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Understanding genetic connectivity plays a crucial role in species conservation decisions, and genetic connectivity is an important component of modern fisheries management. In this study, we investigated the population genetics of four endemic Lates species of Lake Tanganyika (Lates stappersii , L. microlepis , L. mariae , and L. angustifrons) using reduced-representation genomic sequencing methods. We find the four species to be strongly differentiated from one another (mean interspecific F ST = 0.665), with no evidence for contemporary admixture. We also find evidence for strong genetic structure within L. mariae , with the majority of individuals from the most southern sampling site forming a genetic group that is distinct from the individuals at other sampling sites. We find evidence for much weaker structure within the other three species (L. stappersii, L. microlepis , and L. angustifrons). Our ability to detect this weak structure despite small and unbalanced sample sizes and imprecise geographic sampling locations suggests the possibility for further structure undetected in our study. We call for further research into the origins of the genetic differentiation in these four species—particularly that of L. mariae —which may be important for conservation and management of this culturally and economically important clade of fishes. [ABSTRACT FROM AUTHOR]

In this paper, we discuss the value of local knowledge of fishermen from Kigoma, along the North Eastern shores of Lake Tanganyika, regarding fish and climate-related issues of the lake. We explore how that knowledge can be incorporated into sustainable management activities. We used a qualitative approach to investigate the local knowledge and perception of changes and their causes. About 64 respondents comprising fishermen, fish processers, Beach Management Unit leaders, fisheries officers and elders were interviewed between April and December 2016. Our analysis shows that there have been increasing fishing activities in the lake from the 1970s. Increased fishing activities and climate-related changes in the lake have resulted in dramatic decreases in fish landings between the 1990s and the present. It was also revealed that fishermen hold valuable knowledge on fish availability, ecological conditions of the lake, and seasonal weather conditions. While they acknowledge the effects of changes in fishing practices and fishing pressure to explain the gradually decreasing fisheries, they have less understanding of the importance of longer-term changes in the lake environment resulting from climate change. This study concludes that future fisheries management could benefit from further incorporation of fishers' local knowledge such as those related to ecological conditions of the lake and pressures from fishing practices. By expanding mechanisms to include the fishermen's local knowledge, a strong signal is sent to them that their knowledge is valued by fisheries management. This has the potential to further motivate the fishermen to be active participants in contributing to sustainable management practices that can positively impact declining fish resources. In other words, fishermen need to be further "brought at the center" in decision-making processes that influence fisheries management options. [ABSTRACT FROM AUTHOR]

In spite of the fact that cyanobacterial blooms are classically associated with high nutrient loadings, there is also abundant evidence revealing that nitrogen fixing cyanobacteria (diazotrophs) can prevail under oligotrophic conditions. The mechanisms favouring diazotrophs in oligotrophic water bodies, however, remain poorly resolved. Here we analyse biogeochemical and ecological factors regulating the distribution of nitrogen fixing cyanobacteria in the oligotrophic Lake Tanganyika using sensor profiles of hydrodynamic conditions, nutrient and pigment analyses, as well as phytoplankton community assessment. During periods of stable or re-establishing water column stratification, we find evidence that the location of the thermocline and the euphotic depth can create a functional niche for diazotrophic cyanobacteria: Nitrogen limitation provides an ecological advantage for an apparent mutualistic interaction between diazotrophs and diatoms when the upward transport of nitrate into the euphotic zone is reduced by a subjacent thermocline. Diazotrophs, comprising the filamentous genera Dolichospermum and Anabaenopsis, are key players under these conditions (up to 41.7 % of phytoplankton community), while they are rare otherwise. By contrast, a thermocline located within the euphotic zone allows for the rapid vertical transport of nitrate for a thriving nitrate assimilating phytoplankton community that evidently outcompetes diazotrophs. Finally, multiple observations of relatively high diazotroph densities in the upwelling region in the South of Lake Tanganyika imply that they may additionally thrive under high nutrient conditions, when nitrogen is heavily deficient with respect to phosphorous. This study highlights that, under nitrogen deficient conditions, cyanobacterial blooms may form in response to reduced nutrient fluxes to the productive surface waters. [ABSTRACT FROM AUTHOR]

Understanding genetic connectivity plays a crucial role in species conservation decisions, and genetic connectivity is an important component of modern fisheries management. In this study, we investigated the population genetics of four endemic Lates species of Lake Tanganyika (Lates stappersii, L. microlepis, L. mariae, and L. angustifrons) using reduced-representation genomic sequencing methods. We find the four species to be strongly differentiated from one another (mean interspecific FST = 0.665), with no evidence for contemporary admixture. We also find evidence for strong genetic structure within L. mariae, with the majority of individuals from the most southern sampling site forming a genetic group that is distinct from the individuals at other sampling sites. We find evidence for much weaker structure within the other three species (L. stappersii, L. microlepis, and L. angustifrons). Our ability to detect this weak structure despite small and unbalanced sample sizes and imprecise geographic sampling locations suggests the possibility for further structure undetected in our study. We call for further research into the origins of the genetic differentiation in these four species-particularly that of L. mariae-which may be important for conservation and management of this culturally and economically important clade of fishes., (© The Author(s) 2021. Published by Oxford University Press on behalf of The American Genetic Association. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)