ALBERT

Beschreibung: Fütterungsversuche mit Regenbogenforellen zeigen: Magen-Darm-Bakterien von Raubfischen passen sich an vegetarische Nahrung an

Beschreibung: Highlights: • First feeding of wild brown trout fry with partial inclusion of dietary plant proteins is beneficial for subsequent growth • Feeding of 50% dietary plant protein results in same growth when compared to fishmeal as exclusive protein source • The early feeding of plant-based diets did not induce nutritional programming effects in first-feeding fry • Wild brown trout fry exhibit highly plastic responses to different feeding strategies during the first months of life • Pepsin and amylase activities are only partly affected by plant-derived protein sources and rather intrinsically regulated Abstract: Decreasing fishmeal availability and increasing prices promote the usage of plant-derived feedstuff as a substitution for fishmeal in commercial salmonid diets. However, little is known about the impact of plant-derived feedstuff on juvenile brown trout (Salmo trutta), a species that exhibits strong phenotypic plasticity with various genetic sub-structures and high overall genetic diversity. Thus, the production of brown trout for restocking purposes preferentially uses wild fish as broodstock to avoid loss of genetic variability. Because of nutritional programming, the strictly carnivorous feeding habit of wild brown trout broodfish could nevertheless have a negative impact on the digestive physiology of fry and fingerlings that are fed with commercial plant-protein containing trout diets. The present study, therefore, investigated whether the feeding of plant-based diets from first feeding onwards induced a permanent improvement in the utilisation of plant-derived protein sources in wild brown trout juveniles. Any plastic responses to the experimental diets resulting in a long-term physiological effect were hypothesised to be not only observed in growth performance, but also in altered pepsin and amylase activities. We demonstrated that (i) the feeding of wild brown trout fry with inclusion levels of up to 50% of dietary plant proteins is beneficial during the first weeks of life and (ii) continuous feeding of at least 50% plant-derived dietary protein resulted in the same rate of growth when compared to the growth resulting from fishmeal as the exclusive dietary protein source. Pepsin and amylase activities were only partly affected by diet-type and it can be concluded that intestinal pepsin and amylase activities in juvenile brown trout are primarily regulated by intrinsic mechanisms. In the present experiment, we were not able to induce a permanent nutritional programming effect of the first feeding diet; instead, a cross-over diet change applied 89 days post first feeding demonstrated that wild brown trout fry exhibit highly plastic responses to different feeding strategies during the first months of life.

Beschreibung: Ohne das Meer gäbe es kein Leben auf unserem Planeten. Es regelt weitgehend das Klima, gibt uns Nahrung und liefert Energie. Darüber hinaus ist es ein wichtiger Verkehrsweg, ein Erholungsraum und ein Quell ästhetischen Vergnügens. Aber das Meer steht unter Stress, denn das alte Prinzip von der „Freiheit der Meere“ hat zu Überfischung, Artenverlust und einer immensen Verschmutzung der Ozeane geführt. Deshalb muss der Umgang mit dem Meer auf nachhaltige und gerechte Grundlagen gestellt werden. Der Meeresatlas 2017 liefert dazu die Daten, Fakten und Zusammenhänge. Er zeigt in zahlreichen Beiträgen und über 50 Grafiken, in welch schlechtem Zustand sich die Weltmeere befinden, warum das so ist und was man tun muss, um die Situation der Ozeane zu verbessern.

Beschreibung: Plant-derived protein sources are the most relevant substitutes for fishmeal in aquafeeds. Nevertheless, the effects of plant based diets on the intestinal microbiome especially of juvenile Rainbow trout (Oncorhynchus mykiss) are yet to be fully investigated. The present study demonstrates, based on 16S rDNA bacterial community profiling, that the intestinal microbiome of juvenile Rainbow trout is strongly affected by dietary plant protein inclusion levels. After first feeding of juveniles with either 0%, 50% or 97% of total dietary protein content derived from plants, statistically significant differences of the bacterial gut community for the three diet-types were detected, both at phylum and order level. The microbiome of juvenile fish consisted mainly of the phyla Proteobacteria, Firmicutes, Bacteroidetes, Fusobacteria and Actinobacteria, and thus fits the salmonid core microbiome suggested in previous studies. Dietary plant proteins significantly enhanced the relative abundance of the orders Lactobacillales, Bacillales and Pseudomonadales. Animal proteins in contrast significantly promoted Bacteroidales, Clostridiales, Vibrionales, Fusobacteriales and Alteromonadales. The overall alpha diversity significantly decreased with increasing plant protein inclusion levels and with age of experimental animals. In order to investigate permanent effects of the first feeding diet-type on the early development of the microbiome, a diet change was included in the study after 54 days, but no such effects could be detected. Instead, the microbiome of juvenile trout fry was highly dependent on the actual diet fed at the time of sampling.

