Refining monitoring practices and applying novel enhancement strategies to populations of threatened diadromous species.
Diadromous species are those which migrate between marine and freshwater environments. These can be sub-divided into anadromous (breed in freshwater but migrate to the sea to attain maturity, such as Atlantic salmon, Salmo salar) and catadromous species (breed in the sea but mature in freshwater, su...
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| Format: | Thesis |
| Language: | English |
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2022
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| Online Access: | http://eprints.bournemouth.ac.uk/37040/ https://eprints.bournemouth.ac.uk/37040/1/CAMERON,%20Luke%20William%20Joseph_Ph.D._2022.pdf |
| Summary: | Diadromous species are those which migrate between marine and freshwater environments. These can be sub-divided into anadromous (breed in freshwater but migrate to the sea to attain maturity, such as Atlantic salmon, Salmo salar) and catadromous species (breed in the sea but mature in freshwater, such as European eel, Anguilla anguilla). High socioeconomic importance has led to both species listed being subject to widespread and often large-scale commercial and recreational fisheries, with this driving extensive population monitoring and management. However, overexploitation and other anthropogenic impacts mean both species are threatened and/or declining throughout their range. Population monitoring for salmonids generally consists of electrofishing surveys to determine juvenile abundance, where accurate population estimates are critical for conservation target-setting. However, the accuracy of some current population monitoring practices remains untested, with many studies also showing current management techniques to be unproductive, especially enhancing salmonid populations with hatchery reared fish. These two issues are addressed in this research. To evaluate the accuracy of current population monitoring methods, a common population monitoring technique for juvenile salmonids, time-delineated single-pass electrofishing surveys, was tested against a more precise monitoring method (area- delineated single-pass electrofishing surveys), using Atlantic salmon as the focal species. Comparison of these two methods showed a high degree of density-dependent error in abundance estimates from time-delineated surveys. Further analysis showed that the area covered during time-delineated electrofishing surveys is highly variable, leading to imprecision around abundance estimates. The application of time-delineated single-pass electrofishing was then reviewed by analysis of an electrofishing dataset with over 11,000 observations, used to monitor Atlantic salmon fry (age 0+) abundances. Currently these surveys are carried ... |
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