Fish breeding areas: Is this the solution to increasing fisheries productivity of Lake Naivasha, Kenya?

2020 ◽  
Author(s):  
Nicholas Outa ◽  
Edna Waithaka
Keyword(s):  
Sampling Period ◽  
Abundant Species ◽  
Shared Responsibility ◽  
Lake Ecosystem ◽  
Lake Naivasha ◽  
Water Abstraction ◽  
Fish Breeding ◽  
Fish Spawning ◽  
Breeding Grounds ◽  
Over Exploitation

Fish stocks over exploitation and excessive water abstraction in Lake Naivasha have caused drastic changes in the lake’s ecosystem and fisheries. As a result of this, measures were taken by concerned stakeholders to protect and safe guard the fragile lake ecosystem. A study was conducted on the lake’s fishery to identify fish critical habitats and recommended for their protection through a participatory approach. These identified habitats formed the four protected areas in addition to the shoreline area. Gill net surveys are routinely conducted at nine sampling sites spread to cover the whole lake. In the study, six fish species were recorded at breeding and non-breeding grounds of the lake during the sampling period. Oreochromis niloticus was the most abundant species accounting for 72.1% and 56.6% of fish in breeding and non-breeding grounds respectively. Size frequency data revealed that the majority of C. carpio in breeding grounds ranged between 24 and 36 cm whereas in non-breeding areas, they are slightly smaller, majority of individuals ranging between 23 and 32 cm. The number of male fish was generally higher than that of females giving a sex ratio >1 in both breeding and fishing areas. With the exception of O. leucostictus which recorded 64% and 55% in fishing and breeding areas respectively, the spawning biomass was higher in breeding areas than in fishing areas. Protected fish breeding grounds still remain important as fish spawning and nursery grounds. Activities of monitoring and surveillance need to be strengthened in a spirit of shared responsibility and co-management.

scholarly journals The use of groundwater crustacean communities as indicators for aquifers quality in the semi-arid region of north-central Chile

2018 ◽  
Vol 1 ◽  
Author(s):  
Sanda Iepure ◽  
Nicolas Gouin ◽  
Angeline Bertin ◽  
Ana Camacho ◽  
Antonio González-Ramón ◽  
...  
Keyword(s):  
Negative Impact ◽  
Groundwater Resources ◽  
Economic Benefits ◽  
Nutrient Loads ◽  
Groundwater Temperature ◽  
Groundwater Levels ◽  
Water Abstraction ◽  
Over Exploitation ◽  
The Impact ◽  
Semi Arid

Chile has large extensions of arid and semi-arid regions throughout the whole country, where the intensive demands and use of water resources, especially groundwater for irrigations and mining activities, increased dramatically over the last decades. The aquifer depletions due to water abstraction for irrigation and nutrient loads, exert major alterations of water quality, groundwater recharge and the natural renewal rate. All these factors diminish the aquifer value for the users and contribute to the degradation of groundwater as environment and habitat for fauna. This intensive use of groundwater resources in Chile brought to significant social and economic benefits, but their inadequate management resulted in negative environmental, legal and socioeconomic consequences. In this study, we aimed at providing a first assessment of environmental alterations of groundwater ecosystems from agricultural watersheds in northern Chile by specifically evaluating the effects of nitrogen and pesticide loads on groundwater communities and identifing the ecosystem service alterations due to agricultural activities. The study has been performed in a glacial aquifer from Coquimbo region; 250 km north of Santiago de Chile, the floodplain of which is dominated by agriculture (fruits tress, vineyards). Due to low regional precipitations (100-240 mm/year) the aquifer is primarily recharged by snowmelt from the Andean chain and surface runoff. The relative groundwater levels, groundwater temperature, chemical analysis of nitrogen and total phosphorus and pesticide concentrations were examined, along with the evaluation of crustacean biodiversity and spatial distribution pattern. Stygofauna taxonomic richness and the presence of stygobites have been related more to groundwater level stability than to chemical water parameters indicating that over-exploitation has a negative impact on habitat suitability for groundwater invertebrates. Groundwater biota assessment is essential in understanding the impact produced by agriculture activities on groundwater as a resource and as ecosystem, a nexus that becomes more and more widely recognized. The rationale and the preliminary results of this study are summarized in the Suppl. material 1.

