Investment opportunities in fish seed technology

An examination is made of the requirements for the commercial propagation of carp and tilapia in Nigeria. It is concluded that the operation of a successful Fish Hatchery and fry production system will depend on the following factors: 1) Correct initial planning for intended production (both species and intended numbers); 2) Design of the appropriate facilities to enable required production; 3) Selection of top calibre, dedicated and experienced hatchery staff; and, 4) The ethical responsibility taken by the hatchery management to produce only the highest quality seed under the best possible conditions. Purchasing farmers are dependent on this

Evolución y progreso de las asociaciones de desarrollo rural en Gipuzkoa, un modelo necesitado de mayor autonomía y apoyo institucional

[ES] Tras dos décadas dedicadas a la promoción de los espacios rurales las Asociaciones de Desarrollo Rural de Gipuzkoa se han convertido en el vehículo prioritario para el progreso de este tipo de espacios. Su trayectoria ha estado marcada por toda una sucesión de programas con objetivos diversos y directrices políticas y presupuestarias diferentes. Como consecuencia se ha creado un modelo de dinamización rural centrado en la comarca y caracterizado por la diversidad de acciones que aborda y por su capacidad para incorporar nuevos campos, por su alto grado de implicación en la coordinación, ejecución e incluso gestión de servicios y por su capacidad de incorporar actores al desarrollo de los espacios rurales. A pesar de lo acertado del modelo éste aún tiene asignaturas pendientes, especialmente su dependencia de la decisiones políticas que en cada momento se toman y como consecuencia su falta de autonomía, la excesiva ligazón que aún presenta con el que fue el objeto inicial de estas Asociaciones, la realización de infraestructuras y especialmente el estrépito fracaso que ha tenido su pretensión de incorporar a otras instituciones y departamentos además de los propiamente agrarios.

Reproductive biology of black skipjack, Euthynnus lineatus, an Eastern Pacific tuna

(PDF contains 94 pages.)

Successful handstripping of hatchery bred and reared male African catfish, Clarias gariepinus (Burchell, 1822)

A total of 45 Male and 5 female Clarias gariepinus bred and reared in the hatchery in sunning for one year were obtained for this experiment. The fish were then housed separately according to their sexes and maintained on trout diet at 10% body weight for two days before they were subjected to induction. These were then induced using both human chorionic gonadotropin (hCG - 500iu) and carp pituitary suspension (CPS -3mg kg super(-1) suspended in 0.9% saline) either as priming or resolving doses. The milt produced was used to fertilize eggs tripped from females. The results indicated high milt production, motility and fertility in most males

The effect of long term exploitation by the gill net fishery on the multispecies fish stocks in Kainji Lake, Nigeria, 1969-1997

The findings are presented of an assessment made of the gillnet fishery in Kainji Lake, Nigeria from 1969 to the present, on the basis of data sets from commercial and experimental gillnet fishing, with the purpose to detect trends in some key fishery monitoring indicators. During this period, there has been an increase in the number of small meshed nets in the fishery resulting in a shift in the mode to lower mesh sizes; consequently, the average mesh size declined gradually in the fishery. This trend is found to be directly correlated with the decline in the CPUE and mean weight of the fish species. It is argued that the observed trend in CPUE and mean weight is forcing the fishermen to switch effort to gears such as traps which have very small meshes and can indescriminately take all sizes of the fish. It is shown that the catch composition by weight of Citharinus citharus, Lates niloticus and tilapias declined in the gillnet fishery in the late 70's and early 80's. Recent data, from 1994 to 1996, however indicates that C. citharus is recovering, but with declining mean weight. This suggests that the exploitation pattern is shifting to the smaller fish through the use of small meshed nets. In general, however, there has not been drastic changes in species bio-diversity in the Lake as a result of predatory effect and ecosystem overfishing as has happened in other great African Lakes. The species composition since lake formation continued to be dominated by fewer that 20 species. The potential yield for the lake has been estimated to be 32,166 tonnes (excluding clupeids) and the required optimum fishing effort to be 1,814 fishing canoes. In view of the relative stability of the species diversity in the lake and the current fish production level, it is proposed here that this MSY be adopted for all species. This would be achieved with the current effort level in the lake assuming that the efficiency of the fishermen and their gears do not improve. It should be reviewed after 10 or more years of catch and effort data collection. (PDF contains 65 pages)

Attosecond pulse extreme-ultraviolet photoionization in a two-color laser field

Attosecond-pulse extreme-ultraviolet (XUV) photoionization in a two-color laser field is investigated. Attosecond pulse trains with different numbers of pulses are examined, and their strong dependence on photoelectronic spectra is found. Single-color driving-laser-field-assisted attosecond XUV photoionization cannot determine the number of attosecond pulses from the photoelectronic energy spectrum that are detected orthogonally to the beam direction and the electric field vector of the linearly polarized laser field. A two-color-field-assisted XUV photoionization scheme is proposed for directly determining the number of attosecond pulses from a spectrum detected orthogonally. (C) 2005 Optical Society of America.

