University of Bergen

About: University of Bergen is a education organization based out in Bergen, Hordaland, Norway. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 17106 authors who have published 52492 publications receiving 2009844 citations. The organization is also known as: Universitetet i Bergen & Universitas Bergensis.

Feeding behaviour and digestive physiology in larval fish: current knowledge, and gaps and bottlenecks in research

Abstract: Food uptake follows rules defined by feeding behaviour that determines the kind and quantity of food ingested by fish larvae as well as how live prey and food particles are detected, captured and ingested. Feeding success depends on the progressive development of anatomical characteristics and physiological functions and on the availability of suitable food items throughout larval development. The fish larval stages present eco-morpho-physiological features very different from adults and differ from one species to another. The organoleptic properties, dimensions, detectability, movements characteristics and buoyancy of food items are all crucial features that should be considered, but is often ignored, in feeding regimes. Ontogenetic changes in digestive function lead to limitations in the ability to process certain feedstuffs. There is still a lack of knowledge about the digestion and absorption of various nutrients and about the ontogeny of basic physiological mechanisms in fish larvae, including how they are affected by genetic, dietary and environmental factors. The neural and hormonal regulation of the digestive process and of appetite is critical for optimizing digestion. These processes are still poorly described in fish larvae and attempts to develop optimal feeding regimes are often still on a ‘trial and error’ basis. A holistic understanding of feeding ecology and digestive functions is important for designing diets for fish larvae and the adaptation of rearing conditions to meet requirements for the best presentation of prey and microdiets, and their optimal ingestion, digestion and absorption. More research that targets gaps in our knowledge should advance larval rearing.

Viruses as partners in spring bloom microbial trophodynamics.

Abstract: Population sizes of algae, bacteria, heterotrophic flagellates, and viruses were observed through the 1989 spring diatom bloom in Raunefjorden in western Norway. The culmination of the diatom bloom was followed by a peak in the concentration of bacteria and an increase in the concentration of heterotrophic flagellates, a pattern consistent with the concept of a food chain from photosynthetically produced organic material, through bacteria, to bacterivorous flagellates. The concentration of viruses varied through the spring bloom from 5 x 10 in the prebloom situation to a maximum of 1.3 x 10 viruses ml 1 week after the peak of the diatom bloom. Coinciding with the collapse in the diatom bloom, a succession of bacteria and viruses was observed in the mucous layer surrounding dead or senescent diatoms, with an estimated maximum of 23% of the total virus population attached to the diatoms. The dynamic behavior observed for the virus population rules out the possibility that it is dominated by inactive species, and the viruses are suggested to be active members of the microbial food web as agents causing lysis in parts of the bacterial population, diverting part of the bacterial production from the predatory food chain.

Note on breather type solutions of the nls as models for freak-waves

Abstract: Some breather type solutions of the NLS equation have been suggested by Henderson et al (to appear in Wave Motion) as models for a class of 'freak' wave events seen in 2D-simulations on surface gravity waves. In this paper we first take a closer look on these simple solutions and compare them with some of the simulation data (Henderson et al to appear in Wave Motion). Our findings tend to strengthen the idea of Henderson et al. Especially the Ma breather and the so called Peregrine solution may provide useful and simple analytical models for 'freak' wave events.