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  • 1
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    Different property rights regimes in the Lake Victoria multiple species fishery (2006)
    Details
    Publication Date: 2021-05-19
    Description: Greater ecosystem complexity is recognized by studying a two species predator-prey model under two property rights regimes: free entry and a system such as individual quotas which execute an economically optimal solution. A bottom-up management experiment is discussed in the context of Lake Victoria fisheries.
    Description: Published
    Keywords: Predators ; Resource management ; Fisheries ; Freshwater fish ; Predators ; Resource management
    Repository Name: AquaDocs
    Type: Report , Non-Refereed
    Format: 71093 bytes
    Format: application/pdf
    Format: 24
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    PAPER (OA)
  • 2
    Electronic Resource
    Electronic Resource
    Extraction of Anions Using Triphenylmethane Dyes. (1966)
    s.l. : American Chemical Society
    Analytical chemistry 38 (1966), S. 791-793 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac60238a036
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  • 3
    Electronic Resource
    Electronic Resource
    Colocalization of Neurotensin in the Mesocortical Dopaminergic System (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 668 (1992), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1992.tb27359.x
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of straw management, nitrogen fertilization and dosage rates on the dissipation of five sulfonylureas in soil (2001)
    Oxford UK : Blackwell Science Ltd
    Weed research 41 (2001), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The dissipation behaviour of metsulfuron-methyl, tribenuron-methyl, thifensulfuron-methyl, triasulfuron and amidosulfuron were studied in soil following post-emergence spring applications to cereal crops. Incorporation or removal of straw and different fertilizer applications had no influence on the disappearance time (DT50) of the herbicides. However, in laboratory trials dissipation of metsulfuron-methyl, triasulfuron and amidosulfuron at higher application rates was accelerated after incorporation of straw into the soil. The addition of straw decreases soil pH thereby causing faster hydrolysis of the compounds. Addition of nitrogen fertilizer increased the half-lives (t1/2) of the herbicides. Combination of both straw and N fertilizer, however, had no effect. Neither straw nor N influenced the degradation of tribenuron-methyl and thifensulfuron-methyl.The DT50 of all herbicides investigated varied from 6 to 17 days in the field trials. Except for amidosulfuron, herbicides could not be detected 38–68 days after application. In the laboratory, t1/2 values were higher than those in the field at 75 days (amidosulfuron), 63 days (metsulfuron-methyl), 35 days (triasulfuron) and 13 days (tribenuron-methyl). Only the t1/2 of thifensulfuron-methyl was at 29 h faster under laboratory conditions. T1/2 values of all herbicides were influenced by their initial concentration. The t1/2 values of amidosulfuron and tribenuron-methyl at 1 mg a.i. kg−1 soil were 2–2.5 times higher than at the recommended field application rate of 42 μg a.i. kg−1 soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3180.2001.00234.x
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  • 5
    Electronic Resource
    Electronic Resource
    Utilisation de I'isoproturon, seul et en association avec d'autres matiires en actives, en post levée à I'automne at en printemps, sur blé et orge d'hiver. II. Effets secondaires sur I'activiti de la déshydrogénase, la transformation de V azote et la décomposition des chaumes dans le sol (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 31 (1991), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In einem zweijährigen Feldversuch auf zwei Standorten wurde der Einfluß von Isoproturon, allein und in Kombination mit Dinoseb–acetat und Bifenox, auf die Dehydrogenaseaktivität, den Stickstoffumsatz und den Strohabbau im Boden nach einer Anwendung im Nachauflauf Winter (NA–W) und Nachauflauf–Frühjahr (NA–F) zu Winterweizen und Wintergerste untersucht. Isoproturon rief vorübergehend geringe Stimulationen aber auch Hemmungen der Dehydrogenaseaktivität um maximal 40% und des Stickstoffumsatzes um 70–90% hervor. Dinoseb–acetat führte zu Reduktionen der allgemeinen Stoffwechselaktiviät um bis zu 30%. Die Ammonium– und Nitritkonzentrationen lagen zeitweise um mehr als 100%über den Kontrollwerten. Im Labor hatte Isoproturon bei den zu diesen Terminen herrschenden Temperatur– und Feuchtebedingungen nur in wenigen Fällen einen Einfluß auf die Dehydrogenaseaktivität, nach Applikation dereinfachen Aufwandmenge von Dinoseb–acetat war die Aktivität aber um bis zu 50% reduziert. Im Sandboden waren die Herbizideffekte deutlicher ausgeprägt als im Lehmboden. Ein Einfluß der Behandlungstermine auf die durch die Herbizide bedingten veränderten mikrobiellen Aktivitäten wurde nur in den Freiland–versuchen deutlich.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3180.1991.tb01737.x
