Population dynamics of the Nile tilapia (Oreochromis niloticus L. 1758) stock in Lake Langeno, Ethiopia

Nile tilapia, Oreochromis niloticus, is a widely distributed and economically most import fish species in Ethiopia. Effective management is essential to sustain their fisheries and the benefits for the local communities. However, little is known about the population dynamics of the Nile tilapia stock in Lake Langeno. Vital parameters of its population were determined using length frequency data collected from 5,949 specimens ranging from 8.5 to 35.7 cm total length (tl). These specimens were collected from August 2017to July 2018. The population parameters were determined using the elefan I routine in FiSAT software. Estimated von Bertalanffy growth parameters were asymptotic length (L∞) = 35.70 cm, growth curvature (K) = 0.32 yr-1, age at length zero (to) = -0.49, and growth performance index (Փ') = 2.61. Instantaneous total mortality (Z), natural mortality (M), and fishing mortality (F) rates were determined from length-converted catch curve and empirical models, respectively, and their values obtained were Z = 2.31 yr-1, M = 0.82 and F =1.56 yr-1, respectively. The exploitation rate (E) of Nile tilapia computed from its mortality rates was 0.67 yr-1, suggesting state of overfishing. The size at first capture (Lc) was estimated at 14.0 cm which is much lower than the size at first maturity (Lm=16.62 cm), which further substantiated the state of overfishing. The results of the study are very useful for fishery managers and scientists who wish to manage and further explore the Nile tilapia stock in Lake Langeno

Unsupervised Deep Learning-based clustering for Human Activity Recognition

One of the main problems in applying deep learning techniques to recognize activities of daily living (ADLs) based on inertial sensors is the lack of appropriately large labelled datasets to train deep learning-based models. A large amount of data would be available due to the wide spread of mobile devices equipped with inertial sensors that can collect data to recognize human activities. Unfortunately, this data is not labelled. The paper proposes DISC (Deep Inertial Sensory Clustering), a DL-based clustering architecture that automatically labels multi-dimensional inertial signals. In particular, the architecture combines a recurrent AutoEncoder and a clustering criterion to predict unlabelled human activities-related signals. The proposed architecture is evaluated on three publicly available HAR datasets and compared with four well-known end-to-end deep clustering approaches. The experiments demonstrate the effectiveness of DISC on both clustering accuracy and normalized mutual information metrics.Comment: 2022 IEEE 12th International Conference on Consumer Electronics (ICCE-Berlin

The interpreter as intercultural mediator

This thesis looks at the role of the Slovak-English interpreter working in the consecutive mode in the business environment especially with regard to rendering cultural references from source texts, whether these are (British) English or Slovak. Since culture in this thesis is taken in the broad sense of the whole way of life, cultural references can also be wide-ranging. The strategy an interpreter will opt for when interpreting cultural references depends on the circumstances under which he or she operates. Interpreting puts constraints on interpreters which make their activity distinct from translation of written texts, where in cases of unknown cultural references, translators can resort to the use of notes. Interpreters are engaged in mediating communication between (two) clients who do not share the same language and who come from differing cultural backgrounds. Due to differences between the (British) English and the Slovak cultures - in their material, spiritual and behavioural aspects - as well as due to lack of knowledge of cultural references which the clients of English-Slovak interpreting have and which was caused historically, some intercultural mediation is needed. Its particular forms are the outcome of the weighing of the circumstances under which the English-Slovak consecutive interpreter works. Moreover, business interpreting contains challenges in the form of the vocabulary of business, a relatively new area for Slovak interpreters. An interpreter, under all the above mentioned constraints, has to fulfil his or her role: to establish and maintain communication between the two parties. Therefore some of the strategies used will try to prevent miscommunication, while others will try to deal with miscommunication once it has occurred

Perception of Security Issues in the Development of Cloud-IoT Systems by a Novice Programmer

