Effect of broodstock holding environment on egg quality in farmed brown trout (Salmo trutta)

Figueroa

et al. 2021

Animals

The chorion is the primary envelop that protects the fish embryo against mechanical actions, pathogens, and abrupt changes in physical and chemicals conditions of the incubation medium. During embryo development, chorion alterations are not rare, but the occurrence of these is scarcely reported. Increased frequency of chorion alterations can result in increased embryo mortality and thus decreased reproductive performance and losses for fish farms. In this study, we characterize different chorion alterations observed in samples collected over 14 years from 12 salmon and trout farms located in the region of La Araucanía in southern Chile, which sent live eyed-stage embryos (‘eyed-eggs’) for quality analysis to our laboratory. We found soft chorion as the most common alteration observed, being present in the whole 14-year series analyzed in Atlantic Salmon (Salmo salar) and affecting up to 35.0% of the samples examined in a year. This alteration also affected up to 20.0 and 5.7% of Coho Salmon (Oncorhynchus kisutch) and Rainbow Trout (Oncorhynchus mykiss) samples analyzed in a year, respectively. We also found an increase of other chorion alterations, including perforated and white-spotted chorion in Atlantic and Coho Salmon, in the last 8 years. Among the three species, Rainbow Trout exhibited fewer chorion alterations. As the embryonated eggs analyzed here were obtained from broodstocks maintained under standard industrial conditions, these alterations might be linked to changes in environmental conditions affecting the incubation water that need to be further investigated.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Chorion Alterations in Eyed-Stage Salmonid Eggs Farmed in La Araucanía, Chile: A Retrospective Study

Figueroa

et al. 2021

Animals

Aquaculture Fish & Fisheries

Characterisation of Fatty Acid Profiles in Tasmanian Atlantic Salmon Muscle, Oocytes and Eggs in Differing Fully Commercial Settings

Svendsgaard,

Zhan,

Adams

et al. 2024

Tasmanian Atlantic salmon broodstock may be conditioned in flow‐through (FT) systems where water quality fluctuates and temperatures approach their upper limit of thermal tolerance, or in recirculating aquaculture systems (RAS) where conditions are comparatively cool and stable. The impact of broad conditioning approach on the molecular cargo of salmon eggs has never been explored in dynamic commercial settings. Therefore, this study aimed to characterise the reproductive features of broodstock conditioned using different commercial approaches and determine whether the fatty acid (FA) profiles of muscle, oocytes and eggs varied between groups during vitellogenesis and at stripping. The collective conditioning approach had a marked impact on the somatic and reproductive dynamics of female salmon broodstock, and the eggs produced by each group of fish were fundamentally different in terms of their FA composition. Of particular note is the increased maternal investment of saturated FAs (mg.g−1) and monounsaturated FAs (percent and mg.g−1) by FT‐based eggs, and the higher n3 polyunsaturated FA (percent and mg.g−1), docosahexaenoic acid (DHA, percent and mg.g−1), arachidonic acid (ARA, percent), eicosapentaenoic acid (EPA, percent), n3:n6 ratio and ARA:EPA ratio of RAS‐based eggs. These metrics combined with the apparently higher prevalence of neural development and survival of RAS embryos suggest that RAS eggs were of higher quality. On the other hand, there is evidence to suggest that FT broodstock attempt to prepare their offspring for a (presumably) challenging early life environment by producing larger eggs that are proportionally rich in short‐chain FAs and contain a higher total quantity of FAs per egg.

Assessment, causes and consequences of short opercula in laboratory-reared Atlantic salmon (Salmo salar)

Blaker¹,

Ellis²

2022

Anim. welf.

Opercular deformity is a common morphological abnormality of laboratory and other cultured fishes, observed in a wide variety of species but with an unclear aetiology. Following observations of short opercula in stocks of Atlantic salmon (Salmo salar) reared in our laboratory, we developed a photographic key to score individual fish on a scale of 1 to 5. Inter-rater reliability was assessed as 'almost perfect'. This visual method is quick and simple to use, can be used to score live fish in situ in tanks as well as sampled fish, does not require sophisticated equipment and provides quantitative information to investigate the aetiology of short opercula. Opercular size was scored for a cohort of in-house reared Atlantic salmon, in a time series of random samples of ≥ 30 fish (mean weights ranging from 0.8 to 299 g) over 14 months. Short opercula were first recorded during the parr stage, prevalence and severity increased as the fish grew, and the deformity was asymmetrical, occurring predominantly on the left side. Therefore, among the many potential causal factors, nipping is suggested as the primary cause of short opercula within our culture system, with asymmetry due to the clockwise current. We also present evidence that short opercula are associated with gill damage which supports this deformity being a welfare issue that merits assessment.