Tyne Rivers Trust

Abstract Climate change and impoundment increase river temperatures, shifting the bioclimatic envelope in which freshwater biota have evolved and increasing salmonid egg mortality. To mitigate this, conservation flows from reservoirs are often implemented to maintain favourable water temperatures downstream from impoundments throughout salmonid embryo development. However, as water to maintain conservation flows becomes scarcer, there is a need to understand the requirements of salmonid embryos and balance these with anthropogenic demands. This study combines a laboratory‐based and a modelling approach to test the effect of different temperatures on the survival from fertilisation to hatch of a model salmonid species. Further, the effect of dropping temperatures from high to optimal conditions at hatch—a perceived period of greater sensitivity to high temperatures—is tested. The study shows embryo mortality increases with temperature and is greatest during gastrulation and hatch. Also, embryos that experienced high temperatures during gastrulation had high mortality rates at hatch, even when hatch conditions were optimal. This indicates sublethal developmental abnormalities caused by high temperatures during gastrulation increase mortality at hatch. Therefore, to maintain high rates of salmonid embryo survival, cold water resources from reservoirs ideally will target both gastrulation and hatch developmental stages.

This chapter describes the research activity on risks and extremes at Wallingford. With the agreement of the Steering Committee, the Flood Studies Report (FSR) (NERC, 1975) was published in 1975 in five volumes, containing the hydrological recommendations, the meteorological and flood routing studies and the hydrological data and maps. By the mid 1990s, the principal methods of rainfall and flood frequency used in the UK had been based on the FSR for 20 years, and it was recognised that there were significantly more rainfall and flood data available that should be incorporated into estimation methods. In the years following the publication of the Flood Estimation Handbook (FEH), a number of new sources of river flow and catchment data became available and substantial improvements were made to some key elements of the flood estimation procedures. Applied research into flood estimation continues to be an important topic.

Abstract Dissolved oxygen (DO) plays a critical role in the development of the juvenile stages of benthic spawning fish and salmonids in particular. Factors influencing the DO regime within spawning gravels include the accumulation of fine sediment, penetration of groundwater or surface water into the gravels, thermal regime, and the consumption of oxygen by sediment and its associated organic fractions. In this field study, we quantify the DO regime within an artificial salmon redd at high temporal resolution. The environment within the redd is shown to be complex, with large variations in DO. Application of a numerical model (SIDO‐UK) enables for the first time, the quantification of the relative contributions to DO consumption from thermal regime, sediment accumulation and sediment oxygen demand. Sediment accumulation is shown to have a minor impact on DO in the redd whereas upwelling groundwater is identified as the most likely cause of the major changes in DO. Bed mobility has a minor impact on DO regime of the redd. The effects of fine sediment and oxygen supply on salmon embryo survival are estimated. Implications for river catchment management and prospects for future research are discussed. Copyright © 2012 John Wiley & Sons, Ltd.