Fresh aquaculture sludge management with black soldier fly (Hermetia illucens L.) larvae: investigation on bioconversion performances.

Aquaculture solid waste (ASW) is a nutrient rich material that can pose a significant environment challenge if not properly managed. This study investigated the potential of black soldier fly (BSF) larvae in converting this waste into biomass. Five substrates comprising chicken feed supplemented with varying proportions of fresh ASW (0%, 25%, 50%, 75%, 100%) were formulated and evaluated for larval growth and waste bioconversion efficiency. High nutrients retention (N: 23.25 ± 1.40%; C: 21.94 ± 0.99%; S: 12.20 ± 1.33%) and feed conversion ratio (1.78 ± 0.08) were detected on substrate 100ASW, although the limited feeding rate (114.54 ± 5.38 mg dry substrate/larvae) and the high amount of indigestible fibres (ADF = 15.87 ± 0.24%; ADL = 6.36 ± 0.17%) were translated to low larval growth (final larval average weight: 66.17 ± 1.81 mg). Decreasing ASW content resulted in reduced fibres and ash, increase in non-fibrous carbohydrates and C/N ratio, and improved larval growth and substrate utilization. However, high larval metabolic activity suggested higher nutrients loss to the environment. Substrate 75ASW demonstrated the best performances in terms of larval production (final larval average weight: 176.30 ± 12.12 mg), waste reduction (substrate reduction corrected by percentage of ASW: 26.76 ± 0.86%) and nutrients assimilation (N: 22.14 ± 1.14%; C: 15.29 ± 0.82%; S: 15.40 ± 0.99%). This substrate closely aligned with optimal BSF rearing substrates reported in literature. Overall, this study highlights the potential of BSF larvae in managing fresh ASW, offering a dual benefit of waste reduction and insect biomass production.

Pike-Perch (Sander lucioperca) and Rainbow Trout (Oncorhynchus mykiss) Fed with an Alternative Microorganism Mix for Reducing Fish Meal and Oil-Fishes' Growth Performances and Quality Traits.

In the last decades, several plant-based materials were used for the substitution of fish meal and oil in aquaculture. The present study evaluated the fish quality and the sensory differences of rainbow trout (Oncorhynchus mykiss) and pike-perch (Sander lucioperca) from three different feeding groups, which were fed a commercially available industrial (standard) diet, a control diet, and a special microorganism-based feed mix. This feed mainly consisted of a mix made of Rhodotorula glutinis, Crypthecodinium cohnii, and Arthrospira sp. and had 50% less fish meal and fish oil compared to typical control diets. At the beginning, the pike-perch population was six months old, and the rainbow trout population was 15 months old. The feeding study duration was 16 weeks and every four weeks the growth performance and several morphometric parameters were recorded. Afterwards, sensory evaluation took place to identify possible trends. Sensory evaluation revealed that the rainbow trout groups did not show any significant differences to the standard and control fish fillets with regard to odor, texture, and taste. The effects on rainbow trout growth performances and carcass parameters were similar to the standard group. The feed mix was not optimal for pike-perch farming, which was also reflected by significantly adversely affected growth performance and carcass parameters. The sensorial evaluation showed an opposite trend: here, only small differences in the fillets from the feed mix and standard/control diet were observed.

HBCD stereoisomer pattern in mirror carps following dietary exposure to pure gamma-HBCD enantiomers.

1,2,5,6,9,10-hexabromocyclododecane (HBCD) is a brominated flame retardant consisting of a mixture of diastereomeric pairs of enantiomers that is a known omnipresent, environmental contaminant. The present study investigated the possibility of bioisomerization of HBCD stereoisomers. Therefore, mirror carps (Cyprinus carpio morpha noblis) were exposed to pure (+)- and (-)-gamma-HBCD, randomly sampled biweekly over a period of three and a half months and the fillets were subjected to enantiomer-specific determination of HBCD. Considering the background contamination of the fish at the beginning of the feeding period, significant enrichment of the respectively fed gamma-enantiomer was already detectable after two weeks of exposure. However, no significant enrichment of the respectively expected alpha-enantiomer was observed within this period. Thus, no evidence for the isomerization of HBCD stereoisomers was found in mirror carp under the applied conditions.