Spatial heterogeneity of low-density populations of Melanoplus sanguinipes (Orthoptera: Acrididae) associated with grazing and vegetation treatments

2001 ◽  
Vol 133 (6) ◽  
pp. 843-855 ◽  
Author(s):  
Dennis J. Fielding ◽  
M.A. Brusven ◽  
Bahman Shafii ◽  
William J. Price
Keyword(s):  
Spatial Distribution ◽  
Vegetation Type ◽  
Sampling Period ◽  
Weather Conditions ◽  
Abundant Species ◽  
Rangeland Management ◽  
Low Density ◽  
Melanoplus Sanguinipes ◽  
Nymphal Stage ◽  
Dry Conditions

AbstractThe objectives of this study were to determine whether the spatial distribution of Melanoplus sanguinipes F., the most abundant species of grasshopper on rangeland in southern Idaho, varied annually in response to changing patterns of grazing and to investigate how vegetation affects the spatial distribution of low-density populations of M. sanguinipes at scales relevant to most rangeland-management activities. A lattice of 72 sites was established across nine pastures, covering approximately 5000 ha. At each site, densities of M. sanguinipes, percent canopy coverage by plant species, and percent forage utilization by livestock were estimated twice per year, in June when M. sanguinipes was in the nymphal stage and in August during the adult stage, for 4 years, 1991–1994. Spatial analyses of variance were used to evaluate the influence of grazing and vegetation type on densities of M. sanguinipes. In August of each year, densities of M. sanguinipes were lower on heavily grazed sites than on lightly grazed sites, except in 1993, when the opposite trend was observed. Above-normal precipitation in 1993 resulted in abundant growth of annual forbs and regrowth of grazed plants. The distribution of nymphs in June of 1993 and 1994 reflected the grazing patterns of the previous summer. Densities of M. sanguinipes were lower on crested wheatgrass habitats than on annual grasslands for every sampling period from June 1991 to June 1993, after which no differences were observed. We interpret the results to suggest that grazing effects on low-density populations of M. sanguinipes were contingent on weather conditions; under dry conditions, grazed habitats were less favorable to M. sanguinipes but, during relatively cool wet summers, grazing created conditions that were more favorable to M. sanguinipes.

scholarly journals Shifts in Diatom Dominance Associated with Seasonal Changes in an Estuarine-Mangrove Phytoplankton Community

2020 ◽  
Vol 8 (7) ◽  
pp. 528
Author(s):  
Fareha Hilaluddin ◽  
Fatimah Md. Yusoff ◽  
Tatsuki Toda
Keyword(s):  
Environmental Changes ◽  
Skeletonema Costatum ◽  
Sampling Period ◽  
Abundant Species ◽  
Dry Season ◽  
Northeast Monsoon ◽  
Diatom Species ◽  
Phytoplankton Abundance ◽  
Wet Season ◽  
Total Phytoplankton

A study on seasonal phytoplankton abundance and composition in a mangrove estuary, Matang Mangrove Forest Reserve (MMFR), Malaysia, was carried out to determine the phytoplankton structure in this ecosystem, and to identify potential indicators of environmental changes. Phytoplankton samples were collected bimonthly from June 2010 to April 2011, to cover both dry (June to October) and wet (November to April) seasons, at four selected sampling sites along the river. Diatoms showed the highest number of species (50 species) from a total of 85 phytoplankton species from 76 genera. Diatoms contributed more than 90% of the total phytoplankton abundance during the dry season (southwest monsoon) and less than 70% during the wet season (northeast monsoon) as dinoflagellates became more abundant during the rainy season. Two diatoms were recorded as dominant species throughout the sampling period; Cyclotella sp. and Skeletonema costatum. Cyclotella sp. formed the most abundant species (62% of total phytoplankton) during the dry period characterized by low nutrients and relatively low turbidity. Skeletonema costatum contributed 93% of the total phytoplankton in October, which marked the end of the dry season and the beginning of the wet season, characterized by strong winds and high waves leading to the upwelling of the water column. Massive blooms of Skeletonema costatum occurred during the upwelling when total nitrogen (TN) and total phosphorus (TP) concentrations were highest (p < 0.05) throughout the year. The abundance of diatom species during the wet season was more evenly distributed, with most diatom species contributing less than 12% of the total phytoplankton. Autotrophic producers such as diatoms were limited by high turbidity during the northeast monsoon when the rainfall was high. During the wet season, Cyclotella and Skeletonema costatum only contributed 9% and 5% of the total phytoplankton, respectively, as dinoflagellates had more competitive advantage in turbid waters. This study illustrates that some diatom species such as Cyclotella sp. and Skeletonema costatum could be used as indicators of the environmental changes in marine waters.

