How Important It Is to Produce Seeds for The Aquaculture of Bivalve Molluscs?
Tatiana N Olivares-Bañuelos*
Instituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California, México
Submission: September 07, 2018; Published: September 27, 2018
*Correspondence author: Tatiana Nenetzen Olivares Bañuelos, Instituto de Investigaciones Oceanológicas Universidad Autónoma de Baja California, Carretera Tijuana-Ensenada No. 3917, Fraccionamiento Playitas 22860 Ensenada, Baja California, México.
How to cite this article: Tatiana N O B. How Important It Is to Produce Seeds for The Aquaculture of Bivalve Molluscs?. Oceanogr Fish Open Access J. 2018; 8(3): 555740. DOI:10.19080/OFOAJ.2018.08.555740
Fishery products are an important part of the diet in many countries of the world, where demand increases proportionally with population growth. The greater request of seafood products refers to fish, however, the production and harvest of molluscs, especially bivalves, will also play a key role in satisfying this growing market. To meet this demand, it is necessary to have an available number of organisms, which may be the product of either fishing or aquaculture. Nevertheless, there are not enough studies about the biological and ecological characteristics of these resources that guarantee maintainable production. This makes it difficult to carry out sustainable and adequate exploitation of the natural wealth. Alternatives involve either the repopulation of natural banks or the seed production, which can be used in aquaculture farming’s for the production of bivalves until their commercial size. In either case, it is necessary to continue researching in the biology of the bivalves and innovating working methods to produce mollusc seeds and meet the demands of the emergent market.
Bivalve molluscs (oysters, mussels, clams, and scallops) are an important part of the world’s fishing production. According to the most recent statistics compiled by the FAO, worldwide aquaculture production in 2014 reached the historical maximum of 73783.7 thousand tons (live weight), with a value of 160.200 USD million . Of these, 21.8% (16.1 million tons) corresponded to molluscs with a market value of 19.000 USD million. The fact that more than a fifth of the world’s aquaculture production refers to bivalves, indicates that this group of organisms is relevant in the daily diet of the population.
Bivalves are ideal for aquaculture since they are herbivores that require minimal management in the laboratory, and do not need more food than microalgae that are naturally found in seawater . Although they have been cultivated for centuries, recent technological advances in the field of mollusc farming have allowed increasing their production significantly. Farming methods and technologies require constant improvement in order to meet growing demand and to make bivalve farming an economically attractive activity for investors and those wishing to start in that activity. In order to achieve successful cultivation, it is vital to improve the efficiency of aquaculture activities.
First, it is important to consider that in the world the areas where mollusc farming can be practiced are limited, and it will be increasingly difficult to find new sites for this activity due to the
demographic pressure and the urban development of the coasts
. Second, the capture of natural bivalve banks will continue to be important. In many of the natural populations where is practiced the mollusc seed capture, organisms are already close to the maximum sustainable limits, and in some places they have already surpassed them. This situation can be alleviated through aquaculture techniques, which offers an alternative to the exploitation of natural populations .
Currently, in most of the world’s bivalve farms, seeds are collected in natural banks (areas of natural abundance), and the substrate (fixing material) is placed in the hatchery tanks during the breeding process. The larvae are collected in metamorphosis and transferred to the hatcheries until it reaches a commercial size. Having an abundant, reliable and low-cost seed is an essential requirement for any marine cultivation or exploitation activity. Seed collection in areas of natural recruitment will continue to be important for bivalve farms, and undoubtedly, in some areas this practice may be intensified to meet the increased demand. It must be remembered that in many farming areas, there are not natural breeding zones that supply the necessary bivalve seeds for commercialization. In other zones, producers develop and cultivate specific varieties of bivalves that fit their particular needs, sometimes introducing non-allochthonous (exotic) species, for which they do not have a constant source of seed. For this reason, it is necessary to recognize the importance of the natural breeding areas and make a great effort to conserve them, repopulate them or, failing that, to look for alternative
methods that allow us to continue obtaining bivalves without
affecting the ecosystems.
One of the best alternatives consists of harvesting in natural
bivalve banks or producing the seeds in hatcheries or farms.
Bivalve hatcheries have been in operation for more than sixty
years, and are now well established in many countries. They
form an integral part of many farms and constituting the largest
or only source of seed . In order to optimize the performance
in breeding sites, it is sought to extend as much as possible the
duration of the reproductive period of the broodstock adults
using conditioning methods. The purpose of the conditioning
is to enhance the fecundity of the parents, the quality of the
eggs and the larval viability . Conditioning techniques are
based on stabling environments of optimum temperature and
abundance of food. The adequate conditioning of the broodstock
leads to the generation of seeds throughout different times of
the year. If the seeds are produced at the beginning of the cycle,
in colder climates, it ensures that the seed will have a maximum
growth period before the first winter. Seeds produced under
these circumstances will be larger and more resistant to low
Undoubtedly now and in the future, bivalve hatcheries will
play a very important role in the set of aquaculture activities, as
shellfish exploitation becomes specialized and the demand for
seed increases . Bivalve hatcheries offer several advantages
over harvesting in natural banks, as they are reliable and can
supply seed to farmers according to their requirements and
when convenient, often much earlier in the growing season
than with natural banks. Besides, they can provide specific
seeds that are not available in natural banks, as is the case of
either exotic or genetic varieties with improved biological
characteristics for its exploitation in local areas. The cost is the
principal disadvantage of the seed production in the hatchery. It
is more expensive to grow the seed in a farm facility, than collect
it from a natural bank. Even if in the past economic factors have
probably been the cause of the failure of some bivalve hatcheries,
recent technological improvements have greatly enhanced their
reliability and economic viability. Now it is possible to produce
seed at competitive prices, and in fact, in some parts of the world, hatcheries are the only source of seed for the commercial
aquaculture industry. In addition, there is still room to increase
the efficiency of breeding sites and increase their acceptance as
the best source of seed.
The production of bivalve mollusc seeds is an opportunity
area that needs to be improved. Bivalves have an important
commercial role in the group of shellfish organisms. They are
exposed to overexploitation and it is important to start looking
forward to prevent any setback in their production. Thus, the
research groups involved in the production of marine seeds
should be given the task of highlighting the advantages of
acquiring nursery seeds. More importantly, they should be
promoting research that leads to understand the reproductive
biology of marine species, with emphasis on those of commercial
importance. In addition, researches have a duty to strengthen the
working groups focused on improving production, cultivation,
and growth techniques of marine seeds.
The author thanks to the Instituto de Investigaciones
Oceanológicas - Universidad Autónoma de Baja California and
the program “18va Convocatoria Interna”, for the support and
facilities provided for the realization of the manuscript.