Lorenzen Lab @ UF/IFAS

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Tropical freshwater fisheries research

Tropical freshwater biological resources harbour a large share of the world’s aquatic biodiversity (including some 40% of all fish species), and are very important to local people as sources of food and income. We have a long-running programme of collaborative research on freshwater fisheries management in the Greater Mekong and Amazon regions. All projects are carried out jointly with local partners, and most involve close integration of primary research with policy development, management action and extension. Particular foci of our work are:

Small waterbody fisheries in the lower Mekong

Fisheries impacts of irrigation development

Aquatic resource management on rice farms

Amazon river-floodplain fisheries

Conservation strategy for the Mekong giant catfish


Small waterbody fisheries in the lower Mekong


Small, permanent waterbodies such as floodplain lakes, reservoirs and swamps play a key role in maintaining the diversity and productivity of biological resources in seasonally flooded areas such as rice farming landscapes and floodplains. Small waterbody fisheries in the Mekong region are intensively exploited and often actively managed and enhanced. We work with the Regional Development Committee for Livestock and Fisheries in Southern Lao (RDC), the Livestock and Fisheries Section of Savannakhet Province and the Thai Department of Fisheries to evaluate management strategies for small waterbody fisheries. The research builds upon, and aims to help improve indigenous management practices through rigorously designed, participatory experiments. Observational and experimental studies in Laos involving more than 40 small water bodies have shown how management systems that combine harvest restrictions with enhancement using non-native carp and tilapia species can generate substantial productivity, socio-economic, and ecological benefits. Our work on small waterbody fisheries has been supported by the UK Department for International Development .

Arthur, R.I., Lorenzen, K., Homekingkeo, P., Sidavong, K., Sanvilaikham, B. & Garaway, C.J. (2009) Assessing impacts of introduced aquaculture species on native fish communities: Nile tilapia and major carps in SE Asian freshwaters. Aquaculture in press

Garaway, C.J., Arthur, R.I., Chamsingh, B., Homekingkeo, P., Lorenzen, K., Saengvilaikham, B. & Sidavong, K. (2006) A social science perspective on stock enhancement outcomes: lessons learned from inland fisheries in southern Lao PDR. Fisheries Research 80: 37-45. PDF

Lorenzen, K., Almeida, O., Arthur, R., Garaway, C. & Nguyen Khoa, S. (2006) Aggregated yield and fishing effort in multi-species fisheries: an empirical analysis. Canadian Journal of Fisheries and Aquatic Sciences 63: 1334-1343. PDF

Garaway, C., Lorenzen, K. & Chamsingh, B. (2001) Developing fisheries enhancements in small waterbodies: lessons from Lao PDR and Northeast Thailand. ACIAR Proceedings 98: 227-234. PDF

Lorenzen, K. & Garaway C.J. (1998) How predictable is the outcome of stocking? FAO Fisheries Technical Paper 374: 133-152. PDF

Lorenzen, K. (1998) Culture-based fisheries in Asian Reservoirs and Lakes: Key Issues for Sustainability. In: Aquaculture Sustainability and the Environment. Manila/Bangkok: Asian Development Bank/Network of Aquaculture Centers in Asia-Pacific, pp. 321-327.

Lorenzen, K., Garaway, C.J., Chamsingh, B. & Warren, T.J. (1998) Effects of access restrictions and stocking on small water body fisheries in Laos. Journal of Fish Biology 53 (Supplement 1) 345-357. PDF

Lorenzen, K., Juntana, J., Bundit, J. & Tourongruang, D. (1998) Assessing culture fisheries practices in small water bodies: a study of village fisheries in Northeast Thailand. Aquaculture Research. 29: 211-224. PDF

Fisheries impacts of irrigation development

Irrigation development may impact strongly on the ecology of natural aquatic resources in agricultural landscapes, and their role in rural livelihoods. We have worked with the International Water Management Institute ( IWMI ), the Regional Development Committee for Livestock and Fisheries in Southern Laos, and the Universoty of Kelanya in Sri Lanka to conduct impact assessments in different agricultural landscapes, and to develop general guidelines and tools for managing such impacts. Our work on fisheries impacts of irrigation development has been supported by the UK Department for International Development .

