Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, Dec 1, 2011
Type II iodothyronine deiodinase (D2) converts 3,5,3&... more Type II iodothyronine deiodinase (D2) converts 3,5,3',5'-tetraiodothyronine to 3,5,3'-triiodothyronine and is involved in regulating thyroid hormone-dependent processes in various tissues. D2 mRNA expression in the mediobasal hypothalamus is affected by photoperiod, which influences reproductive processes in temperate birds and mammals. We examined whether D2 mRNA is expressed in the hypothalamus (located in the forebrain within the diencephalon area) and whether its abundance is affected by day length, temperature, or food availability in the tropical spinefoot, Siganus guttatus, which is endemic to tropical monsoon areas. The reverse transcription-polymerase chain reaction (RT-PCR) revealed that D2 mRNA is expressed in various brain regions. The abundance of hypothalamic D2 mRNA was higher at 12.00h than at 06.00h or 24.00h. Rearing fish under constant dark conditions resulted in a decrease in D2 mRNA abundance during the subjective night. A single injection of melatonin lowered D2 mRNA abundance within 3h. Collectively, it appears that hypothalamic D2 mRNA abundance is regulated by the circadian system and/or melatonin. No differences in D2 mRNA abundance were observed, when fish were reared at 20, 25, and 30°C. However, food deprivation stimulated D2 mRNA expression during the daytime. These results suggest that photoperiodic and nutritive conditions affect hypothalamic D2 mRNA expression in S. guttatus.
In 2013, the Government of Flanders donated its oceanographic research vessel (RV) Zeeleeuw (rena... more In 2013, the Government of Flanders donated its oceanographic research vessel (RV) Zeeleeuw (renamed RV Mtafiti, Swahili for ‘Researcher’), to the Government of Kenya to advance marine scientific research in the West Indian Ocean (WIO) region. The Kenya Marine and Fisheries Research Institute (KMFRI), as a centre of excellence in marine sciences in the WIO region, was mandated to manage and operate RV Mtafiti. Flanders Marine Institute (VLIZ), within the frame of the VLIZ-KMFRI collaboration, coordinated and facilitated the preparations involved with the translocation of the ship from the harbor of Ostend (Belgium) to Mombasa (Kenya), installed navigation tools and sampling equipment on board and provided training for the navy crew and scientists from KMFRI.
In developing regions, coastal communities are particularly dependent on small-scale fisheries fo... more In developing regions, coastal communities are particularly dependent on small-scale fisheries for food security and income. However, information on the scale and impacts of small-scale fisheries on coastal marine ecosystems are frequently lacking. Large marine vertebrates (marine mammals, sea turtles and chondrichthyans) are often among the first species to experience declines due to fisheries. This paper reviews the interactions between small-scale fisheries and vulnerable marine megafauna in the southwestern Indian Ocean. We highlight an urgent need for proper documentation, monitoring and assessment at the regional level of small-scale fisheries and the megafauna affected by them to inform evidence-based fisheries management. Catch and landings data are generally of poor quality and resolution with compositional data, where available, mostly anecdotal or heavily biased towards easily identifiable species. There is also limited understanding of fisheries effort, most of which rel...
Meiobenthos respond to variability in salinity gradients in estuarine habitats and are thus suita... more Meiobenthos respond to variability in salinity gradients in estuarine habitats and are thus suitable organisms for ecological studies. The vertical and horizontal distribution of the meiofauna community structure of two major estuaries (Sabaki and Tana) on the north coast of Kenya were compared. The aim was to draw a meiofaunal dataset inventory of the two estuaries and to examine how salinity gradient, seasonality and sediment characteristics influence their structure. Replicate samples were collected from three sampling stations along the salinity gradient of each river estuary. A total of 3,556 individuals belonging to 26 taxa were recorded. Based on seasons and across stations, the upper surface (0-5 cm) layer recorded the highest meiobenthic density (90 ± 42 ind.10 cm-2), followed by 46 ± 23 ind.10 cm-2 (5-10 cm) and 30 ± 8 ind.10 cm-2 in the deepest sediment layer (10-15 cm) studied. The southeast monsoon season recorded the highest mean density (160 ± 22 ind.10 cm-2) compared...
