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Meet the Team

Theoretical Ecology team at QUB in 2010: from left to right - Dr Tak Fung, Dr Olga Lyashevska (PhD graduated 2011), Dr Jennifer Houle (PhD graduated 2013),
Dr Axel Rossberg (Senior Research Fellow), Ms Deirdre Duggan and Dr Keith Farnsworth (team leader).

The team is developing theoretical understanding for applied science, mainly in fisheries management ecology
and biodiversity conservation. Today (2013) we have new additions: Senior Research Fellow Dr Francisco De Castro and Research Fellow Dr Sam Shephard (see below for both). Olga now works with the Royal Netherlands Institute for Sea Research and Jennifer, having just graduated with a PhD is working with us as a Research Fellow now.

If you would like to join in, please identify a source of funding and drop us a line.


Dr. Hannes Höffle
Dr. Hannes Höffle

Dr. Hannes Höffle

Research Interest
My research interests broadly cover three areas. Firstly, I am interested in the spatial distribution of marine organism and what factors are limiting the range of species or communities. Secondly, I am interested in the effects of disturbances, whether natural or anthropogenic, on biota, ranging in scale from individual populations up to entire ecosystems. Thirdly, on a more theoretical side, I am interested in the evaluation of uncertainty of survey results as well as model predictions. As it touches all three of these interests, I have worked in fisheries ecology since 2008, mostly working on spatial distributions of early life stages and how they are affected by environmental conditions.

Current Research
As part of the project “Creating the knowledge for precision fisheries management” I am responsible for the creation of an operating model, representing the Celtic Sea fishery and it’s interactions with the marine environment. Pulling together components from a range of existing fish community and fisheries models, the operating system shall strike a balance between capturing the processes of interactions in the community, and ease of parameterization as well as stakeholder acceptance. The model shall serve as a basis for a management strategy evaluation (MSE) of a real time incentive (RTI) management system. The RTI is a modern ‘nudge’ policy, which provides fishermen with an annual contingent of credits and a, periodically updated, map showing how much credits it costs to fish in a given area. It allows fishermen to fish, where and when they want until they run out of credits, thus devolving responsibility to the industry. MSE is a quantitative approach of evaluating harvest control rules, initially developed for the International Whaling Commission (IWC 1993). Essentially, it is a statistical modeling exercise, simulating management scenarios and evaluating the extent to which a management strategy is affected by uncertainty from various sources of error.

Past Research
My first research project, addressed the influence of introduced species on growth and survival of sea grasses in the Baltic Sea and the western Indian Ocean. The study came to the main conclusion that effects of algal mats largely depend on the morphological structure of the algae and their longevity (Höffle et al. 2011, Höffle et al. 2012).

In fisheries ecology I mostly worked on early, planktonic, life stages of demersal fish, which play a major role in establishing year-class strength. These studies, on populations in the North and Barents Seas, led to three main conclusions (Höffle 2012, Höffle et al. 2014). Firstly, that, regardless of the stock and its demographic structure, some environmental variables will have a consistent influence on the spawning distribution. Secondly, that on large temporal and spatial scales, even for fish which do not depend on a certain substrate, spawning grounds are in recurrent locations, while centers of abundance vary between the years. Thirdly, that the importance of environmental factors controlling the population may vary between life stages (Höffle & Kjesbu 2014).

Höffle H (2012) Spatial patterns in the distribution and early life characteristics of North Sea cod - influence from environmental factors and climate change, Ph.D. thesis, Technical University of Denmark, Kongens Lyngby, DK
Höffle H and Kjesbu OS (2014) Some like it cold – consequence of warming seas for the distribution of large bodied fish, oral presentation, ICES ASC 2014, A Coruña, ES
Höffle H, Thomsen MS, Holmer M (2011) High mortality of Zostera marina under high temperature regimes but minor effects of the invasive macroalgae Gracilaria vermiculophylla. Estuarine Coastal and Shelf Science 92:35-46
Höffle H, Solemdal P, Korsbrekke K, Johannessen M, Bakkeplass K, Kjesbu OS (2014) Variability of northeast arctic cod (Gadus morhua) distribution on the main spawning grounds in relation to biophysical factors. ICES J Mar Sci 71:1317-1331
Höffle H, Wernberg T, Thomsen MS, Holmer M (2012) Drift algae, an invasive snail and elevated temperature reduce ecological performance of a warm-temperate seagrass, through additive effects. Mar Ecol Prog Ser 450:67-U85
International Whaling Commission (1993) Report of the scientific committee, annex I. report of the working group on implementation trials. Rep.Int.Whal.Commn 43:153-196


Team Members: 


Francisco de Castro


Ph. D. Ecology. 1993. University of Seville. Spain. Thesis: Simulation model of plant structure.


