Ex-situ breeding of native unionids in Lake Banyoles (Spain) as part of a LIFE project

Póster presentado en: 2nd International Seminar Rearing of unionoid mussels (Clervaux, Luxembourg - Tuesday 24th November – Friday 27th November 2015)Lake Banyoles is the second largest natural lake in the Iberian Peninsula and is one of the first places in the Iberian Peninsula where massive planned fish introductions have taken place. The proliferation of alien fish species explains the current scarcity of the native species that are the natural hosts of the parasitic larvae of unionids. This situation has led to a dramatic regression in the four native unionid species found in this lake (Unio mancus, U. ravoisieri, Potomida littoralis and Anodonta anatina). As a result of management geared towards the preservation of natural heritage, the ecological quality of this site has improved in recent decades. However, the main challenge for the management of the lake and its surrounding areas is now posed by invasive alien species. Projecte Estany (LIFE 08/NAT/E/000078) was a four-year project (2010–2013) whose main aim was to design and implement a large-scale intervention actions that would combat, slow down and revert the decline in species and habitats of Community Interest via (1) the control of invasive alien species, (2) the strengthening of populations of seriously threatened native species, and (3) the restoration of key patches of riparian habitats. As part of the project to recover populations of two Unio species, a breeding laboratory was set up. During the first years of the project, several methodologies were tested to obtain mussel glochidia (larvae), optimize fish infection and design a methodology for fattening juveniles. Up to three different native fish species were tested as hosts for local Unio larvae: Barbus meridionalis, Squalius laietanus and Salaria fluviatilis. All demonstrated their capacity to act as hosts and release viable juveniles; however, due to their larger size, only the first two species are used for intensive mussel breeding, along with Luciobarbus graellsii. Between 2011 and 2013, a total of 108,875 U. mancus and 27,423 U. ravoisieri juveniles were produced via the artificial infection of host fish with larvae grown in a number of semi-natural sequential breeding systems fed by water and sediment from their natural habitats, pools, plastic outdoor channels, and/or cages. In the tested systems, U. mancus reached a mean length of 9.7 mm (SD_1.53) in one year and 12.4 mm (SD_1.55) in two years; for U. ravoisieri these values were 15.8 (SD_0.76) and 21.2 mm (SD_2.45). In the context of the further four years (2014-17) allotted to the project (LIFE Potamo Fauna, LIFE12 NAT/ES/001091), efforts to breed Unio species in this laboratory, which has been enlarged, will continue. We will describe the results of the different juveniles’ collection systems and the facilities created to improve their growth over the past six years. The protocols implemented, the current installations and the results of the captive breeding of Unio species are shown here.Peer reviewe

Naiads and fish, coupled destiny: the case of basins of north-eastern Catalonia

Póster presentado en: 2nd International Seminar Rearing of unionoid mussels (Clervaux, Luxembourg - Tuesday 24th November – Friday 27th November 2015)Native unionids are among the most threatened groups, as a whole, of the fauna of the Iberian continental waters. Most species are currently in regression, and in fact many of these are cataloged at some level of threat, whether international, national or regional level. Several factors explain this situation, including the destruction or alteration of river habitats and declining water quality, but also the degradation of fish communities. In north-eastern Catalonia four species of naiads are considered native: Potomida littoralis, Unio mancus, Unio ravoisieri and Anodonta anatina. The conservation status of these species in Catalonia is uneven, but generally we can consider all of them highly threatened, given the clear regression observed in their distribution. Much of the historical citations are probably missing at present, or have become residual populations with very low population densities and often on the verge of local extinction due to lack of recent recruitment. In north-eastern Catalonia P. littoralis is in the worst situation, with only four known small populations, with a few observed living animals in each site. On the other hand, recently has been detected an exotic naiad, Sinanodonta woodiana, which is currently expanding. We give a general revision of the known populations of naiads on the area, on the basis of their current structure, and in relation with the recent evolution of local fish communities. In general, it is confirmed that the few native unionid populations with current regular recruitment are placed on river stretches with not severely modified fish communities. These fish communities are characterized by a stable presence of at least one native fish species, and also in general by the absence of exotic fish species, or at most a not stable presence. In contrast, the exotic S. woodiana is now expanding in areas where original fish communities are nowadays strongly altered, often without native fish species.Peer reviewe

Expansion of the exotic unionid Sinanodonta woodiana in low Ter River flood plain (Catalonia)

Póster presentado en: 2nd International Seminar Rearing of unionoid mussels (Clervaux, Luxembourg - Tuesday 24th November – Friday 27th November 2015)In the northeast Catalonia, 4 native unionid species have been cited: Potomida littoralis (Cuvier, 1798), Unio mancus Lamarck, 1819, Unio ravoisieri Deshayes, 1847, and Anodonta anatina (L, 1758). Recently the exotic Sinanodonta woodiana (Lea, 1834), has been cited on Ter and Fluvià rivers. Between 1995 and 2014, several specific surveys were carried out, always below the Pasteral dam, both in the Ter river and in several of its tributaries, including Lake Banyoles. Moreover, from 2010 to 2014 a thorough freshwater bivalves prospection campaign was performed in the alluvial plain of lower Ter, including the river and secondary water masses, mainly irrigation channels associated with the traditional system of agricultural irrigation. The prospections were done by manually on the river bed bottom. All over since 2010 a total of 90 sampling stations has been surveyed in this alluvial plain. Status of native species is precarious, with populations intensely fragmented, and densities often low and heavily aged for lack of recruitment. This situation is clearly attributable to the severe rarefaction of native fish species, since in some areas even completely inexistent. In contrast, the exotic S. woodiana is expanding and occupies already the whole alluvial plain and the lower course of the Ter river, where it is very abundant. Moreover, S. woodiana presents a well-structured global population in the alluvial plain of Ter River and a regular recruitment can be observed thanks to the fact that several exotic fish species are abundant in the area, are potential hosts to them. This exotic unionoid appeared in most of the surveyed localities (81%), and was present in all the types of water bodies surveyed. In 16 % of the localities it was the only unionoid found, and it was present in all of the localities were other unionoid species were present. Specimens of this exotic species found alive constituted the 72 % of the total of alive unionoids collected during the surveying campaigns. Besides this species were quantitatively dominant in the whole of the alluvial plain. Therefore, it is the most spread and abundant unionoid species at present, often with very high densities. It presented a continuous distribution in the lower Ter river basin, as well as in the main irrigation canals.Peer reviewe