Refining monitoring practices and applying novel enhancement strategies to populations of threatened diadromous species: Data collected from electrofishing surveys targeting salmonids and European eels to evaluate existing monitoring methods and test proposed translocation-based novel management strategies

Cameron, Luke and Naisbett-Jones, Lewis (2022) Refining monitoring practices and applying novel enhancement strategies to populations of threatened diadromous species: Data collected from electrofishing surveys targeting salmonids and European eels to evaluate existing monitoring methods and test proposed translocation-based novel management strategies.

These datasets were collected as part of experiments to determine the accuracy of a commonly applied population monitoring method for stream-dwelling salmonids (time-delineated electrofishing surveys) and the efficacy of two translocation-based novel management strategies for salmonids and the European eel (Anguilla anguilla); intra- and inter-catchment translocation respectively. The data relate to the doctoral thesis by Luke Cameron entitled 'Refining monitoring practices and applying novel enhancement strategies to populations of threatened diadromous species', with each dataset corresponding to an individual thesis data chapter. The full thesis is available at: https://eprints.bournemouth.ac.uk/37040/ Datasets from chapters 2, 5 and 6 were collected as part of a series of large-scale field experiments conducted by Luke Cameron within the River Erriff catchment from 2019-2021, where Atlantic salmon (Salmo salar) post-emergent larvae ('fry') were translocated from identified high-density riffle sites to low-density riffle sites/stream reaches. This was followed by subsequent electrofishing surveys at the end of the summer period to determine the effects on salmon densities. These experiments were based on the hypothesis that this method could be used to reduce density-dependent mortality over the first summer following fry emergence at the catchment level, and thus increase freshwater production of Atlantic salmon, given this period is often considered a population bottleneck. Additionally, these experiments also included an additional element to evaluate the accuracy of a commonly applied population monitoring method for juvenile salmonids (time-delineated single-pass electrofishing surveys) versus a more established method with known accuracy (area-delineated single-pass electrofishing surveys). In 2019 and 2020 paired time-delineated and area delineated surveys were performed as part of the above experiments, with the former forming a component of the latter. This allowed direct comparison of fry abundance estimates, as provided by the two methods, recorded from the same habitat units at the same time. The datasets from Chapter 4 are adapted from a prior experiment conducted in 2015 by Lewis Naisbett-Jones to evaluate the efficacy of inter-catchment translocations of juvenile European eels in enabling eel colonisation of headwater stream habitats in Wales. Eels were released into the centre of stream reaches under two treatments; trout-populated and trout-free, as defined by the presence or absence of brown trout (Salmo trutta), to determine the effect of trout presence on eel colonisation success. Following release of eels in June, all stream reaches were surveyed using area-delineated single-pass electrofishing surveys in September to determine eel colonisation success.