Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Balanced harvest: concept, policies, evidence, and management implications
Zhou, Shijie ; Kolding, Jeppe ; Garcia, Serge M. ; Plank, Michael J. ; Bundy, Alida ; Charles, Anthony ; Hansen, Cecilie ; Heino, Mikko ; Howell, Daniel ; Jacobsen, Nis S. ; Reid, David G. ; Rice, Jake C. ; Zwieten, Paul A.M. van - \ 2019
Reviews in Fish Biology and Fisheries 29 (2019)3. - ISSN 0960-3166 - p. 711 - 733.
Ecological effect - Ecosystem approach to fishery - Ecosystem structure - Fishing intensity - Production - Selectivity - Sustainability

Balanced harvest has been proposed to reduce fishing impact on ecosystems while simultaneously maintaining or even increasing fishery yield. The concept has attracted broad interest, but also received criticisms. In this paper, we examine the theory, modelling studies, empirical evidence, the legal and policy frameworks, and management implications of balanced harvest. The examination reveals unresolved issues and challenges from both scientific and management perspectives. We summarize current knowledge and address common questions relevant to the idea. Major conclusions include: balanced harvest can be expressed in several ways and implemented on multiple levels, and with different approaches e.g. métier based management; it explicitly bridges fisheries and conservation goals in accordance with international legal and policy frameworks; modelling studies and limited empirical evidence reveal that balanced harvest can reduce fishing impact on ecosystem structure and increase the aggregate yield; the extent of balanced harvest is not purely a scientific question, but also a legal and social choice; a transition to balanced harvest may incur short-term economic costs, while in the long-term, economic results will vary across individual fisheries and for society overall; for its application, balanced harvest can be adopted at both strategic and tactical levels and need not be a full implementation, but could aim for a “partially-balanced” harvest. Further objective discussions and research on this subject are needed to move balanced harvest toward supporting a practical ecosystem approach to fisheries.

Small Fish and Food Security : Towards innovative integration of fish in African food systems to improve nutrition
Kolding, Jeppe ; Overa, Ragnhild ; Kjellevold, Marian ; Zwieten, P.A.M. van; Pucher, Johannes ; Yaro, Joseph ; Atter, Amy ; Njiru, James ; Taabu-Munyaho, Anthony - \ 2018
- 1 p.
Small Fish and Food Security : Towards innovative integration of small fish in African food systems to improve nutrition
Kolding, Jeppe ; Overa, Ragnhild ; Kjellevold, Marian ; Zwieten, P.A.M. van; Pucher, Johannes ; Yaro, Joseph ; Njiru, James ; Taabu-Munyaho, Anthony - \ 2018
In: WSFC 3rd world small-scale fisheries congress, Chiang Mai, Thailand, October 22-26, 2018. - - p. 57 - 57.
Complicit, but Not the Main Culprit: Nile Perch Was Not the Only Cause of the Haplochromine Collapse in Lake Victoria
Kolding, Jeppe ; Zwieten, P.A.M. van; Plank, Michael J. ; Hecky, Robert E. ; Bridgeman, Thomas B. ; Macintyre, Sally ; Seehausen, Ole ; Silsbe, Greg M. - \ 2018
- 1 p.
Small Fish and Food Security : Towards innovative integration of fish in African food systems to improve nutrition
Kolding, Jeppe ; Kjellevold, Marian ; Zwieten, P.A.M. van; Pucher, Johannes ; Yaro, Joseph ; Atter, Amy ; Njiru, James ; Taabu-Munyaho, Anthony - \ 2018
- 3 p.
