Aquatic macrophytes and algae can be divided into two relatively distinct groupings: (a) the microalgae, such as diatoms and most green and blue-green algae, which can only be seen, identified and counted with the aid of a microscope; and (b) those vascular plants and macroalgae that can be seen and assessed by the naked eye. Macroalgae include, in marine systems, the seaweeds and certain filamentous algae, and in freshwater systems the stoneworts (e.g. Chara and Nitella species) and filamentous algae (often lumped under headings such as ‘blanket weed’).

The methodology for surveying and sampling microalgae in their various forms, e.g. single-celled phytoplankton, diatoms growing on substrates and benthic mats, and in various habitats, e.g. freshwater, estuarine and marine systems, has been developed over the years and such methods are generally well described. This section provides an overview of some of the main aspects of the different techniques for surveying and monitoring aquatic microalgae; the reader needs to consult some of the recommended sources at the end of the book for further details or seek advice from an appropriate specialist. Different techniques are required for aquatic macrophytes; perhaps surprisingly, methods are still being developed to ensure that reliable surveying and sampling can be undertaken in a systematic and repeatable form.

Monitoring macrophytes in the aquatic environment presents some problems that have necessitated the development of techniques that are distinct from those used for monitoring terrestrial plants.

The UK has some important natural fish communities, which require active conservation via habitat protection and ensuring that other fish species that may upset the existing ecological balance are not introduced to these key sites.

Where sites contain Lampreys, Vendace, Shad, whitefish, Smelt, Charr Salvelinus alpinus, Bullhead or other fish species of conservation concern, information on the status of stocks is particularly important.

Whether a fish stock is self-sustaining in the long term is an important attribute: some exploited freshwater fish (e.g. Brown Trout Salmo trutta) are now routinely stocked with hatchery-reared individuals. Stocking can have impacts on locally adapted fish populations, and stocked fish can give the impression that a population is abundant when, in fact, it is not self-sustaining. The distribution of successfully reproducing fish is a valuable measure of the ecological condition of a given river system. Tributaries or main river stretches in which fish are unable to spawn successfully may indicate, for instance, habitat degradation of various forms or barriers to migration. Fisheries surveys can therefore produce important insights into the health of the overall aquatic environment.

All natural fish stocks fluctuate in abundance in response to changing environmental conditions and degrees of exploitation. Any single measure of abundance is therefore of limited value unless it is viewed in the context of historical change. Long-term catch records, for instance for Atlantic salmon Salmo salar, can be particularly valuable in helping to determine likely trends in population abundance.

Bats are nocturnal, highly mobile animals that are adapted to foraging for insects in a variety of habitats. Generally during the day they roost in a variety of structures, commonly tree cavities, barns and buildings. In winter, they hibernate in built structures and underground places such as caves and mines.

Most information about bats has been obtained by making emergence counts from roosts, from activity surveys with bat detectors and from monitoring bat boxes, with some records from a variety of other sources. There is scope for gathering good-quality information by the use of novices with minimal training, while skilled enthusiasts, especially helped by modern technology, can produce valid results from a wide spectrum of habitats. The network of bat groups (supported by the Bat Conservation Trust in the UK) provides specialist training of new recruits, although expertise is patchily distributed.

Survey methods (Tables 25.1 and 25.5) include finding roosts by direct observation and locating dispersal routes and feeding habitats, often aided by equipment such as bat detectors (ultrasound detectors), as detailed below:

• Day searches: structures (e.g. buildings, walls, bridges, trees, mines and caves), finding signs and/or bats

• Dusk observations: emergence counts from roosts, dispersal commuting routes, flight paths from roosts, foraging habitats

• Dawn observations: aerial ‘swarming’ at roosts allows location of new roosts

Because of the difficulties inherent in recording bats, and because surveys often produce ‘sample’ rather than absolute results, it is best to encourage keen individuals to undertake projects in which the same methods and dates are used and the same search or time effort is expended, so as to reduce bias.