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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
general
Isotopic signatures induced by upwelling reveal regional fish stocks in Lake Tanganyika
PLoS ONE, Volume 18, No. 11 November, Article e0281828, Year 2023
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Description
Lake Tanganyika’s pelagic fish sustain the second largest inland fishery in Africa and are under pressure from heavy fishing and global warming related increases in stratification. The strength of water column stratification varies regionally, with a more stratified north and an upwelling-driven, biologically more productive south. Only little is known about whether such regional hydrodynamic regimes induce ecological or genetic differences among populations of highly mobile, pelagic fish inhabiting these different areas. Here, we examine whether the regional contrasts leave distinct isotopic imprints in the pelagic fish of Lake Tanganyika, which may reveal differences in diet or lipid content. We conducted two lake-wide campaigns during different seasons and collected physical, nutrient, chlorophyll, phytoplankton and zooplankton data. Additionally, we analyzed the pelagic fish–the clupeids Stolothrissa tanganicae, Limnothrissa miodon and four Lates species–for their isotopic and elemental carbon (C) and nitrogen (N) compositions. The δ13C values were significantly higher in the productive south after the upwelling/mixing period across all trophic levels, implying that the fish have regional foraging grounds, and thus record these latitudinal isotope gradients. By combining our isotope data with previous genetic results showing little geographic structure, we demonstrate that the fish reside in a region for a season or longer. Between specimens from the north and south we found no strong evidence for varying trophic levels or lipid contents, based on their bulk δ15N and C:N ratios. We suggest that the development of regional trophic or physiological differences may be inhibited by the lake-wide gene flow on the long term. Overall, our findings show that the pelagic fish species, despite not showing evidence for genetic structure at the basin scale, form regional stocks at the seasonal timescales. This implies that sustainable management strategies may consider adopting regional fishing quotas. © 2023 Ehrenfels et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Authors & Co-Authors
Ehrenfels, Benedikt
Switzerland, Dubendorf
Eawag - Swiss Federal Institute of Aquatic Science and Technology
Switzerland, Zurich
Eth Zürich
Junker, Julian
Switzerland, Dubendorf
Eawag - Swiss Federal Institute of Aquatic Science and Technology
Switzerland, Bern
University of Bern
Callbeck, Cameron M.
Switzerland, Dubendorf
Eawag - Swiss Federal Institute of Aquatic Science and Technology
Dinkel, Christian
Switzerland, Dubendorf
Eawag - Swiss Federal Institute of Aquatic Science and Technology
Kimirei, I. A.
Tanzania, Dar es Salaam
Tanzania Fisheries Research Institute Tafiri
Mbonde, Athanasio Stephano E.
Tanzania, Dar es Salaam
Tanzania Fisheries Research Institute Tafiri
Mosille, Julieth B.
Tanzania, Dar es Salaam
Tanzania Fisheries Research Institute Tafiri
Sweke, Emmanuel Andrew
Tanzania, Dar es Salaam
Tanzania Fisheries Research Institute Tafiri
Tanzania, Zanzibar City
Deep Sea Fishing Authority Dsfa
Seehausen, Ole
Switzerland, Dubendorf
Eawag - Swiss Federal Institute of Aquatic Science and Technology
Switzerland, Bern
University of Bern
Wagner, Catherine Elise
United States, Laramie
University of Wyoming
Wehrli, Bernhard
Switzerland, Dubendorf
Eawag - Swiss Federal Institute of Aquatic Science and Technology
Switzerland, Zurich
Eth Zürich
Statistics
Authors: 11
Affiliations: 7
Identifiers
Doi:
10.1371/journal.pone.0281828
ISSN:
19326203
Research Areas
Environmental
Genetics And Genomics
Health System And Policy