Beschreibung: Fish - Food and livelihood for a growing world population, industrial sector and finite resource. One quarter of all known edible fish are considered overfished. For this reason, researchers at Kiel University and GEOMAR Helmholtz Centre for Ocean Research Kiel are looking at the resource fish from a wide variety of perspectives. Their common goal: finding new approaches to environmentally sound fisheries management. Kiel biologists, economists and legal experts are working closely together in the Cluster of Excellence "The Future Ocean" toward this goal.

Beschreibung: In marine recirculating aquaculture systems (RAS) ozone is often used in combination with biofiltration for the improvement of process water quality. Especially for disinfection purposes ozone residuals are required, that lead to a fast formation of secondary oxidants in seawater, summed up as ozone-produced oxidants (OPO). We studied the impact of OPO on nitrifying biofilter bacteria in a series of laboratory batch experiments by exposing (i) cell suspensions of the ammonia-oxidizing bacteria (AOB) Nitrosomonas marina strain 22 and the nitrite-oxidizing bacteria (NOB) Nitrospira strain Ecomares 2.1, (ii) a pure culture of the NOB Nitrospira strain immobilized on biocarriers, as well as (iii) a heterogeneous biofilm culture settled on biocarriers from a marine RAS for 1 h to different OPO concentrations up to 0.6 mg/l chlorine equivalent. Subsequent activity tests detected a negative linear correlation between OPO concentration and nitrifying activity of suspended pure cultures. Immobilization on biocarriers increased the tolerance of AOB and NOB dramatically, suggesting the biofilm matrix to be highly protective against OPO. Furthermore, we investigated the chronic effect of moderate ozonation at OPO concentrations of 0, 0.05, 0.10 and 0.15 mg/l chlorine equivalent on biofilter performance in a 21 d exposure experiment using 12 experimental RAS, stocked with tilapia (Oreochromis niloticus). Chronic exposure experiments could not reveal any harmful impact on biofilter performance for OPO concentrations up to 0.15 mg/l, even at continuous exposure. Surprisingly, nitrifying activity was enhanced at all OPO concentrations compared to the control without ozonation, suggesting moderate ozonation to promote biological nitrification. It can be concluded that rather health, welfare and performance of most cultivated fish species are the limiting factors for ozone dosage than nitrification performance of biofilters. The results may further have practical implications in relation to design and operational strategy of water treatment processes in RAS and might thus contribute to the optimization of an effective and safe treatment combination of biofiltration and ozonation

Beschreibung: The aim of the present study was to investigate the impact of dietary plant proteins on the gut microbiome of first feeding brown trout (Salmo trutta) reproduced from wild stocks and to evaluate whether the initial microbiome of brown trout fry can be permanently manipulated by the first feeding diet. Therefore, brown trout fry was fed diets based on either 0%, 50% or 90% plant-derived proteins from first feeding onwards and via 16S rRNA gene sequencing a strong dietary influence on the bacterial gut community on phylum and order level was detected. Proteobacteria and Fusobacteria were significantly enhanced when fishmeal was integrated into the experimental diet, whereas plant-derived proteins significantly promoted Firmicutes and Bacteroidetes. In order to evaluate whether the first feeding diet had a permanent effect on the initially established microbial gut community of juvenile brown trout, a cross-over diet-change was applied 61 days post first feeding. 48 days after the diet-change, the gut microbiome of all dietary groups was significantly different from the one initially established after first feeding. Moreover, the first feeding diet had no statistically significant influence on the gut microbiome after the diet-change, demonstrating no permanent effect on the gut microbiome formation.