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.

Rising temperatures can affect fish survival, especially from shallower waters, as temperatures increase faster and more intensively in these areas; thus, species-specific temperature tolerance can be exceeded. Additionally, the amounts of anthropogenic pollutants are higher in coastal waters. Although increasing metabolic activity at higher temperatures could lead to stronger effects of toxins, there are hardly any studies on this topic. Subsequently, the aim was to investigate the response of fish cells upon exposure to industrial solvents (ethanol, isopropanol, dimethyl sulfoxide (DMSO)) in relation to a temperature increase (20 °C and 25 °C). Concerning the 3Rs (the replacement, reduction and refinement of animal experiments), in vitro tests were used for two threatened, vulnerable fish species: maraena whitefish (Coregonus maraena) and Atlantic sturgeon (Acipenser oxyrinchus). Both cell lines exhibited higher proliferation at 25 °C. However, ecotoxicological results indicated significant differences regarding the cell line, toxin, temperature and exposure time. The evolutionarily older fish lineage, Atlantic sturgeon, demonstrated lower mortality rates in the presence of isopropanol and recovered better during long-term ethanol exposure than the maraena whitefish. Atlantic sturgeon cells have higher adaptation potential for these alcohols. In summary, fish species respond very specifically to toxins and changes in temperature, and new ecotoxicological questions arise with increasing water temperatures.

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.

Pikeperch (Sander lucioperca) is a freshwater fish that has become increasingly popular as a food fish. Within this study, the influence of the spawning process on meat quality was investigated. For this purpose, adult pikeperch was examined directly before and after spawning, and compared regarding physical meat parameters and lipid composition. The results indicate that after spawning, the values of the pH, the electrical conductivity and the yellowness value of fillet were significantly higher than those of the animals sampled before spawning. Analysis of the sum of the total lipid content indicates no differences before and after closed season, but differences in the fatty acid profile were present. Despite significant lower MUFA concentrations, the EPA and DHA showed unaffected high contents. Therefore, the fish muscle indicated an equivalent meat quality. Nevertheless, the significant changes of some physical meat quality parameters after spawning season could have a particular impact on the shelf life and storage of the pikeperch fillet, highlighting the need for further research.

Size differences are common in the aquaculture of fishes. In the larviculture of cannibalistic species such as pikeperch, they majorly influence mortality rates and consequently provoke losses in the aquaculture industry. With this study, we aim to reveal molecular differences between small and large pikeperch of the same age using a set of 20 genes associated with essential developmental processes. Hereby, we applied a general study design to early and late larval pikeperch before the onset of piscivory to explore the causes of growth differences in these developmental groups. The analysis of the expression levels showed developmental but not size-related differences in PGC1A, TGFB1, MYOD1, MRF4, and the collagens COL1A1 and COL1A2. Furthermore, increased head lengths were found in larger late larvae compared to their smaller conspecifics. While no uniquely size-related expression differences were found, the expression patterns of PGC1A in combination with TGFB1 as regulators of the citric acid cycle indicate a possible influence of mitochondrial energy metabolism. Furthermore, expression differences of MYOD1 and MRF4 point out possible temporal advantages of myogenetic processes in the larger late larval group and hypothesise growth advantages of the larger late larvae resulting from various influences, which provide a promising target for future research.