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Yesso Scallops: Aquaculture in Russian Federation

Scallops are the most intensively consumed and fished bivalve mollusks. Over ten scallop species are registered in the seas of the Russian Federation. The most known of them are the Yesso scallop Mizuhopecten yessoensis, which is also well known as Ezo scallop, Giant scallop, Japanese scallop, Russian scallop, Primorsky scallop or Common scallop. For a long time these mollusks have been an object of traditional catching at the coastal waters of the Sea of Japan, Southern Sakhalin, and the Southern Kurile shoal. M. yessoensis is the only scallop species cultured in Russia, in coastal waters of Primorye (maritime province of the Russian Federation) in the northwestern part of the Sea of Japan.

History
After the ban on scallop fishing in Primorye in 1962, its stocks were replenished very slowly. So the first steps in Yesso scallops' mariculture at Russian Far East were made since 1968. In 1971, after some years of research, the first scallop farm was organized in Posjet Bay (southern Primorye). This industry has reached the greatest development in the eighties in Primorye. In addition to southern Primorye, experimental work for spat collection was performed in the seventies in Sakhalin in Bousse lagoon, but further cultivation was discontinued. Mariculture at this time had moneyed assistance from the largest fishing enterprises of region, such as "Dal'ryba" and "Primorrybprom", and from Ministry of Fishery of the USSR.

By the mid-eighties, production reached over 10 million spat a year, and at least 40 million one-year-olds were settled in various sites of Posjet Bay. Since 1977, in addition to its own plantations, the Posjet farm transfers from 2 to 10 million young scallops from other bays to other marine farms. Starting from 1983, scallop cultivators in Posjet collect 30 million spat, while industrial production amounts only to 20-50 tons. Only by 1989, production output exceeds 100 t (Table).

Table.
Twenty years (1981-2000) annual trend in number of organizations involved in Yesso scallop culture and total production (metric tons) in Primorsky Territory. Figures have been compiled from reports of fishery organizations

Years

Number of farms

Yield

 

Years

Number of farms

Yield

1981

3

9.0

 

1991

5

153.0

1982

3

4.5

 

1992

5

150.0

1983

3

18.1

 

1993

5

155.0

1984

3

38.0

 

1994

5

110.0

1985

4

10.4

 

1995

6

113.0

1986

4

48.8

 

1996

8

22.0

1987

4

62.3

 

1997

9

60.0

1988

4

64.0

 

1998

10

131.0

1989

5

196.0

 

1999

18

99.6

1990

5

122.5

 

2000

20

91.2

 

However in the nineties, during crash of socialist system and disintegration of the USSR, practically all the earlier created farms were bankrupted or were crisis-ridden. But since the end of the nineties with formation of the exchange relations in Russian Federation, a new period in mariculture development has been started. After the economic depression in the 1997, the interest in mariculture has been increased and a new period of economic expansion has been started.

Present situation
Lately number of scallop farms in Primorye promptly grows (Table). Now there are 20 farms for Yesso scallop cultivation with exceeding of 700 hectares under single-crop area. 125 hectares of them are under hanging culture and about 600 hectares are under sowing culture. As to Sakhalin region, the development of mariculture there is completely terminated.

Marketing
Almost all of scallop production from scallop farms is unprocessed. Unprocessed Yesso scallops are frozen as packed meats and a very small percentage of scallops (within 1%) is cooled being in the shells. In Vladivostok fish stores and supermarkets, frozen meat may be sold for 280-340 rubles per kilogram (equivalent of $9.3-11.3). Cooled whole scallops are sold for 20 rubles per shell (equivalent of $0.7). For comparison, frozen beef cost is equivalent to $2.5-3.0 (75-90 rubles) per kg. Canned scallops (in sauce, oil and smoked) are sold for equivalent to $2.0-4.0 (30-60 rubles) per 8 oz. In other Russian regions prices are a little bit higher. It is profitable to cultivate scallops at this price. In Vladivostok, several dozen tons are sold every year, which is highly insufficient even for small local market. Frozen scallop meat is in high demand in spite of a high price. Yet, scales of cultivation do not match levels of needs.

