African Lion Population Estimates in Tanzania’s Ruaha National Park

Tanzania is considered a country with the largest number of African lions (Panthera leo). However, the continued absence of ecological population estimates and understanding of the associated factors influencing lion distribution hinders the development of conservation planning. This is particularly true in the Ruaha-Rungwa landscape, where it was estimated that more than 10% of the global lion population currently resides. By using a call-back survey method, we aimed to provide population estimates (population size and density) of African lions in the Ruaha National Park, between wet (March 2019) and dry (October 2019) seasons. We also assessed the key factors that influenced the distribution of the observed lions towards call-back stations. Ferreira & Funston’s (2010) formula was used to calculate population size and in turn used to estimate density in the sampled area, while the Generalized Linear Model (GLMM) with zero-inflated Poisson error distribution was used to determine factors that influence the distribution of the observed lions to call-back stations. The population size we calculated for the sampled area of 3137.2 km2 revealed 286 lions (95% CI, 236 - 335) during the wet season, and 196 lions (95% CI, 192 - 200) during the dry season. The density of lions was 9.1/100 km2 during the wet season, and 6.3/100 km2 during the dry season. Distance to water source had a significant negative effect on the distribution of the observed lions to the call-back stations, while habitat had a marginal effect. Our findings show that, although lion population estimates were larger during the wet season than the dry season, the season had no effect on the distribution of the observed lions to call-back stations. We suggest that the proximity to water sources is important in study design. Further, we suggest that density and population size are useful indices in identifying conservation area priorities and lion coexistence strategies

Fishing fleet selectivity in Lake Victoria's Nile Perch Fishery / Santiago Gómez-Cardona, Johannes Kammerer, Hillary Mrosso

Current regulations regarding the Nile Perch Fishery in Lake Victoria provide gear specifications for the two main gears employed, Gillnets and Longlines, by defining the minimum size available. Additionally, the legal range of catchable fish is regulated: between 50 and 84 cm. Gillnets are legal over 5 inches, and the Hooks, 15 required for Longlining, are legal from number 10 and below (lower numbers refer to higher sizes). Using data from the Catch Assessment Survey, CAS, we identify gear selectivity for Gillnets and Longlines. We use a novel methodology, that is validated using previous results for Gillnets for Lake Victoria. This is particular relevant as there is no much data for selectivity using Longlines. The information on selectivity 20 is used to derive the overall fishing selectivity of the fleet. We find evidence of shift towards higher fish sizes in the Gillnet fleet, but a stagnation on fish sizes for the Longline fleet, even though there has been a compositional change in the hook sizes employed for this activity. The results signal towards a regulatory success among Gillnet users, but challenges in the regulation of Longliners

Fishing Fleet Selectivity in Lake Victoria's Nile Perch Fishery

Current regulations regarding the Nile Perch Fishery in Lake Victoria provide gear specifications for the two main gears employed, Gillnets and Longlines, by defining the minimum size available. Additionally, the legal range of catchable fish is regulated: between 50 and 84 cm. Gillnets are legal over 5 inches, and the Hooks, required for Longlining, are legal from number 10 and below (lower numbers refer to higher sizes). Using data from the Catch Assessment Survey, CAS, we identify gear selectivity for Gillnets and Longlines. We use a novel methodology, that is validated using previous results for Gillnets for Lake Victoria. This is particular relevant as there is no much data for selectivity using Longlines. The information on selectivity is used to derive the overall fishing selectivity of the fleet. We find evidence of shift towards higher fish sizes in the Gillnet fleet, but a stagnation on fish sizes for the Longline fleet, even though there has been a compositional change in the hook sizes employed for this activity. The results signal towards a regulatory success among Gillnet users, but challenges in the regulation of Longliners

Illegal wildlife trade: Trade flows of wildlife products and facilitation methods in the Ruaha landscape, Tanzania

Tanzania’s Ruaha landscape is prominent for its potential wildlife resources, which play a key role in sustaining the economy and livelihoods of the people. However, most of these resources are illegally obtained and traded in different places within and outside the Ruaha landscape. Due to its illegal nature, most of the important information regarding the trade is poorly documented. Therefore, the current study aimed first, to explore the origin and destination of wildlife products; second, to assess the relationship between hunters and buyers or customers; third, to assess the means used to transport wildlife products; and lastly, to assess who influences people to engage in illegal hunting and trade activities. In addition, we assess the materials used in the exchange of wildlife products. Semi-structured questionnaires and face-to-face interviews were used to collect information from 123 respondents. Social network analysis was used to indicate the origin and destination of wildlife products. The findings show that 70% of wildlife products originate from the Ruaha National Park and MBOMIPA wildlife management areas, with the remaining 30% originating from villages. The majority of respondents (65%) reported transporting wildlife products by foot and bicycle as the primary modes of transportation. Suppliers of wildlife products are reported to have close and long-term relationships with their customers and traders, with most of whom being friends and relatives. We found most poachers to be influenced by their friends and relatives in terms making decision to engage in illegal wildlife trade. In addition, crops like maize and rice were the most popular products used to exchange with wildlife products in the Ruaha landscape. Therefore, in order to combat illegal trade in wildlife products at the local level, alternative income-generating activities need to be promoted accompanied by not only well-funded anti-poaching programmes but also more effective surveillance plans. These should entail the use of advanced techniques and skills, such as wildlife forensics

