PhD Studentship -  Predicting the roles of anadromy and freshwater carry-over effects in the sustainability of threatened brown trout Salmo trutta populations 

Our ability to live sustainably with the natural world is dependent on how we derive societal benefits from freshwater ecosystems, including the provision of fresh water, food and energy. Currently, our derivation of these benefits is increasingly recognised as unsustainable; provision of freshwater for drinking and industry results in drying rivers; food supplies either over-exploit wild fish stocks leading to collapse or rely on aquaculture activities that pollute surrounding waters; and energy production transforms aquatic environments through loss of river connectivity. These activities are driving major and unsustainable declines in freshwater biodiversity, with population reductions of over 80% since the 1970s.

These freshwater biodiversity declines are most apparent in species with complex lifecycles, especially diadromous fishes (lifecycles involving movements between freshwater and marine environments), with all 16 European mid- and long-distance migratory fishes suffering substantial population declines in recent decades (by up to 93%). Returning populations of these species back to sustainable levels is thus a high conservation priority globally. Achieving this priority action is, however, highly challenging, as our current understandings of these population declines have major knowledge gaps that arise from the difficulty and complexity of collecting and analysing long-term data across spatially discrete habitats and multiple life-stages. However, developments in fish telemetry technologies now enable the tracking of migrations of individual fishes across key lifetime events.

An example of an anadromous fish species experiencing recent and rapid population declines is the brown/sea trout Salmo trutta. A major impediment to understandings of their declines is that their populations consist of both freshwater resident (non-migratory) and migratory (anadromous ‘sea trout’) forms, with the drivers of this divergent life history strategy remaining unclear. Whilst it is considered that anadromous females provide a greater reproductive contribution to the next generation than freshwater residents, but with trade-offs involving considerably higher energetic costs and mortality risks, why some individuals migrate when others remain river-resident remains a major knowledge gap.

Although brown/sea trout population declines are considered as driven strongly by reduced survival during the marine phase of their life cycle, it is also considered that carry-over effects from freshwater life stages have a strong influence on this survival, as has been already identified in the anadromous Atlantic salmon Salmo salar, where collaborative work between BU and the match funder recently revealed the positive influence on marine survival and river return rates of larger emigrating juveniles (‘smolts’). 

This is a fully-funded PhD studentship which includes a stipend of £18,622 each year to support your living costs. 

Key information

Next start date:

September 2024

Location:

Bournemouth University, Talbot Campus

Duration:

36 months

Entry requirements:

Outstanding academic potential as measured normally by either a 1st class honours degree or equivalent Grade Point Average (GPA), or a Master’s degree with distinction or equivalent. If English is not your first language you'll need IELTS (Academic) score of 6.5 minimum (with a minimum 6.0 in each component, or equivalent). For more information check out our full entry requirements.