Knelpunten in aquacultuur: enkele risicovolle aspecten van de vroege levensstadia van de vis = Bottlenecks in aquaculture: some risky aspects of early life stages of fish

Aquaculture is a fast growing sector. However, during larviculture and fish husbandry, many bottlenecks still occur. Many problems concern nutritional factors and can be avoided by a clear understanding of the development of the gastrointestinal system of the various fish species. Parameters, such as enterocyte height, the presence of enterocytic supranuclear vacuoles and ‘the point of no return’, can be used to monitor and prevent food deprivation. This information can also be used to compose a feeding regime with rotifers, Artemia and copepods

Macrolide resistance in porcine streptococci: a human health hazard?

In order to obtain better insights into the possible exchange of resistance genes between human and porcine streptococci, macrolide and lincosamide resistant streptococci from tonsillar and colon swabs from pigs and pork carcass swabs were isolated and their resistance phenotypes and genotypes were determined. The sequences of the erm(B) genes of 21 human streptococci, 22 porcine streptococci and 15 streptococci isolated from pork carcasses were compared. From each of the 33 pigs and from 88 of 99 carcass swabs, at least one resistant streptococcal strain was isolated. The predominant phenotype was the constitutively expressed MLSB phenotype, mostly encoded by the erm(B) gene. Identical erm(B) gene sequences were present in strains from humans, pigs and pork carcasses

Laboratory study of the impact of repetitive electrical and mechanical stimulation on brown shrimp Crangon crangon

Pulse trawling is currently the best available alternative to beam trawling in the brown shrimp Crangon crangon and Sole Solea solea (also known as Solea vulgaris) fisheries. To evaluate the effect of repetitive exposure to electrical fields, brown shrimp were exposed to the commercial electrodes and pulse settings used to catch brown shrimp (shrimp startle pulse) or Sole (Sole cramp pulse) 20 times in 4 d and monitored for up to 14 d after the first exposure. Survival, egg loss, molting, and the degree of intranuclear bacilliform virus (IBV) infection were evaluated and compared with those in stressed but not electrically exposed (procedural control) and nonstressed, nonexposed (control) brown shrimp as well as brown shrimp exposed to mechanical stimuli. The lowest survival at 14 d (57.3%) occurred in the Sole cramp pulse treatment, and this was significantly lower than in the group with the highest survival, the procedural control (70.3%). No effect of electrical stimulation on the severity of IBV infection was found. The lowest percentage of molts occurred in the repetitive mechanical stimulation treatment (14.0%), and this was significantly lower than in the group with the highest percentage of molts, the procedural control (21.7%). Additionally, the mechanically stimulated brown shrimp that died during the experiment had a significantly larger size than the surviving individuals. Finally, no effect of the shrimp startle pulse was found. Therefore, it can be concluded that repetitive exposure to a cramp stimulus and mechanical stimulation may have negative effects on the growth and/or survival of brown shrimp. However, there is no evidence that electrical stimulation during electrotrawls would have a larger negative impact on brown shrimp stocks than mechanical stimulation during conventional beam trawling