It is very hard (or ineffective) to take an old system and add to it security features like plug-ins. Therefore, a computer system is much more reliable designed with the approach of security-by-design. Nowadays, there are several tools, middlewares, and platforms designed with this concept in mind, but they must be appropriately used to guarantee a suitable level of reliability and safety. A security-by-design approach is fundamental when creating a distributed application in the IoT field, composed of sensors, actuators, and cloud services. The IoT usually requires handling different programming languages and technologies in which a developer might not be very expert. Through a use case, we analyzed the security of some IoT components of Amazon Web Services (AWS) from a novice programmer's point of view. Even if such a platform could be secure by itself, a novice programmer could do something wrong and leave some possible attack points to a malicious user. To this end, we also surveyed a small pool of novice IoT programmers from a consulting engineering company. Even if we discovered that AWS seems quite robust, we noticed that some common security concepts are often not clear or applied, leaving the door open to possible issues

Plankton communities and ecology of tropical lakes Hayq and Awasa, Ethiopia

Der im Hochland von Äthiopien gelegene Lake Hayq dient der ansässigen Bevölkerung als Trinkwasserreservoir, Nahrungsquelle sowie als touristisches Ziel. Der See wurde seit den 1930er Jahren sporadisch untersucht und als oligotrophes Gewässer eingestuft. Vor annähernd 20 Jahren änderte sich dieser Zustand und der See zeigte Eutrophierungserscheinungen. Für diese Verschiebung kamen zwei Hypothesen in Betracht: (i) ein erhöhtes Nährstoff-Volumen-Verhältnis und (ii) planktivore Tilapia Fische (Oreochromis niloticus), welche in den späten 1970er Jahren ausgesetzt wurden. Dies ist die erste Studie, die sich mit beiden Theorien auseinandersetzt, wobei historische Aufzeichnungen analysiert und mit neuesten Daten verglichen wurden. Primärproduktion und Biomasse, Zooplanktonabundanz, Nährstoffe sowie chemisch-physikalische Parameter wurden hierfür monatlich von Oktober 2007 bis Oktober 2008 an zwei Standorten gemessen. Die Ergebnisse zeigten, dass der pH-Wert sowie die Gesamtalkalinität während des letzten halben Jahrhunderts konstant blieben, die elektrische Leitfähigkeit jedoch sukzessiv zunahm. Die aktuelle mittlere Konzentration an gelösten, anorganischen Stickstoff betrug 305 µg L-1, wobei Ammonium den Hauptvertreter stellte. Der löslich reaktive Phosphor betrug 22 µg L-1, der Gesamtphosphor 58 µg L-1 und Si 3.7 mg L-1, wobei letzteres eine höhere Konzentration als bei früheren Aufzeichnungen mit 2.4 mg L-1 zeigte. Die gegenwärtige Studie zeigte ein erhöhtes Aufkommen an Algengruppen und Taxa, während in den 1940er Jahren lediglich Diatomeen dokumentiert wurden. Von den 40 bestimmten Phytoplanktontaxa machten die Chlorophyten und Diatomeen 77% der Gesamtanzahl aus, wobei eine kanonische Korrespondenzanalyse (CCA) auf einen Zusammenhang ersterer mit Nährstoffen und Regen und letzterer mit Silikat und Zooplankton aufzeigte. Das Gesamtmittel der Phytoplanktonbiomasse von 1.10 mm³ L-1, der mittlere Chlorophyll a (Chl a) Gehalt von 12.9 mg m -3 und die Bruttoprimärproduktion von 7.12 g O¬2 m-2 d-1 stellen den Lake Hayq - verglichen mit anderen tropischen Seen - in eine Übergangsposition zwischen meso- eutroph. Die Hauptkomponentenanalyse (PCA) gefolgt von einer Regressionsanalyse wiesen darauf hin, dass der Chl a Gehalt vor allem durch Regenfälle, Temperatur und Verfügbarkeit von Licht gesteuert wird. Lake Hayq kann aufgrund von verschiedenen limnologischen Produktivitätsindices als eutroph eingestuft werden. Als Ursache dürfte jedoch nicht das hohe Nährstoff-Volumen-Verhältnis in Frgae kommen, da bereits sehr hohe Nährstoffkonzentrationen (SRP 96 µg L-1 und NH4-N 300 µg L-1) vorlagen, als der See noch als als oligotroph eingestuft wurde. Vielmehr dürfte der Fischbesatz durch planktivore Tilapien die Hauptursache für die Veränderung des Trophiezustandes des Sees darstellen. Die Veränderung der Zooplanktonzusammensetzung, z.B. das Verschwinden der Cladoceren ist laut verschiedenen Autoren ebenfalls auf Tilapia zurückzuführen. Um diese Hypothese zu bestätigen, bestimmten wir unter Berücksichtigung limnologischen Basisparametern die Zooplanktonzusammensetzung, die Abundanz und die Biomasse innerhalb Kurzzeitintervallen zwischen Oktober 2007 und Jänner 2009. Die dominanten Zooplanktonarten waren Mesocyclops aequatorialis, Thermocyclops ethiopiensis, Ceriodaphnia reticulata, Daphnia magna, Diaphanosoma excisum sowie die häufig auftretenden Rädertiere Euchlanis parva, Keratella tropica und Polyarthra sp.. Das