Scallop aquaculture
Scallop aquaculture is the commercial activity of cultivating (farming)
Cultured species
There are varying degrees of aquaculture intensity used for different species of scallop. Therefore, cultured species can be divided into operations that are commercially well-established, those in the early commercial stages, those in development or experimental stages and those where potential for commercial farming has been expressed. Some species fall under multiple categories in different world regions.
Established commercial operations
- Aequipecten opercularis(United Kingdom, northern France and Spain, Norway)
- Argopecten irradians (China)
- Sub species A. irradians irradians (eastern USA)
- Sub species A. irradians concentricus (eastern USA)
- Argopecten purpuratus (Chile)
- Chlamys farreri(China)
- Chlamys islandica (eastern USA)
- Chlamys nobilis(Japan, China)
- Mizuhopecten/Patinopecten yessoensis(eastern RussiaJapan, China, Western Canada [hybridized with Patinopecten caurinus])
- Pecten fumatus (Australia)
- Pecten maximus (United Kingdom, northern France and Spain, Norway)
- Placopecten magellanicus (eastern USA)
Early commercial operations
- Argopecten ventricosus (Mexico)
- Chlamys islandica (Norway)
- Crassadoma gigantea (western North America)
Developmental or experimental
- Aequipecten tehuelchus (Argentina)
- Aequipecten opercularis(Norway)
- Euvola ziczac (Venezuela)
- Nodipecten nodosus (Brazil, Venezuela)[4]
- Patinopecten caurinus (western North America)
- Pecten maximus (China)
Species with potential
- Amusium balloti(Australia)
- Amusium pleuronectes (Philippines)
- Chlamys varia(northern Europe)
- Chlamys islandica (northern Europe)
- Euvola vogdesi (Mexico)
- Euvola ziczac (Brazil)
- Flexopecten flexuosus (northern Europe)
- Nodipecten subnodosus (Mexico)
Other species of note
Attempts at cultivation of Chlamys hastate and Chlamys rubida in western North America have been halted due to the small size and slow growth of both species.
Initial attempts made at cultivation of Pecten novazelandiae in New Zealand were hampered by large levels of fouling by mussels and by competition from a largely successful natural fishery.
Methods of culture
There are a variety of aquaculture methods that are currently utilized for scallops. The effectiveness of particular methods depends largely on the species of scallop being farmed and the local environment.
Spat collection
Collection of wild
Spat collectors will be set in areas of high scallop productivity where spat numbers are naturally high. However, to establish where the most appropriate areas to collect spat are, trial collectors will often be laid at a variety of different sites. Well-funded farms can potentially set thousands of individual spat bags in collection trials.
Hatcheries
Scallop hatcheries provide a number of advantages over traditional spat collection for supplying seed to aquaculture operations, most notably in selective breeding and genetic manipulation, as well as providing a regular supply of spat at a low price. While initial attempts to culture scallops in hatcheries were fraught with extremely low spawning and high larval mortality rates,[5] a number of successful techniques have now been developed.[6]
One of the most important aspects of hatchery rearing is obtaining and maintaining broodstock.
Grow out stage
There are two recognized systems for the grow out stage of scallops. These are hanging culture and bottom culture. Each has its own benefits and drawbacks in terms of cost, ease of handling and quality of the finished product. Enclosed culture systems still have not yet been fully developed in a commercial context and development continues in this area. Such a system would have large advantages over other forms of culture as tight control of feed and water parameters could be maintained.
