• Biased stock assessment when using multiple, hardly overlapping, tuning series if fishing trends vary spatially

      Kraak, S B M; Daan, N; Pastoors, M A (Oxford University Press, 2009)
      Fishing-effort distributions are subject to change, for autonomous reasons and in response to management regulations. Ignoring such changes in a stock-assessment procedure may lead to a biased perception. We simulated a stock distributed over two regions with inter-regional migration and different trends in exploitation, and tested the performance of Extended Survivors Analysis (XSA) and a statistical catch-at-age model in terms of bias, when spatially restricted tuning series were applied. If we used a single tuning index that covered only the more heavily fished region, estimates of fishing mortality and spawning-stock biomass were seriously biased. If two tuning series each exclusively covering one region were used (without overlap but together covering the whole area), estimates were also biased. Surprisingly, a moderate degree of overlap of spatial coverage of the two tuning indices was sufficient to reduce bias of the XSA assessment substantially. However, performance was best when one tuning series covered the entire stock area.
    • Phosphorus release from forest harvesting on an upland blanket peat catchment

      Rodgers, Michael; O’Connor, Mark; Healy, Mark Gerard; O’Driscoll, Connie; Asam, Zaki-ul-Zaman; Nieminen, Mika; Poole, Russell; Müller, Markus; Xiao, Liwen (Elsevier, 2010)
      The aim of this study was to investigate the release of phosphorus (P) to receiving waters resulting from harvesting 34-year-old lodgepole pine trees in an upland peat catchment. The study site was within a 25.3-hectare (ha) area, and was drained by a stream that received flows from ploughed furrows, mainly, via collector drains, and discharged directly to the salmonid Shrahrevagh River, Burrishoole, Co. Mayo, Ireland. The study site was divided in two parts: the upstream part was left intact and the downstream part was harvested in early Autumn 2005 following implementation of forest guidelines. Good management practices such as proper use of brash mats and harvesting only in dry weather were implemented. Two instrumented stations were established – one just upstream (US) and the other just downstream (DS) of the clearfelled area. The measurement of P concentrations at the two stations commenced in May 2005, two months before the harvesting started. The daily mean P concentration at the DS station increased from about 6 μg L-1 of total reactive phosphorus (TRP) during pre-clearfelling to 429μg L-1 in August 2006. By October 2009, four years after clearfelling, the P concentrations at the DS station had returned to pre-clearfelling levels. In the first three years after harvesting, up to 5.15 kg ha-1 of TRP were released from the harvested catchment to the receiving water; in the second year alone, 2.3 kg ha-1 of TRP were released. Linear regression can be used to describe the relationship between TRP load and water discharge. About 80 % of the total phosphorus (TP) in the study stream was soluble and more than 70 % of the P release occurred in storm events, indicating that traditional buffer strips with widths of 15-20 m might not be efficient for P immobilization. The P concentrations were affected by antecedent weather conditions and highest concentrations occurred during storm events following prolonged drought periods. The water extractable phosphorus (WEP) contents in the soil were significantly higher below windrow/brash material than in brash-free areas, and whole-tree harvesting should be studied as one of the means to decrease P export from blanket peats.
    • Strategies for the elimination of matrix effects in the LC-MS/MS analysis of the lipophilic toxins okadaic acid and azaspiracid-1 in molluscan shellfish

      Kilcoyne, J; Fux, E (Elsevier, 2010)
      Considerable efforts are being made worldwide to replace in vivo assays with instrumental methods of analysis for the monitoring of marine biotoxins in shellfish. Analysis of these compounds by the preferred technique of LC-MS/MS is challenged by matrix effects associated with shellfish tissue components. In methods validation, assessment of matrix interferences is imperative to ensure the accuracy of analytical results. We evaluated matrix interferences in the analysis of okadaic acid (OA) and azaspiracid 1 (AZA1) in mollucscan shellfish by using a conventional acidic method on electrospray triple stage quadrapole (TSQ) and hybrid quadrupole time of flight (QToF) instruments, with matrix matched standards for several species. Using the acidic method, we found no matrix interferences for OA, and matrix suppression for AZA1, with the TSQ instrument; in contrast, we found matrix enhancement for OA, and no matrix interference for AZA1, with QToF. The suppression of AZA1 signal on the TSQ instrument was due to interfering compounds carried over from previous injections. The degree of suppression was dependent on the tissue type, ranging from 20 to 70%. Several strategies were evaluated to eliminate these interferences, including the partitioning of the extract with hexane, optimization of the chromatographic
    • Age and growth estimates for the starry smoothhound (Mustelus asterias) in the Northeast Atlantic Ocean