Lorenzen, K., Smith, L., Nguyen Khoa, S., Burton, M., Garaway, C.J. (2007) Management of impacts of irrigation development on fisheries: guidance manual . International Water Management Institute (IWMI) and WorldFish Center. PDF

Nguyen Khoa, S., Lorenzen, K., Garaway, C.J., Chamsinhg, B., Siebert, D. & Randone, M. (2005) Impacts of irrigation on fisheries in rainfed rice farming landscapes. Journal of Applied Ecology PDF

Smith, L.E.D., Nguyen Khoa, S. & Lorenzen, K. (2005) Livelihood functions of inland fisheries: policy implications in developing countries. Water Policy 7: 359-383. PDF

Nguyen Khoa, S., Smith, L. & Lorenzen, K. (2005) Impacts of irrigation on inland fisheries: appraisals in Laos and Sri Lanka. Comprehensive Assessment Research Report 7. PDF

Nguyen Khoa, S., Smith, L. & Lorenzen, K. (2005) Adaptive, participatory and integrated assessment of the impacts of irrigation on fisheries: evaluation of the approach in Sri Lanka. IWMI Working Paper 89. PDF

Lorenzen, K., Smith, L., Nguyen Khoa, S., Burton, M., Garaway, C.J. (2002) Management of irrigation development impacts on fisheries. Final Technical Report to the DFID Knowledge and Research in Engineering Sectors Programme. 60 pp. PDF

GWP (2004). Integrating fisheries into irrigation planning and management. Water Policy Briefing 12. 8 pp. PDF

Aquatic resource management on rice farms

Rice agro-ecosystems are man-made wetlands that support considerable aquatic biodiversity and often, productive fisheries. Southeast Asian rice farmers often manage aquatic habitats and resources on their land to increase production of wild aquatic organisms. We have worked with the Institute of Aquaculture , Asian Institute of Technology , the Fisheries Departments of Cambodia and Thailand and RIA1 Vietnam to characterize such ‘farmer-managed aquatic systems’ (FMAS) and to evaluate their role in conserving and enhancing fisheries resources.

We characterized ‘farmer-managed aquatic systems’ (FMAS) in six regions of Cambodia, Thailand and Vietnam on the basis of their physical attributes, management practices, and fisheries production and utilisation. More than 80% of rice farming households in Thailand and Cambodia harvest aquatic animals from their land, and over 70% create aquatic habitats such as ponds in order to increase aquatic resource production. Cambodian households tend to create and utilize a wide variety of man-made aquatic habitats on their land, while Thai households use predominantly trap ponds. The majority of households in Cambodia and Thailand harvest wild fish from both FMAS and from open waters, with FMAS accounting for over half of total catches. In both countries, wild aquatic animals account for over 90% of the catch, with the remainder being stocked hatchery fish. By contrast, less than half of Vietnamese farming households harvest wild aquatic animals from their land, and very few undertake habitat management specifically for such animals. Vietnamese FMAS were intensively stocked and managed as aquaculture systems, with wild fish accounting for less than 30% of production. The differences in FMAS characteristics between regions are related to topography, water resource availability, farming practices, and abundance of wild aquatic species. FMAS are found primarily in lower-intensity rice farming systems and contribute substantially to food production and wider ecosystem services from these systems.

A high diversity of wild aquatic organisms was identified in Cambodian and Thai FMAS. The wild fish catches in FMAS were obtained with much lower fishing effort than those from open systems, indicating a positive effect of FMAS management on fisheries productivity. A large share of this positive effect is attributable to lower harvesting effort in FMAS where access is restricted to the owner’s household as compared to open systems. Of the other indigenous management measures, the construction of brush parks and manuring were associated with positive effects on productivity in Cambodia and Thailand. FMAS support substantial aquatic biodiversity in traditional rice farming landscapes, and yield significant benefits to farmers in terms of aquatic resource availability and productivity. Our work on aquatic resource management on rice farms has been supported by the UK Department for International Development .

Amilhat, E., Lorenzen, K., Morales, E.J., Yakupitiyage, A. & Little, D.C. (2009) Fisheries production in Southeast Asian farmer managed aquatic systems (FMAS): I. Characterisation of systems. Aquaculture in press

Amilhat, E., Lorenzen, K., Morales, E.J., Yakupitiyage, A. & Little, D.C. (2009) Fisheries production in Southeast Asian farmer managed aquatic systems (FMAS): II. Diversity of aquatic resources and management impacts on catch rates. Aquaculture in press

Morales, E.J., Little, D.C., Immink, A., Demaine, H., Yakupitayage, A., Amilhat, E. & Lorenzen, K. (2006) Contribution of self-recruiting species produced in farmer-managed aquatic systems in rural areas of Southeast Asia to food consumption.. Journal of Food Composition and Analysis 19: 759-760. PDF

Amilhat, E. & Lorenzen, K. (2005) Habitat use, migration pattern and population dynamics of chevron snakehead Channa striata in a rainfed rice farming landscape. Journal of Fish Biology 67(SB):23-34. PDF

Amilhat, E., Morales, E.J., Immink, A., Little, D.C., Lorenzen, K., Ul Islam, F. & Karapanagiotidis, I. (2005) Self-recruiting species in aquaculture: their role in rural livelihoods. Summary Report. DFID Aquaculture and Fish Genetics Research Programme.

Amazon river-floodplain fisheries

Working with our partners IPAM and NAEA/UFPA , we investigate the role of fishing in the Amazon regional economy, the effects of lake management agreements on fisheries productivity, and the impact of land use change in the floodplains on fish populations.