Bottom trawling is a common fishing method that targets bottom-dwelling fisheries resources. It i... more Bottom trawling is a common fishing method that targets bottom-dwelling fisheries resources. It is non-selective and large amounts of by-catch are discarded, raising serious sustainability and ecosystem conservation concerns. In this study, a shallow-water bottom-trawl fishery was evaluated using logbook catch data between 2011 and 2019 and the species composition data collected by fisheries observers between 2016 and 2019. The logbook data showed a twenty-fold increase in the annual catches with a ten-fold increase in fishing effort and an increase in the proportion of retained catch from 2011 to 2019. The observer data showed that for prawn, the by-catch ratio ranged from 1:3 to 1:9 during the four years. Multivariate analysis revealed significant differences between the compositions of retained and discarded catches mainly attributed to Pellona ditchela, Nematopalaemontenuipes, and Secutor insidiator. There was no significant decline in species diversity and the trophic level of ...
Western Indian Ocean journal of marine science, 2021
Siganus species (rabbitfishes) are caught by artisanal fishers in Kenyan marine waters. The ident... more Siganus species (rabbitfishes) are caught by artisanal fishers in Kenyan marine waters. The identification of recently captured rabbitfish species is based on colour patterns, but colours fade after death or during preservation, making species identification more difficult. Morphometric measurements and meristics are then useful in differentiating between species. Twenty-four morphological and twelve meristic characteristics of rabbitfish were obtained from samples collected at six landing sites along the Kenyan coast. Principal Component Analysis (PCA) and Mann-Whitney U-tests were used to evaluate variability among the species. Four of six rabbitfish species showed similar body morphometry and could not be distinguished using PCA analysis, but Siganus stellatus and S. luridus differed from the other species and each other. No clear morphological evidence of separate stocks of individual rabbitfish species was found, apart from S. rivulatus for which the sample size was small. It i...
In 2011, several non-governmental and government agencies established the Kenya Marine Mammal Net... more In 2011, several non-governmental and government agencies established the Kenya Marine Mammal Network (KMMN) to provide a platform for the consistent collection of data on marine mammals along the Kenyan coast, identify areas of importance and engage marine users and the general public in marine mammal conservation. Prior to the KMMN, relatively little was known about marine mammals in Kenya, limiting conservation strategies. The KMMN collects data nationwide through dedicated surveys, opportunistic sightings and participative citizen science, currently involving more than 100 contributors. This paper reviews data on sightings and strandings for small cetaceans in Kenya collated by the KMMN. From 2011 to 2019, 792 records of 11 species of small cetaceans were documented. The most frequently reported inshore species were the Indo-Pacific bottlenose dolphin and Indian Ocean humpback dolphin. Offshore species, included killer whales, short-finned pilot whale and long-snouted spinner do...
The possible impacts that climate change will have on soil water budget and specifically on deep ... more The possible impacts that climate change will have on soil water budget and specifically on deep percolation, runoff and soil water content have been investigated using HYDRUS, a methodology based on numerical modelling simulations of vertical water movement in a homogenous soil column on a flat surface. This study was carried out on four typical soil types occurring on the Kenyan coast and the adjacent hinterlands of up to an elevation of 200 m above sea level (m a.s.l.) covered by five weather stations (two dry and three wet stations). Results show that deep percolation and runoff are expected to be higher in 2100 for both Relative Concentration Pathways (RCPs) 2.6 and 8.5 scenarios than they were for the reference period (1986–2005). The average deep percolation is expected to increase by 14% for RCP 2.6 and 10% for the RCP 8.5, while the average runoff is expected to increase by 188% and 284% for the same scenarios. Soil water content is expected to either increase marginally or...
Coral reefs face increased environmental threats from anthropomorphic climate change and pollutio... more Coral reefs face increased environmental threats from anthropomorphic climate change and pollution, from agriculture, industries and tourism. They are economically vital for many people worldwide, and harbour a fantastically diverse ecosystem, being the home for many species of fish and algae. Surprisingly little is known about the microbial communities living in and in the surrounding of coral reefs. Here we employ high throughput sequencing for investigating the bacteria living in the water column and upper sediment layer in close proximity to coral reefs on the Kenyan coast of the West Indian Ocean. We show that while the read-level taxonomic distribution of bacteria is similar with ones obtained from 16S metabarcoding, whole metagenome sequencing provides valuable functional insights not available with 16S metabarcoding. We find evidence of pollution, marked by the presence of Vibrio and more importantly the presence of antibiotic resistance notably to vancomycin, that we attrib...