      Farrell, E D; Mariani, S; Clarke, M W (Oxford University Press, 2010)
      This study is the first to estimate age, growth and longevity of M. asterias based on interpretation of band pairs in sectioned vertebrae. Age and growth of 106 male and 114 female starry smooth-hound sharks (Mustelus asterias) were estimated by counting band pairs on unstained sectioned vertebrae. Growth curves were fitted to the length-at-age data using the von Bertalanffy and Gompertz models. The 1-parameter von Bertalanffy-L0 provided the best fit for males (L∞ = 104 cm TL, L0 = 30 cm TL and estimated K = 16 0.224) and females (L∞ = 133 cm TL, L0 = 30 cm TL and estimated K = 0.136). Longevity was estimated to be 11.8 and 20.2 years for males and females respectively. The length weight relationship is also presented for 304 male and 424 female M. asterias. The von Bertalanffy model was fitted to weight-at-age data. These estimates can form the basis of future work on the assessment and management of this species.
    • The preparation of certified calibration solutions for azaspiracid-1, -2, and -3, potent marine biotoxins found in shellfish

      Perez, R; Rehmann, N; Crain, S; LeBlanc, P; Craft, C; MacKinnon, S; Reeves, K; Burton, I W; Walter, J A; Hess, P; et al. (Springer Verlag, 2010)
      The production and certification of a series of azaspiracid (AZA) calibration solution reference materials is described. Azaspiracids were isolated from contaminated mussels, purified by preparative liquid chromatography and dried under vacuum to the anhydrous form. Purity was assessed by liquid chromatography–mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) spectroscopy. Final concentration of each AZA in a CD3OH stock solution was determined accurately by quantitative NMR spectroscopy. This solution was then diluted very accurately in degassed, high purity methanol to a concentration of 1.47 ± 0.08 μmol/L for AZA1, 1.52 ± 0.05 μmol/L for AZA2, and 1.37 ± 0.13 μmol/L for AZA3. Aliquots were dispensed into argon-filled glass ampoules, which were immediately flame-sealed. The calibration solutions are suitable for method development, method validation, calibration of liquid chromatography or mass spectrometry instrumentation and quality control of shellfish monitoring programs.
    • An unintended experiment in fisheries science: a war mediated protected area in the North Sea results in Mexican waves in fish numbers-at-age

      Beare, D; Hölker, F; Engelhard, G H; McKenzie, E; Reid, D (Springer, 2010)
      Marine protected areas (MPAs) are attaining increasing importance in the management of marine ecosystems. They are effective for conservation in tropical and subtropical areas (mainly coral and rocky reefs), but it is debated whether they are useful in the management of migratory fish stocks in open temperate regions. World War II created a large marine area within which commercial fishing was prevented for 6 years. Here we analyse scientific trawl data for three important North Sea gadoids, collected between 1928 and 1958. Using statistical models to summarise the data, we demonstrate the potential of MPAs for expediting the recovery of over-exploited fisheries in open temperate regions. Our age-structured data and population models suggest that wild fish stocks will respond rapidly and positively to reductions in harvesting rates and that the numbers of older fish in a population will react before, and in much greater proportion, than their younger counterparts in a kind of Mexican wave. Our analyses demonstrate both the overall increase in survival due to the lack of harvesting in the War and the form of the age-dependent wave in numbers. We conclude that large closed areas can be very useful in the conservation of migratory species from temperate areas and that older fish benefit fastest and in greater proportion. Importantly, any rise in spawning stock biomass may also not immediately result in better recruitment, which can respond more slowly and hence take longer to contribute to higher future harvestable biomass levels.
    • The occurrence of persistent chlorinated and brominated organic contaminants in the European eel (Anguilla anguilla) in Irish waters

