An assessment of factors influencing the ability of U.K. spawning gravels to support the respiratory requirements of Atlantic salmon (Salmo salar) embryos
In recognition of the importance of oxygen availability to salmonid incubation success, a series of complementary field and flume experiments were undertaken to investigate the flux of oxygen through spawning gravels and its relationship to the respiratory requirements of Atlantic salmon embryos. Th...
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| Format: | Thesis |
| Language: | English |
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University of Southampton
2004
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| Online Access: | https://eprints.soton.ac.uk/465287/ https://eprints.soton.ac.uk/465287/1/939840.pdf |
| Summary: | In recognition of the importance of oxygen availability to salmonid incubation success, a series of complementary field and flume experiments were undertaken to investigate the flux of oxygen through spawning gravels and its relationship to the respiratory requirements of Atlantic salmon embryos. The key findings of the field and flume monitoring programme were: 1) Pre-emergent mortalities result from: (i) lethal oxygen concentrations (concentrations below which respiration is impeded), (ii) insufficient oxygen flux (product of concentration and discharge) to meet respiratory requirements, or (iii) critical intragravel flow velocities (flow velocities that are either insufficient to meet respiration independent of oxygen concentration or insufficient to remove metabolic waste). 2) Fine sediment accumulation restricted the flow of oxygenated water through spawning gravels. Based on the results of the field study, statistically significant linear relationships between sediment accumulation and intragravel flow were developed. However, due to site specificity, these relationships were restricted to environments of similar hydraulic and sedimentary character. 3) Sedimentary oxygen demands reduced intragravel oxygen concentrations. The oxygen demand of material deposited in the incubation environment was assessed at each field site. It was found that sedimentary oxygen demands varied between systems dependent on the proportion of organic material and the magnitude of the demand associated with that material. 4) Surface flow conditions influence the flux of oxygenated water through spawning gravels. In a series of flume experiments, it was shown that surface flow influences both subsurface flow paths (hydraulic head) and intragravel flow velocities. Furthermore, it was shown that flow through a sinusoidal bedform did not conform to simple Darcian principles. It was hypothesised that turbulent driven momentum exchange influenced intragravel flow velocities. 5) Clay particles potentially inhibit the exchange of oxygen ... |
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