Page 223 - Freshwater-Biology-and-Ecology-Handbook

3.1.5 WHPT (Walley Dikerogammarus haemobaphes

Hawkes Paisley Trigg)
indices for older data sets

WHPT is a development of BMWP. Like BMWP, it is
expressed as an ASPT and Ntaxa. The main differences
are that it includes more families, particularly of Diptera.
BMWP-composite families are considered as separate
families, each with their own index values, and different
abundances of each taxon also have their own index
values. This not only improves its accuracy, but allows it to
respond to subtle pressures around the Good-Moderate
status boundary that affect abundances before the
taxonomic composition changes.

WHPT was derived from an analysis of invertebrate data
and BMWP-ASPT values from a very large data set of Variations of the standard WHPT indices have been devised
approximately 100,000 samples collected and analysed so that it can be estimated from older data analysed to the
by standard RIVPACS procedures (see Chapter 2). In its level required for BMWP indices (ie RIVPACS Taxon level
standard form, it is the basis for the UK’s river invertebrate TL1), without records for abundance or the additional families
(general degradation) status classification. Both the used by WHPT but not by BMWP. Whereas the standard
standard form of WHPT and the classification are abundance-related version of WHPT ASPT can only be
described in detail in Chapter 3. calculated from standard RIVPACS samples, the presence-
only version described below is suitable for samples
collected by other methods.

If abundance data is not available or the sample has not been
WHPT – Walley Hawkes collected by standard RIVPACS methods you can estimate

Paisley Trigg indices WHPT ASPT by using index values for the presence of taxa
termed ‘presence only’ or in RICT2 ‘non Ab’ index values.
Index values have also been devised for BMWP composite
WHPT indices were developed from BMWP indices, families (termed ‘CompFam’ in RICT2). These are listed
which they replace. The most common form of WHPT in the paper by Paisley et al. (2014) and included on the
(41)
uses abundance data but versions of WHPT have WHPT calculator spreadsheet. These forms of WHPT ASPT
been devised for use with older data sets without are more accurate than BMWP ASPT, but they are not as
abundance data or identified to the level used for accurate as the abundance-related version of WHPT using
BMWP indices. WHPT indices are more precise and distinct (rather than composite) taxa and they must not be
more accurate than BMWP and are therefore better used to determine WFD status class. Being on the same
able to detect nutrient and other mild pressures. scale, these forms of WHPT ASPT are comparable with
the standard form of WHPT ASPT, but WHPT NTaxa is only
comparable if it is based on the same group of taxa.

Freshwater Biology and Ecology Handbook | 223
–