Biological recording and the
drivers of change in freshwater
Roy Anderson
Objectives

Red list aquatic invertebrates to:

Improve knowledge of

Faunal composition

Habitat association

Change over time
Strategy

Mapping schemes

Require some public participation

Guided by a body of dedicated people driving
and co-ordinating/validating

Ideally with regular updates via websites

Eventually, publication of atlases
Outcome

Mapping schemes
Red Lists

The Red Listing process should:

Obtain and encode all historical data

Compare with modern results

Be subject to periodic update as new data becomes
available

Classify fauna according to IUCN guidelines and register
level of threat

Draw in available habitat, climate and water quality data to
compare with faunal distribution and relate to perceived
changes in that distribution
Adephaga
Aquatic and semi-aquatic Adephaga

Red List published in 2009

244 taxa recorded belonging to 16 families, both fully aquatic
and marginal; 73 red-listed i.e. 30%
Measuring change

Data from early
twentieth century
compared with
recent data to
determine change
in status
Regional extinction risk
A – past, present or future population decline
B – restricted range, fragmentation, continuing decline
C – small population size and continuing decline
D – very small populations in decline
Evaluation






Only a small minority of the declining species were considered to
be in a general population decline i.e. a decline across the country
by comparing distribution pre and post 1980 (category A2)
The vast majority of highly threatened species were considered a
priori to have fragmented ranges or specific requirements
(stenotopy) which was related to decline (category B2)
A large number placed in a lower threat category (VU) were
considered at risk because of the small population size or limited
number of available sites (category D2)
A similar number were also classed as near threatened (category
A3) because of more general decline, but related to reliance on a
specific habitat
Many species associated with fen habitats showed little real
evidence of decline but were classified as at high risk because of
findings outside Ireland
The habitat with most at risk species was fen (next slide) but few
fen species actually show a decline in Ireland!
Habitat associated decline
Siltation - river gravels/lakeshores
Also here: Enicocerus exsculptus, Bidessus minutissimus,
Hygrotus novemlineatus (? diffuse pollution)
Drainage - brackish habitats - lagoons
Also here: Ochthebius marinus, Haliplus apicalis, Helophorus fulgidicollis,
Enochrus halophilus
Warming - montane sites and species
Also here: Dytiscus
lapponicus.
Stictotarsus
multilineatus, Agabus
arcticus
Mollusca
Measuring change

Red List
published in
2009

150 total
native spp of
which 53 are
red-listed:
i.e. 35%

79 aquatic of
which 31 are
red-listed i.e.
39%
Regional extinction risk
A – past, present or future population decline
B – restricted range, fragmentation, continuing decline
C – small population size and continuing decline
D – very small populations in decline
Evaluation
 Very
different from Adephaga
 Risk seems to have its greatest concentration in
category A suggesting general decline rather than
association with rare habitats (stenotopy) or having a
previously fragmented range
 This suggests that an important environmental
variable has changed recently and is affecting many
species
Examples
Eutrophication/diffuse pollution
Myxas glutinosa
Glutinous snail
IUCN Endangered
A2c
A declining species across its entire
west palaearctic range.
Ireland is now its headquarters with
up to 50% of global population.
Needs gently flowing, low-P
calcareous waters.
Also here: Omphiscola glabra,
Anisus vortex, Radix auricularia,
Margaritifera margaritifera, Pisidium
lilljeborgii, P. pulchellum, P.
moitessierianum
Pre-1980
Post-1980
Drainage and Eutrophication
Pre-1980
Omphiscola glabra
Mud snail
[IUCN Extinct ] – Critically
endangered
A declining species across most of
Europe.
Confined to the south-east, and
recently re-discovered at a site in
Co Waterford.
Requires low-P poor fen or
undrained low-nutrient riverine
marshes
Post-1980
Drainage – freshwater marshes, floodplains
Pre-1980
Aplexa hypnorum
Moss bladder snail
IUCN Vulnerable
A2c
Widespread Palaearctic species
living in temporary habitats,
especially on winter-flooding
lakeshores and riverbanks.
Declining thro’ habitat destruction
Also here: Quickella arenaria,
Succinella oblonga, Vertigo
antivertigo, V. moulinsiana,
Musculium lacustre, Sphaerium
nucleus
Post-1980
Drainage - brackish habitats - lagoons
Pre-1980
Hydrobia acuta neglecta
Hydrobiid snail
IUCN Endangered
B2a,b(iii,iv)
A north European endemic.
Confined to coastal lagoons of high
salinity.
Four known sites, two of which
have recently been destroyed by
drainage/changes in management.
Also here: Ventrosia ventrosa,
Truncatella subcylindrica, Mercuria
cf. similis
Post-1980
Warming - montane sites and species
Pisidium conventus
Arctic-alpine pea mussel
IUCN Critically Endangered
B2ab(i,ii,iii,iv)
Boreal relict, probably in steep
decline. Only one recent site.
Conclusions
Drivers of change
 Both Coleoptera and molluscs suffer from diffuse pollution via its
effects on algal growth, de-oxygenation etc.
 This reaction appears more restrained in Coleoptera which are
threatened more by range fragmentation and destruction of specific
fen and peatland types
 Molluscs are possibly unable to escape the effects of diffuse
pollution because they and are less mobile and have a more
permeable integument
 May be good indicators of pollution, both point source & diffuse
 Beetles may be more useful in assessing the decline of specific
habitats
 Brackish habitats home to both groups continue to decline and pose
a threat to many stenotopic species
 Warming affects only one mollusc but a number of beetles