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Total protein levels in fish are widely used in health and welfare studies, providing a simple and accessible measure. However, the multifaceted role of blood proteins makes it sometimes challenging to link total protein content to specific health issues, while specific protein fractions may offer more precise insights into fish biology and health, particularly in farmed fish species where such data is often lacking. Data were gathered from two experiments involving Dicentrarchus labrax and Sparus aurata, key species in European marine aquaculture. The aim was (1) to assess how different globulin fractions contribute to total protein content in blood and (2) how these contributions vary across different sampling times in healthy animals. In D. labrax, the beta1 globulin fraction emerged as the major contributor (34.16%), followed by albumin and alpha2 globulins (18.24% and 16.41%, respectively). In contrast, pre-albumins and alpha1 fractions had the least contribution (5.49% and 7.71%). S. aurata exhibited albumin as the primary contributor (23.39%), followed by beta1 and alpha2 globulins (19.71% and 19.15%, respectively), with gamma and alpha1 fractions contributing the least (5.34% and 8.63%). Notably, the study revealed relatively stable contributions of globulin fractions to total proteins within both species, albeit with minor variations over time, potentially linked to environmental and individual factors. Furthermore, larger fish displayed higher total protein levels. This research underscores the need for further investigation into the diverse factors influencing globulin contributions to total proteins, ultimately enhancing health and welfare monitoring for farmed fish species., (© 2024. The Author(s).)

The large use of fish meal/fish oil in carnivorous fish feeds is the main concern regarding environmental sustainability of aquaculture. Here, we evaluated the effects of an innovative diet, designed to be (1) environmentally sustainable by lowering the marine protein content while being (2) cost effective by using sustainable alternative raw materials with acceptable cost and produced on an industrial scale, on growth performance, gut microbiota composition, health and welfare of European sea bass (Dicentrarchus labrax), a key species of the Mediterranean marine aquaculture, reared in sea cages. Results show that the specific growth rate of fish fed the low marine protein diet was significantly lower than those fed conventional diet (0.67% vs 0.69%). Fatty acid profile of fillets from fish fed a low marine protein diet presented significant lower n-6 and higher n-3 content when compared to conventional ones. Then, a significant increase in the abundance of Vibrio and reduction of Photobacterium were found in the gut of fish fed with the low marine protein diet but effects on sea bass health needs further investigation. Finally, no major health and welfare alterations for fish fed the low marine protein diet were observed, combined with a potential slight benefit related to humoral immunity. Overall, these results suggest that despite the low marine protein diet moderately affects growth performance, it nevertheless may enhance environmental and economic sustainability of the sea bass aquaculture., (© 2023. The Author(s).)

The redclaw crayfish (Cherax quadricarinatus) is a freshwater decapod crustacean, cultured in numerous countries worldwide for both food and ornamental purposes. Redclaw crayfish has become an important aquaculture species due to its physical and biological traits, relatively easy breeding, and a short growing-out period to reach commercial size. Bacterial infections are the second-most studied pathogens of freshwater crayfish. However, redclaw crayfish rickettsiosis, caused by Coxiella cheraxi, was reported in only a few scientific papers in the early 2000s, in Australia and Ecuador. Coxiella cheraxi is a rod-shaped intracellular bacterium that can cause mortality of 22%-80% in naturally infected crayfish. In experimental infections, mortality rates may be even higher (40%-90%). Coxiella cheraxi is closely related to Coxiella burnetii, the agent of Q-fever, which affects ruminants (goats, sheep, and cattle) and occasionally may cause zoonotic infections. According to the scientific knowledge available, C. cheraxi is a species-specific pathogen because it has been only detected in Cherax quadricarinatus and thus far, there is no evidence of a zoonotic potential. In this study, we describe an outbreak of rickettsiosis in a batch of redclaw crayfish imported to Israel from an Australian hatchery, observed 2 months after introduction in a quarantine facility. Initial mortality was evaluated through histopathology, revealing infection by rickettsia-like organisms (RLO) that were subsequently investigated by molecular analysis and transmission electron microscopy examination. Phylogenetic analysis revealed that the detected RLO were closely related to C. cheraxi from a single source (Australian strain TO98), available in free publicly accessible databases. After 5 months in quarantine, almost 99% of the crayfish population had died. Our findings raise valuable questions related to aquatic animal trade and the importance of mitigation measures, such as quarantine and routine diagnostic procedures, to limit the spread of infectious diseases., (© 2021 Wiley-VCH GmbH.)