Member of the International Society of Ecological Modeling (ISEM)
Ecological Society of America (ESA) Member: 110042
Certified Senior Ecologist by the Ecological Society of America (2002 – 2007)

Francisco joined us in 2012 from Potzdam University. Here is what he says: "I am mainly a theoretical ecologist/modeler. Currently, I am working on spatial aspects of food web dynamics. Also on how individual body size, metabolism and efficiency in energy transfer affects community structure. Previously I worked on host-parasite dynamics and its effects on the community and a variety of other subjects: dune movement, tree shape, canopy structure, etc. always trying to extrapolate interactions at small scale to the dynamics of the large-scale system". Francisco is payed out of the Beaufort Marine Award and will be helping to expand our models and theories into spatial domains.


A few of his publications:

Riede, J. O., Brose, U., de Castro, F.,  Rall, B. C., Binzer, A., Curtsdotter, A., Eklo¨f, A. 2011. Food web
characteristics and robustness to secondary extinctions. Basic & Applied Ecology 12(7): 1-9.

de Castro, F., Gaedke, U., Boenigk, J. 2009. Reverse evolution: Driving forces behind the loss of acquired
photosynthetic traits. PloS ONE 4(12):1-6.

de Castro, F., Gaedke, U. 2008. The metabolism of lake plankton does not support the Metabolic Theory of
Ecology. Oikos 117(8): 1218-1226.

de Castro, F., Bolker, B. M. 2005. Mechanisms of disease-induced extinction. Ecology Letters 8(1):117-

de Castro, F., Bolker, B. M. 2005. Parasite establishment and host extinction in model communities. Oikos
111: 501 -513



Jennifer Houle

Jennifer Houle - Research Fellow (size-spectrum marine community models)


BA (2006) Mathematics, University of Maine; MSc (2007) Music Technology, University of Limerick

PhD (2009-2013) QUB: "Structure and dynamics of marine-community interaction networks"

Funded by a Beaufort Marine Research Award from the Republic of Ireland.


My research aims to support the ecosystems approach to fisheries management by studying how fishing affects marine ecological communities.  I am examining this using dynamic numerical models of the marine ecosystem which consist of a network of size-structured populations connected by community interactions.  I am jointly supervised by Dr. Axel Rossberg and Dr David Reid of the Irish Marine Institute.

Research Interests:

  • Mathematical ecology
  • Physiologically structured population models
  • Ecosystem-based fisheries modelling


Tel:  +44 (0)28 9097 2103



Tak Fung


BSc Mathematics with Management, First Class Hons. (2003), Imperial College London;  PhD modelling biological complexity, University College London (2009).  Previous work involved applying mathematics to a range of biological areas, such as visual perception, population genetics and the dynamics of coral reef ecosystems.


PhD Queen’s University

My PhD focuses on using mathematical techniques to investigate the mechanisms behind key ecosystem phenomena such as biodiversity and stability. These include complex systems theory, network theory and size-structured community theory. It is envisaged that new insights will be gained that can be translated into effective biodiversity policy for fisheries operating around the Irish coast and generalised for the Ecosystem Approach to Fisheries Management. My PhD is funded by the Irish Government under the Beaufort Marine Award Scheme and is jointly supervised by Dr Axel Rossberg and Dr David Reid of the Irish Marine Institute.

Image of Deirdre Duggan
Deirdre Duggan

Deirdre Duggan

Congratulations to Deirdre on graduating with a PhD from QUB. Deirdre now works for Masyarakat dan Perikanan, Indonesia (MDPI) in fisheries management development and sustainability in Bali, Indonesia .



