Water requirements of floodplain rivers and fisheries: existing decision support tools and pathways for development

Fisheries / Rivers / Flood plains / Hydrology / Ecology / Models / Decision support tools / Environmental impact assessment / Methodology / Databases

The economic and ecological effects of water management choices in the upper Niger river: Development of decision support methods

One million people in the Inner Niger Delta make a living from arable farming, fisheries and livestock. Upstream dams (one built for electricity generation and one for irrigation) affect this downstream multifunctional use of water. Additionally, the Inner Niger Delta, which is one of the largest Ramsar sites in the world, is a hotspot of biodiversity and accommodates two of the largest known breeding colonies of large wading birds in Africa and in addition, is a vital part of the eco-regional network, supporting up to 3 to 4 million staging waterbirds, residents and migrants from all over Europe and western Asia. The hydrological and related ecological conditions in the Inner Delta largely determine the population size of these waterbird species. The major aim of the three-year study was to develop a decision-support system for river management in the Upper Niger, in which ecological and socio-economical impacts and benefits of dams and irrigation systems can be analysed in relation to different water management scenarios. The study involves various components: hydrology, arable farming, livestock, fisheries, ecology and socio-economics. An economic analysis has been conducted to determine the role of dams in the economy of the Inner Niger Delta and the Upper Niger region. By innovatively combining the above information on hydrology, ecology, fisheries, and agriculture, the study shows that building new dams is not an efficient way to increase economic growth and reduce poverty in the region. In fact, such efforts are counter-effective. Instead, development efforts should be aimed at improving the efficiency of the existing infrastructure, as well as of current economic activities in the Inner Niger Delta itself. This approach will also provide greater certainty for the essential eco-regional network functioning of the Inner Delta. © 2006 Taylor & Francis

Do fish go with the flow? The effects of periodic and episodic flow pulses on 0+ fish biomass in a constrained lowland river

The hydrological regime is a significant driver of fish population dynamics in rivers, but there is a dearth of information regarding the mechanisms behind its effects on temperate species, especially non-salmonids. This study investigated the effects of periodic and episodic flow pulses on 0+ fish biomass in a constrained lowland river. De-seasonalized cross-correlation analysis was used to examine time-lagged correlations in episodic signals, in isolation of seasonal periodicity, to identify the responses and response timings of 0+ fish production to abiotic variables, and whether apparent “pulse-depletions” in biomass occur instantaneously (e.g., due to fish displacement during high pulses) or after a time lag. As anticipated, 0+ fish biomass was highest during periods of low discharge and high temperatures in summer, but cross-correlation analysis revealed a negative impact of high pulses on 0+ fish biomass with a lag of 7 months. There was no evidence for an instantaneous pulse-depletion effect of discharge on 0+ fish biomass, suggesting that the indirect effects of high pulses, such as habitat or food-web modifications, are more influential

Commercial fisheries in a mega unregulated floodplain river: assessment of the most favourable hydrological conditions for its preservation

This paper deals with the hydrological variability effects on the primary commercial fish species inhabiting the main channel and the floodplain of the large Paraná River in its middle reaches in Argentina. Analysing more than eight decades (1935–2016) of information on the most frequent and abundant commercial species in conjunction with hydrological levels and temperature, our results show that spring–summer floods of a certain magnitude (c. 6 m) and durations (> 80 days) are crucial for sustaining commercial fisheries. Moreover, the frequency of these floods was modulated by the decadal climatic fluctuations that have occurred over the past 100 years in the Paraná Basin. An insight into the probable incidence of some anthropogenic influences is also provided.Fil: Rabuffetti, Ana Pia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Espínola, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Abrial, Elie. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Amsler, Mario Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Blettler, Martin Cesar Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Eurich, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Eberle Folmer, Eliana Gisel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentin