We have extensive experience of working with invasive non-native species for a wide range of clients, including government bodies, port authorities and water companies. This includes surveys of marine and freshwater macroinvertebrates and fish, as well as aquatic and riparian plants and algae.

Identification of invasive non-native species

Among APEM’s staff are scientists who are nationally and internationally known in the field of invasive species and who have created identification guides and risk assessments.

They have been instrumental in first identifying several marine and freshwater invasive non-native species new to the UK, including demon shrimp (Dikerogammarus haemobaphes), migrant prawn (Palaemon macrodactylus), the polychaete worm (Hypania invalida) and quagga mussel (Dreissena rostriformis).

Our experts have helped to publicise the presence of these species and produce identification materials.

Survey and monitoring

Field team on a river walkover survey

APEM’s specialists have an in-depth understanding of the methods required to ensure effective surveys of different species, and have applied these extensively in recent years.

These include type-specific and novel methods such as aerial and bathymetric remote sensing of macrophyte coverage and the use of photography to assess the presence of encrusting marine invasive non-native species.

We also carry out desk study assessments of large invertebrate datasets, as well as more standard approaches including signal crayfish trapping, hand searches for zebra mussel and walkover surveys for invasive non-native plants such as Himalayan balsam and Japanese knotweed.

River bank covered with invasive himalayan balsam, showing the pink flowers

Himalayan Balsam, an invasive non-native plant that is tough to eradicate.

We have also surveyed non-native marine species from photographs and in-situ quadrat and timed search surveys, as well as many sampling strategies  including grab and core samples, settlement plates, surface scrapes, trawls and sweep nets.

Some of these survey techniques are designed specifically as a means to assess the presence of non-native species.

Control and eradication of invasive non-native species

APEM field scientist holding signal crayfish

Field scientist with signal crayfish.

APEM designs and applies control and eradication methods for invasive species including signal crayfish and topmouth gudgeon. With our partner organisations, we develop engineering methods to limit dispersal into sensitive water bodies. Read our case study of the eradication of signal crayfish from Dalbeattie reservoir in Scotland here.

Topmouth gudgeon, species of fish that is an invasive non-native species in the UK.

Topmouth gudgeon


We can advise on biosecurity approaches to minimise the risk of spread of invasive non-native species, including specific advice to commercial clients and on publicity approaches for recreational users of waterbodies.


We can advise on the legal obligations of landowners and developers for the control of invasive non-native species.


APEM also delivers workshops on the identification of invasive non-native species, some of which have been run through our involvement in training through the NMBAQC scheme. We also provide advice and training on monitoring strategies.


  • A comprehensive review of the risk of zebra mussels to the UK water industry for UKWIR.
  • An assessment of the spread and effects of zebra mussels in Salford Quays, Manchester.
  • Aerial surveys of floating pennywort on the River Soar in Leicestershire for the Environment Agency.
  • A study of the distribution of the Chinese mitten crab on the Nene Washes and Ouse Washes Sites of Special Scientific Interest.
  • A project to control signal crayfish in the Dalbeattie Reservoir in Dumfries working with Scottish Water and the Scottish Environment Protection Agency.
  • River surveys to identify Japanese knotweed across Greater Manchester.
  • Species Dikerogammarus haemobaphes

APEM staff and invasive non-native species

APEM employs highly skilled taxonomists with a track record of being able to recognise previously un-reported non-native species and of publishing these occurrences both in the marine and freshwater environments.

Scientists at APEM were the first to identify Dikerogammarus haemobaphes and Hypania invalida in fresh waters in Britain, Palaemon macrodactylus in British estuaries and Crepidula fornicata in subtidal waters in Northern Ireland.

Scientists in laboratory

The freshwater team includes Dr Michael Dobson, a recognised national expert in the field of non-native species. A freshwater biologist with over 25 years’ research experience, he has been involved for several years with invasive non-native freshwater invertebrates, working with Defra to create identification guides for invasive crustaceans and with CEH in horizon scanning for species of concern.

He is an acknowledged UK national expert on invasive freshwater shrimps (amphipods and mysids) and has recently co-ordinated publicity of the newly discovered invasive polychaete worm Hypania invalida.

Dr Adrian Williams has been scientific advisor to the Invasive Species Specialist Group (ISSG) part of the Species Survival Commission of The World Conservation Union (IUCN).