Structural requirements for catalysis: studies on RTEM-1 β-lactamase

β-lactamases are a group of enzymes that confer resistance to penam and cephem antibiotics by hydrolysis of the β-lactam ring, thereby inactivating the antibiotic. Crystallographic and computer modeling studies of RTEM-1 β-lactamase have indicated that Asp 132, a strictly conserved residue among the class A β-lactamases, appears to be involved in substrate binding, catalysis, or both. To study the contribution of residue 132 to β-lactamase function, site saturation mutagenesis was used to generate mutants coding for all 20 amino acids at position 132. Phenotypic screening of all mutants indicated that position 132 is very sensitive to amino acid changes, with only N132C, N132D, N132E, and N132Q showing any appreciable activity. Kinetic analysis of three of these mutants showed increases in K_M, along with substantial decreases in k_(cat). Efforts to trap a stable acyl-enzyme intermediate were unsuccessfuL These results indicate that residue 132 is involved in substrate binding, as well as catalysis, and supports the involvement of this residue in acylation as suggested by Strynadka et al.

Crystallographic and computer modeling studies of RTEM-1 β-lactamase have indicated that Lys 73 and Glu 166, two strictly conserved residues among the class A β-lactamases, appear to be involved in substrate binding, catalysis, or both. To study the contribution of these residues to β-lactamase function, site saturation mutagenesis was used to generate mutants coding for all 20 amino acids at positions 73 and 166. Then all 400 possible combinations of mutants were created by combinatorial mutagenesis. The colonies harboring the mutants were screened for growth in the presence of ampicillin. The competent colonys' DNA were sequenced, and kinetic parameters investigated. It was found that lysine is essential at position 73, and that position 166 only tolerated fairly conservative changes (Aspartic acid, Histidine, and Tyrosine). These functional mutants exhibited decreased kcat's, but K_M was close to wild-type levels. The results of the combinatorial mutagenesis experiments indicate that Lysis absolutely required for activity at position 73; no mutation at residue 166 can compensate for loss of the long side chain amine. The active mutants found--K73K/E166D, K73KIE166H, and K73KIE166Y were studied by kinetic analysis. These results reaffirmed the function of residue 166 as important in catalysis, specifically deacylation.

The identity of the residue responsible for enhancing the active site serine (Ser 70) in RTEM-1 β-lactamase has been disputed for some time. Recently, analysis of a crystal structure of RTEM-1 β-lactamase with covalently bound intermediate was published, and it was suggested that Lys 73, a strictly conserved residue among the class A β-lactamases, was acting as a general base, activating Ser 70. For this to be possible, the pK_a of Lys 73 would have to be depressed significantly. In an attempt to assay the pK_a of Lys 73, the mutation K73C was made. This mutant protein can be reacted with 2-bromoethylamine, and activity is restored to near wild type levels. ^(15)N-2-bromoethylamine hydrobromide and ^(13)C-2-bromoethylamine hydrobromide were synthesized. Reacting these compounds with the K73C mutant gives stable isotopic enrichment at residue 73 in the form of aminoethylcysteine, a lysine homologue. The pK_a of an amine can be determined by NMR titration, following the change in chemical shift of either the ^(15)N-amine nuclei or adjacent Be nuclei as pH is changed. Unfortunately, low protein solubility, along with probable label scrambling in the Be experiment, did not permit direct observation of either the ^(15)N or ^(13)C signals. Indirect detection experiments were used to observe the protons bonded directly to the ^(13)C atoms. Two NMR signals were seen, and their chemical shift change with pH variation was noted. The peak which was determined to correspond to the aminoethylcysteine residue shifted from 3.2 ppm down to 2.8 ppm over a pH range of 6.6 to 12.5. The pK_a of the amine at position 73 was determined to be ~10. This indicates that residue 73 does not function as a general base in the acylation step of the reaction. However the experimental measurement takes place in the absence of substrate. Since the enzyme undergoes conformational changes upon substrate binding, the measured pK_a of the free enzyme may not correspond to the pK_a of the enzyme substrate complex.