scholarly journals The diversity of saproxylic beetles’ community from the Natural Reserve Voievodeasa Forest, North-Eastern Romania

2021 ◽  
Vol 64 (1) ◽  
pp. 31-60
Author(s):  
Nicolai Olenici ◽  
Ecaterina Fodor
Keyword(s):  
Species Richness ◽  
Dead Wood ◽  
Trophic Position ◽  
Sampling Period ◽  
Abundant Species ◽  
Structural Features ◽  
Saproxylic Beetles ◽  
Insect Fauna ◽  
Vegetation Season ◽  
North Eastern

Nature reserves harbour considerable richness and diversity of saproxylic organisms since dead wood is preserved in situ, this being also the case of Voivodeasa beech-spruce-fir forest in North-Eastern Romania, the area investigated under the present research. Flight interception traps were employed to capture insects during a vegetation season with the goal to characterize saproxylic Coleoptera community in terms of diversity and several other structural features. Among the captured insects, the majority pertained to obligate saproxylic species (217 species). However, the unexpected high species richness corresponded to an area with modest representation of deadwood due to previous status of commercial forest. The identified beetles were members of different habitat-guilds depending on what type of substrate they colonized: recently dead wood (23%), decomposed dead wood (41%), wood inhabiting fungi (34%) and treehollow detritus (2%). According to their trophic position, the identified saproxylic beetles pertained to the following guilds: xylophagous (40%), mycetophagous (39%), predatory (14%), and species relying on other food resources. The observed richness corresponded to the case of hyperdiverse communities where sampling never leads to the stabilization of species richness under a realistic sampling scheme. The diversity profiles constructed on Shannon, Gini-Simpson, Berger-Parker and evenness indices for the pooled inventory and for separate samples across the vegetation season indicated the aggregated saproxylic community as highly diverse and highly uneven, with rich representation of rare species, dominated by few abundant species. We assembled four bipartite, unweighted, and undirected networks to approach the temporal changes across the sampling period extended over one vegetation season. The topology of beetles’ community and of the three main trophic guilds (xylophagous, mycetophagous and predatory) networks linked to time sequences are characterized by high connectance, high nestedness and modularity, with the exception of the mycetophagous sub-network not displaying significant modularity. Among the identified species, 13% indicate high degree of naturalness of the Voievodeasa forest. 62 of the identified species are included in the Red List of European Saproxylic Beetles of which five are near threatened (Protaetia fieberi, Cucujus cinnaberinus, Crepidophorus mutilatus, Ceruchus chrysomelinus, Prostomis mandibularis), Ischnodes sanguinolentus is vulnerable and Rhysodes sulcatus is an endangered species. During the study, two Coleoptera species, new for Romanian insect fauna were identified: Denticollis interpositus Roubal, 1941 and Hylis procerulus (Mannerheim 1823).

scholarly journals Using Water Footprint Approaches to Estimate Water Demand in the Lake Naivasha Basin, Kenya

2019 ◽  
Vol 9 (1) ◽  
pp. 30
Author(s):  
Tom Mongare Ndege
Keyword(s):  
Water Use ◽  
Water Demand ◽  
Water Footprint ◽  
Demand Elasticity ◽  
Lake Basin ◽  
Lake Naivasha ◽  
Water Abstraction ◽  
Household Water ◽  
Income Data ◽  
Water Volumes

The purpose of this paper is to estimate water demand for households in Lake Naivasha basin. This is important because water demand is increasingly significant to the policy of choice for achieving sustainable water management. Realization of sustainable water use is urgent in Lake |Naivasha water basin not only because of the unstable water volumes in the Lake which have wider wellbeing effects but also because of changing land use strategies that depend on higher water abstraction. Following Mokennen,et al., (2012) this study uses a water footprint approach to estimate the responsiveness of water use choices to changes in prices and income. Data is collected using questionnaires distributed to 418 residents in the lake basin. In this paper a double log water demand function is used to estimate household water demand. This approach has the advantage of providing paramters that are easily comparable with previous studies. The paper is, however, innovative in its application of estimated “total water abstraction” using water footprint approaches. An estimated water demand elasticity of 0.347 is only significant at p=0.01 suggesting a weak but significant impact of water cost on water abstraction choices. These results suggest the potential of applying price/fiscal instruments to enhance sustainable water abstraction within a water stress ecosystem.