La pêche dans les zones arides d’Afrique Subsaharienne: le poisson vient avec la pluie : Favoriser la résilience dans les zones arides pour la sécurité alimentaire et la nutrition des populations qui dépendent de la pêche
Kolding, Jeppe ; Zwieten, Paul van; Marttin, Felic ; Poulain, Florence - \ 2017
Rome : Organisation des Nations Unies pour l'Alimentation et l'Agriculture (Circulaire sur les pêches et l’aquaculture 1118, FIAF/C1118 (Fr)) - ISBN 9789252092193 - 64
Fisheries in the drylands of Sub-Saharan Africa “Fish come with the Rains” : Building resilience for fisheries-dependent livelihoods to enhance food security and nutrition in the drylands
Kolding, Jeppe ; Zwieten, P.A.M. van; Marttin, Felix ; Poulain, Florence - \ 2016
FAO Fisheries and Aquaculture Circular (2016)C1118. - ISSN 2070-6065 - 64
Dryland areas cover more than half of sub-Saharan Africa and are home to nearly 50 percent of
its populations, who depend on agriculture (including livestock, crops and fisheries) as their main
livelihood strategy. Sporadic and irregular rainfall patterns are the most important environmental
driver for these regions and water, in particular surface water, is the primary element of scarcity in drylands. Generally, dryland water bodies are unstable and strongly pulsed ecosystems owing to intermittent and largely unpredictable precipitation. Such systems are characterized by very productive and highly resilient, small opportunistic fish species with “boom and bust” fluctuation adapted to strong environmental disturbances, and are therefore difficult to overfish. As a result of high productivity, they can sustain very high yields in years of good rains, but being largely short-lived they also respond rapidly to environmental changes in hydrological regimes, which means that alternating periods of low productivity are inevitable. The focus of this review is to both document the general resilience of many fish resources to climatic variability − including their underestimation in livelihood importance, particularly in protracted crisis situations − and to enhance the potential supply of fish from dryland areas through improved use of the available water bodies, and in particular small reservoirs. The important role that small water bodies play in supplying essential micronutrients and protein to rural communities has largely been overlooked since the termination of the FAO/ALCOM (Aquaculture for Local Community Development) programme in 1998, although they are more productive on a per unit area basis than the large lakes and reservoirs and, when pooled, constitute a much larger area of water. Most of the fish production, however, is consumed locally and goes unrecorded in official catch statistics. By refocusing attention on the fish productivity of small water bodies and reservoirs in drylands, and in particular by integrating fisheries with developments in water harvesting, irrigation and improved water storage facilities, the potential to increase the role played by fish in the diets of dryland people, and to provide improved livelihood opportunities is great. The overall conclusion is that the potential for increasing fish production in dryland areas is significant, that the resources are highly resilient and productive, but that the general and increased unpredictability of the rainfall required to sustain surface water bodies creates uncertainties in annual production. That must be counteracted by an adaptive and diversified livelihood strategy.
The Nile perch invasion in lake Victoria : Cause or consequence of the haplochromine decline?
Zwieten, Paul A.M. van; Kolding, Jeppe ; Plank, Michael J. ; Hecky, Robert E. ; Bridgeman, Thomas B. ; Macintyre, Sally ; Seehausen, Ole ; Silsbe, Greg M. - \ 2016
Canadian Journal of Fisheries and Aquatic Sciences 73 (2016)4. - ISSN 0706-652X - p. 622 - 643.

We review alternative hypotheses and associated mechanisms to explain Lake Victoria’s Nile perch (Lates niloticus) takeover and concurrent reduction in haplochromines through a (re)analysis of long-term climate, limnological, and stock observations in comparison with size-spectrum model predictions of co-existence, extinction, and demographic change. The empirical observations are in agreement with the outcomes of the model containing two interacting species with life histories matching Nile perch and a generalized haplochromine. The dynamic interactions may have depended on size-related differences in early juvenile mortality: mouth-brooding haplochromines escape predation mortality in early life stages, unlike Nile perch, which have miniscule planktonic eggs and larvae. In our model, predation on the latter by planktivorous haplochromine fry acts as a stabilizing factor for co-existence, but external mortality on the haplochromines would disrupt this balance in favor of Nile perch. To explain the observed switch, mortality on haplochromines would need to be much higher than the fishing mortality that can be realistically reconstructed from observations. Abrupt concomitant changes in algal and zooplankton composition, decreased water column transparency, and widespread hypoxia from increased eutrophication most likely caused haplochromine biomass decline. We hypothesize that the shift to Nile perch was a consequence of an externally caused, climate-triggered decrease in haplochromine biomass and associated recruitment failure rather than a direct cause of the introduction.

