Previous studies examining the effects of riparian cover on stream temperatures have led to highly variable findings. In an attempt to reduce these uncertainties, this study examines the relationship between stream temperature variability and local climatic conditions over discrete 300-m sections of a watercourse. Seventeen stream sections were chosen within the Slaney catchment on the basis of riparian cover and size. Continuous monitoring over a 2-year period from May 2010 found that riparian cover had a measurable cooling effect on water temperatures at small spatial scales. The magnitude of this effect was dependent on stream size and local climactic conditions. K E Y W O R D S : habitat management, nursery streams, riparian shade, solar radiation, stream temperature.
Small scale and recreational fisheries often lack quantitative monitoring, highlighting potential for other reproducible ways of understanding state. The Fisher's Local Ecological Knowledge Surveillance Indicator (FLEKSI) method was developed here to express user's LEK as semi-quantitative fishery SI. FLEKSI was tested using an online questionnaire disseminated in 2021 to capture angler's knowledge of changing marine recreational fisheries around Ireland (Celtic Seas ecoregion). Sets of Likert questions evaluated four fishery descriptors (species, community, catch, and effort). Respondents were asked to report the subregion (Irish Sea, Celtic Sea, or West Coast) in which they usually fish, and the duration (y) of their angling “career.” Likert scores were reported as diverging bar charts, providing SI values that could be evaluated at different spatial or temporal scales. Respondents (N = 657) reported careers of up to > 41 years. ICES assessments of Celtic Seas demersal fish stocks targeted by anglers provide series of SSB/SSBBtrigger against which the FLEKSI SI were compared. FLEKSI suggested long term decline in all four fishery descriptors, and statistical analysis showed that this trend matched ICES assessment outputs averaged across target stocks of cod, pollack, whiting, and sea bass. FLEKSI provides a standardized framework for integrating user's ways of knowing into fishery monitoring.
This study focuses on stream sections within a relatively low nutrient catchment in south-east Ireland in an attempt to characterize the probable effects of riparian canopy on salmonid diet and prey selectivity within two size classes of nursery stream. Sampling found that brown trout Salmo trutta diet changed significantly in response to riparian canopy regardless of stream size. The observation that S. trutta within unshaded stream sites did not feed on drifting terrestrial prey items to the same extent as those within shaded streams was not due to a lack of availability of this food source. There was no evidence to suggest that S. trutta selectively choose particular prey items.
This study investigates temporal stability in the scale microchemistry of brown trout Salmo trutta in feeder streams of a large heterogeneous lake catchment and rates of change after migration into the lake. Laser-ablation inductively coupled plasma mass spectrometry was used to quantify the elemental concentrations of Na, Mg, Mn, Cu, Zn, Ba and Sr in archived (1997-2002) scales of juvenile S. trutta collected from six major feeder streams of Lough Mask, County Mayo, Ireland. Water-element Ca ratios within these streams were determined for the fish sampling period and for a later period (2013-2015). Salmo trutta scale Sr and Ba concentrations were significantly (P < 0·05) correlated with stream water sample Sr:Ca and Ba:Ca ratios respectively from both periods, indicating multi-annual stability in scale and water-elemental signatures. Discriminant analysis of scale chemistries correctly classified 91% of sampled juvenile S. trutta to their stream of origin using a cross-validated classification model. This model was used to test whether assumed post-depositional change in scale element concentrations reduced correct natal stream classification of S. trutta in successive years after migration into Lough Mask. Fish residing in the lake for 1-3 years could be reliably classified to their most likely natal stream, but the probability of correct classification diminished strongly with longer lake residence. Use of scale chemistry to identify natal streams of lake S. trutta should focus on recent migrants, but may not require contemporary water chemistry data.
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