      McHugh, B; Poole, R; Corcoran, J; Pinelopi, A; Boyle, B (Elsevier, 2010)
      The European eel (Anguilla anguilla) is a relatively high lipid, long lived species capable of living in a variety of brackish, fresh and marine habitats. As such, eels can accumulate organic pollutants and have been incorporated into environmental monitoring programs as a suitable “bioindicator” species for the determination of the levels of organic contaminants within different water bodies. The global eel stock is now in decline and while the cause of the collapse remains unidentified, it is likely to include a combination of anthropogenic mortality in addition to environmental degradation. This study provides valuable data on a range of contaminants (PCDD/Fs, PCBs, OCPs, PBDEs, HBCD, TBBPA and PBBs) and extractable lipid levels in eel muscle tissue collected from five Irish catchments. Extractable lipid levels were lower in the yellow eels compared to those in the silver eels. These levels were similar to those reported elsewhere and it has been posited that a decline in the lipid content in yellow eels may have consequences for the future viability of the stock. With the exception of higher substituted dioxins (especially OCDD), in three samples collected from one catchment (Burrishoole) in the West of Ireland, POP levels in general were determined to be low in eels from Irish waters compared to those in other countries.
    • When good neighbours become good friends: observing small scale structures in fish aggregations using multibeam sonar

      Gerlotto, F; Jones, E; Bez, N; Reid, D G (EDP Sciences, 2010)
      Converging results in different scientific fields (behavioural ecology, fisheries biology, acoustic tagging, fisheries acoustics, behavioural modelling) suggest the existence of “micro-groups” inside fish schools. These would comprise a few (5–10) fish maintaining contact during a period long enough to allow individuals to recognise each other. It is hypothesised that they would prefer to share the space with familiar rather than anonymous conspecifics. To evaluate whether acoustic methods could be used to recognise “micro-structures” inside fish schools and help test the “micro-group” hypothesis we analysed acoustic data from anchovy schools off Peru, and gadoids in the North Sea. Data collection used a multibeam sonar (Reson SeaBat 6012). In the Peruvian case study, the sonar was mounted set horizontally on a drifting research vessel and the internal structure of the schools of anchovies was analysed, although individual fish could not be discriminated. In the North Sea case study, the sonar was orientated vertically above a demersal trawl to allow observation of individual fish entering the trawl. Geostatistical analyses were used to evaluate the existence of small spatial structures in anchovy schools. In these schools, “micro-structures” with a scale as small as 0.5 m were observed acoustically. For the gadoids nearest neighbour distance (NDD) measurements were carried out, suggesting that the fish aggregated in small groups (2 to 25 individuals, with an average of 3.7 fish per group) in the trawl catches. The perspectives and limitations of these results are discussed.
    • The occurrence of persistent chlorinated and brominated organic contaminants in the European eel (Anguilla anguilla) in Irish waters

      McHugh, B; Poole, R; Corcoran, J; Anninou, P; Boyle, B; Joyce, E; Foley, M B; McGovern, E (Elsevier, 2010)
      The European eel (Anguilla anguilla) is a relatively high lipid, long lived species capable of living in a variety of brackish, fresh and marine habitats. As such, eels can accumulate organic pollutants and have been incorporated into environmental monitoring programs as a suitable “bioindicator” species for the determination of the levels of organic contaminants within different water bodies. The global eel stock is now in decline and while the cause of the collapse remains unidentified, it is likely to include a combination of anthropogenic mortality in addition to environmental degradation. This study provides valuable data on a range of contaminants (PCDD/Fs, PCBs, OCPs, PBDEs, HBCD, TBBPA and PBBs) and extractable lipid levels in eel muscle tissue collected from five Irish catchments. Extractable lipid levels were lower in the yellow eels compared to those in the silver eels. These levels were similar to those reported elsewhere and it has been posited that a decline in the lipid content in yellow eels may have consequences for the future viability of the stock. With the exception of higher substituted dioxins (especially OCDD), in 3 samples collected from one catchment (Burrishoole) in the West of Ireland, POP levels in general were determined to be low in eels from Irish waters compared to those in other countries.
    • Reproductive biology of the starry smooth-hound shark (Mustelus asterias): geographic variation and implications for sustainable exploitation

