The population, reproductive biology and physical habitat requirements of endangered freshwater pearl mussel (<I>Margaritifera margaritifera</I> (L.)) populations in Scotland were investigated. Surveys of viable populations revealed overall densities, based on 1m<sup>2</sup> quadrat counts, of 0.27-7.98 mussels.m<sup>-2</sup>. Total estimates for rivers, based on extrapolations of 50m transect counts, ranged from 2,000 to 0.9-3.7 million mussels. The expected predominance of young mussels was not achieved in any population. In order to test a hypothesis that juveniles were under-represented in samples, six populations first studied in 1984/85 were re-investigated in 1996/97. The relative numbers of 11-20y old individuals found in 1996/7 were consistently larger than those of 1-10y olds found a decade earlier. This provides strong evidence of sampling bias. <I>M.margaritifera</I> grow in an approximately asymptotic fashion and the von Bertalanffy equation is an appropriate descriptor. Growth may be influenced by temperature. In general, large mussels grow in large, cold rivers and vice versa; although there are exceptions, which suggest that additional factors may be involved. The timing of annual reproduction seems to be related to temperature. Mussels in the warmest rivers tend to spawn earliest. The prevalence and magnitude of natural parasitic mussel larval (glochidial) infections in wild salmon (<I>Salmo salar</I> L.) and trout (<I>S.trutta</I> L.) stocks were comparable to those reported elsewhere. Older fish seem to be less susceptible to glochidiosis than 0+ fish. Some trout stocks appear to be under-utilised by <I>M.margaritifera</I>, possibly due to differences in behaviour and/or place of origin. River bed substratum characteristics appear to be the best physical parameters for describing <I>M.margaritifera</I> habitat. Boulder-stabilised refugia, which contain enough sand/gravel for borrowing, are ideal habitats for juveniles.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:494121 |
| Date | January 1999 |
| Creators | Hastie, Lee Clark |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=158482 |
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