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Assessment of Species Catch Composition in Fisheries Posing a Risk to Biodiversity

Project Outputs

Static net fisheries are known to pose a potentially widespread risk of capture to a number of designated species including grey seal, harbour seal and small cetaceans (i.e. porpoises and dolphins). Furthermore some metiers within the static net fleet also have a by-catch of rare and endangered fish species, of commercial species subject to TAC, and potentially there are also incidences of seabird by-catch. However, because of the nature of the fishery operations (e.g., vessel sizes, seasonality, variable soak times and depths, weather constraints) and of the prevalence and distribution of this by-catch, especially seals and cetaceans, it is difficult to quantify and assess the current spatial/temporal dimension of the interaction and its population level effects. More scientific sampling data are required from relevant regions to increase the precision and accuracy of the existing by-catch estimates. This enhanced data collection could usefully be combined with sample provision to existing studies (e.g., population genetics) to augment information on the population ecology of species that are incidentally caught. High uncertainty of by-catch is one of the gaps identified in the fisheries Natura risk assessment for seals and cetaceans. By-catch is also flagged as an important pressure/threat in Ireland’s reporting on the conservation status of such species to the European Commission under Article 17 of the Habitats Directive. Although Ireland currently has an observer programme on many of the commercial inshore and offshore fleet metiers these programmes are optimised for assessment of fish catches for the Data Collection Framework (DCF). Designated or rare and endangered species are not typical in fish catches but occur sporadically but also potentially catastrophically in the case of small or localised/resident populations (i.e. potentially high but infrequent by-catch). Estimates for such zero inflated data are difficult to obtain and the resolution of this problem requires in the first instance an enhanced observer programme for fleet metiers that pose the highest risk of by-catch of such species. 

Project Tasks include the following:

  1. The fishing vessels:
    The first task is to identify the population of vessels to be sampled under an enhanced observer programme and the historic fish catch composition of these vessels to identify the metiers (vessel gear catch profiles). Previous work by BIM is a basis for this as is the Marine Institute’s logbook database. However, the level of activity by static net vessels under 10m (no logbook) and the location of activity of vessels under 12m (no VMS) will require profiling through a review of expert and local knowledge held in BIM and the industry. This was last completed in 2013 for the Natura fisheries risk assessment project and again the risk assessment report is a starting point. Metiers will include large mesh tangle nets targeting crayfish, offshore tangle netting for hake and monkfish, inshore gillnetting for cod, pollack and mixed demersal fish and trammel netting for bait in shallow water.
  2. Sampling design:
    Once the population of vessels in each metier is known an observer programme can be designed in order to provide unbiased estimates of by-catch and catch composition using methods for statistically sound sampling described by ICES. The observer programme can also be enhanced, for example to collect small tissue samples from by-caught species for laboratory analysis (i.e. skin and blubber biopsy) or to collect seabird carcasses.
  3. Co-ordination of the observer programme:
    A co-ordinating observer will be contracted to manage the enhanced observer programme. This will include the identification and allocation of trips to observers across the different metiers and logging of data & sample returns. All SOPs and data management procedures for this type of work are already established in the Marine Institute. In 2017, observers will be provided with small toolkits related to the collection and storage of tissue samples.
  4.  Genetic profiling of seal and cetacean by-catch:
    One of the central questions in the risk assessment of the interaction between seals and set net fisheries in Ireland is the origin of the animals caught in set nets. This issue may also apply where some cetacean species are concerned. If the by-caught animals belong to comparatively small Irish breeding populations then the risk to the population from by-catch mortality can be much more significant than if they originate from much larger transnational populations for instance. In order to address such questions, tissue samples will be collected from all by-caught seals and cetaceans for genetic screening through separate projects. There is currently one such project in place with co-supervision by the National Parks & Wildlife Service (NPWS). Samples collected through the enhanced monitoring project will therefore be made available to NPWS via arrangement with the coordinating observer.
  5. Screening of stranded carcasses of seals and small cetaceans:
    Although the observer programme observes a sample of the fisheries by-catch in real time and can provide estimates of total by-catch for different metiers if there is adequate coverage, additional information can be obtained if the cause of mortality of stranded animals is determined. Under Ireland’s ongoing Cetacean Strandings Scheme a small proportion of the annual stranding records show scientifically established external signs of fisheries by-catch, including broken bones, obvious net marks, gear entanglement or fins cleanly removed. In parallel with its at-sea observation method, the enhanced monitoring programme provides an important opportunity to subsample stranded marine mammal carcasses for evidence of by-catch interaction, if this occurs. It is aimed to use both components of the study to inform one another, improve the assessment of relevant metiers of concern and to enhance scientific and management understanding of such interactions and their risk to protected species. This project will establish contracts for the targeted recovery and post-mortem examination of a sub-sample of small cetaceans stranded around the south and west coasts of Ireland through liaison with the coordinator of the Cetacean Strandings Scheme and through international best practice in post-mortem examination (PME).
  6. Future sampling recommendations:
    Results from the enhanced by-catch monitoring programme will be reviewed in relation to end-user requirements. Recommendations on sampling methodologies and sampling effort for bycatch monitoring will be drafted to inform future data collection programmes (link to Union Priority 3 – Data collection Scheme).

The project is carried out in close collaboration with the Marine Institute (Fisheries Ecosystem Advisory Services), National Parks and Wildlife Services, and its parent department, Department of Culture, Heritage and the Gaeltacht (DCHG). The post-mortem examinations of stranded cetaceans are carried out on behalf of the project partners by the Irish Whale and Dolphin Group (IWDG), Galway Mayo Institute of Technology and the Veterinary Laboratory of the Department of Agriculture, Food and the Marine (DAFM) benefitting from specimen collected under the Cetacean Strandings Scheme.


The project has a 2 year duration and runs between 2017 and 2018.

Project Outputs:
  1. Data on by-catch of seals, small cetaceans, seabirds and rare and endangered species by fishing metier in enhanced observer programme based on selected fishing metiers that pose a higher risk to biodiversity, these to include the static net fisheries (2017+) and pelagic fisheries (2018+)
  2. Collection of scientific specimen of by-caught animals in the enhanced observer programme to be disseminated late 2018 for further scientific studies
  3. Results of post mortem examinations of subset of stranded cetaceans from the national stranding’s scheme, stratified by geographic region and species presented in project reports
  4. Collection of scientific specimen of stranded animals used for post mortem examination to be disseminated late 2018 for further scientific studies
  5. Integration of results with data collection scheme and dissemination of data to end-user including DCHG and ICES
  6. Report summarising the results from the enhanced bycatch programme
  7. Inclusion of data in related data calls and advisory requests through ICES, European commission and others as required
Expected Benefit:

1. Improved scientific reporting in 2017+ on bycatch events of seals, small cetaceans, seabirds and rare and endangered species by fishing metier
2. Scientific reporting in 2017+ on the evidence, if any, for fisheries by-catch in the population of stranded cetaceans around the Irish coast
3. Training of Irish scientists in international best practice where PME of marine mammals is concerned
4. Contribution of key tissue samples of relevance in assessing population structure and ecology among the species by-caught in monitored metiers
5. Future estimates of the population level effects of by-catch on seals, small cetaceans and rare and endangered species

Further Information:
Contact Leonie O’Dowd at
Project Cost - Projected:
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