Please cite this article as: Horton, M., Keys, A., Kirkwood, L., Mitchell, F., Kyle, R., Roberts, D.,Sustainable catchment restoration for reintroduction of captive bred freshwater pearl mussels Margaritifera margaritifera., Limnologica (2014), http://dx. AbstractThe Ballinderry River, Co. Tyrone (SAC), is one of only six rivers in Northern Ireland that still supports a population of the globally endangered freshwater pearl mussel, Margaritifera margaritifera. Fewer than 1000 individuals still exist in the river; without intervention it is predicted the Ballinderry pearl mussel will be extinct by 2098. This paper aims to identify key catchment pressures on remaining mussel stocks and prioritise tributaries within the catchment for remediation work to ensure effective targeting of limited resources. A combination of redox assessment, river surveys and SCIMAP modelling was used to rank tributaries, taking into consideration their size and proximity to the main mussel population at the "sanctuary site". Diffuse and point sources of sediment were identified within the prioritised catchment. The Tulnacross tributary was selected as the highest priority tributary and has been used in a pilot remediation study. A number of different hard and soft engineering techniques have been used for remediation as well as replacing cattle drinkers with pasture pumps and fencing alongside the river. Initial observations suggest river substrate is cleaner. This study is an example of how to tackle problems within a large-scale catchment with limited resources with participation of local stakeholders and riparian landowners.

This is the author accepted manuscript. The final version is available from Springer via http://dx.doi.org/Freshwater pearl mussel (Margaritifera margaritifera) populations are declining in Northern Ireland to the extent that a captive breeding programme was established on the Upper Ballinderry river in 1998. Previous genetic analysis of the hatchery broodstock and their first cohort of offspring showed significant levels of inbreeding (FIS = 0.166). The broodstock, which currently numbers ca. 90 individuals, was supplemented with new individual mussels, whilst in 2013, a previously unknown population was discovered on the Lower Ballinderry river. The aim of the present study was to determine whether the rotation of the broodstock has led to a decrease in the levels of inbreeding in the second cohort of juveniles, and to determine whether the new population found in the Lower Ballinderry was genetically distinct from the captive bred population and populations from the Upper Ballinderry, which represent the source of the hatchery broodstock. Genotyping using eight microsatellite markers indicated that levels of inbreeding in the second cohort of captive-bred mussels were high, (FIS = 0.629), and were comparable to those sampled from the original cohort and the hatchery broodstock (FIS = 0.527 and 0.636 respectively). Bayesian analysis of population structure indicated that the newly discovered Lower Ballinderry population was genetically distinct from the broodstock and its source populations on the Upper Ballinderry. The observed differentiation was primarily due to differences in allele frequencies, and was most likely a result of genetic drift. The occurrence of ten alleles, albeit at low frequency, in the Lower Ballinderry population, including four private alleles, suggests that this new population could be incorporated into the broodstock with the aim of decreasing levels of inbreeding in the future.Peer reviewe

Biodiversity loss is a global problem with freshwater bivalves considered among the most endangered biota. The freshwater pearl mussel, Margaritifera margaritifera, is declining throughout its range owing to habitat degradation and overexploitation. In most of its range, populations are regarded as reproductively non‐functional, which has led to the development of captive breeding programmes. A novel method of releasing M. margaritifera was tested, with captive‐bred juveniles being released into the rivers caged in ‘mussel silos’ (protective concrete domes with ventilation creating upwelling to ensure water through‐flow). In total, 240 juvenile mussels were released and survival and growth rates were monitored for 18 months after release for three size classes: A (13.01–20.00 mm); B (10.01–13.00 mm); and C (4.01–10.00 mm). Two experimental treatments were tested: one in which sediment was added to each silo (allowing mussels to orientate and burrow) and one without sediment. Survival by the end of the experiment at month 18 was significantly higher for the largest size class at 97% (although growth was lowest in this cohort), and lowest for the smallest size class, at 61% (although growth was highest in this cohort). Survival and growth were unaffected by the experimental treatment suggesting that adding sediment offered no advantage. Growth was positively correlated both with water temperature and with particle size of suspended solids (both of which were collinear, peaking in summer). There are many ex situ breeding programmes for freshwater pearl mussels throughout Europe and the results of this study suggest that the use of mussel silos may be a useful tool to protect juvenile mussels, allowing them to be released at a relatively early stage of development and minimizing the risk of domestication. Copyright © 2016 John Wiley & Sons, Ltd.

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