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  • 6
    Electronic Resource
    Electronic Resource
    Utilisation de l'isoproturon seul ou en association avec d'autres matières actives, en post-levée en hiver et au printemps sur blé et orge d'hiver (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 30 (1990), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In einem zweijährigen Versuch auf zwei Standorten (Sand- und Lehmboden) wurde Isoproturon allein und in Kombination mit Dinoseb-acetat und Bifenox zum Nachauflauf Winter (NA-W) Termin und zum Nachauflauf Frühjahr (NA-F) Termin in Wintergerste und Winterweizen eingesetzt. Obwohl nach einer Nachauflauf-Winter Behandlung die anfänglichen Herbizidbelastungen im Böden höher waren, sind nach unseren Ergebnissen im Vergleich zu einer Nachauflauf-Frühjahr Behandlung am Ende der Vegetationsperiode keine erhöhten Rückstände von Isoproturon zu erwarten. Die DT-50-Werte von Isoproturon in den beiden Versuchsjahren und Böden lagen zwischen 12 und 33 Tagen, die DT-90-Werte schwankten im Bereich von 34 bis 68 Tagen. Ein Einfluß der mit Isoproturon kombinierten Wirkstoffe auf dessen Abbau im Boden war nicht festzustellen. Eine bessere Unkrautwirkung der NA-W-Behandlung führte besonders bei starker Verunkrautung zu höheren Erträgen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3180.1990.tb01711.x
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  • 7
    Electronic Resource
    Electronic Resource
    Studies on the semen biology and sperm cryopreservation in the sterlet, Acipenser ruthenus L. (2004)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 35 (2004), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The present study investigated motility, acrosome reaction, fertility and cryobiological parameters of the semen of the sterlet, Acipenser ruthenus L. Sperm motility persisted for about 4 min in water, and the main swimming type was the linear motion. Motility was prolonged at osmolalities of 12.5 mosmol kg−1 and in the presence of magnesium ions, while calcium had no effect. Also a pH in the range of 7.0–9.0 had no effect on ` motility. At osmolalities of 25–50 mosmol kg−1 the sperm motility was partly inhibited, at osmolalities of 100 mosmol kg−1, completely and irreversibly. In 50 mosmol kg−1 solutions with 2.5–5 mM L−1 KCl the motility inhibition was total, but reversible. The acrosome reaction was not induced by one of the described solutions, but the percentage of spermatozoa with reacted acrosomes was low (〈20%) and highly variable in all experiments. The optimal extender base for cryopreservation was a solution consisting of 50 mM L−1 NaCl, 5 mM L−1 KCl, 10 mM L−1 Tris (pH 8.5). From the tested cryoprotectants only dimethylsulphoxide (DMSO) and methanol provided sufficient cryoprotection. After freezing and thawing, the motility rates and swimming velocities were higher with DMSO than with methanol. However, the fertility was very significantly reduced with DMSO (10.3±0.5%) while with methanol fertilization rates in a similar range (32.7±4.4%) as with fresh semen (33.90±0.8%) could be obtained. Optimal freezing conditions for sterlet semen were in the vapour of liquid nitrogen 3–5 cm (−95°C to −85°C) above its surface, the optimal thawing conditions at 25°C for 30 s. The acrosome reaction was not induced by these cryopreservation protocols.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2109.2004.01034.x
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  • 8
    Electronic Resource
    Electronic Resource
    Characterization of the testicular semen of the African catfish, Clarias gariepinus (Burchell, 1822), and its short-term storage (2004)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 35 (2004), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Semen of the African catfish, Clarias gariepinus (Burchell, 1822), was investigated with respect to its cellular composition, sperm cell density, maturation grade, motility and fertility. Storage conditions were tested, whereby sperm viability was assessed by measurement of the motility after activation and by fertility tests. Testicular semen differed in its composition, i.e. the sperm density and numbers of spermatids, according to the maturity grade of the testis. Two semen types could be distinguished: semen type I was characterized by high sperm densities and low numbers of spermatids and semen type II had lower sperm densities and higher numbers of spermatids. Two semen types did not differ in motility and fertility (when adjusted for differences in sperm density). During storage, the sperm viability was influenced by the sodium concentration of the storage medium, temperature, membrane stabilizers as bovine serum albumen (BSA) or hen egg yolk, antibiotics and oxygen. Semen viability was maintained best when it was diluted at a ratio of 1:5 in storage solution (150 mmol L−1 NaCl, 2.5 mmol L−1 KCl, 1 mmol L−1 CaCl2, 1 mmol L−1 MgSO4, 20 mmol L−1 Tris (pH 8.5) and 0.5% BSA or 0.5% hen egg yolk) and stored at 4 °C. Oxygen gassing and addition of antibiotics (1 mg mL−1 gentamycine sulphate) to the storage solution affected the two semen types in different ways. Antibiotics had no effect on type I semen, but had a positive effect on type II semen. Oxygen gassing had a positive effect on type I semen but a negative effect on type II semen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2109.2004.00993.x