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, Dec 1, 2011
Type II iodothyronine deiodinase (D2) converts 3,5,3&... more Type II iodothyronine deiodinase (D2) converts 3,5,3',5'-tetraiodothyronine to 3,5,3'-triiodothyronine and is involved in regulating thyroid hormone-dependent processes in various tissues. D2 mRNA expression in the mediobasal hypothalamus is affected by photoperiod, which influences reproductive processes in temperate birds and mammals. We examined whether D2 mRNA is expressed in the hypothalamus (located in the forebrain within the diencephalon area) and whether its abundance is affected by day length, temperature, or food availability in the tropical spinefoot, Siganus guttatus, which is endemic to tropical monsoon areas. The reverse transcription-polymerase chain reaction (RT-PCR) revealed that D2 mRNA is expressed in various brain regions. The abundance of hypothalamic D2 mRNA was higher at 12.00h than at 06.00h or 24.00h. Rearing fish under constant dark conditions resulted in a decrease in D2 mRNA abundance during the subjective night. A single injection of melatonin lowered D2 mRNA abundance within 3h. Collectively, it appears that hypothalamic D2 mRNA abundance is regulated by the circadian system and/or melatonin. No differences in D2 mRNA abundance were observed, when fish were reared at 20, 25, and 30°C. However, food deprivation stimulated D2 mRNA expression during the daytime. These results suggest that photoperiodic and nutritive conditions affect hypothalamic D2 mRNA expression in S. guttatus.
In 2013, the Government of Flanders donated its oceanographic research vessel (RV) Zeeleeuw (rena... more In 2013, the Government of Flanders donated its oceanographic research vessel (RV) Zeeleeuw (renamed RV Mtafiti, Swahili for ‘Researcher’), to the Government of Kenya to advance marine scientific research in the West Indian Ocean (WIO) region. The Kenya Marine and Fisheries Research Institute (KMFRI), as a centre of excellence in marine sciences in the WIO region, was mandated to manage and operate RV Mtafiti. Flanders Marine Institute (VLIZ), within the frame of the VLIZ-KMFRI collaboration, coordinated and facilitated the preparations involved with the translocation of the ship from the harbor of Ostend (Belgium) to Mombasa (Kenya), installed navigation tools and sampling equipment on board and provided training for the navy crew and scientists from KMFRI.
In developing regions, coastal communities are particularly dependent on small-scale fisheries fo... more In developing regions, coastal communities are particularly dependent on small-scale fisheries for food security and income. However, information on the scale and impacts of small-scale fisheries on coastal marine ecosystems are frequently lacking. Large marine vertebrates (marine mammals, sea turtles and chondrichthyans) are often among the first species to experience declines due to fisheries. This paper reviews the interactions between small-scale fisheries and vulnerable marine megafauna in the southwestern Indian Ocean. We highlight an urgent need for proper documentation, monitoring and assessment at the regional level of small-scale fisheries and the megafauna affected by them to inform evidence-based fisheries management. Catch and landings data are generally of poor quality and resolution with compositional data, where available, mostly anecdotal or heavily biased towards easily identifiable species. There is also limited understanding of fisheries effort, most of which rel...
Meiobenthos respond to variability in salinity gradients in estuarine habitats and are thus suita... more Meiobenthos respond to variability in salinity gradients in estuarine habitats and are thus suitable organisms for ecological studies. The vertical and horizontal distribution of the meiofauna community structure of two major estuaries (Sabaki and Tana) on the north coast of Kenya were compared. The aim was to draw a meiofaunal dataset inventory of the two estuaries and to examine how salinity gradient, seasonality and sediment characteristics influence their structure. Replicate samples were collected from three sampling stations along the salinity gradient of each river estuary. A total of 3,556 individuals belonging to 26 taxa were recorded. Based on seasons and across stations, the upper surface (0-5 cm) layer recorded the highest meiobenthic density (90 ± 42 ind.10 cm-2), followed by 46 ± 23 ind.10 cm-2 (5-10 cm) and 30 ± 8 ind.10 cm-2 in the deepest sediment layer (10-15 cm) studied. The southeast monsoon season recorded the highest mean density (160 ± 22 ind.10 cm-2) compared...
