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Barry J.,University of Glasgow | Bodles K.J.,Queens University of Belfast | Boylan P.,Loughs Agency | Adams C.E.,University of Glasgow
Biology and Environment | Year: 2015

This study presents evidence of the decline in European eel abundance in a transitional water body in the Northern Ireland from 1967-2013. The available historical data is from an important period, representative of the baseline abundance of eels in a transitional water body before recruitment collapse. The results from this study indicate the current eel population in the Foyle estuary is 3.38% of historical levels. © ROYAL IRISH ACADEMY.

Barry J.,University of Glasgow | Newton M.,University of Glasgow | Dodd J.A.,University of Glasgow | Hooker O.E.,University of Glasgow | And 3 more authors.
Hydrobiologia | Year: 2016

A fixed receiver array was used to examine the movement patterns and space use of the European eel Anguilla anguilla in an oligotrophic Irish lake between July and September. We assessed home range size, temporal change in spatial behaviour and activity patterns of broad-headed (n = 11) and narrow-headed (n = 8) morphotypes. Broad-headed individuals displayed a larger home range (mean KUD95 (km2):0.296 ± 0.04 S.E.) in comparison to narrow-headed individuals (mean KUD95 (km2):0.143 ± 0.02 S.E.). Eel activity was strongly dependent on light conditions. Narrow-headed individuals’ movement peaks occurred at dawn and dusk in comparison to broad-headed individuals which exhibited a more stable movement pattern throughout night and into dawn, suggesting that narrow-headed eels are more crepuscular in nature whereas broad-headed individuals are more nocturnal. Lunar phase period also influenced eel movement within the lake. These results provide valuable insights into the spatio-temporal distribution of yellow eels in a lake system, demonstrating that individuality in foraging behaviour has direct influence on spatial patterns. © 2015, Springer International Publishing Switzerland.

Bromley C.,Queens University of Belfast | McGonigle C.,Loughs Agency | Ashton E.C.,Queens University of Belfast | Roberts D.,Queens University of Belfast
Hydrobiologia | Year: 2016

Habitat degradation is a contributory factor to poor recruitment and sustainability of the European native oyster, Ostrea edulis. Bed cleaning (harrowing) is a widely referenced but little studied habitat management measure aimed at exposing clean shell for oyster larvae to settle upon. This study carried out a large-scale field experiment in Lough Foyle on the border of Northern Ireland and Ireland over 3 years aimed at investigating the effects of harrowing on oyster spat settlement, substratum condition, suspended particulate matter and associated faunal assemblage. The results demonstrated that O. edulis spat settlement was higher in unharrowed areas and there was no significant difference in bivalve settlement between the two treatments. Harrowing had no significant effect on percentage cover of fouling organisms, but there was a significant difference between assemblages in harrowed and unharrowed treatments. This study concluded that harrowing is not suitable for all oyster production areas and should only be employed with caution. © 2015, The Author(s).

de Eyto E.,Marine Institute of Ireland | White J.,Marine Institute of Ireland | Boylan P.,Loughs Agency | Clarke B.,University College Cork | And 7 more authors.
Fisheries Research | Year: 2015

Management of many salmon populations is based on maintaining individual stocks above a conservation limit defined as the maximum sustainable yield point from a stock recruitment (SR) relationship. A crucial input parameter of any SR analysis is an accurate measure of fecundity. Atlantic salmon (Salmo salar L.) fecundity data from nine rivers in Ireland were collated and analysed, providing the first comprehensive multi-river assessment of egg numbers for Irish stocks. The number of eggs in wild 1SW fish (1 sea winter, also known as grilse) varied with fish size and also according to the source river. When expressed as eggs per kg of fish, river was a less important explanatory variable. The number of eggs in wild fish averaged 3441 for 1SW fish and 6059 for MSW (multi-sea winter) fish, respectively. Egg diameter also varied with fish size and source river. A negative binomial model of egg number per fish, with weight as the only explanatory variable, accounted for 60% of the explained deviance in this dataset. When applied to a large national dataset of fish weights from angling records, this model allows river-specific fecundity to be estimated for salmon populations with varying life history characteristics. The model predicts that the fecundity of Irish salmon is at the lower end of the range reported for Atlantic salmon across Europe. © 2014 Elsevier B.V.

Bromley C.,Queens University of Belfast | McGonigle C.,Loughs Agency | Ashton E.C.,Queens University of Belfast | Roberts D.,Queens University of Belfast
Ocean and Coastal Management | Year: 2016

The study was aimed at learning lessons from historical translocations of the European native oyster, Ostrea edulis and contributing to the debate on best practice for restoration projects. An extensive literature review of over 100 documents spanning 200 years was conducted to look at translocations of Ostrea edulis and investigate temperature related reproduction. Differences among geographical locations were assessed by multivariate analysis of reproductive data. Translocations of hundreds to millions of Ostrea edulis have taken place over the past 200 years, mainly for commercial purposes. Movements were either single actions or regular events over many years. Whilst 75 separate records of Ostrea edulis movements from within European waters were documented, it is likely that many more took place. Introductions have also been made outside Europe for aquaculture; translocations back to European waters, have led to the introduction of pathogens. The timing and duration of reproductive periods and spawning temperature thresholds of Ostrea edulis in the middle region of its distribution range were similar. Cluster analysis of documented periods of reproduction indicated that introduced and restocked populations clustered with their putative donor populations. Whilst the Irish production areas clustered together, reproductive cycles in Lough Foyle in the northwest of the island of Ireland showed greater similarity to the now extinct deeper water English Channel beds. Historically, the ability of oysters to breed after translocation was not considered important. Successful reproduction and recruitment is however fundamental to conserving the species. Where translocation of stock is used to restore Ostrea edulis in areas where it has been extirpated, this study suggests that restocking should be at high densities and carried out over several years and that harvesting should be restricted to increase the chances of establishing self-sustaining populations. © 2016 Elsevier Ltd.

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