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Fish species occurrence and food-web dynamics in a coastal lagoon

Project Outputs

This project will support he Marine Strategy Framework Directive (MFSD) requirement for data and reporting under Descriptor 1 (Marine Biodiversity, Diadromous fish), Descriptor 4 (Trophic Guilds, Food Webs) and Descriptor 6 (Habitats, including coastal lagoons) and will provide data into Ireland’s food-web contributions to the 2023 OSPAR Quality Status Report (QSR) for the NE Atlantic.

Coastal lagoons have been identified as vulnerable to climatic and anthropogenic impacts has led to their classification as an Annex I priority habitat (“in danger of disappearance”) under the EU Habitats Directive (EU, 1992). By their nature, coastal lagoons can change rapidly in response to site specific changes in salinity regime due to changes in freshwater discharge and sea level rise. The protection of these habitats represents a unique challenge in terms of conservation. Coastal lagoons are dynamic habitats, with varying marine and freshwater inputs determining the presence and extent of stratification, and the physical and chemical environment of the epi- and hypolimnion. The biotic assemblages that thrive in such environments are a diverse mix of species, with wide ranges of tolerances.

Lough Furnace, north-east Clew Bay, is described as a good example of a deep, stratified coastal lagoon in a very natural state (NPWS, 2011). Furnace, one of the few permanently stratified lakes known in Ireland and Britain, is at the tidal limit of the highly monitored Burrishoole catchment, itself an SAC.

Diadromous fish present in the lagoon are Atlantic salmon, trout, stickleback and European eel.  The rivers entering Furnace are designated SAC status (Owenduff/Nephin Complex SAC No. 0534) and salmon and otter are listed in Annex II.  Furnace is protected within the Clew Bay Complex SAC No.1482, which is designated for (among other things) its Coastal Lagoons. Eel recruitment is in serious decline and stocks are under the recovery plan of the EU Regulation 1100/2007. Other marine species known to frequent the lagoon include pollack, sea bass, TL grey mullet, herring, spratt, goby spp, flounder, plaice, sole. The status of other diadromous fish in the lagoon, such as lamprey species is unknown. The relict mysid species Neomysis integer, and two rare amphipods (Lembos longipes and Leptocheirus pilosus) have been recorded but their current status is unknown.

Climate Change is likely to have an impact on the physical characteristics of tidal lagoons, their biodiversity and capacity to act as nursery areas for many marine fish species. Conditions may also become untenable for returning migratory species such as salmon and sea trout. Changing temperatures, rainfall patterns and mean sea level rise may have significant impacts on future oxygen dynamics and habitat suitability of such coastal areas.

As part of the reporting obligations under the MSFD, and given the new pressures being applied by factors related to climate change, it is important to establish a baseline for protected coastal lagoons (Natura Habitat, MFSD D6C5) against which Good Ecological Status (GES) can be measured.

Project Outline: This project will establish a fish species list, including the marine and diadromous species, study their diet and establish the relative energy inputs (Carbon and Nitrogen) from both freshwater and marine sources. Existing surveys and data collection can be used as a platform of opportunity for the collection additional ecosystem data to support the reporting requirements for environmental legislation including MFSD (D4 Trophic guilds), WFD, Natura (Habitats Directive Species – salmon, sea trout) and fisheries management plans (i.e. salmon, eel). Vulnerabilities towards changing environmental conditions, including sea level rise and climate, may be identified.

This will be a one-year study with the aim of establishing some baselines:

·         Quantitative assessment of the stock of salmon, sea trout and eel

·         Identify fish species presence, distribution, seasonality and relative abundance

·         Diet analysis of each fish species, and establish a pilot food web

·         Partition the energy inputs into freshwater or marine origin

·         Compare current data with previous surveys, plankton (1969, 1972, 1973), macro-invertebrates (1969), fish data since 1970

This project will set a baseline against which the assessment of possible impacts of various current or proposed anthropogenic impacts can be judged. This study will assist in determining the relationship between the baseline, observed trends in environmental parameters (i.e. salinity, temperature) and species occurrence and abundance and future planning of such anthropogenic activities in the coastal zone. 



This is a 1 year project starting in the summer of 2020

Project Outputs: 

The data will establish new baselines in the tidal waters of the Burrishoole (a typical coastal lagoon) against which impacts and changes can be assessed. Relevant to the monitoring of the status of the Clew Bay SAC habitat and listed species (such as salmon) under Natura.

Expected outputs are:

  1. Species lists of phytoplankton, zooplankton, macro-invertebrates, fish
  2. Relative abundances of fish for one year, comparisons with previous surveys
  3. Quantitative information on the trophic guilds, food-web and energy flow
  4. Relative position in the food chain of the different fish species
  5. Partitioning of the marine and freshwater inputs to the energy cycle.
Expected Benefit: 
  1. The project will provide baseline information on a vulnerable habitat (coastal lagoon) classified as an Annex I priority habitat (“in danger of disappearance”) under the EU Habitats Directive (EU, 1992).  Also relevant to Descriptor 1 in the MFSD, setting a baseline for species and habitats identified under national and international legislation, such as the Clew Bay Complex SAC.
  2. The project will give preliminary listing of species and food webs for a coastal lagoon, relevant to Descriptor 4 in the MFSD.
  3. The baseline information in combination with the high resolution time series data currently being collected in the lough will establish the Burrishoole as a true Long-term Ecological Observatory in both freshwater and tidal saline waters for the assessment of climate change and other impacts.
Further Information: 
For further information contact Russell Poole. Email: Russell.poole@marine.ie
Project Cost - Projected: 
Project Staus: