Line of action:

Status:

Execution date:

General:

To implement new optimised farming techniques and the restocking methodology of the sea urchin Paracentrotus lividus, which contribute to improving the quality of the gonads produced, extending their marketing period on the market, as well as to the recovery of populations in overexploited areas and the associated fishing activity.

Specific:

1. To develop and implement innovative techniques in the different stages of sea urchin cultivation that improve the biological parameters of the individuals obtained.

2. To design new innovative and improved repopulation methodologies that ensure greater survival success for released individuals.

3. Enhance the value of the commercial product by improving the quality of the gonads.

4. To promote the conservation of species of sea urchin native to Galicia (through cryopreservation), susceptible to reproduction in captivity by replicating the techniques of P. lividus cultivation.

A.1.Identification and bibliographic review for implementation

A.2. Design and implementation of pilot tests for the repopulation of the sea urchin P. lividus

A.3. Definition of management protocols for the improvement of the breeding phase of P. lividus: larval culture and fixation-metamorphosis

A.4. Improvement of the pre-fattening phase of P. lividus

A.5. Mass collection of juveniles for repopulation

A.6. Creation of a biobank of various species of sea urchin as a tool for the conservation of the biodiversity of urchin species

A.7. Communication and dissemination

A.8. Coordination and monitoring of the project

The entity has managed to implement new optimized methodologies for the cultivation and repopulation of the sea urchin Paracentrotus lividus, for which it has had the collaboration of the “San Xosé” Fishermen’s Guild of Cangas. The project has thus contributed to increasing knowledge about methods to improve the quality of the gonads produced, extending their marketing period in the market and supporting the recovery of populations in overexploited areas.

For the execution of the project, more than a hundred scientific publications have been consulted, a bibliographic review of all the existing marking techniques for sea urchins used to date, as well as a study of the physical and biological characteristics of the restocking area with the aim of confirming its suitability for the development of juvenile individuals of Paracentrotus lividus.

Subsequently, the pilot tests were carried out after the selection of the reforestation area based on its biological and physical variables. Two small-scale reforestations were carried out in the natural environment with juvenile urchins marked, specifically, on stones near the coast, on the coast of Liméns and Barra beach (Cangas do Morrazo). However, on neither of the two occasions were the urchins tagged and released in the area recovered, probably due to the fact that the individuals of this species showed a much greater mobility than expected, which has prevented a study of the impact of the methodology applied.

Regarding the management protocols for the improvement of the breeding phase of P. Lividus, three larval cultures were carried out, during which different larval densities, sizes of the culture tanks and frequencies of exchange of water from the tanks were tested. In the fixation‐metamorphosis stage, wavy collectors were used to increase the attachment surface of the larvae, the optimal size of the echinonian rudiment was determined for its transfer to the fixation collectors and different species of benthic diatoms were tested, as a substrate for the fixation of the larvae and for the feeding of the post-larvae once transformed. In this regard, a comprehensive cultivation manual of this species was developed, identifying the optimal physical and biological parameters for the larval development of this species until metamorphosis, and detailing the conditions of cultivation and fattening of this species until it reaches commercial size. The larval survival rate increased by 26% compared to that obtained with previous protocols. A comparative study of the survival results and developmental status of hedgehog post-larvae was also carried out compared to the results obtained with other existing management protocols. In addition, four types of improved diets and two existing commercial diets were designed, developed and tested (3 diets were planned), preparing a comparative study of the results of the diets compared to the traditional diets in the fattening phase, both in terms of the increase in somatic growth and their characteristics and composition.

As a result, more than 50,000 specimens of P. lividus were obtained to repopulate an overexploited area. The minimum optimal release size has been identified as between 15 and 20 mm in head diameter. Once the minimum size was reached, 50,000 juvenile urchins were tagged with the new marking methods and released in the selected area of the coast of Cangas do Morrazo (Costa de ‘Os Castros’). Regarding the monitoring and recapture, it was not possible to carry out the subsequent monitoring of the released urchins due to the temporary delay suffered by the covid‐19 pandemic.

The project also included the creation of a biobank of various species of sea urchin as a tool for the conservation of the biodiversity of native species of sea urchin, in collaboration with the Atlantic Islands National Park. To this end, a study of the protocols for the cryopreservation of different cell types of P. lividus, S. granularis and E. cordatum was carried out. Success was achieved for the first time worldwide with the cryopreservation of sperm from the three species and embryos of S. granularis. In addition, the sensitivity to cryoprotective agents of sea urchin cells was confirmed, which is specific at the species level and at the level of cell development.

On the other hand, fertilizations of S. granularis and E. cordatum were carried out, obtaining high quality in the laying of S. granularis, being able to carry out a study of larval development until settlement. However, the quality of E. cordatum was low and, as it lost the experimental spring 2020 season due to the pandemic, there was no time to delve into this species. Likewise, data of great interest were obtained on the cultivation potential of other alternative species to P. lividus.