The overall economic importance of the Amazon fisheries sector is far greater than previously realised. This provides strong policy-level incentives for the conservation of fisheries and the habitats upon which they depend. There is a high degree of regional differentiation in fleet characteristics of the commercial fishery, and the relative importance of commercial and subsistence-oriented fisheries.Fishing is the dominant source of income in varzea households. However, fishing is subsistence-oriented and there is little indication that households substitute fishing for other activities even when returns are high. Hence it is unlikely that fisheries management initiatives will reduce reliance on other activities that may be more damaging to the varzea environment. Empirical data show that co-management agreements are effective at increasing productivity of managed lakes, at least in the short term. Modelling studies suggest that such increases will be at least partially compensated by reduced productivity in the river fisheries. The expansion and further development of co-management initiatives was seen as crucial to safeguarding the productivity of the fishery in the face of possible market expansion, despite the limited overall effectiveness of such measures under current conditions. By providing a transparent and rigorous analysis of management issues, the projects have fostered a constructive dialogue on the future development of Amazon fisheries, and their role in the conservation of floodplain habitats. Our work on Amazon fisheries has been supported by the Darwin Initiative , the Fisheries Society of the British Isles , and the Gordon & Betty More Foundation .

Almeida, O., Lorenzen, K. & McGrath, D.G. (2009) Fishing agreements in the lower Amazon: for gain and restraint. Fisheries Management and Ecology 16: 61-67.

Martelo, J., Lorenzen, K., Crossa, M. & McGrath, D.G. (2008) Habitat associations of exploited fish species in the Lower Amazon river-floodplain system. Freshwater Biology 53: 2455-2464. PDF

Lorenzen, K., Almeida, O., Arthur, R., Garaway, C. & Nguyen Khoa, S. (2006) Aggregated yield and fishing effort in multi-species fisheries: an empirical analysis. Canadian Journal of Fisheries and Aquatic Sciences 63: 1334-1343. PDF

Almeida, O., Lorenzen, K., McGrath, D. & Amaral, L. (2006) O setor de pesca na economia regional. In: Almeida, O. (Ed.) Manejo de Pesca na Amazônia Brasileira. São Paulo: Peirópolis. pp. 25-36.

Almeida, O., Lorenzen, K. & McGrath, D. (2006) A frota comercial pesqueira na Amazônia e o co-manejo no Baixo Amazonas. In: Almeida, O. (Ed.) Manejo de Pesca na Amazônia Brasileira. São Paulo: Peirópolis. pp. 37-50.

Almeida, O., Lorenzen, K. & McGrath, D. (2006) Pescadores rurais de pequena escala e o co-manejo no Baixo Amazonas. In: Almeida, O. (Ed.) Manejo de Pesca na Amazônia Brasileira. São Paulo: Peirópolis. pp. 51-72.

Lorenzen, K., Almeida, O. & Azevedo, C. (2006) Interações entre a pesca comercial e a de subsistência no Baixo Amazonas: utilizando um modelo bio-econômico. In: Almeida, O. (Ed.) Manejo de Pesca na Amazônia Brasileira. São Paulo: Peirópolis. pp. 73-94.

Almeida, O.T. & Lorenzen, K. & McGrath, D.G. (2004) The fisheries sector in the Amazon regional economy. Proceedings of the Second International Large Rivers Symposium . In: Welcomme, R.L. (Ed.) Proceedings of the 2nd International Large Rivers Symposium. Phnom Penh/Rome: Mekong River Commission/FAO.

Almeida, O.T., Lorenzen, K. & McGrath, D.G. (2003) Commercial fishing in the Brazilian Amazon: regional differentiation in fleet characteristics and efficiency. Fisheries Management and Ecology 10: 109-115. PDF

Lorenzen, K., Almeida, O. & McGrath, D.G. (2002) Fisheries management for biodiversity conservation in the Brazilian Amazon. Final Report to the Darwin Initiative, DEFRA. 36 pp. PDF

Almeida, O.T., Lorenzen, K. & McGrath, D.G. (2002) Oficina de Politicas Pesqueiras para o Baixo Amazonas. IPAM, Santarem, Brazil. 28 pp. PDF

Almeida, O.T., Lorenzen, K. & McGrath, D.G. (2002) Impact of co-management agreements on the exploitation and productivity of floodplain lake fisheries in the lower Amazon. Proceedings of the Ninth International Conference of the IASCP.

Lorenzen, K., Almeida, O.T., Avzeiro, C. Interactions between commercial and  subsistence-oriented fisheries in the lower Amazon: a bio-economic analysis. Manuscript.

Almeida, O.T., McGrath, D.G. & Ruffino, M.L. (2001) The commercial fisheries of the lower Amazon: an economic analysis. Fisheries Management and Ecology 8: 253-269.

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