Functional heterogeneity of habitats and dry season forage variability in an Okavango Delta landscape, northern Botswana

2021 ◽  
Vol 195 ◽  
pp. 104613
Author(s):  
Keoikantse Sianga ◽  
Richard W.S. Fynn
Keyword(s):  
Dry Season ◽  
Okavango Delta ◽  
Functional Heterogeneity

Effects of Long-Term Variability on Water Resources Management Along the Boteti River in Botswana

2019 ◽  
pp. 25-47
Author(s):  
Dominic Mazvimavi ◽  
Moseki R. Motsholapheko
Keyword(s):  
Water Resources ◽  
Water Resources Management ◽  
Aquatic Plants ◽  
Dry Season ◽  
Okavango Delta ◽  
Crop Cultivation ◽  
Resources Management ◽  
Water Flows ◽  
Downstream Section

This chapter examines how the availability and non-availability of river flows has affected benefits realized by communities residing along the Boteti River in Botswana. The Boteti River, which is about 350 km long, derives all its flows from outflows of the Okavango Delta and then discharges into the Makgadikgadi Pans. Peak outflows from the delta occur during the dry season, June to October, and during wet years such as from 1974 to 1982, water flows along the whole river from the delta to the Makgadikgadi Pans. Since 1991, outflows from the delta have only covered about 50 km, with the rest of the river being dry. There has been lack of flows on the downstream section in some years (e.g., 1929-39, 1941-47). Communities residing along the 50 km stretch that is annually flooded benefit from the river through livestock watering, flood recession crop cultivation, fishing, and harvesting of aquatic plants for food and construction. These benefits were not realized by those residing along the rest of the 300 km stretch that was not receiving flows from the delta during the 1991-2008 period.

scholarly journals Waterbirds in the panhandle of the Okavango Delta: dry season counts over two seven-year periods

2019 ◽  
Vol 29 (1) ◽  
pp. 15-27 ◽  
Author(s):  
Grzegorz Kopij ◽  
Mark Paxton
Keyword(s):  
Species Diversity ◽  
Shallow Water ◽  
Deep Water ◽  
Dry Season ◽  
Striking Feature ◽  
Okavango Delta ◽  
Waterbird Species ◽  
Game Reserve ◽  
Okavango River ◽  
Foraging Guilds

We counted waterbirds along a fixed route in the panhandle of the Okavango River in Mahango Game Reserve in the dry season during two seven-year periods (1991–1997 and 2000–2006). Palearctic migrants represented by 11 species in 1991–1997 and nine species in 2000–2006 together composed only a small percentage of all birds recorded in both periods. The two most numerous foraging guilds were birds foraging in shallow water and those foraging in deep water. The former guild was more numerous in 2000–2006, while the latter guild was more numerous in 1991–1997. The proportion of other foraging guilds varied little between the two periods. The most numerous diet guild was piscivores, they were more numerous in 1991–1997 than in 2000–2006. If the total numbers of birds of each particular species in the years 1991–1997 were pooled and compared with those for the years 2000–2006, then highly significant changes in their numbers between these periods could be seen for 53 out of 93 waterbird species. Over the timespan 1991–2006, 12 species significantly increased in numbers while one species, the Cattle Egret, declined; seven other species showed no significant changes in abundance. The increase can be linked to the volume of water flowing through the river. While during the years 1991–1997 the total volume measured at Mohembo was 45.9 km3 (SD = 1.43), during the years 2000–2006 the volume was 60.9 km3 (SD = 1.41). Diversity was very similar during the two periods (1991–1997: S = 1.4; 2000–2006: S = 1.3), with no difference in evenness. The striking feature is that species diversity and abundance of birds was far greater than any records from other southern African rivers to date.

Functional heterogeneity of dry-season fish refugia across a Mediterranean catchment: the role of habitat and predation

2002 ◽  
Vol 47 (10) ◽  
pp. 1919-1934 ◽  
Author(s):  
M. Filomena Magalhães ◽  
Pedro Beja ◽  
Catarina Canas ◽  
Maria João Collares-Pereira
Keyword(s):  
Dry Season ◽  
Functional Heterogeneity

scholarly journals Seasonal hydrology influences energy channels in food webs of rivers in the lower Okavango Delta

2021 ◽  
Author(s):  
Thethela Bokhutlo ◽  
Friedrich W. Keppeler ◽  
Kirk O. Winemiller
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Species Interactions ◽  
Trophic Position ◽  
Fish Population ◽  
Dry Season ◽  
Okavango Delta ◽  
Foraging Strategies ◽  
Single Source ◽  
Wet Season

Abstract Describing species interactions and resource use can elucidate patterns of energy flow in ecosystems. Here, we analyzed stable isotope ratios (δ13C and δ15N) to infer seasonal variation in energy pathways and species foraging strategies in two rivers of the lower Okavango Delta, Botswana. We sampled fish during wet and dry seasons and estimated proportions of basal production sources assimilated by fish using Bayesian isotopic mixing models. We estimated modal trophic position for each fish population and assessed its correlation with the degree that biomass was supported by one production source. In the Boteti River during the wet season, biomass of most fishes was supported by food chains originating mainly from seston. During the dry season, C4 grasses assumed greater importance, and the degree of dependence on a single source was inversely related to trophic position. In the Boro River, seston was inferred to be an important production source supporting most species during both periods, and the degree of dependence on a single source was positively related to trophic position during the dry season, suggesting that species higher in the food web assimilated material disproportionately from one source during this period. Our findings support the idea that fish foraging habits shift in response to seasonal patterns of connectivity and habitat availability. We showed that consumers in river food webs are supported by multiple basal production sources and that seasonal hydrological pulsing, despite causing short-term changes in food web dynamics, may promote long-term population and community stability.

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