The culture methods
All the methods used in cultivation of Yesso scallop can be assigned to one of two categories; they are either off-bottom cultivation or on-bottom cultivation. Also experiments were performed to obtain spat in closed and running controlled systems involving artificial spawning and larvae feeding. Nevertheless, this technique still fails to enjoy popularity because it is too complicated and expensive. Attempts were also made to create industrial scallop accumulations by using artificial reefs. However, the results proved inefficiency.

There are two main Japanese methods for commercial cultivation such as hanging culture - cultivation of the scallop in cages and sowing culture - cultivation on bottom grounds of bays and inlets (Ventilla, 1982).

Spat collection
Typical long-line structures with plates or bags collectors are everywhere used for spat collection in Primorye. Long-line is a series of floats ( 240-300 mm) connected together by horizontal lines ( 19-22 mm) that supports a large number of vertical ropes with attached collectors. There are two types of collectors:

  1. Conical plates of perforated plastic ( 250 mm) covered by mesh stockings (7-12 mm). Twenty-five collector plates are stringing onto the rope ( 6-8 mm) as garland up to 2.5 meters long.
  2. Commercial onion bags with mesh or monofilament filling (capron or polyethylene). The bags with filling are attached in tens to the rope ( 6-8 mm) as garland up to five meters long.

Prepared garlands of collectors are placed at a depth of 5-10 m in semi-closed bays and inlets place and at a depth of 15-20 meters in open waters. Mass scallop spawning in southern Primorye starts from mid-May. In order not to miss the settling peak, collectors are hung deep under water in 15-20 days in early June, so the substrates could be covered with a bacteria-algae film to promote spat attachment prior to larvae settling (Belogrudov, 1986). In southern Primorye settlement occurs from mid-June, i.e. in 22-30 days after spawning begins. The size of settling larvae is 250-275 mkm. At the beginning of August, the spat average 3 mm in size and have a growth rate of 3-4 mm per month.

There is direct relation between larvae concentration in plankton and spat abundance onto collectors. At larvae concentration in the range of 20-30 specimens per cubic meter spatfall are about 100-400 specimens per collector; and at 50-100 specimens per cubic meter - up to 500-1500 spat specimens. The long-term maximal larvae concentration in plankton amounts to 600 specimens per cubic meter (Belogrudov, 1981).

In one month after settling spat size averages to 10 mm. When at least 200 spat specimens had settled in the collector, the result is considered commercially profitable. In bonanza years up to 400-600, and even 1'000 larvae can settle in the collector. However in lean years, settling from several to several dozen specimens can make processing commercially unprofitable.

Intermediate culture
The long-line for intermediate culture is similar in set up to that of spat collector lines. Horizontal lines support a large number of vertical garlands of cages.

In autumn, the collected spat (by 200-250 samples) is manually removed to hanging multi-tier cages (0.12 square metre). Spat is collected and placed in cages directly from a raft above the plantation. The collectors are lifted from the water to remove the substrate and scrape off the spat into vats filled with water. All foreign organisms, first of all mussels, and empty shells are removed during the transfer operation. The necessary number of scallop is poured into cages and instantly placed into the water. When performing the work, the scallop farmer shall put a tent over the raft to protect the scallops from the sun and from desiccation. In wintertime, the floating structures on which the cages are hanging shall be placed under ice to protect them from destruction by moving ice floes. All structures shall preferentially be placed under the water to be protected from heavy waves.

