Population genetics and PBDE analysis of English and Welsh otters. Integrated catchment science programme

Otter populations declined drastically across many areas of England and Wales during the 1960s to 1980s. The main cause of this decline is thought to have been high concentrations of organic pollutants, in particular PCBs and dieldrin. This report investigates the health of present day otter populations in England and Wales and, in particular, populations in southwest England. The research focuses on otter numbers and the genetic diversity of populations. It also investigates a possible new threat from organic pollutants, polybrominated diphenyl ethers (PBDEs).In southwest England, research focused on two catchments, the River Camel in Cornwall and the River Itchen in Hampshire. A non-invasive, spraint genotyping study of the otter population inhabiting the Camel, revealed that a minimum of 16 otters used the river during the two consecutive seasons of study (October 2005 - May 2006 and October 2006 - June 2007). The research also provided insight into the ranges and genetic relationships of otters using the river. A genotyping study was also carried out on the otter population on the Itchen. This population declined drastically in the 1950s and 1960s, to just a few isolated individuals, before being supplemented with otters released as part of a captive breeding programme. Microsatellite genotyping of tissue samples showed the Itchen otter population to be relatively diverse, indicating a successful population recovery Additional analysis of genetic haplotypes indicated that captive bred otters have successfully interbred with wild otters, contributing to the genetic profile of the current Itchen population.In a second strand to the project, PBDEs were added to the existing list of organic pollutants detected in otter livers. The concentrations of PBDEs found in otters rival the high concentrations observed in many marine mammal species and are approaching the concentrations of PCBs and DDTs already reported in otters. The profile of PBDE congeners found in otters shows that BDE-47 is by far the most concentrated BDE congener, following the trend found in many aquatic environmental samples. Congeners BDE-99 and -100 are also found at significant concentrations. Otters contain relatively high concentrations of the congeners BDE-153 and BDE-209, a trend more typical of terrestrial top predators.In summary, the otter populations studied in southwest England appear to be recovering well. Genetic diversity of the populations appears to be recovering and levels of diversity observed in the Camel and in the Itchen, a river known to have received substantial input from captive bred animals, are similar. The extant otter population of the Itchen shows evidence of genetic input from releases of captive bred animals. High concentrations of PBDEs have been detected in a range of otter tissues; what effect these levels may be having upon the species is unknown