Spawning habitat characteristics of lithophilic fish - using experimental approaches to inform river restoration

In a rapidly changing world characterised by acute anthropogenic pressures, knowledge regarding the effects of environmental change on biodiversity is of key importance. Within-channel degradation of riverine habitats, often through excess fine sediment pollution, is amongst the most common and widely studied forms of freshwater degradation, with deterioration in spawning substrate quality through fine sedimentation associated with global declines in freshwater biodiversity. Despite this, knowledge regarding the environmental tolerances of many species, particularly during their early development, remains limited. This is particularly true for lithophilic (substrate spawning) fishes. Whilst a body of literature on the influence of fine sediment content ("fines") on the spawning success of some salmonid fishes exists, knowledge of the effects of fines and the variability of other environmental parameters on the spawning of other, typically non-salmonid species, remains limited, despite their ecological, recreational and socio-economic importance in many European rivers. This has consequences which transcend our understanding of fish ecology and without better understanding of the tolerances of river fish eggs and larvae to spawning substrate characteristics and variable abiotic parameters, we do not know whether in-situ spawning habitats are conducive to successful reproduction. This also means we do not currently have any readily quantifiable or transferable method of gauging the success (or failure) of river restoration activities in relation to species-specific environmental parameters or thresholds. In addition, some river restoration projects are limited in their success due to a lack of specific objectives, post-monitoring evaluation and/or consideration of landscape processes that provide the context for specific sedimentation problems. Thus, studies that utilise robust experimental designs are essential for understanding the factors that contribute to successful spawning habitat restoration. This project therefore aims to increase our understanding of the environmental tolerances of some poorly studied yet ecologically, recreationally and economically important freshwater fishes. Further, spawning habitat, nest characteristics and levels of natural recruitment of target species (including Barbel Barbus barbus, Chub Squalius cephalus, Brown Trout Salmo Trutta, Grayling Thymallus thymallus) will be assessed in the natural environment. The project will also investigate how degraded habitats might be improved to increase reproductive success.
The research will involve the acquisition of experimental data in field and laboratory settings. The project will involve an interdisciplinary approach comprising the following elements: (1) laboratory experiments utilising the Environment Agency recirculating aquaculture systems at their national hatchery in Calverton (Nottinghamshire, UK) to quantify environmental tolerances of eggs and larvae of one or more poorly studied lithophiles. Fitness physiology and/ or behaviour of emerged larvae may be monitored through time to assess legacy effects of conditions during early development. (2) A multi-river study of the spawning habitats, nest characteristics and recruitment of target species to develop better understanding of where, how and how successfully fish spawn in different rivers. (3) Field experiments to investigate the ecological and physical effects of some commonly applied spawning substrate restoration techniques.