Gesamtmittel der bestehenden Biomasse aus Crustaceen-Zooplankton mit 237 mg Trockengewicht m-3 ist durchaus mit anderen tropischen Seen vergleichbar. Unter den Copepoden war fast ausschließlich Thermocyclops ethiopiensis mit einem Maximalwert von 469 Indl L-1 und einem Mittelwert von 92 Indl L-1 zu finden. Diese Abundanzzahl stimmt mit anderen Autoren, die einen Maximalwert von 577 Indl L-1 für cyclopoide Copepoden dokumentierten, überein. Die CCA deutete darauf hin, dass die zeitliche Variation von Thermocyclops durch die Verfügbarkeit von Nahrung und Wassertemperatur beeinflusst wurde. Die planktivoren Fische spielen eine Schlüsselrolle in der Strukturierung der Cladoceren, vor allem der großen Daphnia magna. Im Jänner 2008 beobachteten wir ein massives Fischsterben planktivorer Fische gefolgt von einer hohen Algenbiomasse, die von der großen Daphnia magna beweidet wurde. Dieser kaskadenartige Ablauf demonstriert die trophischen Interaktionen im natürlichen Ökosystem. Wir entwickelten ein Massen-Gleichgewichts-Modell, um die pelagische Struktur des Nahrungsnetzes und die trophischen Interaktionen der funktionellen Hauptgruppen des Lake Hayq zu bestimmen. Die Studie bildet außerdem eine Datenbasis für zukünftige ökosystem-orientierte Untersuchungen und Managementpläne. Zwischen Oktober 2007 und Mai 2009 wurden ausführlich Daten gesammelt. Die ökotrophische Effizienz (EE) von verschiedenen funktionellen Gruppen inklusive Phytoplankton (0.8) und Detritus (0.85), war hoch, was auf eine Nutzung der Gruppen innerhalb des Systems schließen lässt. Der EE von Mesocyclops (0.03) und Thermocyclops (0.3) war jedoch sehr gering, was bedeutet, dass diese Ressourcen eher einen „Sink“ in der trophischen Hierarchie darstellen. Stoffflüsse, die auf trophischen Niveaus sensu Lindeman basieren, lassen die Bedeutung von Phytoplankton und Detritus zu höheren Trophieniveaus erkennen. Die berechnete durchschnittliche Transfereffizienz von 11.5% für die ersten vier Trophieniveaus lag innerhalb des Bereichs für hocheffiziente afrikanische Seen. Die Primärproduktions-Respirations-Rate (P/R = 1.05) vom Lake Hayq spiegelt die das Klimaxstadium des Ökosystems wider. Wir modellierten unter Ausschluss von Tilapia ein Nahrungsnetz und reduzierten die Phytoplanktonbiomasse, um einen Einblick in das Massengleichgewicht zu bekommen, bevor Tilapia besetzt wurde. Die Analysen resultierten in einem geringeren System Omnivorie Index (SOI) (0.016) und einer niedrigeren P/R Rate (0.13), die den See als Ökosystem in Sukzession beschrieben und darauf hinweisen, dass Tilapia zur Weiterentwicklung des Sees beitrug. Tilapia füllte im Lake Hayq eine ökologisch leere Nische als pelagischer Planktivore und steuerte einen Beitrag zur besseren Transfereffizienz bei, die von der Primärproduktion bis zum Fischertrag beobachtet werden konnte. Unter den Rift Valley Seen in Äthiopien wurde der verhältnismäßig gut untersuchte Lake Awasa herangezogen, um die Langzeiteffekte der anthropogenen und natürlichen Einflüsse auf Planktongemeinschaften zu untersuchen. Lake Awasa liegt in der Nähe einer wachsenden Stadt und erhält dadurch viele Industrieabflüsse und kommunale Abwässer. Rund um den See wird das Land wirtschaftlich genutzt, wobei ausreichende Managementpläne derzeit fehlen. Der See wird als Erholungsort mit vielen Freizeitaktivitäten genutzt. Wir untersuchten die Phyto- und Zooplanktongemeinschaft zwischen November 2003 bis August 2004 und verglichen unsere Daten mit den historischen Datensätzen seit den 1980er Jahren, um potentielle Veränderungen abschätzen zu können. Die Phytoplanktontaxa ähnelten sich mit den in früheren Studien, abgesehen von einigen Arten, die Neufunde in diesem System darstellen, wie z.B.: Pediastrum simplex mit zwei Unterarten und Scenedesmus ecornis. Die Phytoplanktonabundanz aus 2003/04 beinhaltete 54% Chlorophyta, 26% Cyanoprokaryota, 18% Diatomeen und 2% „sonstige Gruppen“ und stellte eine proportionale Ähnlichkeit zu früheren Aufzeichnungen dar. Die mittlere Phytoplanktonbiomasse in Form von Chl a (19 µg L-1) war jedoch geringer als in früheren Studien. Im Gegensatz dazu veränderte sich die flächenbezogene Rate der Bruttophotosynthese des Lake Awasa in den letzten zwei Dekaden nach oben (0.35 to 2.21 g O2 m-2 h-1). In ähnlicher Weise, trotz gleich bleibender Zooplanktongemeinschaft, unterschieden sich die Abundanz und die dominanten Taxa in den letzten Dekaden. Die mittlere Abundanz der cyclopoiden Copepoden lag bei 58 000 ± 9200 (SE) Indl m-3 und die Cladocerenabundanz (2 600 ± 640 SE Indl m-3) war 2003/04 im System gering. Die Rotifera übertrafen zahlenmäßig andere Komponenten mit einem Maximalwert von 263 670 Indl m-3, der ca. das 5-fache von Werten von früheren Studien ausmacht. Die adult zu cyclopoid Nauplen Rate von 0.27 in