Hanging culture
Hanging culture relies on either a raft or longline system (with buoys and lines) that floats on the sea surface from which the cultured scallops are suspended, usually on ropes to which they are attached in some manner. Rafts are considerably more expensive than the equivalent distance of longline and are largely restricted to sheltered areas. However, raft systems require much less handling time. Longlines have proved effective for most farms to date and have the added advantage of being able to be completely submerged (with the exception of marker buoys) so to reduce visual pollution. From a raft or longline a variety of culture equipment can be supported. The main advantage of any form of hanging culture is in the exploitation of mid-water algal populations that cannot be fully utilized in other forms of culture.[8]
Pearl nets
Once scallop spat have been collected, the most common way of growing them further is in pearl nets (small pyramid shaped nets usually about 350mm across with 2-7mm mesh). Here, they are usually grown to approximately 15mm in high stocking densities. Pearl nets are typically hung ten to a line and have the advantage of being light and collapsible for easy handling. Scallops are usually not grown to larger sizes in pearl nets due to the light construction of the equipment. Once juveniles have reached a desired size they can be transferred to another form of culture.[8]
Lantern nets
Lantern nets were first developed in Japan and are the most common method of growing out scallops following removal of juveniles from pearl nets. They allow the scallops to grow to adulthood for harvest due to their larger size and more sturdy construction. Lantern nets are employed in a similar fashion in the mid-water column and can be utilized in relatively high densities. Flow rate of water and algae is adequate and scallops will usually congregate around the edges of the circular net to maximise their food intake.[8]
Ear hanging
Ear hanging methods were developed to be a cheaper alternative to lantern nets. Subsequently, research has shown that growth of ear-hung scallops can also be higher than those in lantern nets. Ear hanging involves drilling a hole in the scallop ear (the protruding margin of shell near where the two shells join) and attaching it to a fixed submerged line for growth. Such a process can be relatively labor-intensive as each scallop must be individually handled and drilled (however, many operations now have machines for this process). Furthermore, high mortality rates can result from drilling if scallops are too small, are drilled incorrectly, or spend too much time out of water and become physiologically stressed. This has resulted in research being conducted into the optimal drilling size. This size has been shown to be species specific with small species not having good survival rates. As such, ear hanging is an effective method of growing out larger scallop species. If ear hanging is an appropriate method, scallops can be densely stocked in pairs on lines with as little as 100 mm between pairs. Scallops are maintained in this fashion for two to three years until harvested.[9] A variety of attachment products are constantly being tested with the best growth so far being obtained with a fastener called a securatie.[8]
Rope culture
Rope culture is very similar in principle to ear hanging with the only difference being the method of attachment. In rope culture, instead of scallops being attached by an ear hanging, they are cemented by their flat valve to a hanging rope. This method results in a similar growth and mortality rates as ear hanging but has the advantage of being able to set scallops from a small size. New cementing technologies are being continually developed with the aim of producing quicker setting adhesives to minimize the time scallops spend out of water so to minimize stress.[8]
Pocket nets
Pocket netting involves hanging scallops in individual net pockets. Pockets are most often set in groups hanging together. Pocket nets are not used extensively in larger farms due to their cost. However, handling time is low and so can be considered in smaller operations.[8]
Hog rigging
Hog rigging involves netting pockets of three or four scallops tied around a central line. This method is quick and cost effective and has been used to a great extent in the European
Plastic trays
Growing scallops in suspended plastic trays such as oyster cages can serve as an alternative to equipment like lantern nets. However, such systems can be expensive and have a rigid structure so cannot be folded and easily stored when not in use. In general, plastic trays are mostly used for temporary storage of scallops and for transportation of spat.[8]
Bottom culture
Methods of bottom culture can be used in conjunction with or as an alternative to hanging culture. The main advantage of using methods of bottom culture is in the lower cost of reduced buoyancy needs as equipment is supported by the seabed. However, growing times have been noted as being longer in some cases due to the loss of use of mid-water plankton.[8]
Plastic bottom trays
Plastic trays such as oyster cages can again be utilized in bottom culture techniques. They provide simple and easy to use system. Plastic trays are effective in large numbers but their size is limited by the growth rates of scallops near the centre of cages due to reduced water and food flow rates.[8]
Wild ranching
Wild ranching is by far the cheapest of all forms of scallop farming and can be very effective when large areas of seabed can be utilized. However, there can often be problems with predators such as
Feeding
Scallops are
Diseases, parasites and phycotoxins
Diseases
As with any aquaculture species, the incidence of
Parasites
A similar situation is seen with parasites as is seen with diseases: at this stage little is known about scallop parasites and few have been identified. As of 2006, no mass deaths caused by parasites have been reported.[2] There are only 17 parasites and commensals that have been described as being associated with scallops (for a full list see Shumway & Parsons [2006], pp. 1187–1188).
Phycotoxins
The occurrence of phycotoxins is generally associated with specific bodies of water and must be considered during establishment of farms as many phycotoxins derived from toxic algae can have detrimental effects on consumers of infected meat.
End product
Once scallops have been grown, harvested and processed the principal end product is the meat, which usually consists of just the adductor muscle (fresh or frozen). However, it is becoming increasingly popular to sell the muscle with the roe still attached and also to sell whole animals (primarily in North America). Thus, the industry now produces three distinguishably different products.