Fisheries, the inverted food pyramid
Kolding, J. ; Bundy, A. ; Zwieten, P.A.M. van; Plank, M. - \ 2016
ICES Journal of Marine Science 73 (2016)6. - ISSN 1054-3139 - p. 1697 - 1713.
A global assessment of fishing patterns and fishing pressure from 110 different Ecopath models, representing marine ecosystems throughout the world and covering the period 1970–2007, show that human exploitation across trophic levels (TLs) is highly unbalanced and skewed towards low productive species at high TLs, which are around two TLs higher than the animal protein we get from terrestrial farming. Overall, exploitation levels from low trophic species were <15% of production, and only 18% of the total number of exploited groups and species were harvested >40% of their production. Generally, well-managed fisheries from temperate ecosystems were more selectively harvested at higher exploitation rates than tropical and upwelling (tropical and temperate) fisheries, resulting in potentially larger long-term changes to the ecosystem structure and functioning. The results indicate a very inefficient utilization of the food energy value of marine production. Rebuilding overfished components of the ecosystem and changing focus to balancing exploitation across a wider range of TLs, i.e. balanced harvesting, has the potential to significantly increase overall catches from global marine fisheries.
Maximizing fisheries yields while maintaining community structure
Kolding, J. ; Jacobsen, N.S. ; Andersen, K.H. ; Zwieten, P.A.M. van - \ 2016
Canadian Journal of Fisheries and Aquatic Sciences 73 (2016)4. - ISSN 0706-652X - p. 644 - 655.
Under the Ecosystem Approach to Fisheries an optimal fishing pattern is one that gives the highest possible yield while causing the least structural impact on the community. Unregulated, open access African inland fisheries have been observed to sustain high catches by harvesting a broad spectrum of species and sizes, often in conflict with current management regulations in terms of mesh and gear regulations. Using a size and trait-based model we explore whether such exploitation patterns are commensurable with the Ecosystem Approach to Fisheries, by comparing the impacts on size spectrum slope and yield with the different size limit regimes employed in the Zambian and Zimbabwean side of man-made Lake Kariba. Long-term multispecies data under fished and unfished conditions are used to compare and validate the model results. Both model and observations show that the highest yields and low structural impact on the ecosystem are obtained by targeting small individuals in the community. These results call for a re-evaluation of the size based management regulations that are ubiquitous in most fisheries.
The Optimal Fishing Pattern
Kolding, J. ; Law, R. ; Plank, M. ; Zwieten, P.A.M. van - \ 2016
In: Freshwater Fisheries Ecology / Craig, J.F., New York : Wiley-Blackwell - ISBN 9781118394427 - p. 524 - 540.
Conventional fisheries management encourages highly selective fishing patterns for various purposes, such as increase relative yield, reduce unwanted bycatch, protect various species or sizes and rebuild ecosystems. Recent empirical and theoretical studies, however, show increasing evidence that selective removals of targeted components have unintended adverse effects on stocks, fish communities and the ecosystem. Based on case studies from artisanal African freshwater fisheries, and results from dynamic size-based models, this chapter supports the renewed suggestion that an application of a more balanced fishing pattern will mitigate adverse effects and enhance food security better than increased selectivity. Contrary to common belief, small-scale unregulated artisanal fisheries, with a high diversity of seasonally adapted fishing methods, are probably the closest empirical examples we have of an optimal exploitation pattern with the least disruptive effects on the structure of the ecosystem. As such they are among the best examples of an ecosystem approach to fisheries that we have.