dieser Studie deutet darauf hin, dass heutzutage der Kannibalismus möglicherweise durch die höhere Anzahl an Rotifera als Beutemöglichkeit abnimmt. Der menschliche Einfluss ist ahrscheinlich, da der Lake Awasa in der Nähe der schnell wachsenden Stadt Awasa liegt, in der der demographische Druck sehr hoch ist. Der See wird zu Fischereizwecken genutzt und der kommerziell wichtige O. niloticus ist stark überfischt (LFDP, 1998). Eine permanente Betreuung und ein angemessenes Management wären von großer Bedeutung, um ökologischen Schäden zu verhindern, die sich nicht nur auf die Biodiversität, sondern auf die gesamte Wirtschaft auswirken würden.Lake Hayq, located in the highlands of Ethiopia, offers its natural services to the local inhabitants including drinking water, fishes and tourism. Though sporadically, the lake has been visited since 1930-ies and used to be an oligotrophic water body. However, its trophic status changed some 20 years ago to an eutrophic level. For this shift, two hypotheses were proposed: (i) an increased nutrient to volume ratio and (ii) planktivorous Tilapia fish (Oreochromis niloticus), which were introduced in the late 1970-ies. This is the first study to disucss about these hypotheses and historical records were analyzed and compared with recent data. For this, primary production and biomass, zooplankton abundance, nutrients and physico-chemical variables were measured on a monthly basis from October 2007 to October 2008 at two stations. The results indicated that pH and total alkalinity have remained within the same range during the last half a century; however, electrical conductivity has shown a gradual increase over the last 5 decades. The overall mean actual concentration of dissolved inorganic nitrogen was 305 µg L-1, with ammonium being the prominent species. Similarly, soluble reactive phosphorus was 22 µg L-1, total phosphorus 58 µg L-1 and Si 3.7 mg L-1, the latter shows higher concentrations than previous reports of 2.4 mg L-1. In the 1940-ies only diatoms were reported; algal groups and taxa numbers in the present study have increased. Out of 40 phytoplankton taxa identified, chlorophytes and diatoms together contributed 77% to the overall taxa number, and Canonical Correspondence Analysis (CCA) indicated that the former were coincided with nutrients and rainfall, and the latter with silica and zooplankton. An overall mean phytoplankton biomass of 1.10 mm3 L-1, mean Chlorophyll a (Chl a) of 12.9 mg m-3 and gross primary production of 7.12 g O2 m-2 d-1 gave Lake Hayq an intermediate position compared to other tropical lakes. Principal Component Analysis (PCA) followed by regression analysis indicated that Chl a was influenced by rainfall, temperature and light supply. Lake Hayq is categorized as eutrophic condition after employing various limnological productivity indices. However, the first hypothesis ascribed to eutrophication, high nutrient: volume ratio, is unlikely true since the nutrient concentrations (SRP 96 µg L-1 and NH4-N 300 µg L-1) were very high when the lake was reported as oligotrophic in the previous investigations. Hence, we support the second hypothesis that the stocked planktivorous fish was most probably the major cause for the trophic change of the lake. Hence, we support the second hypothesis that the stocked planktivorous fish was most probably the major cause for the trophic change of the lake. Similarly, the change in zooplankton composition including the disappearance of cladocerans, were also related to the stocked Tilapia fish. To address this hypothesis, we determined zooplankton composition, abundance and biomass on short-time intervals, between October 2007 and January 2009, and the underlying limnological variables were also considered. The dominant zooplankton species were Mesocyclops aequatorialis, Thermocyclops ethiopiensis, Ceriodaphnia reticulata, Daphnia magna, Diaphanosoma excisum and the common rotifers Euchlanis parva, Keratella tropica and Polyarthra sp.. Total mean standing biomass of crustacean zooplankton was 237 mg dry mass m-3, which gave Lake Hayq an intermediate position when compared with other tropical lakes. Of copepods, Thermocyclops ethiopiensis was almost an exclusive species, reaching a maximum value of 469 Indl L-1 and a mean of 92 Indl L-1. This numerical abundance is somewhat in agreement with other authors who reported a maximum value of 577 Indl L-1 for cyclopoid copepod. CCA indicated that the temporal variation of Thermocyclops was influenced by food supply and water temperature. We refute the hypothesis that Tilapia was the cause for the seasonal disappearance of cladocerans, and attribute it to the adverse effect of episodic mixing. However, the planktivorous fish plays a key role in structuring the