Fishing for conservation of freshwater tropical fishes in the Anthropocene

1. The ecosystem services provided by freshwater biodiversity are threatened by development and environmental and climate change in the Anthropocene.
2. Here, case studies are described to show that a focus on the shared dependence on freshwater ecosystem functioning can mutually benefit fisheries and conservation agendas in the Anthropocene.
3. Meeting the threat to fish biodiversity and fisher livelihood is pertinent in developing regions where there is often a convergence between high biodiversity, high dependency on aquatic biota and rapid economic development (see Kafue River, Logone floodplain, Tonle Sap, and Rio Negro case studies).
4. These case studies serve as evidence that biodiversity conservation goals can be achieved by emphasizing a sustainable fisheries agenda with partnerships, shared knowledge and innovation in fisheries management (see Kafue River and Kenai River case studies).
5. In all case studies, aquatic biodiversity conservation and fisheries agendas are better served if efforts focused on creating synergies between fishing activities with ecosystem functioning yield long‐term livelihood and food security narratives.
6. A unified voice from conservation and fisheries communities has more socio‐economic and political capital to advocate for biodiversity and social interests in freshwater governance decisions.

     

Wetlands: conservation's poor cousins

1. About 5–10% of the world's land surface is currently wetland but possibly >70% is already destroyed or impaired. Conservation of these unique ecosystems lags progress in other realms, reflected in high rates of biodiversity loss. Wetlands provide a range of critically important ecosystem services including fresh water, nutrient cycling, food and fibre production, carbon fixation and storage, flood mitigation and water storage; water treatment and purification and habitats for biodiversity. There is increasing recognition that these services provide real economic values.
2. Wetlands are affected by numerous threats including habitat loss and degradation, climate change, pollution, invasive species, overharvesting and disease. The most serious impact is from habitat loss and degradation caused by upstream water resource developments and conversion to agriculture, industry and transport, and urban development.
3. The status of the distribution and extent of the world's wetlands remains poorly known, varying among countries. Wetland loss has varied internationally, with generally higher impacts in the Northern Hemisphere, with its long history of conversion to urban centres, ports and agriculture and yet there are increasing losses occurring in developing continents in the south.
4. Wetland conservation needs to focus primarily on identification of priority areas for biodiversity conservation and legal protection, including Ramsar‐listing. Identification of wetland biodiversity hotspots for conservation should be an imperative, with associated Ramsar‐listing. There also needs to be effective protection of flow regimes. Mitigation of other deleterious processes, pollution, overharvesting, invasive species and disease, also remains particularly important.
5. Conservation of wetlands remains especially challenging, given the importance of fresh water for human communities, industry and agriculture. Without effective conservation actions, mitigation of threats, rigorous risk assessment and acknowledgement of the value of wetland ecosystem services, wetland conservation will continue to lag behind conservation in other realms in protecting the Earth's biodiversity.

Copyright © 2016 John Wiley & Sons, Ltd.     

Development and practical test of a weighable groundwater lysimeter for floodplain sites

Presently, the soil water balance of flood‐influenced soils in fluvial plains is insufficiently described. The new development of a weighable groundwater lysimeter is the basis for recording the water‐balance components precipitation, evapotranspiration, groundwater recharge, capillary rise, and interaction with the water course. Soil‐hydrologic measuring setups at two floodplain sites of the Elbe river serve for direct comparability of lysimeter measurements with data obtained on site. A groundwater control was designed for lysimeters that automatically adjusts the current groundwater level at the floodplain measuring setups and quantifies inflow into or outflow from the lysimeter. It turned out that the lysimeter developed is capable of identifying the individual water‐balance quantities at high accuracy. Contrary to previous assumptions, it was possible to prove groundwater recharge for the floodplain sites.     

The Traditional Whedo Aquaculture System in Northern Benin

The traditional whedo system involves the digging of large ditch-like ponds that fill seasonally with flood water, trapping fish which are subsequently harvested during the dry season. Although whedos are well described in the South of Benin, basic information necessary for their management in the North is lacking. Since 1998, the commune of Malanville has experienced a kind of ‘blue revolution’ because up to now, approximately 500 whedos (known locally as tschifi dais) have been constructed covering a total surface area of 9.3 ha, thus reflecting the high acceptance of the practice among the local population. Despite the fast development this system has received little attention from national development planners and international agencies, but in view of the disastrous state of the river Niger's fishery, sustainable aquaculture, fully relying on local species should be supported to release pressure on natural fish stocks. Instead of focussing all efforts on the introduction of modern aquaculture, it is important to enhance the existing system because of the knowledge and acceptance by the local population.

