Though the main criteria in selecting the type of collector are easy availability, ease of handling and the surface area offered for the attachment of spat, the larvae of some species appear to exhibit preferences for certain types of substrates. As mentioned earlier, different types of collectors are in use, and they may be placed on the bottom or on raised structures. Generally, spawning occurs at temperatures of 15–20☌ in summer and autumn, but tropical species spawn throughout the year at higher temperatures.Īs well as the time and place of spat collection, the type of spat collector used is also of importance. Regular examination of plankton in the area will help to determine the actual time and place of spat-fall. Early setting of the spat collectors will result in the substrate becoming covered with fouling organisms, whereas late setting may result in poor collection of spat. Even though spat may settle at a wide range of depths, their survival is greatest in the intertidal zone, relatively safe from predators. For successful spat collection, suitable collecting devices have to be set in the proper place at the proper level and time. There is considerable variation in the time and abundance of spat-fall in any area, depending on a number of environmental factors including temperature and salinity. Countries like Japan export large quantities of seed oysters to other oyster-growing countries. Similarly, hatchery production of seed oysters is a separate specialized activity, and oyster farmers often start their operations with purchased seed. As spat-fall often occurs in areas away from environments suitable for oyster growing, the collection, transport and sale of oyster spat has developed into a separate industry.
Oyster larvae normally settle in sites with low current velocities, but these areas may not be rich in plankton and so may not be conducive to good growth rates.
Though the value of and need for hatchery-produced seed oysters are well recognized, it would appear that production costs have stood in the way of wider application of this technique. Methods for hatchery production of seed oysters have been developed and are being practised on a commercial scale by a small number of producers.
#OYSTER SPAT COLLECTION METHODS TRIAL#
Although, this was symptomatic of the low spatfall and high mortality rate in the trial location and the wider Blackwater and Colne estuaries in 2020 and was not isolated to our discs.įollowing the initial success of attracting the limited number of oyster spat, further opportunities have been developed to test this product and technology across different marine environments in order to establish a wider evidence base for its effectiveness.As stated earlier, most present-day production of oysters is from collected wild spat. However, numbers were not sufficient to state that this new technology has the potential to replace traditional methods. Native flat oyster spat ( Ostrea edulis) was found on our discs, as well as spat from the Pacific oyster ( Crassostrea gigas), evidencing that our innovative product was successful in attracting oyster spat. Our discs attracted a host of marine organisms during the period from June 2020 to March 2021, including Sea Slugs, Star Ascidian, Sea Squirts and Coralline Algae, Gastropods, Amphipods, Isopods and Polychaeta. The development of innovative oyster spat collector discs from waste dredged material helped to establish a sustainable alternative to traditional plastic collectors by removing carbon emissions associated with waste disposal and plastic products.
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