Effects of sub-lethal concentrations of corexit 9500® dispersant on growth and condition factor of juvenile Clarias gariepinus (Burchell 1822), Rivers state, Nigeria

2020 ◽  
Vol 29 (1) ◽  
pp. 111-121
Author(s):  
K.N.O. Bob-Manuel ◽  
A. Ugbomeh ◽  
O. Taylorharry
Keyword(s):  
Condition Factor ◽  
Ph Value ◽  
Clarias Gariepinus ◽  
Corexit 9500 ◽  
Fish Breeding ◽  
Toxicant Concentration ◽  
Breeding Grounds ◽  
Test Organisms ◽  
Test Treatments ◽  
Rivers State

The effects of sub-lethal concentrations of Corexit 9500 on growth and condition factor of juveniles of Clarias gariepinus was investigated after 21days, in 2018. 160 fishes were used as test organisms with a loading of 10/treatment and were exposed to 0.00, 0.0125, 0.025 and 0.05 ml/L concentrations of Corexit 9500. Treatments were in triplicate and Complete Randomised Design was adopted. The growth in length and weight of C. gariepinus was significantly higher in the control than the test treatments (P<0.05). The increase in weight of the control was significantly different from the three treatments. Temperature was not significantly different (P>0.05); however, the DO of control was significantly higher (P < 0.05) than that of the treatments, with the lowest DO in the 0.05ml/l treatment. pH was acidic for all treatments including the control but was more acidic with increasing concentration of Corexit 9500. The pH value for each treatment was significantly different (P<0.05). The conductivity was significantly different from each other (P<0.05) with higher values at the 0.025 ml/L concentrations. The condition factor (K) decreased with increasing toxicant concentration and was significantly different (P<0.05) at 0.0125ml/L and at Weeks 2 and 3 of 0.05 ml/L. Corexit 9500 dispersants should be appropriately assessed before deployment, and their use near fish breeding grounds should be avoided. Key words: Clarias gariepinus, dispersant, growth, physicochemical parameters, sub-lethal

scholarly journals Environment and Distribution of Age 0 Fishes in River Canard, a Lowland Ontario River

2005 ◽  
Vol 119 (1) ◽  
pp. 16 ◽  
Author(s):  
John K. Leslie ◽  
Charles A. Timmins
Keyword(s):  
Reproductive Strategies ◽  
Abundant Species ◽  
Gizzard Shad ◽  
Lowland River ◽  
Dorosoma Cepedianum ◽  
Variable Flow ◽  
Suspended Particulate ◽  
Wide Range ◽  
Fish Spawning ◽  
Annual Discharge

Age 0 fishes were collected to determine occurrence, relative abundance and species composition at three sites in River Canard, Ontario in spring-autumn, 1994-1995. This small lowland river (mean annual discharge, 3.2 m3 s-1) has variable flow during fish spawning and early nursery periods, high suspended particulate load, and sparse rooted vegetation and other physical cover. Forty-two taxa (12 families; 24,544 specimens) collected with beach seines and a plankton net represented a wide range of reproductive strategies and a diverse taxocene. Gizzard Shad Dorosoma cepedianum (67% of total catch), Orangespotted Sunfish Lepomis humilis (8%), and Brook Silverside Labidesthes sicculus (6%) were the most abundant species. Environmental conditions were such that fish attained autumnal lengths comparable to species in various systems throughout the ecoregion.

A comparison of fish assemblages from seagrass and unvegetated areas of a southern Australian estuary

1994 ◽  
Vol 45 (6) ◽  
pp. 1033 ◽  
Author(s):  
RM Connolly
Keyword(s):  
Fish Assemblages ◽  
Statistical Significance ◽  
Open Water ◽  
Sampling Period ◽  
Abundant Species ◽  
Small Fish ◽  
Habitat Differences ◽  
Distinct Grouping ◽  
One Year ◽  
Australian Estuary