      Farrell, E D; Mariani, S; Clarke, M W (Wiley-Blackwell, 2010)
      Examination of the reproductive biology of Mustelus asterias in the north-east Atlantic Ocean highlighted apparent geographical variation in maturity, fecundity and ovarian cycle between Atlantic and Mediterranean populations. The stretch total length (LST) and age at 50% maturity for Atlantic males and females were estimated at 78 cm LST and 4–5 years and 87 cm LST and 6 years, respectively. Size at maturity of females was considerably smaller than in Mediterranean specimens (96 cm LST). Ovarian fecundity ranged from eight to 27 oocytes and uterine fecundity from six to 18 embryos. The gestation period was c. 12 months, followed by a resting period of c. 12 months, resulting in a biennial cycle. Females stored sperm in the oviducal gland and, unlike Mediterranean specimens, no uterine compartments were observed in Atlantic specimens. This study reveals the existence of strong, possibly adaptive, divergence in life-history traits in an elasmobranch, whose northern populations may be more susceptible to overexploitation than previously believed.
    • Differences in habitat selection of male and female megrim(Lepidorhombus whiffiagonis, Walbaum) to the west of Ireland. A result of differences in life-history strategies between the sexes?

      Lordan, C; McGrath, D; Gerritsen, H.D. (Elsevier, 2010)
      The sex ratio in the catches of megrim (Lepidorhombus whiffiagonis, Walbaum) varied systematically with depth on three independent trawl survey series off the west coast of Ireland. Female megrim dominated the shallow catches, while males were more common in catches from deeper waters. The size difference between the sexes alone cannot explain this pattern because it remained evident when fish length was taken into account. Therefore size-specific habitat preferences or size-selective fishing mortality cannot fully explain the observed trend in the sex ratio of megrim. Female megrim grow to a larger size, at a faster rate than males and it is likely that their differences in habitat preferences are related to this. Shallower waters are warmer during the growing season and are likely to provide better conditions for fast growth. An understanding of the mechanisms behind these patterns is an important consideration in the management and conservation of this fish stock, which might be particularly vulnerable because the commercial landings are to a large extent dominated by female megrim
    • Testes and brain gene expression in precocious male and adult maturing Atlantic salmon (Salmo salar)

      Guiry, A; Flynn, D; Hubert, S; O'Keeffe, A; LeProvost, O; White, S L; Forde, P F; Davoren, P; Houeix, B; Smith, T J; et al. (Biomed Central, 2010)
      Background: The male Atlantic salmon generally matures in fresh water upon returning after one or several years at sea. Some fast-growing male parr develop an alternative life strategy where they sexually mature before migrating to the oceans. These so called ‘precocious’ parr or ‘sneakers’ can successfully fertilise adult female eggs and so perpetuate their line. We have used a custom-built cDNA microarray to investigate gene expression changes occurring in the salmon gonad and brain associated with precocious maturation. The microarray has been populated with genes selected specifically for involvement in sexual maturation (precocious and adult) and in the parr-smolt transformation. Results: Immature and mature parr collected from a hatchery-reared stock in January were significantly different in weight, length and condition factor. Changes in brain expression were small - never more than 2-fold on the microarray, and down-regulation of genes was much more pronounced than up-regulation. Significantly changing genes included isotocin, vasotocin, cathepsin D, anamorsin and apolipoprotein E. Much greater changes in expression were seen in the testes. Among those genes in the testis with the most significant changes in expression were anti-Mullerian hormone, collagen 1A, and zinc finger protein (Zic1), which were down-regulated inprecocity and apolipoproteins E and C-1, lipoprotein lipase and anti-leukoproteinase precursor which were upregulated in precocity. Expression changes of several genes were confirmed in individual fish by quantitative PCR and several genes (anti-Mullerian hormone, collagen 1A, beta-globin and guanine nucleotide binding protein (G protein) beta polypeptide 2-like 1 (GNB2L1) were also examined in adult maturing testes. Down-regulation of anti-Mullerian hormone was judged to be greater than 160-fold for precocious males and greater than 230-fold for November adult testes in comparison to July testes by this method. For anti-Mullerian hormone and guanine nucleotide binding protein beta polypeptide 2-like 1 expression changes in precocious males mirrored mature adults (November) but for collagen 1A and beta-globin the pattern was more complex. Conclusions: Expression changes in the fish brain during the process of precocious sexual maturation were small compared to those in the testes. Microarray analysis suggested down-regulation of housekeeping functions and up-regulation of a small number of specific processes. Transcriptional changes in the testes were much more pronounced with anti-Mullerian hormone playing a major role. Expression profiles for mature parr and maturing adult testes indicate subtle differences in gene expression between these two related groups.
    • Suspended solid yield from forest harvesting on upland blanket peat

