The Modelling Group Research Projects
 
 

Sustainable harvesting of marine resources: interactions between demographic, ecological, and evolutionary effects of fishing
 

Today, fishing is the dominant source of mortality in most commercially exploited fish stocks. According to the United Nation’s Food and Agricultural Organization, world capture fisheries have reached a ceiling, with three stocks out of four being maximally exploited or overexploited. However, fishing does not affect all fish equally, and evolutionary changes follow whenever there are survival differences between genotypes. In other words, fishing not only decreases the abundance of fish, but also changes their genetic composition and thus the species itself.
 

Project Leader:
      Professor Mikko Heino, Institute of Marine Research
 
Employed by the Project:
      Postdoc Erin Dunlop, Institute of Marine Research
      PhD Student Anders Frugård Opdal, Department of Biology, University of Bergen
 
Associated Researchers:
      Associate Professor Øyvind Fiksen, Department of Biology, University of Bergen
      Postdoc Christian Jørgensen, Department of Biology, University of Bergen

 

Field and laboratory experiments have shown that life histories can evolve considerably in just few generations. In this project, we will investigate the effects of fisheries-induced evolution in general and on cod, herring and blue whiting in particular. We do this by a combination of theoretical life-history models, species-specific life-history models, ocean circulation models, and selection experiments. Addressing both basic science and applied questions, the project will develop theory that will help detect early signals of evolutionary change, predict stock-specific scenarios, explore potential managerial counter-measures, and experimentally test underlying assumptions of current methods.

The project will consist of three parts:

	Models of life history evolution based on energy allocation. Energy use embodies many essential life history trade-offs, and how this limited resource is used determine how growth and reproduction change according to ecological conditions. By adding fisheries to such models, we can investigate how life history traits are expected to evolve given different levels of fishing mortality and under different patterns of selecetivity. Energy allocation models will be parameterized for Atlantic cod Gadus morhua, herring Clupea harengus, and blue whiting Micromesistius poutassou.
	Coupling between oceanographic circulation models and dispersal of early life history stages Egs and larvae of many marine species disperse with ocean currents, and the location and timing of spawning is therefore important for how junveiles distribute and which conditions for growth and predation they experience. In this part, we will investigate how different spawning locations along the Norwegian coast influence the gorwth and survival of the eggs and larvae spawned. This determines the 'fitness function', describing the benefits for reproductin of a short versus a longer spawning migration. These models will first focus on Atlantic cod Gadus morhua and herring Clupea harengus.
	Experiments of fisheries-induced evolution The project will also set up experimental populations of zebrafish Danio rerio which will be harvested in manners similar to fisheries on the marine harvested stocks. Life history traits will be measured in individual fish throughtout several generations to assess experimentally induced life history evolution. The experiments will also be questioning fundamental assumption made in current statistical methods for identifying fisheries-induced evolution from fisheries data.

The project is funded by the Research Council of Norway and jointly organized and run by the Institute of Marine Research (IMR) and the Department of Biology (BIO) at the University of Bergen. More details on the project can be found in the full project description.

Fishing may potentially lead to evolution of the harvested species within only a few generations. To investigate this, one aim of this project is to set up an experiment where several populations of zebrafish are subjected to different harvest regimes. Several traits may evolve, and we will investigate changes in both life history traits and behaviour. To interpret the results, it is important to have a basic understanding of the life history of the baseline populations. Potential Masters students should start discussing their project as early as possible and even before official admission to the Masters program if possible. If any of the topics below sound interesting, or if you have own ideas that you think could relate to the projects described below, please contact Øyvind Fiksen, Mikko Heino, Christian Jørgensen, or Anne Christine Utne Palm. Our aim is that each of the projects will end up as an article published in a peer-reviewed international journal, but whether it is possible or not will depend on the strength of the results and the ability of the candidate to present the results and place them in a scientific context. The following topics will be suited for Masters theses: 1. Maturation reaction norms for zebrafish at different food rations The timing of maturation is one of the most important life history events during an organism's life-time. During and after maturation, resources that before were used for growth are diverted towards reproduction. The timing of maturation therefore largely determines also the adult size of the individual. There is seldom a single age or size that is optimal for maturation; in stead the tendency to mature can be described as following a reaction norm. Depending on the growth rate, individuals may for example mature earlier than the average if they are large for their age. This project aims at describing the reaction norm for age and size at maturation in zebrafish. It will involve rearing individual zebrafish at various food rations to induce differences in growth, and record the age and size as they become sexually mature.   This project will be done simultaneously and in close collaboration with Masters project 2 provided that there is a student. 2. Growth and size-dependent fecundity of zebrafish at different food rations To assess the costs and benefits of age and size at maturation, one needs to establish how growth and fecundity vary with age. In addition to the timing ofmaturation, the schedules of growth and fecundity also after maturation may affect the fitness of a life history strategy. This project involves rearing individual zebrafish at various food rations to induce differences in growth rates, and then estimate size- and age-dependent fecundity of single individuals.   This project will be done simultaneously and in close collaboration with Masters project 1 provided that there is a student. 3. Effects of temperature on growth rates and fecundity of zebrafish Temperature affects an array of physiological processes, which again may influence behavioural and life-history trade offs. In this project, we will establish how different rearing temperatures affect immature and mature growth rates as well as age-specific fecundity in zebrafish. This project involves rearing individual zebrafish at three different temperatures, and then measure size- and age-dependent growth and fecundity of single individuals.   This project will be done simultaneously and in close collaboration with Masters project 4 provided that there is a student. 4. Effects of temperature on the maturation reaction norm of zebrafish To detect evolutionary signals in harvested fish stocks, one method is to statistically calculate the probabilistic maturation reaction norm from fisheries data. This method disentangles the effects of environment (on growth rate) and evolution (changes in the gene pool over time) as it describes the combination of ages and sizes at which fish are most likely to mature. One underlying assumption is that whatever affects growth rate should not influence the position of the maturation reaction norm. To validate this important statistical method, it is therefore necessary to check whether environmental characteristics that affect growth rate indeed leave the reaction norm unchanged.   This project will rear individual zebrafish at three different temperatures and measure the age and size at which individual fish mature. The data will be used to construct probabilistic maturation reaction norms for each temperature, compare them, and discuss the implictions the findings have for the conclusions that are currently being drawn from fisheries data.   This project will be done simultaneously and in close collaboration with Masters project 3 provided that there is a student. 5. Modelling effects of temperature and food ration on growth of zebrafish An individual is an ensemble of physiological processes taking place at a cellular level. By understanding key mechanisms of these processes, it is possible to scale the effects of temperature and energy availability on these processes up to rates of energy use and growth at the individual level. For example, the temperature-dependency and allometric scaling exponents for metabolism and growth are often perceived as universal constants. By adopting a cellular view, this project will show that these relationships are not constant and that they vary in a predictable manner.   This project will involve mathematical modelling in excel or in a basic but more flexible language such as Fortran. The student should not be afraid of arithmetics and simple mathematics, or of using computers, but no special skill or knowledge in mathematics or computer science is required. Associate supervisor: Professor Dag L. Aksnes.