This paper characterizes the current management and the technical as well as economical features of the tschifi dais in the commune of Malanville, northern Benin.     

Assemblage patterns of fish functional groups relative to habitat connectivity and conditions in floodplain lakes

Miyazono S, Aycock JN, Miranda LE, Tietjen TE. Assemblage patterns of fish functional groups relative to habitat connectivity and conditions in floodplain lakes.
Ecology of Freshwater Fish 2010: 19: 578–585. © 2010 John Wiley & Sons A/S Abstract – We evaluated the influences of habitat connectivity and local environmental factors on the distribution and abundance patterns of fish functional groups in 17 floodplain lakes in the Yazoo River Basin, USA. The results of univariate and multivariate analyses showed that species–environmental relationships varied with the functional groups. Species richness and assemblage structure of periodic strategists showed strong and positive correlations with habitat connectivity. Densities of most equilibrium and opportunistic strategists decreased with habitat connectivity. Densities of certain equilibrium and opportunistic strategists increased with turbidity. Forested wetlands around the lakes were positively related to the densities of periodic and equilibrium strategists. These results suggest that decreases in habitat connectivity, forested wetland buffers and water quality resulting from environmental manipulations may cause local extinction of certain fish taxa and accelerate the dominance of tolerant fishes in floodplain lakes.     

Growth-Oriented Logging (GOL): A new concept towards sustainable forest management in Central Amazonian várzea floodplains

Against a background of increasing human populations in developing countries, and global climate change, conservation of tropical forests remains one of the most important ecological challenges of our time. One of the biggest difficulties for ecologically sustainable management of tropical forests is obtaining reliable growth data for trees, which is a prerequisite for determining harvesting volumes and cutting cycles. GOL is the first concept for sustainable management of tropical timber resources in Amazonian floodplain forests (várzea) based on species-specific management criteria, such as minimum logging diameters (MLDs) and cutting cycles. From timber species with varying wood densities of different successional stages, volume stocks have been estimated in 1-ha plots and 12 growth models have been developed based on tree rings, which are annually formed as a consequence of the regular, long-term flooding. The MLDs of timber species vary between 47 and 70 cm and the estimated cutting cycles differ the 10-fold, from 3 to 32 years. These enormous differences in the growth rates between tropical timber species are not considered in current management practices, which apply only one diameter cutting limit and one cutting cycle to harvest many tree species. This practice risks the overexploitation of slow-growing timber species, while the fast-growing timber species with low wood densities cannot be efficiently used. Based on the timber stocks and lifetime growth rates, the GOL concept has been created as an aid to improve forest management in the Central Amazonian várzea. The model is unique for tropical silviculture.     

景观规划对滩地型旅游地旅游资源类型的多样化促进分析——以郑州黄河滩地为例

景观规划可以有效增加滩地型旅游地的旅游资源的类型。以郑州市黄河滩地为例,定量化分析景观规划前后旅游资源类型的变化。郑州黄河滩地原旅游资源有主类7、亚类16、基本类型25。通过景观规划使旅游资源类型达到主类8、亚类25、基本类型68,较景观规划前分别增加了14%、56%、172%。地文景观、水域景观、生物景观、天象与气候景观、遗址遗迹、建筑与设施、旅游商品、人文活动等的基本类型新增数分别占总数的20%、33%、45%、67%、0、80%、100%、80%。郑州黄河滩地的旅游资源主类、亚类、基本类型占全国的比例分别由景观规划前的87.5%、51.6%、16.1%提高到100%、76%、43.9%,分别增加了12.5%、24.4%和27.8%。     

Reducing Sediment Connectivity Through man‐Made and Natural Sediment Sinks in the Minizr Catchment,Northwest Ethiopia