Where there is water there is fish – Small-scale inland fisheries in Africa: dynamics and importance
Kolding, J. ; Zwieten, P.A.M. van; Mosepele, K. - \ 2015
In: A History of Water : Vol 3 Water and Food: From hunter-gatherers to global production in Africa London : I.B. Tauris - ISBN 9781780768717
Balanced Harvest in the Real World. Scientific, Policy and Operational Issues in an Ecosystem Approach to Fisheries
Garcia, S.M. ; Bianchi, G. ; Charles, A. ; Kolding, J. ; Rice, J. ; Rochet, M.J. ; Zhou, S. ; Delius, G. ; Reid, D. ; Zwieten, P.A.M. van; Atcheson, M. ; Bartley, D. ; Borges, L. ; Bundy, A. ; Dagorn, L. ; Dunn, D. ; Hall, M. ; Heino, M. ; Jacobsen, B. ; Jacobsen, N.S. ; Law, R. ; Makino, M. ; Martin, F. ; Skern-Mauritzen, M. ; Suuronen, P. ; Symons, D. - \ 2015
Gland, Switzerland : IUCN - 94 p.
The concept of the Ecosystem Approach has entered the fishery harvesting discussions both from fishery perspectives (Reykjavik Declaration; FAO 2003 Annex to the Code of Conduct and from the principles of the Ecosystem Approach adopted by the CBD in 1995. Both perspectives establish the need to maintain ecosystem structure and functioning, whether for sustainable use of biodiversity (CBD) or simply to keep exploited ecosystems healthy and productive (fisheries). In response, the “Balanced Harvest” (BH) concept was suggested by a group of scientists brought together by the IUCN Fisheries Experts Group during the CBD CoP 10 in 2010. The meeting and the BH concept as consolidated there highlighted some of the collateral ecological effects of current fishing patterns and unbalanced removals of particular components of the food web, stimulating a critical rethinking of current approaches to fisheries management. The meeting on “Balanced Harvest in the real world - Scientific, policy and operational issues in an ecosystem approach to fisheries” (Rome, September 29-October 2, 2014) examined the progress made since 2010 on a number of fronts. It considered questions related to the scientific underpinning of the BH concept, including theory, modelling, and empirical observations. It began to explore the economic, policy and management implications of harvesting in a more balanced way.
Coupled human and natural system dynamics as key to the sustainability of Lake Victoria’s ecosystem services
Downing, A.S. ; Nes, E.H. van; Balirwa, J.S. ; Beuving, J. ; Bwathondi, P.O.J. ; Chapman, L.J. ; Cornelissen, I.J.M. ; Cowx, I.G. ; Goudswaard, P.C. ; Hecky, R.E. ; Janse, J.H. ; Janssen, A.B.G. ; Kaufman, L. ; Kishe-Machumu, M.A. ; Kolding, J. ; Ligtvoet, W. ; Mbabazi, D. ; Medard, M. ; Mkumbo, O.C. ; Mlaponi, E. ; Munyaho, A.T. ; Nagelkerke, L.A.J. ; Ogutu-Ohwayo, R. ; Ojwang, W.O. ; Peter, H.K. ; Schindler, D.E. ; Seehausen, O. ; Sharpe, D. ; Silsbe, G.M. ; Sitoki, L. ; Tumwebaze, R. ; Tweddle, D. ; Wolfshaar, K.E. van de; Dijk, J.W.M. van; Donk, E. van; Rijssel, J.C. van; Zwieten, P.A.M. van; Wanink, J. ; Witte, F. ; Mooij, W.M. - \ 2014
Ecology and Society 19 (2014)4. - ISSN 1708-3087
cyprinid rastrineobola-argentea - perch lates-niloticus - nile perch - east-africa - water hyacinth - mwanza gulf - oreochromis-niloticus - morphological-changes - introduced predator - biological-control
East Africa’s Lake Victoria provides resources and services to millions of people on the lake’s shores and abroad. In particular, the lake’s fisheries are an important source of protein, employment, and international economic connections for the whole region. Nonetheless, stock dynamics are poorly understood and currently unpredictable. Furthermore, fishery dynamics are intricately connected to other supporting services of the lake as well as to lakeshore societies and economies. Much research has been carried out piecemeal on different aspects of Lake Victoria’s system; e.g., societies, biodiversity, fisheries, and eutrophication. However, to disentangle drivers and dynamics of change in this complex system, we need to put these pieces together and analyze the system as a whole. We did so by first building a