Marine_Scotland_FishDAC_12547 eng dataset Scottish Government (Marine Scotland) +44 (0)300 244 4000 marinescotland@gov.scot pointOfContact 2025-06-25 MEDIN Discovery Metadata Version 2.3.7 urn:ogc:def:crs:EPSG::4326 OGP Juvenile salmon and trout benchmark densities 2025-06-25 publication Marine_Scotland_FishDAC_12547 Electrofishing data are one of the most commonly collected sources of information on the status of stream-dwelling salmonid populations. However, interpretation of these data is challenging because densities vary naturally among habitats. Benchmark models provide an expected density against which observed densities can be compared for assessment purposes. Benchmarks have been developed for salmon (Malcolm et al., 2019a) and trout (Malcolm et al., in prep) using historical electrofishing data and spatial data that acts as a proxy for physical habitat. Benchmark densities can be considered the average expected density for a particular habitat having removed substantial anthropogenic negative impacts identified during analysis. Such benchmarks can thus be considered a target for healthy populations, which is similar in concept to meeting “intrinsic habitat potential” (Burnett et al., 2007). When combined with robustly collected electrofishing data (for example from the National Electrofishing Programme for Scotland - NEPS) these benchmarks are able to provide a fully scalable (site, catchment, region, national) catch independent, juvenile salmonid assessment. In this dataset, benchmark densities were predicted at each river node (point at the start and end of a spatial line feature) for salmon and trout, for fry and parr. Where nodes had the same river order, the edge (spatial line feature or river segment) benchmark was the geometric mean of the two values. Where the downstream node had a higher river order than the upstream node (e.g. a tributary entering a larger river) then upstream benchmark predictions were assigned to the edge to avoid inflating benchmark estimates for the segment. Where benchmark predictions were only available for a single node (e.g. a river source) then this was used alone (see Malcolm et al., 2023 for further details). Predictions are only provided for rivers where the individual covariates (predictor variables) are within the range of data used to fit both benchmark models. This does not account for covariate combinations that may also be out the range of observed data in the benchmark models. The national juvenile salmon density benchmark model reported by Malcolm et al. (2019a) was used to predict salmon densities. A new trout benchmark model, derived following similar procedures was used to predict trout benchmark densities (Malcolm et al., in prep.) Preliminary information on this model can be found in Jackson et al., 2025. Four benchmarks predictions are provided; 1) Salmon Fry 2) Salmon Parr 3) Trout Fry and 4) Trout Parr Benchmark densities (fish per m2) are visualised on the log-scale. NAs reflect where benchmark densities are not generated (e.g. within lochs, or in rivers where their covariates are outside of the range of data used to fit benchmark models). Scottish Government (Marine Scotland) +44 (0)300 244 4000 Mailpoint 11, Area 1B South, Victoria Quay Edinburgh EH6 6QQ United Kingdom marinescotland@gov.scot pointOfContact Scottish Government (Marine Scotland) +44 (0)300 244 4000 Mailpoint 11, Area 1B South, Victoria Quay Edinburgh EH6 6QQ United Kingdom marinescotland@gov.scot custodian Scottish Government (Marine Scotland) +44 (0)300 244 4000 Mailpoint 11, Area 1B South, Victoria Quay Edinburgh EH6 6QQ United Kingdom marinescotland@gov.scot distributor MARINE SCOTLAND SCIENCE FFL 01312442498 FASKALLY PITLOCHRY PH165LB United Kingdom FAYE.JACKSON@GOV.SCOT originator Marine Scotland Science Iain.Malcolm@gov.scot originator unknown Marine Environmental Data and Information Network Fish abundance in water bodies Habitat characterisation Habitat extent SeaDataNet Parameter Discovery Vocabulary 2018-12-12 revision Fish Fisheries Habitat SeaDataNet Agreed Parameter Groups 2017-05-03 revision Environment Fisheries and aquaculture SeaDataNet Parameter Disciplines 2017-02-03 revision Habitats and biotopes Species distribution GEMET - INSPIRE themes, version 1.0 2009-07-31 revision Predictions are plotted on the CEH Rivers dataset which is held under license and can only be shared with individuals/organisations that hold a license. Citations of underlying publications on benchmark modelling should be included in any papers, reports or web-based material using juvenile fish benchmark predictions as appropriate. otherRestrictions public access limited according to Article 13(1)(e) of the INSPIRE Directive 200.00 eng biota environment inlandWaters -9.470215 0.02197266 54.199 61.6361 SeaDataNet vertical extent keywords 2010-01-01 revision The entire body of water between the bed and the atmosphere. 2025-06-11 2025-06-11 NMPi download dataset Use constraints and citations Predictions are plotted on the CEH Rivers dataset which is held under license and can only be shared with individuals/organisations that hold a license. The following citations should also be included in any papers, reports or web-based material using juvenile fish benchmark predictions as appropriate: Benchmark juvenile densities: Malcolm, I.A. et al. (in prep) Development of an assessment benchmark for juvenile brown trout (Salmo trutta) using juvenile electrofishing data. Malcolm I.A., Millidine K.J., Glover R.S., Jackson F.L., Millar C.P., Fryer R.J. (2019) Development of a large-scale juvenile density model to inform the assessment and management of Atlantic salmon (Salmo salar) populations in Scotland. Ecological Indicators 96: 303–316 DOI: 10.1016/J.ECOLIND.2018.09.005 The following reports should be referenced for full details on the National Electrofishing Programme for Scotland (NEPS) survey design and assessment methodologies: Jackson F.L., Gilbey J., Eagle L.J.B., Fryer R.J., Malcolm I.A. (2025). The status of juvenile Atlantic salmon and brown trout populations in Scotland’s rivers: The National Electrofishing Programme for Scotland (NEPS) 2023. Scottish Marine and Freshwater Science Vol 16 No 1, 107p. DOI: 10.7489/12543-1 Malcolm I.A., Jackson F.L., Millidine K.J., Bacon P.J., McCartney A.G, Fryer R.J. (2023). The National Electrofishing Programme for Scotland (NEPS) 2021. Scottish Marine and Freshwater Science Reports Vol 14, No 2, pp. 63 DOI: 10.7489/12435-1 Spatial data (digital rivers network): The following copyright and acknowledgement should be placed on all copies of information or images derived from the licensed CEH river network data: ‘© Scottish Government (Marine Scotland) [Year]. Based on digital spatial data licensed from the Centre for Ecology & Hydrology, © NERC (CEH)' (preceded if appropriate by 'Some features of this map are'). And: 'Contains Ordnance Survey data © Crown copyright and database right [year]'. The following citation must be included in the reference list of any reports or publications in which the licensed CEH river network data, or derived data, have been used. ‘Moore RV, Morris DG and Flavin RW, 1994. Sub-set of UK digital 1:50,000 scale river centre-line network. NERC, Institute of Hydrology, Wallingford.’