The use of bird assemblages as wetland indicators is now well established in the UK. An indicator based on a single taxonomic group can, however, have limitations. Conversely, a multi-taxa approach can potentially provide a more robust reflection of the health of fresh waters. In this paper, we consider the inherent suitability of different taxonomic groups for inclusion in a multi-taxa indicator, based upon taxon characteristics, species richness and prevalence across a range of freshwater habitats, and their practical suitability, based upon quality and quantity of available data. We conclude that, in addition to birds, there are six candidate groups of taxa throughout the world that are currently suitable for inclusion in a multi-taxa indicator. These are: mammals, amphibians and reptiles, fish, dragonflies and damselflies (based on adult recording), benthic macroinverte-brates and macrophytes. Of these taxa, all but amphibians and reptiles and fish are suitable for inclusion in a UK indicator. The types and limitations of currently available datasets are reviewed. We provide recommendations for advancing this approach in the assessment of freshwater systems.

After a short introduction to the classification of medicinal leeches, their historical use in phlebotomy (blood-letting) and contemporary use in neurobiology and medicine are summarised. Over-collecting of wild Hirudo medicinalis in Europe led to reduced populations and the need to import other species, especially the closely related Hirudo verbana from Turkey and, more recently, the Caribbean and Asian leech, Hirudinaria manillensis. The limited information on the quantitative ecology of European medicinal leeches is summarised next. They require warm-water ponds with a range of suitable hosts, especially amphibians, to survive and prosper. Medicinal leeches can persist with a low minimum viable population size, which may be typical of rare freshwater invertebrates in isolated habitats, especially species limited by high temperature requirements and specialised food sources. Phylogenetic relationships, using molecular methodology, show that there are at least two independent lineages of medicinal leeches with Hirudo medicinalis, H. verbana and Hirudinaria manillensis being closely related. The type species, H. medicinalis, was once abundant in Europe but is now rare and on the endangered list in several countries. Genetic studies have confirmed the erroneous marketing of H. verbana as H. medicinalis. It is highly probable that H. verbana has already escaped into the wild. Unlike H. medicinalis, H. verbana has no legal protection. We conclude that the major factor in the decline of medicinal leech populations has been the general loss of wetlands, especially eutrophic ponds and marshes throughout Europe. Destruction of these water bodies has also led to a decline in amphibians that are an important source of blood-meals for the leeches and are crucial for the survival of their juveniles. More quantitative information is required on H. medicinalis, and especially H. verbana, to facilitate their conservation and management, and to prevent them becoming extinct in the wild.

The United States Clean Water Act (CWA) is one of the key legal means in the USA to ‘restore and maintain the chemical, physical and biological integrity of the nation's waters’. Given the pervasive influence of human development and associated climate change in increasing water temperatures in streams of the USA, salmonids are particularly susceptible to reduction in productivity and geographic distribution. Native and introduced, self-sustaining salmonid populations can be found in most of the 50 States of the US. Despite this commonly shared resource, the highly similar temperature sensitivity among salmonids, and the legal imperative under the CWA to provide full protection to the most sensitive uses, the States supporting these thermally sensitive species have adopted a wide range of standards. As these standards are so divergent, even though the protection goal under the CWA applies uniformly to all States, it is clear that water temperature standards have been developed under conflicting interpretations of the best science available or there is a misunderstanding of the level of protection needed. The current EPA Gold Book guidance for development of protective standards, dating from 1973, still recommends the use of MWAT (maximum weekly average temperature) as a means of assigning protective chronic temperature standards to coldwater fisheries. MWAT, applied according to EPA guidance, is typically used in conjunction with an acute upper limit. From its inception, evidence was available to show that MWAT was inadequate to protect against chronic thermal impairment. This review of temperature standards, applied across the 50 States, collectively reveals a set of ecologically based principles that can be extracted from available standards and would provide a better measure of protection. It is deduced that standards might better apply to optimum temperatures for each life-history stage to protect against chronic thermal effects. These should include: geographic identification of core spawning and rearing areas; recognising cumulative warming from multiple sources; a limit on rate of warming or cooling; special standards for salmonids with exceptionally lower specific temperature requirements, requiring natural thermal patterns on a daily, seasonal, and annual cycle; and regulating the frequency of exceedence of standards on a multi-year basis. The diverse temperature standards found in the statutes of individual States to protect fish species with highly similar biological requirements are indicative of the failure of States to provide consistently high levels of protection and of the EPA to ensure State application of the best science through its standards approval process. In addition to appropriate standards, monitoring, listing of streams as water quality impaired, and development of restoration plans are essential to the success in protecting the coldwater fish resource.