qualitative model of the lake’s social-ecological system. We then investigated the model system through a qualitative loop analysis, and finally examined effects of changes on the system state and structure. The model and its contextual analysis allowed us to investigate system-wide chain reactions resulting from disturbances. Importantly, we built a tool that can be used to analyze the cascading effects of management options and establish the requirements for their success. We found that high connectedness of the system at the exploitation level, through fisheries having multiple target stocks, can increase the stocks’ vulnerability to exploitation but reduce society’s vulnerability to variability in individual stocks. We describe how there are multiple pathways to any change in the system, which makes it difficult to identify the root cause of changes but also broadens the management toolkit. Also, we illustrate how nutrient enrichment is not a self-regulating process, and that explicit management is necessary to halt or reverse eutrophication. This model is simple and usable to assess system-wide effects of management policies, and can serve as a paving stone for future quantitative analyses of system dynamics at local scales.
Sustainable fishing of inland waters
Kolding, J. ; Zwieten, P.A.M. van - \ 2014
Journal of Limnology 73 (2014)s1. - ISSN 1129-5767 - p. 132 - 148.
size-based indicators - multispecies fisheries - marine ecosystems - celtic sea - body-size - exploitation - community - abundance - patterns - fluctuations
Sustainability in fisheries has over the past decades evolved from a single species maximization concept to covering ecosystem and biodiversity considerations. This expansion of the notion, together with increased evidence that the targeted removal of selected components of the fish community may have adverse ecological consequences, poses a serious dilemma to the conventional fisheries management approach of protecting juveniles and targeting adults. Recently, the idea of balanced harvest, harvesting all components in the ecosystem in proportion to their productivity, has been promoted as a unifying solution in accordance the ecosystem approach to fisheries, but this will require a fundamental change to management. In this paper, we review theoretical background, and practicalities of securing high yielding fisheries in inland waters, with empirical examples freshwater fisheries which satisfy the extended objectives of minimal impact on community and ecosystem structure. We propose framework of ecological indicators to assess these objectives.
Status, trends and management of the Lake Victoria Fisheries
Kolding, J. ; Medard, M. ; Mkumbo, O. ; Zwieten, P.A.M. van - \ 2014
In: Inland fisheries evolution and management. Case studies from four continents / Welcomme, R.L., Valbo Jørgensen, J., Halls, A.S., Rome : FAO (FAO Fisheries and Aquaculture Technical Paper 579) - ISBN 9789251081259 - p. 49 - 62.
Is catch a function of effort or is effort a function of catch?
Kolding, J. ; Zwieten, P.A.M. van - \ 2013
In: Proceedings of the MARE conference people and the sea VII: Maritime Futures, June 26-28 2013, Amsterdam, The Netherlands. - - p. 106 - 106.
Balanced Harvesting
Zwieten, P.A.M. van; Kolding, J. - \ 2013
Catching the right size of fish: are size regulations harmful for small scale fisheries?
Zwieten, P.A.M. van; Kolding, J. - \ 2013
In: Proceedings of the MARE conference people and the sea VII: Maritime Futures, June 26-28 2013, Amsterdam, The Netherlands. - - p. 106 - 106.
Lake Kariba revisited: an update on fish community developments from 1960 to 2012
Kolding, J. ; Songore, N. ; Nagelkerke, L.A.J. ; Ndhlovu, N. van; Zwieten, P.A.M. van - \ 2013
In: Abstracts of the Fifth International Conference of the Pan African Fish and Fisheries Association (PAFFA5): African Fish and Fisheries: Diversity, Conservation and Sustainable Management, 16 – 20 September 2013, Bujumbura, Burundi,. - - p. 96 - 96.
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