By April and May, scallops grow in cages up to 25-30 mm in height. When cultivation is performed accurately, survival rate is about 90 % when using this stage. Mortality occuring mostly at the beginning is due to stress at transfer and to the fragility of the thin shell. The viability of these scallops is in dozens of times higher than in autumn, and several methods are used to subsequently cultivate them to marketable size. At 30 mm, the juveniles can be sowed on the open waters. About 70 % are used for sowing culture, and the rest are used for hanging culture at less dense cages.

Transport of scallop seed
When scallop seed are sold to other farms, or delivered for sowing onto the bottom grounds, they are packed up to the boxes (volume of 20-60 liter) with perforated walls and bottoms. The boxes are put under the canvas on board a transport deck, and they should be instantly filled by mollusks with layer of 20-30 centimeters. Scallop seed should be covered with moist algae or seaweed leaves after taking out of water. During transportation, the boxes are poured by outboard water every 30 minutes. Transportation is preferable when the water and air temperature is approximately the same (about 5-10 C); then the scallops can survive during 24 hours.

Sowing or on-bottom culture
Sowing cultivation is based on the principle of transferring scallop juveniles from areas where they settled in great abundance, to bottom grounds, where they can be spread at lower density in order to obtain much better growth and fattening of the scallops. Sowing culture is practiced more widely in Primorye.

Scallops are usually transferred from collectors or cages after intermediate culture to bottom grounds in May and June when they are about one year old. Specific sites should be pre-selected before the sowing on sandy-silty soil or, probably, on shingle shell admixture and should be without starfishes (at the most of 0.5 specimens per square metre. The content of finely dispersed silt (particles smaller than 130 mkm) shall not exceed 30 %. Bottom grounds shall be at least 3 m deep in the inlets protected from wave action. They should be over 10 m deep in open waters, partially protected from prevailing winds and over 20 m deep at bays opened to all winds, so that storms would not ruin the floor plantation. Areas with natural scallop accumulations (past or present) are preferable for sowing culture. The selected site should be established by taking bearings of shore reference marks and then mapped. Prior to sowing, the water space shall be contoured with buoys. The vessel should sail between them at slow speed, and the one-year-old scallops will be evenly scattered all along bottom grounds with density of 10-20 specimens per square metre. Sowed scallops usually weighed less and are 10-15 mm smaller in shell height than native scallops are (Silina, 1994). This difference usually continued throughout the life of scallops. It is believed that slower growth of scallops in collectors or cages unfavorably affects growth during winter and spring when the density is high. Moreover, some growth inhibition resulted from shell breakage during transportation and sowing on the bottom. Growth of sowed scallops was further affected while the animals adapted to the new habitat and generated new shell at the ventral margins. Depending on the temperature and other ground conditions, the scallop will grow up to marketable sizes in two or four years. Survival on the sea floor will depend on predators' activity and wave intensity, and sometimes can vary from 5 to 20 % in the same grounds during different cultivation cycles.

In two or four years after sowing, SCUBA divers collect marketable scallops. Their productivity on shallow grounds (3-5 m deep) with scallops density over 10 samples per square metre amounts to 1.5-3 thousands scallops per hour. In case of lower densities or larger depths, and in turbid water, divers' productivity will progressively decline up to 300 scallops per hour.

Hanging or off-bottom culture
Hanging cultivation adds a third dimension that of depth, to the essentially two-dimensional sowing culture. The crop is spread over, and can be utilized, a much great proportion of the water column.

The long-line for intermediate culture is set up in the same manner as that for the intermediate culture. They are usually set deep, down to 5-15 m from the surface, to escape wave action and particularly the thermocline building up in summer months. There are two schemes for hanging culture:

  1. Young scallops with shell height of 10-15 mm are placed into cages by 200-250 specimens. One-year old scallops (20-30 mm) are transferred into cages by 20-25 samples and two-year-olds (50-70 mm) by 5-7 specimens. In three years the scallops have reached marketable size of 100 mm in height.
  2. Young scallops with shell height of 10-15 mm are placed into cages by 20-30 samples and in 1.5 years are transferred by 5-7 specimens. The number of transfers in the second case is smaller, but the strong fouling appears on cages due to a longer period between operations, and this has a negative effect on scallop growth and its survival.