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  • 9
    Electronic Resource
    Electronic Resource
    Fine structure and motility of spermatozoa and composition of the seminal plasma in the perch (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 47 (1995), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The fine structure and motility of spermatozoa and the composition of the seminal plasma of the perch Perca fluviatilis are investigated by electron microscopy, computer assisted cell motility analysis (CMA) and biochemical methods. The spermatozoon is asymmetrical as the flagellum inserts mediolateral on the nucleus. It lacks an acrosome, has an ovoid head and a small midpiece with one mitochondrion. Sperm motility–initiated in distilled water (10° C)–is characterized as follows: 85·0 ± 2·7% of the spermatozoa are motile, the main swimming type (10 ± 1 s after motility initiation) is the linear motion (61·4 ± 24·4%) and the average swimming velocity is 122·4 ± 21·9 μm s–1. When motility is initiated with NaCl, glucose or sucrose solutions of 100 mosmol kg–1 the percentage of motile spermatozoa and the swimming types are similar as in water, but the swimming velocity (174·0 ± 22·3 μm s–1) is significantly higher. Motility is inhibited by high osmolality of the diluent: when increasing the osmolality of the saline solutions to 350 mosmol kg–1 sperm motility is totally suppressed while potassium (10–40 mmol 1–1) does not affect motility parameters. pH optimum for sperm motility is between pH 7·0 and 8·5. The seminal fluid contains 124·01 ± 21·68 mmol 1–1 sodium, 10·22 ± 1·11 mmol 1–1 potassium and 0·72 ± 0·26 mmol 1–1 calcium. pH is 8·25 ± 0·09, and osmolality 283·90 ± 37·19 mosmol kg–1. The following organic components were determined: monosaccharides (glucose 63 ± 19 μmol 1–1, fructose 54 ± 28 μmol 1–1, galactose 59 ± 25 μmol 1–1), lipids (cholesterol 5·51 ± 6·42 μmol 1–1, triglycerides 72 ± l00 μmol l–1, cholesteryloleate 15–150 μmol 1–1, phosphatidylcholine 26 · 31 μmol 1–1, glycolipids 1–10 mg 100 m1–1), lactate 108 ± 99 μmol 1–1, hydroxybutyrate 102 ± 99 nmol 1–1, choline 59 ± 159 μmol 1–1, protein 344·75 ± 59·06 mg 100m1–1, enzymes (β-d-glucuronidase l.4 ± 0.7 μmol h–1 100 ml–1, protease (caseolytic activity) 1·0 ± 0·6 μmol h–1 100 ml–1, alkaline phosphatase 2520·0 ± 861·0 μmol h–1 100 ml–1, acid phosphatase 44.0 ± 16.0 μmol h–1 100 ml–1, glucose-6-phosphate dehydrogenase 38·9 ± 86·9 μmol h–1 100 ml–1, lactate dehydrogenase 134·4 ± 69·6 μmol h–1 100 ml–1, butyrylcholine esterase 0·014 ± 0·010 μmol h–1 100 ml–1, adenosine triphosphatase 562·8 ± 665·4 μmol h –1 100 ml–1).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1995.tb01917.x
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of inorganic and organic pollutants on sperm motility of some freshwater teleosts (2004)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 65 (2004), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Using four different sperm types from brown trout Salmo trutta fario(Salmonidae), chub Leuciscus cephalus(Cyprinidae), burbot Lota lota(Gadidae) and African catfish Clarias gariepinus(Clariidae) the effect of inorganic (cadmium, copper, mercury, lead, zinc and nitrite) and organic (cyclohexane and 2,4-dichlorophenol) environmental pollutants on sperm motility was investigated. Spermatozoa were activated in double distilled water containing the different test substances and the motility was compared to controls of similar pH. From the investigated motility variables the sperm motility rate and swimming velocity reacted most to the environmental pollutants whereby the changes depended on the species and on the test substance. African catfish spermatozoa were the most resistant, chub and burbot spermatozoa showed medium resistance and brown trout spermatozoa were the most sensitive to the pollutants. With exception of 2,4-dichlorophenol and zinc the effective concentrations of the tested pollutants exceeded the recommendation for surface waters 100–10·000-fold and were in a range lethal for the fish themselves. Therefore, it was concluded that fish sperm motility is not a suitable marker for risk assessment of environmental pollutants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0022-1112.2004.00528.x
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