Bottom trawling is a common fishing method that targets bottom-dwelling fisheries resources. It i... more Bottom trawling is a common fishing method that targets bottom-dwelling fisheries resources. It is non-selective and large amounts of by-catch are discarded, raising serious sustainability and ecosystem conservation concerns. In this study, a shallow-water bottom-trawl fishery was evaluated using logbook catch data between 2011 and 2019 and the species composition data collected by fisheries observers between 2016 and 2019. The logbook data showed a twenty-fold increase in the annual catches with a ten-fold increase in fishing effort and an increase in the proportion of retained catch from 2011 to 2019. The observer data showed that for prawn, the by-catch ratio ranged from 1:3 to 1:9 during the four years. Multivariate analysis revealed significant differences between the compositions of retained and discarded catches mainly attributed to Pellona ditchela, Nematopalaemontenuipes, and Secutor insidiator. There was no significant decline in species diversity and the trophic level of ...
Western Indian Ocean journal of marine science, 2021
Siganus species (rabbitfishes) are caught by artisanal fishers in Kenyan marine waters. The ident... more Siganus species (rabbitfishes) are caught by artisanal fishers in Kenyan marine waters. The identification of recently captured rabbitfish species is based on colour patterns, but colours fade after death or during preservation, making species identification more difficult. Morphometric measurements and meristics are then useful in differentiating between species. Twenty-four morphological and twelve meristic characteristics of rabbitfish were obtained from samples collected at six landing sites along the Kenyan coast. Principal Component Analysis (PCA) and Mann-Whitney U-tests were used to evaluate variability among the species. Four of six rabbitfish species showed similar body morphometry and could not be distinguished using PCA analysis, but Siganus stellatus and S. luridus differed from the other species and each other. No clear morphological evidence of separate stocks of individual rabbitfish species was found, apart from S. rivulatus for which the sample size was small. It i...
In 2011, several non-governmental and government agencies established the Kenya Marine Mammal Net... more In 2011, several non-governmental and government agencies established the Kenya Marine Mammal Network (KMMN) to provide a platform for the consistent collection of data on marine mammals along the Kenyan coast, identify areas of importance and engage marine users and the general public in marine mammal conservation. Prior to the KMMN, relatively little was known about marine mammals in Kenya, limiting conservation strategies. The KMMN collects data nationwide through dedicated surveys, opportunistic sightings and participative citizen science, currently involving more than 100 contributors. This paper reviews data on sightings and strandings for small cetaceans in Kenya collated by the KMMN. From 2011 to 2019, 792 records of 11 species of small cetaceans were documented. The most frequently reported inshore species were the Indo-Pacific bottlenose dolphin and Indian Ocean humpback dolphin. Offshore species, included killer whales, short-finned pilot whale and long-snouted spinner do...
The possible impacts that climate change will have on soil water budget and specifically on deep ... more The possible impacts that climate change will have on soil water budget and specifically on deep percolation, runoff and soil water content have been investigated using HYDRUS, a methodology based on numerical modelling simulations of vertical water movement in a homogenous soil column on a flat surface. This study was carried out on four typical soil types occurring on the Kenyan coast and the adjacent hinterlands of up to an elevation of 200 m above sea level (m a.s.l.) covered by five weather stations (two dry and three wet stations). Results show that deep percolation and runoff are expected to be higher in 2100 for both Relative Concentration Pathways (RCPs) 2.6 and 8.5 scenarios than they were for the reference period (1986–2005). The average deep percolation is expected to increase by 14% for RCP 2.6 and 10% for the RCP 8.5, while the average runoff is expected to increase by 188% and 284% for the same scenarios. Soil water content is expected to either increase marginally or...
Coral reefs face increased environmental threats from anthropomorphic climate change and pollutio... more Coral reefs face increased environmental threats from anthropomorphic climate change and pollution, from agriculture, industries and tourism. They are economically vital for many people worldwide, and harbour a fantastically diverse ecosystem, being the home for many species of fish and algae. Surprisingly little is known about the microbial communities living in and in the surrounding of coral reefs. Here we employ high throughput sequencing for investigating the bacteria living in the water column and upper sediment layer in close proximity to coral reefs on the Kenyan coast of the West Indian Ocean. We show that while the read-level taxonomic distribution of bacteria is similar with ones obtained from 16S metabarcoding, whole metagenome sequencing provides valuable functional insights not available with 16S metabarcoding. We find evidence of pollution, marked by the presence of Vibrio and more importantly the presence of antibiotic resistance notably to vancomycin, that we attrib...
Uploads
Papers by Nina Wambiji