cladocerans in particular the large-sized Daphnia magna. In January 2008, we observed a massive planktivorous fish mortality that triggered high algal biomass, which was later grazed by larger-sized Daphnia magna demonstrating the cascading trophic interactions hypothesis in a natural ecosystem. We further generated a mass-balance model to figure out the pelagic food web structure and trophic interactions of the major functional groups of Lake Hayq. Moreover, the study lay down a baseline data for future ecosystem-based investigations and management activities. Extensive data collection have been taken place between Oct. 2007 and May 2009, and a number of parameters are system-specific. Ecotrophic efficiency (EE) of several functional groups including phytoplankton (0.8) and detritus (0.85) was high indicating the utilization of the groups within the system. However, the EE of Mesocyclops (0.03) and Thermocyclops (0.3) was very low implying these resources were rather a ‘sink’ in the trophic hierarchy. Flows based on aggregated trophic level sensu Lindeman revealed the importance of both phytoplankton and detritus to higher trophic levels. The computed average transfer efficiency of 11.5% for the first four trophic levels was within the range for highly efficient African lakes. The primary production to respiration (P/R) ratio (1.05) of Lake Hayq indicates the maturity of the ecosystem. We also modelled the food-web by excluding Tilapia and reduced phytoplankton biomass to get insight into the mass balance before Tilapia was introduced. The analysis resulted in a lower system omnivory index (SOI) (0.016) and P/R ratio (0.13) that described the lake as an immature ecosystem, suggesting the introduction of Tilapia might have contributed to the maturity of the lake. Tilapia in Lake Hayq filled an ecological empty niche of pelagic planktivore, and contributed for the better transfer efficiency observed from primary production to fish yield. Of Ethiopian rift-valley lakes, the comparatively well-studied Lake Awasa was chosen to assess the long-term effect of antropogenic and natural impacts on plankton communities. Lake Awasa is located in the vicinity of the growing city receiving many potentially adverse effluents from factories and municipal sewage apparently with little treatment. Moreover, there are high levels of recreational activities and poor land-use management practices around the lake, and thus the lake system is exposed to intense human-induced pollution. Therefore, we studied phyto- and zooplankton communities between November 2003 to August 2004, and compared these data with historical data since the 1980-ies to assess potential inter-decadal changes. The phytoplankton taxa were similar with the previous study, except some species that are new findings to the system such as Pediastrum simplex with two subspecies and Scenedesmus ecornis. Phytoplankton abundance in 2003/04 comprised 54% Chlorophyta, 26% cyanoprokaryotes, 18% diatoms and 2% others, a proportion similar to previous records. However, the mean phytoplankton biomass in terms of Chlorophyll–a (19 µg L-1) was lower than in previous studies. In contrast, the integral rate of gross photosynthesis of Lake Awasa has changed in the last two decades with higher values recorded at present (0.35 to 2.21 g O2 m-2 h-1). In a similar way, even though zooplankton community composition remained the same, the abundance and the dominant taxa differed in the last decades. The mean abundance of cyclopoid-copepods was 58 000 ± 9200 (SE) Indl m-3 and cladocerans abundance (2 600 ± 640 SE Indl m-3) was low in the system in 2003/04. Interestingly, rotifers outnumbered other components with a maximum value of 263 670 Indl m-3, which is about five-times greater than the previous reports. The adult cyclopoid to nauplii ratio of 0.27 in the present study suggested that cannibalism has diminished at present probably due to high number of rotifers as prey, contradicting a previous hypothesis about high cannibalism in cyclopoids. Human impact is most likely as Lake Awasa is located nearby the fast growing town Awasa, where demographic pressure is high. The lake is used for fishing, and the commercially important O. niloticus is over-exploited (LFDP, 1998). The lake is also used for bathing and washing clothes, domestic use and recreational purpose. Moreover, the lake is surrounded by agricultural land, hence anthropogenic influences are inevitable. Besides, it receives affluent from industries. Once the concentration of pollutants passes the threshold limit, it will bring irreversible damage to the ecosystem. So care and appropriate management should be taken before such ecological damage happen, which would affect not only the biodiversity but the economy as well

