Although aquaculture has been the fastest growing food sector for decades, there are no standardized parameters for most of the fish species regarding physical meat quality. Therefore, this study provides for the first time an overview of the physical meat characteristics of the most important fish species of the German Baltic Sea coast. Traditional farmed salmonids (rainbow trout (Oncorhynchus mykiss) and maraena whitefish (Coregonus maraena) as well as two percids (European perch, Perca fluviatilis and pikeperch, Sander lucioperca) were utilized for this comparison. The results demonstrate that the meat of the salmonids is very analogous. However, the post mortem degradation process starts faster in trout meat. In contrast, the meat quality characteristics of the percids are relatively different. The meat of pikeperch has comparatively low shear strength with a high water-holding capacity resulting in high meat tenderness. The opposite situation is present in European perch. The results indicate that it is not possible to establish the overall quality characteristics for fish or production form, as there is a high range of variability. Consequently, it is particularly important that meat quality characteristics are developed for important aquaculture species for further improvement through changes in husbandry conditions when necessary.

Three red cell populations have been distinguished in genotypically low potassium (LK) newborn sheep by an improved electrical sizing method and were best approximated by a logarithmic normal distribution. Labeling studies with 51Cr and 59Fe exclude transformation of the three red cell populations into each other. Population I, consisting of large red cells (mean volume 36 pm3), with a comparatively slow electrophoretic mobility is present a t birth and disappears within three to four weeks from circulation. These cells possess a high potassium (HK) steady state concentration, a K' pump influx activity at least 5-fold greater than observed in adult LK red cells, very low amounts of the L antigens generally associated with the LK property, and do not respond to the stimulatory action of the L antibody. The first population is gradually replaced by population I1 comprising small red cells (mean volume 28 pm3) of intermediate electrophoretic mobility and with a peak production around day 20 after birth. The potassium concentration, [K'l,, in these cells appears to be lower than in the cells of population I but the L antigen content is increased. Formation of population I11 (mean volume 30 pm3 and comparatively fast electrophoretic mobility) follows closely that of population I1 and is preceded by a sharp increase in reticulocytosis. The red cells of population I11 exhibit parameters characteristic for adult LK cells: low [K'I, and K' pump activity, fully developed L antigen content, and a n almost maximal response to the K' pump stimulating effect of anti-L. In L and M antigen positive LK red cells of newborn sheep, the development of the M antigen parallels that of the L antigen. The data are consistent with the hypothesis that cellular replacement and not maturation is the major factor in controlling the HK-LK transition in newborn sheep.The erythropoietic differentiation in mammals after birth is characterized by changes of various erythrocyte parameters. For example, red cells from newborn sheep have osmotic properties (Widdas, '511, cell volume (Riegel e t al., '61; Ullrey e t al., '65; Moore et al., '661, enzymes (Kornfeld e t al., '67), protein (Fesus and Rasmusen, '71) and hemoglobins (Moore e t al., '66; Huisman e t al., '69; Huisman, '74; Blunt and Huisman, '75) different from those found in red cells of adult animals. A basic question is whether these parameters change independently, each due to a different stimulus, or simultaneously at a given time induced by one stimulus. The concept of a simultaneous switch of several parameters implies the existence of several production programs or gene regulation patterns in the precursor cell which, according to the needs of the organism, are activated or repressed. The general interest in such a mechanism stems from hematopoietic disorders characterized by a n acute arrest or a deviation of differentiation.A simultaneous differentiation switch in the hematopoietic system during postnatal development is supported by several investigations on mammalian orga...

Pikeperch is a new focus species in freshwater aquaculture. It has large economical potential as it already has a broad consumer base as well as the biological capability to produce large numbers of offspring (Lappalainen et al., 2003;Steenfeldt et al., 2015). Still, it is rare in aquaculture, as high mortality rates occur during its rearing and husbandry (Policar et al., 2019). This is especially severe during the early development between embryonic and larval ontogeny. During this period, the loss of around half or more of the reared specimens can occur, which highly affects the economic success of pikeperch aquaculture (Ostaszewska et al., 2005;Szkudlarek & Zakęś, 2007).Several developmental changes occur during this time including late embryonic organ formation, hatching, the transition from endogenous to exogenous feeding and several organ changes connected to

Sander lucioperca is an organism of growing importance for the aquaculture industry.Nonetheless, the rearing of S. lucioperca larvae is proving to be a difficult task as it is facing a high mortality rate during hatching and the change to exogenous feeding. To gain insight into growth patterns during this period, the authors analysed pikeperch embryos and larvae from 9 days before hatching to 17 days after hatch. Hereby they were able to describe a natural development by using close to natural conditions based on using a direct flow-through supply of lake fresh water on specimens from a local wild population. The results show that between the early embryonic stages a steady growth was visible. Nonetheless, in between hatching and the start of exogenous feeding, a phase of growth stagnation took place. In the following larval stages, an increased growth with large size variations between individual specimens appeared. Both factors are conspicuous as they can indicate a starting point for cannibalism. With this analysis, the authors can provide a fundament to support the upcoming research on S. lucioperca and aid to optimize size-sorting procedures for a higher survival of pikeperch stock in aquaculture.