      Rodgers, Michael; O'Connor, Mark; Robinson, Mark; Muller, Markus; Poole, Russell; Xiao, Liwen (Wiley Online Library, 2011)
      Forest harvesting activities, if not carefully carried out, can disturb the forest soils and can cause significant suspended solid concentration increases in receiving water. This study examined how harvesting, following forestry guidelines, influenced suspended solid concentrations and loads in the receiving water of a blanket peat salmonid catchment. The study site comprised of two forest coupes of 34-year-old conifers drained by a first-order stream. The upper coupe was not felled and acted as a baseline ‘control’ catchment; the downstream coupe was completely harvested in summer 2005 and served as the ‘experimental’ catchment. Good management practices such as the proper use of brash mats and harvesting only in dry weather were implemented to minimize soil surface disturbance and streambank erosion. Stream flow and suspended solid measurements at an upstream station (US) and a downstream station (DS) in the study stream commenced over a year before felling took place. The suspended solid concentrations, yields and release patterns at US and DS were compared before and after harvesting. These showed that post-guideline harvesting of upland blanket peat forest did not significantly increase the suspended solid concentrations in the receiving water and the aquatic zone need not be adversely affected by soil releases from sites without a buffer strip.
    • The effects of growth phase and light intensity on toxin production by Dinophysis acuminata from the northeastern United States

      Tong, M; Kulis, D M; Fux, E; Smith, J L; Hess, P; Zhou, Q; Anderson, D M (Elsevier, 2011)
      For many years, the study of toxic Dinophysis species was primarily restricted to field populations until it was recently demonstrated that some of these organisms can be mixotrophically cultured in the laboratory with the ciliate prey, Myrionecta rubra, which had previously been fed with cryptophytes of the genus Teleaulax and Geminigera. Here we investigated the influence of growth phase and light intensity on the production of diarrhetic shellfish poisoning (DSP) toxins and pectenotoxins (PTXs) in cultures of Dinophysis acuminata from the northeastern United States. The cell toxin content of okadaic acid (OA), dinophysistoxin-1 (DTX1), pectenotoxin-2 (PTX2), and the okadaic acid diol ester (OA-D8) varied significantly with growth phase under all light treatments, at 6 °C. Each toxin quota remained low during middle and late exponential phases, but significantly increased by mid-plateau phase. DTX1 and OA-D8 were variable through plateau phase, while OA and PTX2 significantly decreased as the culture aged. Although maximum toxin content was not achieved until middle plateau phase, the rate of toxin production was generally greatest during exponential growth. The low and relatively constant cellular toxin levels observed during exponential and early-plateau phase indicate a balance between toxin production and growth, whereas in the middle-plateau phase, toxin production continues even though the cells are no longer capable of dividing, leading to higher toxin quotas. Light was required for Dinophysis growth and the production of all toxins, however, there was no significant difference in growth rates or toxin quotas between the higher light treatments ranging from 65 to 300 μmol photons/sq.m/s. These results demonstrate that DSP production in D. acuminate is constitutive, and that specific toxins are differentially produced or accumulated during the cells’ growth phase, possibly in response to changes to their environment.
    • A mussel tissue certified reference material for multiple phycotoxins. Part 1: design and preparation

