APEM - Wels catfish

Non-native fish can damage our aquatic environments and threaten biodiversity on a global scale. We need to be aware of upcoming threats and prepared for the arrival of new species.

Among the Invasive Non-Native Species (INNS) in the UK, there are thirteen freshwater fish species currently known to be inhabiting our waterways. Their distribution is highly variable, with species such as the pumpkinseed (Lepomis gibbosus) being limited to the southernmost extremes, whilst zander (Sander lucioperca) have become established in numerous waterways throughout central and eastern England.

The current status of invasive non-native fish in the UK

Fish INNS are key stressors to aquatic environments through competition for resources, increased predation pressure, introduction and spread of pathogens, loss of genetic integrity through hybridisation and altering food webs. Moreover, they are already estimated to be threatening 40% of native European freshwater fishes and yet climate change models are predicting a further increase in the spread of INNS and thus their impact.

Non-native fish species have been introduced to the UK through a variety of pathways, including ornamental purposes, as tools for aquatic habitat management, through water supply transfers, and accidentally via aquaculture routes and poor biosecurity measures around fishing equipment when moving between catchments. It was estimated that the rate of introduction of fish INNS doubled from 1980 to 2010.

Fish INNS impact our native fish species in numerous ways. The topmouth gudgeon (Pseudorasbora parva) rapidly colonises new water bodies and establishes numerical dominance very quickly, enabling it to outcompete native species for space and resources. In contrast to this ubiquitous approach, zander can thrive under turbid conditions due to a specially adapted eye, enabling colonisation of less suitable habitats that native species may be unable to utilise. Some INNS are thought to be able to coexist with native fish species, such as the bitterling (Rhodeus amarus), whilst others are deliberately introduced to assist with aquatic habitat management, such as grass carp (Ctenopharyngodon idella).

The future of invasive non-native fish in the UK

It is critically important that we identify potential areas that are at risk of INNS influx, and equally important to identify pathways through which these species may be introduced and further spread through our ecosystems.

In 2015 the UKTAG Alien Species Group published an alarm list of potentially future invasive species that pose a risk to the ecological status of British fresh waters. This list highlights five species (with an additional three on a reserve list) which are believed to have the ability to invade waterways in the UK. It is hoped that highlighting these species at such an early stage will enable regulatory bodies to implement suitable management options to prevent further spread and aid in future eradication programmes. The alarm list species are:

  • Tubenose goby (Proterorhinus marmoratus / semilunaris)
  • Eastern mosquitofish (Gambusia holbrooki)
  • Monkey goby (Neogobius fluviatilis)
  • Racer goby (Neogobius gymnotrachelus)
  • Round goby (Neogobius melanostomus)
  • Oriental weatherfish (Misgurnus anguillicaudatus) (reserve species)
  • Chinese weatherloach (Misgurnus mizolepis) (reserve species)
  • Asian swamp eel (Monopterus albus) (reserve species)

Rapid colonisation of these species in Europe has already been observed with both climate change (increase in water temperature) permitting a range increase northernly and anthropogenic factors (dam construction) noted to be exacerbating their rates of distribution. It is likely that should these species become established, they will have a preference to heavily modified water bodies, notably the canal network, canalised highly productive rivers and transitional waters.

Given the typically high costs associated with a reactive management approach (i.e. implementing remedial or mitigatory measures to attempt to combat introduction invasive non-native species), it is imperative that efforts are focused on preventative measures, such as the UK fish invasiveness screening kit (FISK), which allows the potential invasiveness of non-native freshwater fish species to be assessed. Such tools, together with the UKTAG approach outline above, are our best strategies for identifying non-native species with the potential to become invasive, and to prevent their colonisation in the UK.

How APEM can help

APEM has extensive experience in identifying, assessing and managing INNS. Our teams were the first to confirm the arrival of several INNS in the UK, and we have strong a track record in INNS monitoring and removal. Combining a suite of dedicated tools, site-specific risk assessment and bespoke mitigation and management techniques, we offer tailored biosecurity plans aimed at reducing the risk of INNS spread.

We also provide a comprehensive range of fisheries science and management options, ranging from assessments of fisheries stocks and analysis of population parameters, to carrying out environmental impact assessments and fish rescues and relocations.

In recent years, APEM has led on important projects assessing impacts of major water resources developments on coarse fish in the River Thames, investigating the use of acoustic behavioural deterrents to protect young twaite shad for Dwr Cymru Welsh Water, and researching and writing a guidance manual on restoring salmon habitats in UK rivers for the Environment Agency.

If you have any queries regarding APEM’s fisheries services, please contact Nicola Teague, Director of Physical Aquatic Consultancy, or Peter Dennis, Director of Field Operations by emailing enquiries@apemltd.co.uk. Alternatively call 0161 442 8938.

If you are experiencing issues with INNS, have a regulatory requirement to manage them, or want to understand more about our approach please visit our website or contact Dr Paul Stebbing to discuss your needs.

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APEM are a global environmental consultancy providing independent advice and guidance to support government and environmental regulatory guidelines.