New Sex Chromosomes in Lake Victoria Cichlid Fishes (Cichlidae: Haplochromini)

African cichlid fishes harbor an extraordinary diversity of sex-chromosome systems. Within just one lineage, the tribe Haplochromini, at least 6 unique sex-chromosome systems have been identified. Here we focus on characterizing sex chromosomes in cichlids from the Lake Victoria basin. In Haplochromis chilotes, we identified a new ZW system associated with the white blotch color pattern, which shows substantial sequence differentiation over most of LG16, and is likely to be present in related species. In Haplochromis sauvagei, we found a coding polymorphism in amh that may be responsible for an XY system on LG23. In Pundamilia nyererei, we identified a feminizing effect of B chromosomes together with XY- and ZW-patterned differentiation on LG23. In Haplochromis latifasciatus, we identified a duplication of amh that may be present in other species of the Lake Victoria superflock. We further characterized the LG5-14 XY system in Astatotilapia burtoni and identified the oldest stratum on LG14. This species also showed ZW differentiation on LG2. Finally, we characterized an XY system on LG7 in Astatoreochromis alluaudi. This report brings the number of distinct sex-chromosome systems in haplochromine cichlids to at least 13, and highlights the dynamic evolution of sex determination and sex chromosomes in this young lineage.https://doi.org/10.3390/genes1305080

Divergent selection on opsins drives incipient speciation in Lake Victoria cichlids

Divergent natural selection acting on ecological traits, which also affect mate choice, is a key element of ecological speciation theory, but has not previously been demonstrated at the molecular gene level to our knowledge. Here we demonstrate parallel evolution in two cichlid genera under strong divergent selection in a gene that affects both. Strong divergent natural selection fixed opsin proteins with different predicted light absorbance properties at opposite ends of an environmental gradient. By expressing them and measuring absorbance, we show that the reciprocal fixation adapts populations to divergent light environments. The divergent evolution of the visual system coincides with divergence in male breeding coloration, consistent with incipient ecological by-product speciation.status: publishe

Patterns of genomic differentiation between two Lake Victoria cichlid species, Haplochromis pyrrhocephalus and H. sp. ‘macula’

Abstract Background The molecular basis of the incipient stage of speciation is still poorly understood. Cichlid fish species in Lake Victoria are a prime example of recent speciation events and a suitable system to study the adaptation and reproductive isolation of species. Results Here, we report the pattern of genomic differentiation between two Lake Victoria cichlid species collected in sympatry, Haplochromis pyrrhocephalus and H. sp. ‘macula,’ based on the pooled genome sequences of 20 individuals of each species. Despite their ecological differences, population genomics analyses demonstrate that the two species are very close to a single panmictic population due to extensive gene flow. However, we identified 21 highly differentiated short genomic regions with fixed nucleotide differences. At least 15 of these regions contained genes with predicted roles in adaptation and reproductive isolation, such as visual adaptation, circadian clock, developmental processes, adaptation to hypoxia, and sexual selection. The nonsynonymous fixed differences in one of these genes, LWS, were reported as substitutions causing shift in absorption spectra of LWS pigments. Fixed differences were found in the promoter regions of four other differentially expressed genes, indicating that these substitutions may alter gene expression levels. Conclusions These diverged short genomic regions may have contributed to the differentiation of two ecologically different species. Moreover, the origins of adaptive variants within the differentiated regions predate the geological formation of Lake Victoria; thus Lake Victoria cichlid species diversified via selection on standing genetic variation

Intraspecific sexual selection on a speciation trait, male coloration, in the Lake Victoria cichlid Pundamilia nyererei.

The haplochromine cichlids of Lake Victoria constitute a classical example of explosive speciation. Extensive intra- and interspecific variation in male nuptial coloration and female mating preferences, in the absence of postzygotic isolation between species, has inspired the hypothesis that sexual selection has been a driving force in the origin of this species flock. This hypothesis rests on the premise that the phenotypic traits that underlie behavioural reproductive isolation between sister species diverged under sexual selection within a species. We test this premise in a Lake Victoria cichlid, by using laboratory experiments and field observations. We report that a male colour trait, which has previously been shown to be important for behavioural reproductive isolation between this species and a close relative, is under directional sexual selection by female mate choice within this species. This is consistent with the hypothesis that female choice has driven the divergence in male coloration between the two species. We also find that male territoriality is vital for male reproductive success and that multiple mating by females is common