 30 kg per square meter. This does not appear to stress them and, in this respect, they are similar to other farmed flatfish such as the European turbot and Atlantic halibut.

Flounders accept dry formulated feeds well and convert them efficiently, the feed conversion ratio (the weight of distributed feed per unit weight gain) being equal to 1:1 or a little more. This might be due to an intrinsic virtue of flounder metabolism and/or to a sedentary life style. If such excellent feeding efficiency could be achieved in large scale commercial systems, it would provide flounder farmers with a significant advantage from the economic point of view.

The Southern Flounder (Paralichthys lethostigma) is gaining interest as an aquaculture species. Gulf of Maine Times report on a joint venture with a power company and a summer flounder hatchery.

A number of academic researchers are working on developing techniques for consistent flounder management. Virginia Tech have also been working with Summer Flounder (Paralichthys dentatus), as well as Southern Flounder.

North Carolina State University researchers, lead by Dr. Harry Daniels, are working on establishing practical culture methods and defining nutritionally balanced diets for the mass rearing of weaned fingerlings and commercial-scale production of fish. The researchers have also produced a variety of resources related to flounder aquaculture. The research team have also experimented with increasing temperatures to promote the development of all-female cultured stocks. Studies have shown that female flounder grow two to three times larger than male flounder within two years – a worthwhile investment from a marketing perspective. According to this report, Japan leads the way in technology for producing farm-reared flounder. They are rewarded with a market price that more than doubles that of hybrid striped bass, tilapia or trout.

Aquanic have produced a document summarising the culture and potential of southern flounder. Southern flounder have a number of advantages, not the least of which is: “Because these flounder appear to grow well in low salinity water, growout operations could be located farther from high-priced coastal areas, reducing the fixed costs associated with flounder farming.”

Seabass (Dicentrarchus labrax) have widespread popularity in the Mediterranean region as a farmed species. The European Aquaculture Society, in a report from 1997, note that seabass was being farmed across the Mediterranean, including Corsica, Malta, Greece, France, Sardinia, and Sicily. In 1996, 70% of the 600 mt of seabass produced by Croatia were reared in its 10 island farms; favoured in Croatia because of their excellent environmental conditions, fewer user conflicts and less competition for sites. Most of Croatia’s production of seabass goes to Italy.

The FAO have produced a detailed summary of the culture of seabass noting that Greece, Turkey, Italy, Spain, Croatia and Egypt are the biggest producers. Seabass are farmed in seawater ponds and lagoons, however the bulk of production comes from sea cage farming. The Mediterranean seabass industry, in less than 15 years, has grown from a few thousand tonnes to 57,000 tonnes today, peaking at nearly 71 000 tonnes in 2000. The United Nations Environment Programme Mediterranean Action Plan (Mariculture in the Mediterranean. MAP Technical Reports Series No. 140, UNEP/MAP, Athens, 2004) further underlines the importance of seabase as an aquacultural species.

Charles Cotton has published a research thesis entitled Optimizing Growth for Aquaculture of Juvenile Black Sea Bass Centropristis striata L. : Effects of Temperature, Salinity, Commercial Diet and Feeding Ration. Although the focus of the research is Black Sea Bass, the European Seabass in mentioned in context with grow out conditions.

The FAO’s Fisheries Global Information System has produced a fact sheet on the farming of turbot (Psetta maxima).

Production statistics:
French production rose from an estimated 150 tonnes in 1993 to a peak of 980 tonnes in 1997; since then it has fluctuated, being 728 tonnes in 2002. In Portugal productions seems to be fluctuating around 350-390 tonnes/yr. By far the largest producer is Spain, whose annual production has nearly doubled since 1998. In 2002, Spanish turbot production was 3847 tonnes (75.9% of the global total). Besides the three countries mentioned above, no other country reported production above 50 tonnes in 2002.

The global production of turbot in 2002 was valued at US$ 41.38 million.

Market and trade:
Most farmed turbot is currently consumed in the producing countries. In Spain, about 75% of production is consumed internally; the rest is exported to France, Italy and Germany. The product is generally sold fresh and whole, though in France a small proportion of the production is sold gutted. The European turbot market has no specific regulations, and there are no limits on trade within EU countries, no minimum sizes, and no withdrawal price.

Status and trends:
Turbot aquaculture can currently be considered a mature technology. It seems likely that the industry will see marked expansion in the future, with the construction of new rearing units and augmentation of the capacity of existing farms. Nevertheless, continued research and development effort is required in the following areas:

* Fry production, with the aim of increasing larval survival rates.
* Improved culture systems and automation.
* Disease prevention and control.
* Stock monitoring and genetic improvement.
* Improved marketing, with the consolidation of existing markets and development of new markets.
* Avenues for processing need to be explored.
* Training for technical personnel with combined skills in aquaculture technology and business management.