Effect of Time Synchrony on Barents Sea cod larvae survival
Master subject on marine ecology 2018-2020
Northern marine ecosystems have been studied to varying degrees over the last half-century. At a fundamental level, baseline understanding of seasonal to decadal change in those ecosystems is limited to some focused studies of selected components, physical and biochemical patterns observed from satellite datasets and model simulations.
In the recent years a lot of focus has been put on fish population and fisheries in regard to the effects of climate change. In the context of global ecosystem changes driven by long-term modification of environmental conditions, we expect a decoupling of the food web and a disruption of the otherwise tight window of time for the co-occurrence between the harvested fish and their prey (match-mismatch relationship (Cushing 1990)). The variation in cohort abundance of fish and its recruitment to fisheries is thought to mainly result from changes in the availability of food for fish larvae.
In the Barents Sea ecosystem, many important commercial fish stocks are spawning along the Norwegian Coast (cod, herring, haddock); early-life stages i.e. eggs and larvae then drift northward with the Norwegian coastal current back to the Barents Sea. Studies predicting drift trajectories have shown that their survival is to a large extent determined by the location reached in the Barents Sea.
In the master thesis, we would like to investigate how the larvae survival depends on the access to food once reaching the Barents Sea as described by the match-mismatch relationship. Here, the student will explore the difference in timing (phenology) between the arrivals in the Barents Sea of cod (Gadus morhua) larvae and available zooplankton food source and to what extend it can explain the variation in cod recruitment.
Objectives of the Master thesis:
"The effect of difference in phenology of drift larvae and plankton productivity on the recruitment of harvested fish species."
- What we know:
We know that the copepod Calanus finmarchicus is important in the diet of the first feeding cod larvae (Tilseth et al. 1987, ICES CM) and that the timing of plankton production is affecting the size of the cod larvae (Cushing 1990, Adv Mar Biol); size affecting in turn survival and recruitment to the population (Stige et al. 2015, Progr Oceanogr).
- What we have:
From particles tracking analysis we will extracted the timing of arrival of the larvae in the Barents Sea.
From published relationships we will get the timings of the plankton productivity and the recruitment of the cod.
- What will the student do:
Using advanced statistical modelling (such as Generalized Additive Model) the student will explore the effect of asynchrony of events on larval survival and cod recruitment. This thesis will thus require computer work and statistical competences (R language).
- What effect:
We expect that depending on the timing of the larvae arrival relative to the peak of plankton productivity that the cod recruitment will be different. Alternatively, the lack of relationship may indicate that the stock recruitment function should focus on older age abundance and survival (Stige et al. 2013, MEPS). This hypothesis could be explored in a second time.
- What we look at:
Effect of climate (Sea temperature or climate package such as the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation) on the cod recruitment through trophic interaction.
- What the student will learn:
With this thesis the student will get an intrinsic knowledge of the Barents Sea ecosystem and its trophic interactions. The student will get a hands-on experience and supervision on the use of a versatile programming software (R-core) and advanced statistical modelling. Those are common tools used to solve ecological questions across topics. We expect the master thesis to be published in a good international journal.
The Master work will be conducted within the Marine Ecology Group at the Centre for Ecological and Evolutionary Synthesis of the Department of Biosciences (http://bit.ly/1psRR6n). The marine group is a multidisciplinary group that bring together ca 15 researchers, PhD and Master Students working on the domains of ecology and statistic. It has shown over a decade competence in answering ecological questions around climate change and marine productivity through statistical analysis and interdisciplinary collaborations. The Master will be able to train in a friendly environment her presentation skills at the monthly marine meetings.
September 2018 – September 2020