Assemblages of small fish from eelgrass (mainly Zostera muelleri) and unvegetated patches in a shallow, marine-dominated estuary were compared over one year as a preliminary step towards finding the consequences of eelgrass loss to small fish. There were more species and more individuals at eelgrass sites than at unvegetated sites at every sampling period. Multivariate analysis (MDS ordination) of assemblages showed distinct grouping of eelgrass and unvegetated sites. The statistical significance of groupings was tested by using an analysis of similarities (ANOSIM) randomization routine. The cryptic syngnathid Stigmatopora nigra and juvenile whiting, Sillaginodes punctata, the species of greatest economic importance in the estuary, were predominantly over eelgrass, whereas the flounder Rhombosolea tapirina was usually caught at unvegetated sites. Atherinosoma microstoma, the most abundant species, was more common over eelgrass at two dates but had similar abundances over both habitats at other dates. The limitations of survey work caused by possible associations between the presence of vegetation and environmental factors have been partially offset by interspersion of sites and by measurement of water temperature and salinity. Secondarily to habitat differences, fish assemblages were weakly grouped according to distance of sites from open water.

Habitat and temporal differences among soil microfungal assemblages in Ontario

1998 ◽  
Vol 76 (10) ◽  
pp. 1798-1805 ◽  
Author(s):  
Linette Keller ◽  
Michael J Bidochka
Keyword(s):  
Forest Soils ◽  
Deciduous Forest ◽  
Species Turnover ◽  
Abiotic Factors ◽  
Sampling Period ◽  
Abundant Species ◽  
Old Field ◽  
Temporal Differences ◽  
Fungal Abundance ◽  
Alfalfa Field

A survey of the soil microfungi in the A horizons of soils taken from four sites (deciduous forest, cedar forest, old field, and alfalfa field) in Central Ontario at three times (May, June, and August) in one year was conducted to determine habitat and temporal differences of fungal assemblages. Approximately 70 species of fungi were identified. In all habitats, species in the genera Penicillium, Acremonium, Talaromyces, Cladosporium, Cunninghamella, and Paecilomyces were isolated most frequently. Cedar forest soils showed the lowest species turnover with time, and Aspergillus fumigatus (Fres.) was consistently one of the most abundant species throughout the sampling period. Total fungal abundance increased over the sampling period in cedar forest soils, a trend not observed in deciduous forest soils. Fungal abundance, as well as the total number of species, in soils from the alfalfa field and old field sites decreased in August. Narrow-amplitude, broad-amplitude, and occasional species were characterized. Results are discussed with reference to the biotic and abiotic factors that may influence fungal occurrence and abundance.Key words: fungal soil ecology, microfungi, Ontario, fungal species composition.

scholarly journals Short-term variability of copepod abundance in Jurumirim Reservoir, São Paulo, Brazil

2001 ◽  
Vol 61 (4) ◽  
pp. 577-598 ◽  
Author(s):  
E. A. PANARELLI ◽  
M. G. NOGUEIRA ◽  
R. HENRY
Keyword(s):  
Rainy Season ◽  
Sampling Period ◽  
Abundant Species ◽  
Sao Paulo ◽  
Dry Season ◽  
Dispersion Pattern ◽  
São Paulo ◽  
Short Term ◽  
Copepod Abundance ◽  
Short Term Variability

Short-term variability in composition and abundance of copepod populations were studied during the dry (winter) and rainy (summer) seasons, at the dam region of Jurumirim Reservoir, São Paulo, Brazil. An intensive sampling program was carried out during 30 days in each period of the year. Samples and measurements were taken every other day at 0, 5, 10, 15, 20 and 25 m depths. The relationship between variability of the populations and some environmental factors was analyzed. The main species were: Argyrodiaptomus furcatus (Sars), Notodiaptomus iheringi (Wright), Mesocyclops longisetus (Thiébaud), Thermocyclops decipiens (Fischer), and T. minutus (Lowndes). Thermocyclops minutus was the most abundant species in dry season and its abundance varied significantly between sampling days. A large increase in abundance of calanoids occurred during the rainy season. This increase was correlated with higher temperature values. At that time, Notodiaptomus iheringi was dominant. This species showed significant short-term variations in abundance in both dry and rainy seasons. Significant variation in density of populations within the same sampling period might result from either the dispersion pattern of the populations or continuous substitution of the water masses. Significant correlation was observed between copepod abundance and temperature, especially for species of calanoids and there was also some correlations between densities of particular species of copepods and some phytoplankton taxa, mainly during the dry season. As for vertical distribution, most organisms were found between the surface and 15 m deep. During the rainy season, there was some evidence of the occurrence of spatial segregation between species of cyclopoids and calanoids, with the cyclopoids in a deeper position within the water column.

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