Browsing by Subject "Great Lakes"

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  • De Keyzer, Els L. R.; De Corte, Zoe; Van Steenberge, Maarten; Raeymaekers, Joost A. M.; Calboli, Federico C. F.; Kmentova, Nikol; Mulimbwa, Theophile N'Sibula; Virgilio, Massimiliano; Vangestel, Carl; Mulungula, Pascal Masilya; Volckaert, Filip A. M.; Vanhove, Maarten P. M. (2019)
    BackgroundClupeid fisheries in Lake Tanganyika (East Africa) provide food for millions of people in one of the world's poorest regions. Due to climate change and overfishing, the clupeid stocks of Lake Tanganyika are declining. We investigate the population structure of the Lake Tanganyika sprat Stolothrissa tanganicae, using for the first time a genomic approach on this species. This is an important step towards knowing if the species should be managed separately or as a single stock. Population structure is important for fisheries management, yet understudied for many African freshwater species. We hypothesize that distinct stocks of S. tanganicae could be present due to the large size of the lake (isolation by distance), limnological variation (adaptive evolution), or past separation of the lake (historical subdivision). On the other hand, high mobility of the species and lack of obvious migration barriers might have resulted in a homogenous population.ResultsWe performed a population genetic study on wild-caught S. tanganicae through a combination of mitochondrial genotyping (96 individuals) and RAD sequencing (83 individuals). Samples were collected at five locations along a north-south axis of Lake Tanganyika. The mtDNA data had low global FST and, visualised in a haplotype network, did not show phylogeographic structure. RAD sequencing yielded a panel of 3504 SNPs, with low genetic differentiation (F-ST=0.0054; 95% CI: 0.0046-0.0066). PCoA, fineRADstructure and global F-ST suggest a near-panmictic population. Two distinct groups are apparent in these analyses (F-ST=0.1338 95% CI: 0.1239,0.1445), which do not correspond to sampling locations. Autocorrelation analysis showed a slight increase in genetic difference with increasing distance. No outlier loci were detected in the RADseq data.ConclusionOur results show at most very weak geographical structuring of the stock and do not provide evidence for genetic adaptation to historical or environmental differences over a north-south axis. Based on these results, we advise to manage the stock as one population, integrating one management strategy over the four riparian countries. These results are a first comprehensive study on the population structure of these important fisheries target species, and can guide fisheries management.
  • De Keyzer, Els L R; De Corte, Zoë; Van Steenberge, Maarten; Raeymaekers, Joost A M; Calboli, Federico C F; Kmentová, Nikol; N’Sibula Mulimbwa, Théophile; Virgilio, Massimiliano; Vangestel, Carl; Mulungula, Pascal M; Volckaert, Filip A M; Vanhove, Maarten P M (BioMed Central, 2019)
    Abstract Background Clupeid fisheries in Lake Tanganyika (East Africa) provide food for millions of people in one of the world’s poorest regions. Due to climate change and overfishing, the clupeid stocks of Lake Tanganyika are declining. We investigate the population structure of the Lake Tanganyika sprat Stolothrissa tanganicae, using for the first time a genomic approach on this species. This is an important step towards knowing if the species should be managed separately or as a single stock. Population structure is important for fisheries management, yet understudied for many African freshwater species. We hypothesize that distinct stocks of S. tanganicae could be present due to the large size of the lake (isolation by distance), limnological variation (adaptive evolution), or past separation of the lake (historical subdivision). On the other hand, high mobility of the species and lack of obvious migration barriers might have resulted in a homogenous population. Results We performed a population genetic study on wild-caught S. tanganicae through a combination of mitochondrial genotyping (96 individuals) and RAD sequencing (83 individuals). Samples were collected at five locations along a north-south axis of Lake Tanganyika. The mtDNA data had low global FST and, visualised in a haplotype network, did not show phylogeographic structure. RAD sequencing yielded a panel of 3504 SNPs, with low genetic differentiation (FST = 0.0054; 95% CI: 0.0046–0.0066). PCoA, fineRADstructure and global FST suggest a near-panmictic population. Two distinct groups are apparent in these analyses (FST = 0.1338 95% CI: 0.1239,0.1445), which do not correspond to sampling locations. Autocorrelation analysis showed a slight increase in genetic difference with increasing distance. No outlier loci were detected in the RADseq data. Conclusion Our results show at most very weak geographical structuring of the stock and do not provide evidence for genetic adaptation to historical or environmental differences over a north-south axis. Based on these results, we advise to manage the stock as one population, integrating one management strategy over the four riparian countries. These results are a first comprehensive study on the population structure of these important fisheries target species, and can guide fisheries management.
  • Lohi, Saska (Helsingin yliopisto, 2015)
    Bats can act as potential vectors for various zoonotic diseases and other pathogens. Therefore their interactions with people should be examined to mitigate potential risks. Bats are small flying mammals and hide in small crevices during daylight hours, making them difficult to observe. Consequently, they have a capacity to “hitchhike” on ships to be dispersed over large distances. This study focused on anthropogenic unintentional bat translocations, i.e. hitchhiking bats. The study area is the Great Lakes region in North America. Using a web-based questionnaire survey, I asked the public about the frequency of bat-human encounters on ships, their nature, and perceived risks and incidents. I found that bats are commonly seen by people working on ships at the Great Lakes. Bats do not cause trouble other than scaring people. Based on photographic evidence, at least one bat was seen on a ship outside of its native range. Therefore ships might act as vectors, helping bats to disperse to new areas. This might provide pathways for pathogens to spread along, from bats to bats or from bats to humans. The risks related to hitchhiking bats seem to be rather limited. Rabies risk is the most obvious, but no cases of people getting rabies infection from hitchhiking bats were acknowledged. The possibility of ships translocating bats infected with Pseudogymnoascus destructans remains unknown. This study demonstrates how by engaging the public it is possible to gather novel scientific knowledge, and deepen our understanding about the relationship between man and wildlife. There are numerous hidden ways of how people interact with animal species. This study illuminates one of these ways, but many more are yet to be studied.