“With the contribution of the LIFE programme, the European Union’s financial instrument supporting environmental, nature conservation and climate action projects.”
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Translocation of pen shell exposed to desiccation to deeper areas
In the Alfacs Bay (Ebro Delta, Spain), the disease has only affected some parts of the bay. It is of utmost interest to search for possible survivors, which could be resistant to the disease. A large number of juveniles and also some adults have been spotted in very shallow areas of the Alfacs Bay not subjected to MMEs. These individuals are at risk due to intense human activities and desiccation in the area. This month, IRTA has performed different census of the shallow areas (<30m depth) to examine for these survivors. Finally, a total of 200 out-of-water individuals have been translocated to deeper, safer areas, with the collaboration on the Zoo of Barcelona. Three new reservoirs in the Trabucador location have been created where repopulation could be successful. A follow up of the translocated individuals will be conducted monthly from now on.
This action will be carried out in two levels. In the first level, because most individuals that needed urgent translocation have already been moved, this has become a maintenance task for juveniles in reservoirs and for punctual movement of new survivors that could be found after the end of the project.
In the second level, until enough resistant fan mussels are found and capable to achieve reproduction naturally, periodical translocation of individuals may have to be conducted among the different reservoirs periodically (once every several few years) and indefinitely, either to maintain a high genetic diversity, or to recover the populations in case any of them could collapse by natural or anthropogenic causes. This artificial recovery of areas optimal for fan mussels, would be an artificial adaptation of metapopulation theory, necessary to avoid the extinction of the species, until the numbers of resistant individuals could increase to safety values for the species.
Reproduction assays and tank maintenance of healthy individuals in IMEDMAR-UCV (Calpe, Valencia) and UA installations (Murcia)
Two replicate actions with 20 individuals each is being carried out at the marine station of IMEDMAR-UCV in Calpe and the installations of Murcia Aquarium (subcontracted by UA). The individuals will be maintained during the entire project in closed circuits. Both institutions have experience in the maintenance of fan mussels in captivity. The objective of the action is to develop culture protocols to maximize the possibilities of captive reproduction, while ensuring the long-term survival of stabled individuals. Once reproduction in captivity is achieved, it will be possible to apply the same methodologies learned to the few resistant individuals, to produce seed with a higher potential of being resistant to the disease. The seed could be released in open waters to recover fan mussel populations. A common protocol will be used for the evaluation of growth rates and maturation degree of individuals in order to establish the best possible diet for the captive maintenance of the species.
On the other hand, different food types and quantities are being tested in Calpe, including phytoplankton gel (Isochrysis, Tetraselmis and Phaeodactylum), rotifers and Artemia nauplii. Furthermore, experiments of enrichment of Rotifers and Artemia, with high quality fatty acids, vitamins, antibiotics, when necessary, are being conducted. The condition and status of the individuals is being periodically evaluated by endoscopy and by the calculation of bioenergetic models (dynamic energy budget model) from faeces and pseudofaeces production, oxygen consumption, etc. Tank conditions (variable water temperatures, nutrients, nature of the sediment -porosity and type-, light cycles and wavelength) is being also modified and adapted to improve the microcosm conditions in the closed circuits.
Shallow census in the Fangar Bay
The Fangar Bay was recently hit by Storm Gloria (January 2020), which decimated hundreds of individuals due to reduced salinity and high turbidity. In a census after the event, only 12 individuals of Pinna nobilis were found alive (see Prado et al., 2020). However, an inner region of the bay has also been observed to host individuals in the recent past and a follow up of the healthy individuals in these shallow areas is being carried out in order to assess the survival of the species in this region, where there is no evidence of disease.
Additionally, some pen shells from IMEDMAR-UCV were returned to their natural habitat after having been part of reproduction assays in controlled tanks, and another group of individuals was removed from the area for the continuation of these experiments in captivity.
At the same time, the production of a professional video describing the main objectives of the LIFE PINNARCA project has been carried out these days in order to record the Fangar Bay census and the reproduction assays, among other things.
Revision of possible emerged P. nobilis at the Alfacs Bay
A large number of juveniles have been observed in a very shallow sandbar area of the Alfacs Bay. Estimated abundance in 2018 was over 3,000 juveniles. Last year, many of them were translocated after being found fully emerged at low tide conditions. The aim of this action is to find new individuals in extreme circumstances and areas where to translocate the survivors. These sub-optimal sites are adjacent deeper and safer zones, at least at 80 cm depth.
First follow up of translocated individuals in the 2023
Monitoring of juvenile individuals transplanted to deeper areas adjacent to the main sand bar of the Alfacs Bay (Ebro Delta, Spain) is being conducted monthly. At each sampling time, the survival and growth of individuals and the physicochemical variables of the area are being recorded. For salinity and temperature, which are likely to be the most determinant variables influencing the dispersal of the Haplosporidian parasite, recording is conducted in continuum using a Hobo data logger.
Implementation of sedimentation fances in Alfacs Bay (Ebro Delta, Spain)
In order to carry out the C6 conservation action described in the LIFE project, different measures will be implemented in each country in the main sanctuaries observed as an environmental improvement action in fan mussel sanctuary areas. In Alfacs Bay (Torre Sant Ramon), IRTA is implementing sedimentation fences in front of two freshwater and sediment discharges points (in front of Ala irrigation channel and Magdalenes drain).
The use of sedimentation fences has been demonstrated to act as a green filter, increasing the retention of suspended sediments, the establishment of new estuarine vegetation, and to minimize erosion and impacts caused by sea level rise. Most of the north shore of the Alfacs Bay is greatly affected by agricultural freshwater discharges, containing nutrients and organic matter as well as agrochemicals used in rice cultivation that constrict the habitat available for pen shells, including water quality and the availability of benthic seagrass meadows of Cymodocea nodosa. The present distribution of the species is mostly relegated to the south coast of the Alfacs Bay, further away from the discharge areas and where seagrass meadows feature enhanced quality conditions. Hence, the implementation of sediment fences along 1-2 km of coast is expected to improve the quality of local habitats which may favour the recruitment of new juvenile individuals in the southern coast.
In addition to sediment fences, IRTA is currently coordinating a proposal with the Spanish government, Catalonian government, Ebro Delta Natural Park and the local council of Sant Carles de la Ràpita aimed at implementing areas of navigation exclusion in shallow zones with high densities of individuals. Another objective is to use freshwater inputs to regulate salinity ranges in certain areas at the northern shore. These objectives are ultimately dependent on the public administration and are being negotiated with the Catalan government and the local community of agricultural irrigators.
