The experience of the Nutrition Division of Acuinuga in bivalve nutrition begins with the R&D project “Industrial production of microagglomerated and microencapsulated diets”, carried out within the National Food Plan, with results presented at the National Congress of Aquaculture held in Santander (Spain) in 2001. This applied research project aimed at the experimental production of new microdiets allowing for diets adjusted to the needs of each species and developmental phase, prepared from raw materials of local origin.
These diets aim to reduce the need for phytoplankton and zooplankton, high-cost live diets requiring complex management protocols. The replacement of live diets by inert microdiets allows for seed production throughout the year, regardless of the amount of natural food available, in addition to correcting the heterogeneity in particle size and composition, thus reducing production costs.
We consider several factors in the production of microdiets, such as diet formulation, since each species and state of development has different nutritional requirements; and food buoyancy, which must ensure even distribution in the water column making it available for the animals, which in the larval stage have a very limited range of displacement. Buoyancy will also vary depending on salinity. Also food particle size must take into account the size of the mouth of each animal, as an excessive particle size makes it impossible to eat and a very small size forces the animal to invest too much energy in its capture and intake, affecting its growth. Our innovative production process results in the production of food with a range of particles between 3 and 500 microns in diameter, maintaining maximum homogeneity.
Finally, water quality is a key factor for the proper larval development of the crop. To do this, we incorporate ingredients in the formula that maintain particle integrity in the water column while preserving water quality, such as pH regulators and nitrifying substances that minimize the production of ammonium. The data from the tests carried out so far reveal a success in the substitution of live food of up to 80%, and a reduction in production costs of up to 60%, depending on species, developmental stage and production system.
Since then, interest in bivalve seed and juvenile production has increased, transcending the scope of food production to interest in environmental regeneration, coastal management and restocking or carbon sequestration (CSS) projects. Because of their higher protein content per calorie than beef, rich in omega 3 fatty acids and with a powerful macro and micromineral complex, the production of bivalves is very attractive from a nutritional point of view.
In addition, the deposition of calcium carbonate required for the formation of the bivalve exoskeleton or shell, as well as a very low carbon footprint, lower than that of meat production from livestock or fish farming, and even lower than that of many agricultural crops such as wheat, soybeans or rice, make the cultivation of bivalves an extraordinarily sustainable activity.
Their great capacity for water clarification, being filter feeding organisms, render them as very useful biological tools for the consolidation of environmental projects, particularly those involving high sediment removal (dredging, landscaping, environmental regeneration of eutrophic areas, coastal management, etc.).
Recently, a number of projects have identified the depuration period, during which bivalves are kept in tanks with treated water for 48 hours after harvest to ensure their sanitary safety before marketing, as a window of opportunity for the application of new nutritional strategies.
Unlike most animal protein foods, bivalve meat is consumed whole including its digestive tract, facilitating its use as a vehicle for the intake of nutrients administered during depuration, which will then be quickly accessible to the consumer. This is a much more effective strategy for fortifying food in micronutrients (minerals, pigments, vitamins) than fortifying livestock feed, as these have to be consumed for long periods by animals to raise basal levels in their tissues. Food fortification strategies have gained relevance for the correction of mineral deficiencies such as iodine or iron in organic meats, or vitamins A and D and their precursors, of great importance in the immune response to the SARS-CoV2 coronavirus.
However, and in our experience which has been expanding for more than 20 years, the excessive legal regulation characteristic of the southern European environment makes it very difficult to advance not only in nutritional innovation in bivalves, but in general terms, in improving their production. In addition to the legal insecurity for the implantation of new farming sites in the coast, as well as the administrative lack of coordination, with a miriad of organisms intervening without a common criterion -when not directly confronted to each other-, often obsolete normative frames and the delay in incorporating new developments must be taken into account.
This was the case, for example, of the diagnosis of lipophilic biotoxins in mussels, responsible for a large number of closures of production areas and with a high impact on the profitability of mussel farming. The replacement of the traditional method for their detection by mouse bioassay with more modern chromatographic methods took more than a decade to implement. Mention may also be made of the regulation of new water treatment technologies during purification, which is still concentrated in today’s almost obsolete strategies such as chlorination, ozonation or ultraviolet irradiation, or the slowness in the implementation of effective programs for monitoring infectious diseases using molecular techniques (Marteilia, Bonamia, herpesvirus, Perkinsus etc.).
From a regional perspective, when improved mussel seed production remains unresolved after several decades of failed attempts in Galicia, the European leader with an annual production output approaching 300,000 tons, it can hardly be expected that much more ambitious strategies such as food fortification of bivalves during depuration see their successful incorporation in the local aquaculture industry. Technological leadership requires facts, rather than words. And when technological leadership is lost, the next casualty is production leadership.