BSc (2004-2008):  Marine Science, National University of Ireland, Galway.
MSc (2009-2010):  Applied Marine Science, University of Plymouth, United Kingdom.
PhD (2010-present):  "Modelling the Ecosystem Approach to Fisheries Management"


Fisheries management is moving from maximising the sustainable yield of a single stock towards a community perspective. This ecosystem approach requires far more complex models of multi-species interactions and community structure than previously encountered by fisheries managers and other stakeholders.  My PhD aims to bridge the gaps between scientists and fishermen caused by this expansion of complexity.  I am investigating and selecting appropriate indicators of community health which can summarise ecological complexity in a 'dash-board' describing the system's state to managers.  I am incorporating size-structured multi-species models into fisheries simulation tools to enable rapid scenario exploration and conceptual learning.  I work in close collaboration with fisheries management professionals at the Irish Marine Institute to ensure the practical applicability of the decision support tools that I am building.  The ultimate aim of my work is to enable fishers to take greater responsibility for the sustainability of the resources they exploit by providing accurate, comprehensive and understandable information on the behaviour of the marine community under fishing.

My PhD is funded by the Irish Government under the Beaufort Marine Award Scheme and I am under the joint supervision of Dr Axel Rossberg and Dr David Reid.

Dr Sam Shephard

Samuel Shephard


PhD Fisheries Ecology, Department of Wildlife and Fisheries, Mississippi State
University, U.S.A. 2003.

MSc Fisheries Management, Development and Conservation, University College Cork, Ireland. 2000.

BSc Environmental Science, University of Westminster, London, UK. 1994.


I first became involved in fishing as a commercial deckhand, which introduced me to the fascinating and troubling complexity of fisheries systems. My current research is in the development of flexible indicators for the Ecosystem Approach to Fisheries Management, especially in the context of the Marine Strategy Framework Directive. This work comprises empirical modelling and collaboration with mathematical modellers, and includes connections with ICES WGECO and STECF. A related focus is analytical and sea-going experimental work on the ecosystem effects of fishing. In particular, bottom-up trophic effects on demersal fishes caused by trawling-induced change in benthic communities. Using high-resolution Vessel Monitoring System (VMS) data, I am currently extending these analyses to incorporate the real spatial scale of fisheries / fish community interactions and the application of MPAs.

I have recently joined the FP7 project MYFISH , where I will be working on Irish Sea elasmobranch and western waters pelagic fisheries case studies.

Axel Rossberg

Axel, has been our Beaufort Senior Research Fellow, but is now reduced to 10% part time. During that 10% he still helps the team, especially with the use and interpretation of the Population Dynamic Matching Model. Axel now works at the CEFAS institute in Lowerstoft, England.

Olga Lyashevska


Olga Lyashevska

Olga has successfully defended her PhD and now lives in Holland.


BSc (1999-2003) Economics and Management, National Academy of Environmental Protection and Tourism, Ukraine;

MSc (2003-2004) Economics and Management, National Academy of Environmental Protection and Tourism, Ukraine;

MSc (2005-2007) Environmental Sciences (specialisation Environmental Economics), Wageningen University, The Netherlands

PhD (2011) Queen's University Belfast.  "Quantifying Biodiversity for Valuation".

Funded under STRIVE doctoral programme, EPA, Republic of Ireland.


Biodiversity, arising at multiple levels, is known as a multi-dimensional and complex con-
cept, but is also has a rather loose definition. Imprecise definitions are not very suitable
for ob jective quantification or the rigour of economic valuation.
Therefore, to construct a more substantial definition of value for biodiversity, a theore-
tical argument aiming to link biodiversity and functional (meaningful) information needs
to be developed. A working hypothesis is that biodiversity is a measure of the total dif-
ference within a biological system, which can be summarised in terms of the system’s
total information content, of which functional information is a subset. Since functional
information has systematic (non-random) patterns, it coincides with the scientific meaning
of biological complexity, thus providing the foundation of value in biodiversity.
The theory presented sets the goal of estimating biological complexity from the potentially
valuable information derived from empirical biodiversity metric data (ecological measures).
To achieve this, the ecological properties of a system, as they are measured by ecologists,
were translated into a simply defined single valued property. This led to a conclusion that
if there exists a systematic relationship among empirical biodiversity metrics, then there
must be a unifying property underlying intrinsic value of biodiversity.
Then, an advantage of a representation of biodiversity as information was demonstrated
by comparing it with the most commonly used metric – species richness. It was shown
that species richness missed a large proportion of diversity, emphasising the importance
of additional ecological properties and the need for species databases to record functional
traits, presence, and abundances in communities, as well as phylogenetic information.
Finally, by providing intellectual foundations and developing an analytical tool for biodi-
versity quantification, this study sets the goal for further research. An advantage of the
approach in this study to economic valuation is that value is based on real, measurable, and
intrinsic properties of systems, such that it is ob jective in contrast with present opinion-
based economic methods applied to biodiversity.  

PDF of full Thesis