Trenngitter - eine Alternative zu den Trichternetzen in der Garnelenfischerei

Experimental fishing trials were conducted in the Elbe Estuary using an experimental 3 m-standard beamtrawl. To avoid the by-catch of fish, a sorting grid was used. The elliptical grid was constructed of 6 mm diameter stainless steel bars with a spacing of 13 mm between the bars and housed in a cylindrical frame of 400 mm diameter. It was installed in the extension piece just in front of the codend angled at 45°, with a fish outlet at the top. A series of 10 tows of 15 minutes duration at a towing speed of 3 kn was done. The catch of the main codend was compared with the catch separated by the sorting grid. This achieved a reduction of 56 % of plaice (Pleuronectes platessa), 75 % of flounder (Platichthys flesus), 99 % of whiting (Merlangius merlangus), 94 % of cod (Gadus morhua) and 49 % of smelt (Osmerus eperlanus) with a mean loss of 43 % of shrimps (Crangon crangon). English grid trials in the Humber estuary using a flapper set or guiding funnel in front of the sorting grid device demonstrated reasonable lower escapement rates for fish and shrimps.

Evaluation of two alternative carbon capture and storage technologies

4 p.

Alternative trajectories for decarbonizing urban transportation

4 p.

Precipitation of nanocrystals in glasses by electron irradiation: An alternative path to form glass ceramics?

This letter demonstrates an alternative method to form gallium silicate glass ceramics using high-energy electron irradiation. Compared with glass ceramics obtained from the conventional thermal treatment method, the distribution and crystal sizes of the precipitated Ga2O3 nanoparticles are the same. An advantage of this method is that the spatial distribution of the precipitated nanoparticles can be easily controlled. However, optically active dopants Ni2+ ions do not participate in the precipitation during electron irradiation. (c) 2007 American Institute of Physics.

Evaluation of Two Alternative Carbon Capture and Storage Technologies: A Stochastic Model

30 p.

The lakes of Michoacan (Mexico): A brief history and alternative point of view

This article is intended to open a discussion about the historical development of lakes Zirahuen, Patzcuaro and Cuitzeo in the state of Michoacan, and the postulated relationships between lake ecology and evolution. Dr Fernando De Buen was the first man dedicated to limnology in Mexico who came to the country in the 1930s. He was adviser at the Estacion Limnologica de Patzcuaro and wrote outstanding papers dealing with Mexican lakes. The lakes of Michoacan probably formed in the late Pliocene or Holocene, and were part of a tributary to the Lerma River, which became isolated by successive volanic barriers to form lake basins. Lake Zirahuen is a warm monomictic waterbody with unique water dynamics amongst the Michoacan lakes. Because it is relatively deep (max depth 40m), seasonal patterns of alternating circulation and thermal stratification develop in the lake, a feature not shared by the other two polymictic shallow lakes, Patzcuaro and Cuitzeo.

An alternative management strategy for Lake Victoria (Kenya)

In Kenya, fisheries resource management has been based on the top-down centralized approach since the colonial days. Stakeholders have never been consulted concerning management decisions. The 4-beaches Study was undertaken to investigate the potential for an alternative management system for Lake Victoria.

Transparent colloid containing upconverting nanocrystals: An alternative medium for three-dimensional volumetric display

We report an alternative medium of transparent upconverting colloid containing lanthanide ion doped NaYF4 nanocrystals for three-dimensional (3D) volumetric display. The colloids exhibit tunable upconversion luminescence with a wide spectrum of colors by adjusting the doping concentrations of the nanocrystals and the compositions of the colloids. Our preliminary experimental result indicates that an upconverting colloid-based 3D volumetric display using a convergent, near infrared laser beam to induce a localized luminescent spot near the focus is technically feasible. Therefore arbitrary 3D objects can be created inside the upconverting colloid by use of computer controlled 3D scanning systems. (C) 2008 Optical Society of America

Age and growth of spiny dogfish (Squalus acanthias) in the Gulf of Alaska: analysis of alternative growth models

Ten growth models were fitted to age and growth data for spiny dogfish (Squalus acanthias) in the Gulf of Alaska. Previous studies of spiny dogfish growth have all fitted the t0 formulation of the von Bertalanffy model without examination of alternative models. Among the alternatives, we present a new two-phase von Bertalanffy growth model formulation with a logistically scaled k parameter and which estimates L0. A total of 1602 dogfish were aged from opportunistic collections with longline, rod and reel, set net, and trawling gear in the eastern and central Gulf of Alaska between 2004 and 2007. Ages were estimated from the median band count of three independent readings of the second dorsal spine plus the estimated number of worn bands for worn spines. Owing to a lack of small dogfish in the samples, lengths at age of small individuals were back-calculated from a subsample of 153 dogfish with unworn spines. The von Bertalanffy, two-parameter von Bertalanffy, two-phase von Bertalanffy, Gompertz, two-parameter Gompertz, and logistic models were fitted to length-at-age data for each sex separately, both with and without back-calculated lengths at age. The two-phase von Bertalanffy growth model produced the statistically best fit for both sexes of Gulf of Alaska spiny dogfish, resulting in L∞ = 87.2 and 102.5 cm and k= 0.106 and 0.058 for males and females, respectively.

A survey of ichthyofauna of Lake Kanyaboli and other small waterbodies in Kenya: alternative refugia for endangered fish species

In 1988, the World Conservation Union (WCU) Red Book of Endangered Species listed hundreds of endemic fishes of Lake Victoria under a single heading - "ENDANGERED". Most of the endemic native food fishes are either endangered or extinct. However, a survey of the fauna of Lake Kanyaboli, revealed that a few remaining samples of these native fishes are actually thriving. These include several unidentified Haplochromis spp., Oreochromis esculentus and Oreochromis variabilis. As a result, a stock rehabilitation and management strategy has been designed to use Lake Kanyaboli and other small waterbodies as conservation 'Refugia' for endangered fish species of the larger Lake Victoria.

Pen fish culture in reservoirs: an alternative to land based nurseries

An experiment to rear carp seed was conducted in Tamil Nadu, India during October 2001 to April 2002 as a part of an ambitious programme aimed at standardization of pen fish rearing technology for production of stocking material of desired size at a lower cost. The experiment used six pens erected using locally available materials in the exposed marginal area of an existing reservoir. The high survival rate of carps (67.2-94.7%) and reasonable returns on investment (26.2%) obtained in the experiment indicated that fish seed rearing in pens erected in suitable areas of existing reservoirs could serve as a cheaper alternative to the expensive land-based nursery ponds.