Performance of Typha australis cut at three different heights

The response of Typha australis to stem cut at three different heights was studied for four weeks. This was carried out in the field between August and September 2003. Matured Typha australis naturally occuring along the stream within the Institute Integrated Fish Pond Complex, New Bussa were randomly selected. The shoots were cut at 10cm, 20cm, and 30cm, above the soil level. The responses of the plant were assessed. Plant cut at 10cm showed re-growth for one week and later died, while those cut at 20cm and 30cm showed re-growth through out the period of experiment. Result showed previous height between 10cm and 20cm is significant (P>0.05) between 10cm and 30cm height re-growth rates. But plant cut at 20cm and 30cm showed no significant (P>0.05), in height. The results show the susceptibility of Typha australis to stem cut at 10cm or below. Typha australis cut at 10cm above soil level are not likely to survival

超短激光脉冲的绝对相位对三能级Λ型原子布居的影响

通过数值求解含时薛定谔方程,研究超短激光脉冲与三能级Λ型原子相互作用过程中影响原子电离态跃迁几率的几个因素,如：绝对相位,啁啾率等。研究结果表明激光绝对相位、啁啾率的大小是关系态跃迁几率的重要因素,通过调节超短激光脉冲的绝对相位和啁啾率,可以将态跃迁几率控制到较大的水平。本文研究结果为实验上对态跃迁几率的控制提供了相关理论基础。

Internationaler Rotbarschsurvey auf den ozeanischen Sebastes mentella in der Irminger See unter isländischer, deutscher und russischer Beteiligung

A hydroacoustic survey on the oceanic redfish (oceanic Sebastes mentella) in the Irminger Sea and adjacent waters South and East of Greenland was carried out by Iceland, Germany and Russia. During this, about 250 000 nm2 were covered. The acoustic assessment yielded a stock size of approximately 1.6 x 10(6) tonnes or 2.6 x 10(9) individuals. This however, is considered to be an underestimation of the stock, as a result of partial mixing of the stock with the scattering layer. The oceanic redfish concentrations were densest at 200-300 m depth, mainly within temperatures of 3.5 °C to 5 °C. 61 % of the stock were males at an average length of 36 cm and an average weight of 582 g.

Deutsche und internationale Bestandsuntersuchungen an Heringen mit hydroakustischen Methoden

The international hydroacoustic herring survey in the North Sea is carried out since the early eighties with Dutch, Scottish, Danish und Norwegian contribution. Since 1994 Germany also participates in this survey on a regular basis and has taken over a sector in the easter part between the Dogger Bank and the Danish coast. This area is known for the abundance of chiefly juvenile herring and sprat. During the 1995 cruise some 420000 t of herring were found here, most of them being juveniles of age group I. Analyses of plankton hauls showed that planktonic echos were not caused by juvenile herring, instead the echos were apparently produced by small pelagic gastropodes of the genus Spiratella.

Über die Trogmuschel und deren Nutzung in der Deutschen Bucht

Obwohl seit längerem bekannt ist, dass diese wohlschmeckende Muschel in der Nordsee vorkommt, gab es dort bis vor wenigen Jahren keine Trogmuschelfischerei. Das änderte sich erst, als es niederländischen Muschelverarbeitungsfirmen gelungen war, aus Trogmuscheln ein exportfähiges Produkt herzustellen. Dementsprechend beantragte auch ein niederländischer Muschelfischerbetrieb als Erster eine erlaubnis zum Fischen von Trogmuscheln in deutschen Gewässern außerhalb von 3 Seemeilen. Inzwischen erhielten auch vier weitere Muschelkutter die Fangerlaubnis. Allerdings wird wegen der begrenzten Absatzmöglichkeiten nur zeitweilig gefischt. Deshalb sind bisher auch noch keine Anzeichen einer Überfischung zu sehen.

Lassen sich die Erträge der deutschen Schleppnetzfischerei auf Hering durch technische Maßnahmen verbessern?

Seitdem die wirtschaftlich wichtigen Rundfischbestände in der Nord- und Ostsee immer stärker zurückgehen, ist wiederholt eine Intensivierung der Heringsfischerei vorgeschlagen worden. Zur Begründung dieses Vorschlages wird angeführt, daß sich die Heringsbestände in einem relativ guten Zustand befinden und daß die Deutschland zugeteilten Heringsquoten bislang weitgehend unausgeschöpft geblieben sind. So betrug die deutsche Heringsquote beispielsweise 1990 in der Nordsee 50 000 t, gefangen wurden aber lediglich ca. 5OOO t. In neuester Zeit hat allerdings der Einsatz großer Schwarmfischfänger eine bessere Quotennutzung bewirkt.