The Foundation IMC – International Marine Centre, as a pole of the Science and Technology Park of Sardinia, is committed in the development of research projects aimed to promote the introduction of innovative and sustainable techniques for the management of marine and coastal resources. In this perspective, IMC has been focusing its attention on biology, ecology and conservation of the sea urchin Paracentrotus lividus.
By the point of view of resource management, the challenge might be to develop on a regional scale a production chain of sea urchin based on the rearing of juveniles for reseeding and adults for the market, also through polyculture techniques integrated with other species of commercial relevance characterized by shorter production cycles. In order to provide a scientific contribution to this debate, the IMC has developed over time a set of projects specifically addressed tothe biology, ecology and resource management of the sea urchin, in nature and in breeding.
Interest for sea urchin started in 2000 with a pilot study on the experimental culture of P.lividus in rearing tanks, named “Advanced Technologies and Innovation for the valorization of marine bioresources”, funded by The Ministry of Education, Universities and Research (MIUR). The optimal diet was identified after investigation on the feeding habits of the wild sea urchin population in the gulf of Oristano, whose genome was then characterized through mitochondrial DNA sequencing (Homeobox genes, fingerprinting technique), in order to use this genetic markers for a possible “active repopulation”. The results were preparatory to the set-up of a controlled culture systems for sea urchin rearing, with the aim of obtaining a final product (cultured adults) with the same organoleptic characteristics of the wild populations. Larvae gained metamorphosis in 23 days after fertilization, with a mean survival rate of 70%. Mean rate of larvae which gained metamorphosis was 81%. Thereafter, sea urchin natural resources were investigated in the eyes of their sustainable management in the Penisola del Sinis – Isola di Mal di Ventre Marine Protected Area (Sardinian central western coasts). Through the STM project, after the characterization of the major environmental parameters of Sinis, the optimal habitat and the preferred diet for P.lividus were identified, results pointed out that sandstone was preferred by small individuals and basalt by bigger ones, and Phaeophyceae and Rodophyceae were the favourite algae. In addition, suggestions to better regulate sea urchin harvesting in the MPA were given to the managing authority; the probable impact on the marine environment of an active repopulation of sea urchins was estimated.
From that moment onward, IMC began a close collaboration with Sardinian Marine Protected Areas (Penisola del Sinis – isola di Mal di Ventre, Tavolara – Punta Coda Cavallo MPAs) and Parks (La Maddalena Park), suggesting guidelines to improve the sustainable management of the resource. Methods for the assessment of sea urchin population dynamics developed by IMC in the AMPAMED project, i.e. abundance and structure of whole population and stock, predicting models of stock variations due to fishery and natural mortality, have been applied to the Bouche de Bonifacio Nature Reserve, in the Ventilègne Gulf (Corsica).
Recently, IMC has worked on the study of stock assessment and population structure of P.lividus in some MPAs to assess the effectiveness of protection measures and design management strategies, through studies of population dynamics and growth. Results indicate that, where sea urchin harvesting pressure is intense the mean size of P. lividus population dramatically reduces, as in Penisola del Sinis – Isola di Mal di Ventre MPA, with low densities for large sized sea urchins. On the contrary, in Tavolara – Punta Coda Cavallo MPA and La Maddalena Park large-sized individuals represent a relevant portion of the sea urchin populations (over 50%), suggesting a low pressure of harvesting in these areas. Age and growth rate, respectively through the count of growth rings and application of the Gompertz equation, were assessed in the populations of Tavolara and Penisola del Sinis – Isola di Mal di Ventre MPAs; at equal age, individuals from Tavolara had larger diameters and a higher growth rate than those from Sinis, probably due to a low levels of harvesting pressure and natural predation in the MPA area. IMC was the promoter of the advanced workshop, the “Sea Urchin Aquaculture” which led to the publication of the book “The Sea Urchin: From Basic Biology to Aquaculture”(2002, Yokota Y., Matranga V., Smolenicka Z., Eds.), published by A.A. Balkema, and involved scientist from national and international Institutes and Universities of the caliber of the Aichi Prefectural University (Japan) and the Israel Oceanographic and Limnological Research-National Centre for Mariculture (Israel), which continue to collaborate up to now with IMC. IMC is currently cooperating with important scientific partners such as the Sardinian Universities (Cagliari and Sassari) and Porto Conte Ricerche, pole located in Alghero of the Science and Technology Park, and is involved in two important Regional projects: “Integrated approach for the protection, management and valorization of the sea urchin resource in Sardinia”, in collaboration with the Sardinian Universities, and “Molecular characterization of sea urchin gonads finalized to the determination of the quality of the product”, together with Porto Conte Ricerche. The first project aims at contributing to the protection of P. lividus in Sardinia through the acquisition of scientific knowledge about reproduction of wild stocks, recruitment and possibility of active repopulation in the wild, to define those factors that mainly determine the variability in abundance of populations and identify useful tools for a proper management and economic valorization. The goal of the second one is characterizing the biochemical composition which determines the quality of the roe of P. lividus and how it varies in different environmental conditions, to maximize the speed of growth and the quality of the product. Researches for both projects are simultaneously carried on in two Sardinian areas (Su Pallosu, western coast, and Tavolara-Punta Coda Cavallo MPA, north-eastern coast) with different environmental characteristics as prevailing wind, substrate and algal coverage. The trend of the gonadosomatic index (GSI, relationship between gonads weight and total body weight) shows higher values in individuals of the north-eastern coast, probably linked to a greater strength and frequency of winds in the western area, which generate mechanical stress for individuals that automatically feed less intensely, contributing to reduce gonads size. Histological analysis of gonads points out a slight asynchrony of reproductive cycles between the two populations examined, with a probable earlier spawning event in the western coast reasonably due to the different environmental conditions. One year of results will led to gain useful knowledge for a appropriate management of resources and, in addition to preserve the species in the crucial moment of the reproduction, they should be used to highlight the most profitable moment for collecting the gonads of wild and cultured individuals. Challenges IMC has always been focused on improving the conservation of P.lividus by means of its sustainable management. IMC researchers are aware that wild resources should be investigated through studies on reproductive biology, ecology, growth and population dynamics (stock assessment, population structure), in areas with different grade of protection; but they are also developing new methods to release into the wild (reseeding) juveniles obtained by in vitro fertilization of mature adults (collected in the wild to preserve the natural genetic diversity), after preliminary studies on the best environmental conditions which optimize the survival of small individuals, as well as recruitment and predation. Rearing of larvae and adults in controlled tanks for commercial purposes should be promoted, to avoid the overexploitation of wild resources; aquaculture systems allow to gain briefly juveniles which can be released in the wild or maintained in the farm up to the achievement of a commercial size, and then directly sold to trades. In particular, IMC is investing energies and knowledge in sustainable integrated aquaculture, which contemplate the resence of sea urchins as an integral part of the system. IMC is working for the improvement of aquaculture techniques with the purpose of obtaining gonads with enhanced size and quality (determined by taste, colour, shape and firmness), crucial prerequisites to profitable sea urchin aquaculture. Enhancing the quality of gonads of P. lividus in reduced time of growth represents one of the future challenges of IMC researchers.
Barbara Loi, Maura Baroli, Paolo Mossone
Foundation IMC – International Marine Centre
Torregrande, Loc. Sa Mardini – 09170 – Oristano (Italy)
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