All operations on scallops' transfer are performed in spring and autumn at relatively low temperature (about 10 C). When the work is performed accurately, survival rate is about 90 % when using this technology. Mortality occuring mostly at the beginning is due to stress at transfer and to the fragility of the thin shell.

Harvesting method implies the lifting of the cages and taking out scallops of marketable size. Manual harvesting is time-consuming, laborious and labor intensive, assisted only by mechanical winches for lines lifting.

Obstacles to mariculture development
There are following obstacles to mariculture development in Russia:

  • Financial problems on account of protracted payback period in mariculture and necessity of huge investment in equipment. Lump-sum investments for creation of mariculture farm exceed $200'000. And it is very difficult to find investors for such a long-term project.
  • Ethnic and gastronomic problem as the seafood is not traditional nourishment for Russian people.
  • Legal problems are absence of the laws regulating sea farming.
  • Socioeconomic problems are concerned with undeveloped infrastructure of inshore centers of population.

Ecological problems, associated with cultivation
Predation. Young scallops are often preyed upon by various starfish species. In mariculture, when their bipinnaria larvae achieve concentrations of up to 20 specimens per cubic meter in plankton, and when inside collectors they develop twice as fast as the scallop spat, causing up to 100 % mortality (Belogrudov, 1981; Gabaev, 1981). During settling starfish larva attaches to the same collectors where there are most of all scallops juveniles. Scallops also preyed by gastropod Nucella heyseana can cause a similar problem (Gabaev, Kolotukhina, 1999).

Epibioses. Farmed scallops constitute an excellent substrate for the settlement of many epifaunal and epifloral organisms. Almost 60 species of algae and invertebrates were noted at shells of cultured scallops. In hanging culture, scallops are most frequently inhabited by bivalve mollusks and barnacles (Silina, Ovsyannikova, 2000). The dominant species in epibioses are mussels Mytilus trossulus (with abundance up to 110 samples and biomass up to 46 g per shell), Modiolus kurilensis (up to 32 specimens per shell) and Hiatella arctica (up to 27 specimens). Subdominants of epibioses community are barnacles Balanus improvisus (up to 268 specimens per shell), B. crenatus (up to 189 specimens) and Hesperibalanus hisperius (up to 27 specimens). Scallops from natural populations had epibioses only on the upper valve. But in cultured scallops the fouling is presented on both valves and in cage culture epibioses are more abundant on the lower valve than on the upper valve. Because of cage overcrowding and immobility epibioses in hanging culture are more magnificent than in sowing culture.

In sowing culture, epibioses on scallops' shells are mainly presented by barnacle H. hisperius. Their abundance can reach up to 77 specimens per a shell on two-year scallops and up to 337 specimens on three-year mollusks (Silina et al., 2000; Silina, Ovsyannikova, 2000).

Excessive fouling is a scallop-farming problem mainly by virtue of the extra effort required to clean the crop for marketing. It may also have some influence on growth rate and productivity through competition for space, and reduction of water circulation. Again, farm management provides the best means of alleviating this problem i.e. using optimal technique for cultivation tending to sustain less fouling.

Biofouling of the structures for cultivation. According to technique of hanging culture existing in Russia, the cages are placed at depths of 5-15 meters. These depths teem with the larvae of various organisms, which may form abundant fouling on all the parts of the structures for scallop cultivation. So, S. I. Maslennikov and I. A. Kashin (1993) reported about strong fouling, which occurs at cages during cultivation. The biomass of fouling reached 5.7 kg per square metre at a depth of 5-7 m. The dominant species, which gave more than 84 % of the total biomass, are M. trossulus (4.9 kg per square metre at population density over of 10'000 specimens per square metre). The biomass of the fouling of collectors at this horizon was 6.5 kg per square metre, from which M. trossulus and B. improvisus contributed 61.2 and 36.4 %, respectively.

