Mr. Johnstone Omukoto Omuhaya, a research scientist at the Kenya Marine and Fisheries Research Institute (KMFRI) and a member of the SPACES team reports on his visit to the University of British Columbia that was part of bringing together the team working on the Ecopath with Ecosim (EwE) models.


Mr. Johnstone Omukoto working on parameterization and documentation of the Ecopath model at the UBC, Oceans and Fisheries Center

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Mr. Johnstone Omukoto (right) and Dr. Colette Wabnitz at the UBC, Oceans and Fisheries Center

During 25th January to 24th February 2016, I had the opportunity to be a visiting research scientist at the Changing Ocean Research Unit of the Oceans and Fisheries Centre at the University of British Columbia (UBC) in Canada. During the visit, I worked with Prof. William Cheung (Co-PI on the SPACES project), Dr. Colette Wabnitz (A Postdoctoral research scientist with expertise on Ecopath with Ecosim and Value chain analysis) and Ms. Xueying (a PhD student working on Ecopath models) to co-develop the ecological models for the SPACES Project under which I am a participating research scientist.

Ecopath with Ecosim model is an ecosystem model made up of three main components. The first is Ecopath, a network definition tool that allows for the construction of static, mass-balanced snapshots of the network and biomass pools in an ecosystem (including fisheries fleets’ activities). The second component is Ecosim, which takes the Ecopath snapshot as an initial condition and then adds time-dynamic components to allow for simulations of scenarios and policy exploration. The third and which was beyond the scope of the current study is Ecospace, which adds a spatial dimension to the Ecosim simulations and is designed for exploring spatially explicit fisheries questions, such as the impact of fisheryes management zones and protected areas. These tools are a quite useful means of addressing ecological questions, evaluating potential trophically driven ecosystem effects of fishing, exploring management policy options, and (more recently) modeling the effect of environmental changes (Bulman et al. 2006).

Since the base Ecopath parameterization is based on solving a set of simultaneous equations that describe how total production for each ecosystem functional group is divided among predation, yield/catch, other mortality, any biomass accumulation and migration (Christensen and Pauly 1992; Pauly et al. 2000; Walterset al. 1997) to forms a basis for all the other EwE components, the parameters used need to be carefully sourced and documented to build a representative model of the system under study. Thus during my stay at UBC I was able to:

  1. Document the sources of the draft Ecopath parameters;
  2. Derive preliminary revised Biomass, PB and QB ratios for all fish groups;
  3. Re-derive diet matrix for the new Ecopath model setup

Future work on the model entails the finalization of the Kenyan model by:

  1. Finalizing diet composition matrix;
  2. Balancing the model; and
  3. Writing up the report – making sure to draw from the existing literature for general context and setting and to discuss parameters as well as results; and to set up the Ecosim simulations through:
  4. Summarizing relevant information from the literature;
  5. Ground-truthing and updating fish price data;
  6. Obtaining fleet-cost data where possible.

The simulations allow us to understand how this fishery could be optimized to meet different fisheries goals such as (i) Optimum harvesting situation to maximize profit; (ii) Optimum harvesting situation to maximize employment; (iii) Optimum harvesting to maximize food production and (iv) business as usual.

This work contributes to the SPACES objectives of understanding the fisheries in terms of the relationship between Stocks, Flows and Goods. I am currently working on finalization of the diet composition matrix before embarking on balancing the model and running the four scenarios for the Kenyan Mombasa model.

My visit to UBC was an eye-opener to me as I met and worked well with Dr. Colette Wabnitz who taught me new ways on proper model parameterization and documentation under the keen supervision of Prof. William Cheung. I also appreciated the opportunity to have met some of the world’s renowned fisheries scientists such as Professors Villey Christensen, Daniel Pauly and Rashid Sumaila.” I am thankful to the ESPA SPACES project PIs (Dr. Tim Daw and Dr. Kate Brown) for the funding of the trip and my stay at the University of British Columbia in Canada.