When Rivers Speak: Exploring Fish Welfare in a Changing Mekong
By the OTS South Africa Team
Interest in animal welfare is expanding beyond traditional subjects of mammals and birds to include invertebrates and lower-order vertebrates including fishes. This shift reflects growing recognition that human activities may affect not just populations but also individual welfare.
Dr. Josephine Pegg, lecturer with the Organization for Tropical Studies South Africa, has recently been awarded a grant from WWF Laos to collaborate on a new study examining fish welfare in the Mekong Basin. The project compares growth and stress in fish populations in free-flowing and dam-impacted rivers in southern Laos — a region undergoing rapid hydropower development.
The work focuses on five species across three rivers. One key method involves reading fish scales — a technique comparable to interpreting tree rings. Each scale contains growth rings, that reflect how rapidly a fish has grown over time. During periods of slower growth, these rings become more tightly spaced. By analysing these patterns, we can determine fish age and assess how growth differs between systems. This analysis is complemented by scale cortisol assessment to see if changes in hormonal stress and physical growth co-occur.
OTS South Africa is funding Siphelele “Jobe” Sithole, an honours student at the University of the Witwatersrand, to carry out this work for his thesis under Dr. Pegg’s supervision. His involvement reflects our commitment to capacity building and the development of regional expertise in freshwater ecology.
Across the globe — from the United States to South Africa — freshwater managers are re-evaluating the legacy of in-river dams. In Kruger National Park, home of OTS South Africa, efforts are ongoing to remove redundant weirs and reconnect river systems.
This project aims to inform policy and freshwater management not only in Laos, but in tropical river systems more broadly — integrating biodiversity conservation with animal welfare in a changing world.