      McCarron, P; Emteborg, H; Nulty, C; Rundberget, T; Loader, J I; Teipel, K; Miles, C O; Quilliam, M A; Hess, P (Springer Berlin / Heidelberg, 2011)
      The development of multi-analyte methods for lipophilic shellfish toxins based on liquid chromatography–mass spectrometry permits rapid screening and analysis of samples for a wide variety of toxins in a single run. To ensure accuracy of results, validated methods and appropriate certified reference materials (CRMs) are required. CRMs are essential for accurate instrument calibration, for assessing the complete analytical method from sample extraction to data analysis, and for verifying trueness. However, CRMs have hitherto only been available for single toxin groups. Production of a CRM containing six major toxin groups was achieved through an international collaboration. Preparation of this material, CRM-FDMT1, drew on information from earlier studies as well as improved methods for handling bulk tissues, production of reference materials, and isolation of toxins. Previous investigations of stabilisation techniques indicated freeze-drying to be a suitable procedure for preparation of shellfish toxin RMs and applicable to a wide range of toxins. CRM-FDMT1 was initially prepared as a bulk wet tissue homogenate with planned concentrations of domoic acid, okadaic acid, dinophysistoxins, azaspiracids, pectenotoxins, yessotoxin and spirolides. The homogenate was then freeze dried, milled and bottled in aliquots suitable for distribution and analysis. The moisture content and particle size distribution were measured, and determined to be appropriate. A preliminary toxin analysis of the final material showed a comprehensive toxin profile.
    • Integrating vessel monitoring systems (VMS) data with daily catch data from logbooks to explore the spatial distribution of catch and effort at high resolution.

      Lordan, C; Gerritsen, H.D. (Oxford University Press, 2011)
      Vessel monitoring systems (VMS) automatically collect positional data from fishing vessels. The VMS data can be linked to catch data from logbooks to provide a census of spatially resolved catch-and-effort data. We explore and validate the most appropriate and practical method for integrating Irish VMS and logbook data. A simple speed rule is applied to identify VMS records that correspond to fishing activity. These data are then integrated with the catch data from logbooks using date and vessel identifier. A number of assumptions were investigated, and the resulting distribution maps of catch and effort appear to be unbiased. The method is illustrated with an example of a time-series of spatially explicit catch-per-unit-effort (cpue) estimates. The proposed method is relatively simple and does not require specialist software or computationally intensive methods. It will be possible to generalize this approach to similar datasets that are available within the EU and many other regions. Analysis of integrated VMS and logbook data will allow fisheries data to be analysed on a considerably finer spatial scale than was possible in the past, which opens up a range of potential applications.
    • Combined oral toxicity of azaspiracid-1 and yessotoxin in female NMRI mice

      Aasen, J A B; Espenes, A; Miles, C O; Samdal, I A; Hess, P; Aune, T (Elsevier, 2011)
      For many years, the presence of yessotoxins (YTXs) in shellfish has contributed to the outcome of the traditional mouse bioassay and has on many occasions caused closure of shellfisheries. Since YTXs do not appear to cause diarrhoea in man and exert low oral toxicity in animal experiments, it has been suggested that they should be removed from regulation. Before doing so, it is important to determine whether the oral toxicity of YTXs is enhanced when present together with shellfish toxins known to cause damage to the gastrointestinal tract. Consequently, mice were given high doses of YTX, at 1 or 5 mg/kg body weight, either alone or together with azaspiracid-1 (AZA1) at 200 μg/kg. The latter has been shown to induce damage to the small intestine at this level. The combined exposure caused no clinical effects, and no pathological changes were observed in internal organs. These results correspond well with the very low levels of YTX detected in internal organs by means of LCMS/MS and ELISA after dosing. Indeed, the very low absorption of YTX when given alone remained largely unchanged when YTX was administered in combination with AZA1. Thus, the oral toxicity of YTX is not enhanced in the presence of sub-lethal levels of AZA1.
    • Complex pattern of genetic structuring in the Atlantic salmon (Salmo salar L.) of the River Foyle system in northwest Ireland: disentangling the evolutionary signal from population stochasticity