Agoric computation: trust and cyber-physical systems

In the past two decades advances in miniaturisation and economies of scale have led to the emergence of billions of connected components that have provided both a spur and a blueprint for the development of smart products acting in specialised environments which are uniquely identifiable, localisable, and capable of autonomy. Adopting the computational perspective of multi-agent systems (MAS) as a technological abstraction married with the engineering perspective of cyber-physical systems (CPS) has provided fertile ground for designing, developing and deploying software applications in smart automated context such as manufacturing, power grids, avionics, healthcare and logistics, capable of being decentralised, intelligent, reconfigurable, modular, flexible, robust, adaptive and responsive. Current agent technologies are, however, ill suited for information-based environments, making it difficult to formalise and implement multiagent systems based on inherently dynamical functional concepts such as trust and reliability, which present special challenges when scaling from small to large systems of agents. To overcome such challenges, it is useful to adopt a unified approach which we term agoric computation, integrating logical, mathematical and programming concepts towards the development of agent-based solutions based on recursive, compositional principles, where smaller systems feed via directed information flows into larger hierarchical systems that define their global environment. Considering information as an integral part of the environment naturally defines a web of operations where components of a systems are wired in some way and each set of inputs and outputs are allowed to carry some value. These operations are stateless abstractions and procedures that act on some stateful cells that cumulate partial information, and it is possible to compose such abstractions into higher-level ones, using a publish-and-subscribe interaction model that keeps track of update messages between abstractions and values in the data. In this thesis we review the logical and mathematical basis of such abstractions and take steps towards the software implementation of agoric modelling as a framework for simulation and verification of the reliability of increasingly complex systems, and report on experimental results related to a few select applications, such as stigmergic interaction in mobile robotics, integrating raw data into agent perceptions, trust and trustworthiness in orchestrated open systems, computing the epistemic cost of trust when reasoning in networks of agents seeded with contradictory information, and trust models for distributed ledgers in the Internet of Things (IoT); and provide a roadmap for future developments of our research

A survey of foster home care for children in the New England states

Thesis (M.A.)--Boston University, 1947. This item was digitized by the Internet Archive