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The use of closed containment (CCS) or semi‐closed containment systems (S‐CCS) for Atlantic salmon Salmo salar aquaculture is under evaluation in Norway. One such system is the Preline S‐CCS, a floating raceway system that pumps water from 35 m depth creating a constant current through the system. Exposing fish to moderate water currents is considered aerobic exercise and it is often perceived as positive for fish welfare, growth, food utilization, muscle development and cardiac health. The present study compared fish reared in the Preline S‐CCS and in a reference open pen. Samples were taken in fresh water before being transferred to the seawater systems and after 1, 2 and 4 months in seawater and analysed for growth, mortality, muscle development and plasma insulin‐like growth factor I (IGF‐I) levels. Moreover, gene transcription were determined in the skeletal muscle [igf‐I, insulin‐like growth factor 1 receptor a (igf1ra) and insulin‐like growth factor 1 binding protein 1a (igf1bp1a)] and cardiac transcription factors [myocyte‐specific enhancer factor 2C (mef2c), gata4 and vascular endothelial growth factor (vegf)]. While the results suggest that post‐smolts in Preline S‐CCS were smaller than reference fish, fish from Preline S‐CCS have less accumulated mortality at the end of the experiment and showed 2.44 times more small muscle fibres than the reference group fish after 4 months in seawater. These results confirmed what was previously observed in the second generation of Preline. Similar levels of big muscle fibres between Preline S‐CCS and reference suggest a similar hypertrophy of muscle fibres even with lower IGF‐I expression in the Preline S‐CCS. Cardiac gene transcription suggests cardiac hypertrophy was observed after 4 months in seawater in the Preline S‐CCS group. Altogether, Preline S‐CCS is a promising technology able to produce more robust S. salar with a faster growth and lower mortality in the subsequent standard open cage system growth period. [ABSTRACT FROM AUTHOR]

Morphometry has been used in the investigation of the common shrimp Crangon crangon subpopulation structure at a local scale (100 km) around the UK. In the present study C. crangon populations were sampled over the whole distributional range from northern Norway to the Mediterranean and Black Sea to test whether the same method could be applied to describe subpopulation structure at a much larger scale (1000 km). Spatial variability in morphometric characters was determined by sampling 25 locations across the distributional range. In addition, the temporal variability in morphology was studied at 4 sites (Bodo, Norway; Wadden Sea, The Netherlands; Minho and Lima estuaries, Portugal). Contrary to expectations, temporal variability was observed in three of those sites resulting in an inability to distinguish between populations at the local scale. However, the large scale subdivision of shrimp populations from the Adriatic, Black Sea, Mediterranean and Atlantic were clearly identified. It is concluded that, while there are clear morphological differences between major zoogeographical zones, at a local scale, subpopulations frequently cannot be identified because of individual variability. [ABSTRACT FROM PUBLISHER]

Smoltification in salmonids occurs during spring in response to increasing photoperiod to prepare for marine life. Smoltification is associated with increased hypo-osmoregulatory ability and enhanced growth potential, mediated by growth hormone and insulin-like growth factor (IGF)-1. Rainbow trout is uniquely insensitive to the induction of smoltification-associated changes by photoperiod, such as the activation of gill Na + ,K + -ATPase (NKA). We measured the circulating IGF-1 and IGF-binding protein (IGFBP)-2b levels in yearling rainbow trout exposed to natural and manipulated photoperiods during spring and correlated these with gill NKA activity and body size. Although the effect of photoperiod manipulation on body size and circulating IGF-1 and IGFBP-2b was negligible, they were positively correlated with gill NKA activity in fish under simulated natural photoperiod. We next pit-tagged yearling rainbow trout and fed them a restricted ration or to satiation under a natural photoperiod. In April, gill NKA activity was higher in the satiation group than in the restricted group and positively correlated with body size and growth rate. In addition, circulating IGFBP-2b was positively correlated with gill NKA, size and growth, whereas circulating IGF-1 was correlated only with size and growth. The relationship between circulating IGF-1 and growth intensified from May to June, suggesting that the IGF-1-growth relationship was disrupted in April when gill NKA was activated. Two additional IGFBPs were related to growth parameters but not to gill NKA activity. The present study suggests that circulating IGFBP-2b and IGF-1 mediate the size-dependent activation of gill NKA in yearling rainbow trout during spring., (Copyright © 2022 Elsevier Inc. All rights reserved.)