      Ensing, Dennis; Prodöhl, Paulo A.; McGinnity, Philip; Boylan, Patrick; O’Maoiléidigh, Niall; Crozier, Walter W. (Blackwell Publishing Ltd., 2011)
      Little is known about the microevolutionary processes shaping within river population genetic structure of aquatic organisms characterized by high levels of homing and spawning site fidelity. Using a microsatellite panel, we observed complex and highly significant levels of intrariver population genetic substructure and Isolation-by-Distance, in the Atlantic salmon stock of a large river system. Two evolutionary models have been considered explaining mechanisms promoting genetic substructuring in Atlantic salmon, the member-vagrant and metapopulation models. We show that both models can be simultaneously used to explain patterns and levels of population structuring within the Foyle system. We show that anthropogenic factors have had a large influence on contemporary population structure observed. In an analytical development, we found that the frequently used estimator of genetic differentiation, FST, routinely underestimated genetic differentiation by a factor three to four compared to the equivalent statistic Jost's Dest (Jost 2008). These statistics also showed a near-perfect correlation. Despite ongoing discussions regarding the usefulness of “adjusted” FST statistics, we argue that these could be useful to identify and quantify qualitative differences between populations, which are important from management and conservation perspectives as an indicator of existence of biologically significant variation among tributary populations or a warning of critical environmental damage.
    • A potential solution to mitigate phosphorus release following clearfelling in peatland forest catchments

      O’Driscoll, Connie; Rodgers, Michael; O’Connor, Mark; Asam, Zaki-ul-Zaman; de Eyto, Elvira; Poole, Russell; Xiao, Liwen (Springer, 2011)
      Since the 1950s, large areas of upland peat have been afforested in northern European countries. Due to the poor phosphorus (P) adsorption capacity and low hydraulic permeability in blanket peat soil and increased labile P sources, harvesting these blanket peat forests can significantly increase P concentrations in the receiving aquatic systems. This paper briefly reviews the current management practices on the control of P releases from forestry in Ireland and the UK, and proposes a possible novel practice—grass seeding clearfelled areas immediately after harvesting, which should reduce P release from blanket peat forest harvesting. The study was conducted in the Burrishoole Catchment in the west of Ireland. A field trial was carried out to identify the successful native grass species that could grow quickly in the blanket peat forest. The two successful grass species—Holcus lanatus and Agrostis capillaris—were sown in three blanket peat forest study plots with areas of 100, 360, and 660 m2 immediately after harvesting. Areas without grass seeding were used as controls. One year later, the P content in the aboveground vegetation biomass of the three study plots were 2.83, 0.65, and 3.07 kg P ha−1, respectively, which were significantly higher than the value of 0.02 kg P ha−1 in the control areas. The water extractable phosphorus in the three study plots were 8.44, 9.83, and 6.04 mg (kg dry soil)−1, respectively, which were lower than the value of 25.72 mg (kg dry soil)−1 in the control sites. The results indicate that grass seeding of the peatland immediately after harvesting can quickly immobilize significant amounts of P and warrants additional research as a new Best Management Practice following harvesting in the blanket peatland forest to mitigate P release.
    • Impact of early infestation with the salmon louse Lepeophtheirus salmonis on the subsequent survival of outwardly migrating Atlantic salmon smolts from a number of rivers on Ireland's south and west coasts

      Jackson, D.; Cotter, D.; Ó Maoiléidigh, N.; O'Donohoe, P.; White, J.; Kane, F.; Kelly, S.; McDermott, T.; McEvoy, S.; Drumm, A.; et al. (Elsevier, 2011)
      The potential impact of sea lice infestation on outwardly migrating Atlantic salmon smolts has been investigated by treating populations of ranched salmon, prior to release, with a prophylactic sea lice treatment conferring protection from sea lice infestation, for up to 9 weeks. Established populations of ranched Atlantic salmon with well described rates of return were chosen to investigate the potential contribution of early infestation with the salmon louse, Lepeophtheirus salmonis to mortality in Atlantic salmon. Results of five releases from four locations are presented and compared with a time series of releases from Lough Furnace in Newport, County Mayo. The results of this study would suggest that infestation of outwardly migrating salmon smolts with the salmon louse (L. salmonis) was a minor component of the overall marine mortality in the stocks studied.