Man‐made and natural sediment sinks provide a practical means for reducing downstream reservoir sedimentation by decreasing soil erosion and enhancing the rate of sedimentation within a catchment. The Minizr catchment (20 km²) in the northwest Ethiopian highlands contains numerous man‐made soil and water conservation (SWC) structures such as soil bunds (Erken), fanya juu ridge (Cab) and micro‐trenches and natural sediment sinks such as wetlands, floodplains and grassed waterways. These sediment sinks reduce downstream sedimentation into the Koga reservoir, located at the catchment outlet, however, a large quantity of sediment is still reaching the reservoir. This study evaluates the function and effectiveness of both man‐made SWC structures and natural sediment sinks in reducing sediment export from the Minizr catchment. SWC structures and natural sediment sinks were digitized using Google Earth Imagery. Sediment pins and vertical sampling through the deposit were used to quantify the amount of deposited sediment. In addition, inflow and outflow of suspended sediment data were used to calculate the sediment‐trapping efficacies (STE) of man‐made SWC structures (soil bunds and fanya juu ridges) and natural sediment sinks. Results reveal that 144 km soil bunds and fanya juu ridges trapped 7,920 Mg y⁻¹ (55 kg m⁻¹ y⁻¹) and micro‐trenches trapped 13·26 Mg y⁻¹, each micro‐trench on average trapped 23 kg y⁻¹. The 17 ha floodplain located in the centre of the catchment trapped 9,970 Mg y⁻¹ (59 kg m⁻² y⁻¹), while a wetland with a surface area of 24 ha, located near the outlet of the catchment, trapped 8,715 Mg y⁻¹ (36 kg m⁻² y⁻¹). The STEs of soil bunds and fanya juu ridges, wetlands and floodplains were 54%, 85% and 77%, respectively. Substantial differences were observed between the STE of grassed and un‐grassed waterways at 75% and 21%, respectively. Existing man‐made and natural sediment sinks played an important role in trapping sediment, with 38% (26,600 Mg y⁻¹) of transported sediment being trapped, while 62% (43,000 Mg y⁻¹) is exported from the catchment and thus enters the Koga reservoir. Therefore, additional catchment treatment measures are required as an integrated catchment scale sediment trapping approach to help reduce sediment loads entering Koga reservoir. Moreover, to maximize the effectiveness of sediment trapping measures, avoid structural failure and ensure their sustainability, regular maintenance is needed. Copyright © 2016 John Wiley & Sons, Ltd.     

Trophic structure of fish assemblages from Mamoré River floodplain lakes (Bolivia)

Abstract –  The fish assemblage of the floodplain of the Mamoré River (Bolivia) was estimated in eight lakes, corresponding to four habitat types, situated on an environmental gradient related to the river distance: lakes situated near the river, in the forested floodplain, at the floodplain edge and lakes isolated in the savanna. This paper documents the diet of 71 fish species (among the 140 recorded) and compares the taxonomic and trophic structure of fish assemblages between four lake types. The diet analysis was conducted to determine five trophic guilds: algivores/iliophages, herbivores, zooplanktivores, invertivores and piscivores. The taxonomic and trophic structures of the fish assemblages were not similar in the different lake types of the Mamoré River. The trophic structure of assemblages showed a coarse pattern of dominance of algivores/iliophages and invertivores, but different situations were observed in relative abundance of the trophic groups in relation to the spatial position of the lakes (except for piscivores). Lakes close to the river appeared more favourable to the microphages (algivores/iliophages, zooplanktivores) although remote lakes appeared more favourable to the macrophages (invertivores, herbivores). These results support the general idea that fish distribution follows a pattern linked to the ecology of the species, and related to environmental characteristics of the lakes.     

Feeding patterns in five predatory fishes of the high Paranà River floodplain (PR, Brazil)

Abstract— Between March 1992 and February 1993 five piscivorous fish species, Acestrorhynchus lacustris (Reinhardt, 1874), Hoplias malabaricus (Bloch, 1794), Rhaphiodon vulpinus Agassiz, 1829, Salminus maxillosus , Valenciennes, 1840 and Plagioscion squamosissimus (Heckel, 1840), of the high Paranà River floodplain showed a wide total prey spectrum though only three to four taxa were dominant in their diet. Shrimp, Macrobrachium amazonicum , were also common to the majority of species. Seasonal and spatial variations occurred throughout the study period probably due the availability of prey species. The main resources shared by the predators were also the most abundant in the area, with consumption markedly focused on prey about 5.0 cm long. Detrended correspondence analysis was effective in discriminating two groups of predators species that exploited distinct microhabitats. The predators with the least scores consumed small characids that inhabit mid-water or the littoral region, whereas those with the largest scores consumed prey associated to the bottom.