Because of the fouling, the weight of maricultural structures is sharply increased and their storm resistance is decreased with the reduction in their life span (Bregman, Kalashnikov, 1983). When strong, fouling may also make the collectors and cages an inhospitable environment by restricting flow through the bag and depleting nutrients, thereby hindering the growth of scallops within the collectors and cages. The rate of growth of the scallops (height and mass) is also strongly affected by fouling organisms.

Many ways of fouling removal at sea farms (mechanical, physical, chemical and biological) are known now. The chemical methods are not suitable for scallops' cultivation, because they use toxic substances. The application of physical and mechanical methods is considerably limited, because they damage cultivated mollusks or are very labor consuming.

Future prospects
In general, the future of the Yesso scallop farming is very promising. The market is constantly developing as demand continues to exceed supply and there is some potential for increased farming. Production of scallop farms might be increased through better scallop farm management and manufacturing application of technological innovations for mariculture.

There are presuppositions for future mariculture development in Primorye and northern part of Russian Far East such as historical, organizational, market opportunities, resource environment and socioeconomic (Arzamastsev, 2000). According to experts inshore water suitable for development of maricultural farms makes up approximately 6-10 thousands hectares only in Primorye. This allows providing commercial output of 700 thousand tons (Mokretsova, 1996). In coastal waters of Sakhalin and Kurile Islands, natural resources and environment are also favorable. The optimum for mariculture development was found in shoaling waters of southern Sakhalin (Kochnev, 2000) and South Kurile Shoal (Ponurovsky et al., 2000).

The one of perspective trends of mariculture is polyculture - joint cultivation of a few species of plants and animals. Scallop accumulations, which had developed spontaneously under the kelp plantations in kelp farms, are well known in practice. (Shaldybin, 1983). Moreover joint cultivation kelps with scallops will protect an environment against excessive eutrophication, which often appears at mollusk and kelp farms because of overcrowding (Arakawa et al., 1971; Ventilla, 1982; Rosenthal et al., 1988; Ivin, 1999).

Not long ago a project on joint cultivation of Yesso Scallop M. yessoensis, Japanese kelp Laminaria japonica and Common sea cucumber Apostichopus japonicus was offered (Ivin, Maslennikov, 2000; 2001). The methods for cultivation and constructions of structures applied in the project are original development protected by patent of Russian Federation No. 2149541 (Maslennikov, Kashin, 2000). One hectare of sea-farms can give up to 400 thousand market sized scallops. It is equal to 8 tons of scallops' meat. Kelp productivity is not less than 50 ton in wet weight or about 10 ton in dry weight. Technology of sea cucumber cultivation can give up to 10 thousand market sized individuals. The projected profitability of the seafarms will make about 15-18 %.

The world experiences of mariculture evidenced the necessity of seafarms transposition from the closed bays to open waters. The offered technology uses open seawaters with depths of more than 30 meters, which are unsuitable for traditional in Russia mariculture. The shallow bays with depths of 10-15 meters are used only during a short period (not longer 6 months) for the scallop spat and sea cucumber juveniles' collection. Areas, which are occupied by maricultural structures, will cover no more than 33 % from general area for seafarm making. The remaining water space is used as reserve for rotation of areas occupied in cultivation of sea organisms. After termination of each biotechnological cycle the plantations will be replaced to a new place. It allows keeping areas that are used in mariculture practically in a native status. Such turnover of used squares allows long-term usage of seafarms, without negative environmental impact. Such scheme of plantations turnover is applied in agriculture for a long time.

Manufacturing application of this project was started in 2000 by one of the biggest joint stock Companies of aquaculture. Last year about 100 millions of spat was collected; more then 40 millions of scallop seeds and 30 thousand of juvenile sea cucumbers were sowed.


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