Evaluating the distribution of freshwater fish diversity using a multispecies habitat suitability model to assess impacts of proposed dam development in Gabon, Africa

Abstract

Data scarcity impedes a comprehensive impact assessment of the 38 dams currently proposed within the highly biodiverse central African nation of Gabon.Here, we present a multiple-species MaxEnt distribution modeling approach to assess species richness for freshwater fishes at the landscape level and demonstrate its utility in identifying proposed dam sites in Gabon that fall in highly diverse areas. We modeled habitat suitability for 202 of Gabon's fresh and brackish water fish species based on georeferenced presence data from museum specimens and a set of ecologically meaningful environmental conditions. We removed poor performing species from the model and compiled the distributions of 114 well-performing species to generate a new metric, the species pseudorichness index (pR), defined as the cumulative number of species that are highly suited to the habitat in a given segment of river. We used pR as a proxy for true species richness and use this metric to evaluate the distribution of freshwater fish diversity relative to the proposed dam development in Gabon. We found that more than 80% of the proposed dams in Gabon overlap with areas of high pR, implying that planned hydroelectric development in Gabon may disproportionately affect high diversity areas. These dams deserve more focused baseline assessments and conservation action. This approach provides a rapid way to initiate a landscape-scale assessment of freshwater fish diversity to inform conservation decisions in areas that are species rich, but data poor.

Description of two new miniature species of Hylopanchax Poll & Lambert, 1965 (Cyprinodontiformes: Procatopodidae), from northeastern Gabon, with an updated diagnosis of the genus based on morphology, colouration and osteology

“…The presence of (a) teeth along the alveolar arm of the premaxilla and (b) a wider anterior tip of the fifth ceratobranchial, first described in Parenti (1981) and Ghedotti (2000), respectively, was confirmed for all taxa belonging to the four genera mentioned earlier. In addition, a sinuous nasal bone was first recorded in this study and is tentatively con- Plataplochilus terveri (Procatopodidae)] (Cutler et al, 2019;Stiassny et al, 2011;Thieme et al, 2005). Despite the lower human population density in the middle and upper portions of the Ogowe and its main tributaries, logging and mining are considered to be major threats to the freshwater communities in this area, resulting in (a) an increase in water pollution, (b) an increase in sediment run-off and (c) a decrease in the allochthonous input of plant material in the system due to deforestation (Stiassny et al, 2011).…”

“…Despite the lower human population density in the middle and upper portions of the Ogowe and its main tributaries, logging and mining are considered to be major threats to the freshwater communities in this area, resulting in (a) an increase in water pollution, (b) an increase in sediment run-off and (c) a decrease in the allochthonous input of plant material in the system due to deforestation (Stiassny et al, 2011). In addition, the plan to build several hydroelectric dams along the Ivindo River (Cutler et al, 2019), within the known distribution range of both species, is considered to be a major threat as the resulting flooding of the small clear-water creeks will alter the habitats in which H. multisquamatus and H. thysi occur. Both species are from a Key Biodiversity Area that includes the Lower Guinea rainforests, comprising the upper Ogowe tributaries (Holland et al, 2011).…”

Quantifying habitat overlaps between native and non-native fishes in the Himalayas using MaxEnt models optimized for data-deficient stream networks

“…ENMs that use vectorized river variables coupled to rasterized climatic variables preserve the hierarchical properties of rivers and increase their predictive performance 18 . Speci cally, MaxEnt (Maximum Entropy) models 19 can predict the presence of suitable habitats in river sections using georeferenced occurrence data coupled with basic climatic variables in raster format 20 . Yet, high resolution instream and topographic variables are available only for some regions including North America, Europe, and New Zealand 21 .…”

Climate change can disproportionately reduce habitats of stream fishes with restricted ranges

“…In this context, understanding the potential impacts of climate change on species distribution is crucial for effective conservation planning 10 . In data-de cient regions of the world, predictive spatial-statistical models can serve as coste cient tools to inform the conservation and management of freshwater biodiversity under scenarios of environmental change 11 .…”

“…Species distribution models (SDMs) are spatially explicit representations of species distributions based on statistical relationships between species observations and environmental variables 12,13 . This approach is particularly useful for understudied species occupying data-poor regions 11,14 . SDMs can be used as the rst step to develop hypothesis-based research and projections to better understand changes in species distributions under future environmental scenarios 15,16 .…”