The marine laboratory team includes Dr Chris Ashelby, a recognised caridean shrimp taxonomist and Dr Tim Worsfold, both acknowledged experts in invasive species identification.

Both have published on non-native marine and estuarine species, including the first UK records of Palaemon macrodactylus and range extensions for several marine non-native and cryptogenic species.


APEM staff have been heavily involved in publishing work relating to invasive species. Below are some examples, with APEM authors highlighted in bold.

Elliott J.M. & Dobson M. (2015) Freshwater leeches (Hirudinea) of Britain and Ireland. Keys and a Review of their Ecology. Scientific Publication No. 69. Freshwater Biological Association, Ambleside. Includes invasive species that may appear in the UK.

Mansfield R., Williams A., Hendry K. & White K. (2014) Drivers of change in a redeveloped urban lake: long term trends in a simplified system. Fundamental and Applied Limnology, 185, 91-105. Includes impacts of zebra mussel filtering activities on dynamics and water quality in the lakes.

Moorhouse T.P., Poole A.E., Evans L.C., Bradley D.C. & Macdonald D.W. (2014) Intensive removal of signal crayfish (Pacifastacus leniusculus) from rivers increases numbers and taxon richness of macroinvertebrate species. Ecology and Evolution, 4, 494– 504.

Roy H.E., Peyton J., Aldridge D.C., Bantock T., Blackburn T.M., Britton R. Clark P., Cook E., Dehnen-Schmutz K., Dines T., Dobson M. and 16 others (2014) Horizon scanning for invasive alien species with the potential to threaten biodiversity in Great Britain. Global Change Biology, 20, 3859-3871.

Ashelby C.W., De Grave, S. & Johnson, M.L. (2013). The global invader Palaemon macrodactylus (Decapoda, Palaemonidae): an interrogation of records and a synthesis of data. Crustaceana, 86(5): 594-624.

Dobson M. & Watson S. (2013) Hypania invalida – a remarkable freshwater invasive new to the UK. FBA News, 61 (Autumn/Winter 2013/2014), 9.

Dobson M., Pawley S., Fletcher M. & Powell A. (2012) Guide to Freshwater Invertebrates. Scientific Publication No. 68. Freshwater Biological Association, Ambleside.

Liu H.-P. Hershler R., Marn J. & Worsfold, T.M. (2012). Microsatellite evidence for tetraploidy in invasive populations of the New Zealand mudsnail, Potamopyrgus antipodarum (Gray, 1843). Journal of Molluscan Studies, 78(2), 227-230.

Worsfold T.M. & Ashelby C.W. (2008). Additional UK records of the non-native prawn Palaemon macrodactylus (Crustacea: Decapoda). Marine Biodiversity Records, 1(e48): 1-3.

Ashelby C.W. (2006). Records of the introduced amphipod Grandidierella japonica Stephensen 1938 (Crustacea: Amphipoda: Gammaridea: Aoridae) from the Orwell Estuary, Suffolk. Suffolk Natural History, 42: 48-54.

Ashelby C.W. (2005). The occurrence and distribution of non-native fauna in Harwich Harbour and the Stour and Orwell estuaries, including new records of Caprella mutica Schurin 1935 and Bugula stolonifera Ryland 1960. Essex Naturalist (New Series), 22: 103-116.

Williams A.E. (2005). Water hyacinth: the world’s most problematic aquatic weed. In: Water Encyclopaedia. Surface and Agricultural Water Eds. Lehr J. & Keeley J., John Wiley & Sons, Inc., Publishing.

Williams A.E., Duthie H.C. and Hecky R.E. (2005). Water hyacinth (Eichhornia crassipes) in Lake Victoria – why did it vanish so quickly and will it return? Aquatic Botany, 81, 300-314.

Ashelby C.W., Worsfold T.M. & Fransen C.H.J.M. (2004). First records of the oriental prawn Palaemon macrodactylus (Decapoda: Caridea), an alien species in European waters, with a revised key to British Palaemonidae. Journal of the Marine Biological Association of the United Kingdom, 84, 1041-1050.

If you have any queries, please contact Dr Michael Dobson, head of limnology.
Alternatively you can email us here. Or call 0161 442 8938.