While the shelf life of a live scallop is limited, the marketing of this product allows scallop farmers to sell smaller animals and so increase cash flow. Top quality scallop muscle can demand a high market price, which fluctuates with production, success of wild scallop fisheries and a number of other global factors.[2]
Environmental impacts
Contrary to common perception concerning the negative impacts of many aquaculture practices (particularly finfishes
With this considered, such positive impacts are very area specific and one of the main negative environmental impacts scallop culture can create in some other areas is the
References
- ^ Kinoshita T (1935) A test for natural spat collection of the Japanese scallop. Report of the Hokkaido Fish Research Station, 273:1-8.
- ^ a b c d e f g h i j k l Shumway SE & Parsons GJ (2006). Scallops: Biology, Ecology and Aquaculture. Elsevier B.V., Amsterdam.
- ^ "Ifremer". wwz.ifremer.fr. Archived from the original on 9 September 2016. Retrieved 13 January 2022.
- ^ Cervigon, Fernando (Editor), 1983: La acuicultura en Venezuela. Caracas. 123p
- ^ Dabinett PE (1989). Hatchery production and grow-out of the giant scallop Placopecten magellanicus. Bulletin of the Aquaculture Association of Canada, 89(3):68-70.
- ^ a b Neima PG (1997). Report on commercial scallop hatchery design. Canadian Technical Report of Fisheries and Aquatic Sciences, No. 2176. 55 pp.
- ^ Ryan CM (2000). Effect of algal cell density, dietary composition, growth stage and macronutrient concentration on growth and survival of giant scallop Placopecten magellanicus (Gmelin, 1791) larvae and spat in a commercial hatchery. MSc Thesis. Memorial University, Newfoundland.
- ^ a b c d e f g h i j k Hardy D (1991). Scallop Farming. (ed. D Hardy) Fishing News Books, Blackwell Science, Oxford.
- ^ Loew, Chris (Mar 13, 2019). "CEI releases market analysis of ear-hung scallops farmed in Maine". Seafood source. Retrieved March 13, 2019.
- ^ Lucas A (1982). La nutrition des larves de bivalves. Oceanis 8(5):363-388.
- ^ Coutteau P & Sorgeloos P (1992). The use of algal substitutes and the requirement for live algae in the hatchery and nursery rearing of bivalve molluscs: an international survey. Journal of Shellfish Research, 11:467-476
- ^ Robert R & Trintigna P (1997). Substitutes for live microalgae in mariculture: a review. Aquatic Living Resources, 10:315-327.
- ^ Farías A & Uriarte I (2001). Effect of microalgae protein on the gonad development and physiological parameters of Chilean scallop Argopecten purpuratus (Lamark, 1819). Journal of Shellfish Research, 20:97-105.
- ^ Uriarte I (2000). Informe de Avance No.3, FONDECYT 1970807, Chile. 11p.
- ^ Ball MC & McGladdery SE (2001). Scallop parasites, pests and diseases: implications for aquaculture development in Canada. Bulletin of the Aquaculture Association of Canada, 101(3):13-18.
- ^ "An Overview of China's Aquaculture", p. 6. Netherlands Business Support Office (Dalian), 2010. Accessed 13 Aug 2014.
- ^ Ren W, Chen H, Renault T, Cai Y, Bai C, Wang C, Huang J (2013) Complete genome sequence of acute viral necrosis virus associated with massive mortality outbreaks in the Chinese scallop, Chlamys farreri" Virol J 10(1) 110
- ^ Shumway SE, Sherman-Caswell S & Hurst WJ (1988). Paralytic shellfish poisoning in Maine: monitoring a monster. Journal of Shellfish Research, 7:643-652.
- ^ Yautomo T, Murata M, Oshima Y, Matsumoto GK & Clardy J (1984). Diarrehetic shellfish poisoning. In: Seafood Toxins (ed. EP Ragelis). American Chemical Society, Washington D.C. pp. 207-214.
- ^ Tovar A, Moreno C, Mánuel-Vez MP & García-Vargas M (2000). Environmental impacts of intensive aquaculture in marine waters. Water Research, 34(1):334-342.
- ^ Shumway SE, Davis C, Downey R, Karney R, Kraeuter J, Parsons J, Rheault R & Wikfors G (2003). Shellfish aquaculture — In praise of sustainable economies and environments. World Aquaculture, 34(4):15-17