Investigation of growth performance of post-smolt Atlantic salmon (Salmo salar L.) in semi closed containment system: A big-scale benchmark study

The Norwegian salmon industry faces challenges related to sea lice (Lepeophtheirus salmonis) infestations, escapees, diseases and environmental impact. Semi-closed containment systems (S-CCS) have been proposed to abate these challenges. In the S-CCS, cultured fish are separated from the natural environment by a physical barrier, reducing the time fish spend in open sea cages. Production data from six cohorts of salmon were used to compare growth and performance of fish raised in S-CCS and in open sea cages (control group) incorporating different seasons. The study was carried out in two phases. Phase one used post-smolts from approximately 100 to 800 g in seawater, and fish in S-CCS were compared with a reference group from an open sea cage. The second, grow-out phase covered the size range from approximately 800 to 5000 g in open sea cages; here fish previously reared in S-CCS were compared with fish from a control group. The study showed a significantly lower infestation of sea lice in S-CCS (0.02–0.04) fish compared with the control group (0.18–0.62) during the post-smolt phase. Furthermore, in the grow-out phase the S-CCS group showed higher growth rate and higher final weight (4680 g [spring], 4890 g [fall]) for the S-CCS group compared with the control group (3800 g [spring] and 4080 g [fall]). Salmon raised in S-CCS showed significantly higher survival compared with the control group in open pens, indicating increased resilience in fish raised in S-CCS when transferred to open net pens in sea. It is concluded that S-CCS have advantages compared with exposure to the natural environment in open pens in western Norway.publishedVersio

Interaction of temperature and photoperiod on male postsmolt maturation of Atlantic salmon (Salmo salar L.)

Maturation of Atlantic salmon male postsmolts is a concern in aquaculture due to its increasing occurrence under intensive rearing conditions and its negative impact on growth, welfare and seawater readiness. The effect of temperature and photoperiod on maturation was assessed in male postsmolts kept in freshwater. We used a 2 × 2 factorial design with two temperatures (12.5 and 15 °C) and two photoperiods (a group in continuous light LD24:0 or LL, and another receiving a 5-week LD12:12 winter signal or WS). Salmon in the four resulting treatments (1000 parr, initial mean weight 52.1 ± 5.2 g) were reared in a flow-through system from 28 October 2019 to 30 May 2020. Morphology (body weight, condition factor), maturation indicators including gonadosomatic index (GSI), plasma 11-Ketotestosterone (11-KT), pituitary follicle-stimulating hormone β-subunit (fshb) and luteinizing hormone β-subunit (lhb) transcript levels, as well as smoltification markers (Na+, K+- ATPase activity) were assessed. Results revealed that rearing salmon at 15 °C was the most important factor promoting early maturation, leading to 100% of males maturing in late May in 15-WS, and 75% in 15-LL. However, the groups receiving a winter signal (WS) displayed a highly synchronized onset and progression of maturation specially at 15 °C, revealed by the low variability observed among individuals in GSI and fshb transcription after the WS. This evidences the role of the photoperiod switch from short to long day as zeitgeber for sexual maturation. On the contrary, under constant light (LL), entry into maturation was not synchronized among individuals, and onset of maturation occurred spontaneously in a proportion of males highly dependent upon temperature (75% in 15-LL, 25% in 12.5-LL). Signs of smoltification were poor at both temperatures, and the WS did not induce development of hypo-osmoregulatory abilities in any case. This suggests that a winter signal may not induce smoltification if introduced at high temperature or when fish have reached large size, and instead may increase the risk of a sexual maturation response. These findings are relevant for the aquaculture industry, since similar rearing conditions are currently used in the industry, including constant high water temperature and winter signal regimes. The use of such conditions can increase the risk of early maturation, as well as of poor hypo-osmoregulatory performance.publishedVersio

Acoustic Delicing of Atlantic Salmon (Salmo salar): Fish Welfare and Salmon Lice (Lepeophtheirus salmonis) Dynamics

Acoustic lice treatment (AcuLice) is a newly developed system, which uses a composite acoustic sound image with low-frequency sound to remove salmon lice (Lepeophtheirus salmonis) from Atlantic salmon (Salmo salar). This field study documents the stress effects on Atlantic salmon and the effect on salmon lice dynamics during large-scale use of the AcuLice system. The effect of the AcuLice treatment on salmon lice dynamics was measured by weekly salmon lice counting at the facilities from mid-summer 2019 to late-spring 2020. The number of salmon lice treatments in the same period was also compared to a reference group. In addition, the number of weeks until the first salmon lice treatment (mechanical treatment) was compared between the two groups. Apart from a slight increase in plasma glucose, no significant differences were observed in the primary, secondary, or tertiary stress responses measured. For the mature female salmon lice, a significantly lower number (mean ± SEM) was shown for the AcuLice group (0.24 ± 0.03) compared to the reference group (0.44 ± 0.04). In addition, a lower number (mean ± SEM) of salmon lice treatments and a longer production period before the first salmon lice treatment occurred was observed at the AcuLice facilities (33.2 ± 3 weeks) compared to the reference facilities (20.3 ± 2 weeks). These data suggest that the use of the AcuLice system reduces the need for traditional salmon lice treatments with no added stress to the fish.publishedVersio

Effect of Photoperiod and Transfer Time on Atlantic Salmon Smolt Quality and Growth in Freshwater and Seawater Aquaculture Systems

Smoltification is a key process in Atlantic salmon aquaculture, given it prepares the fish for a successful transit from fresh to seawater. However, industry players have not yet reached a consensus on the best protocols to produce high-quality smolts. In this study, we assessed how the combination of two photoperiod regimes in freshwater (continuous light or LL, and natural photoperiod or LDN) and four transfer times to seawater (February, March, April, and May) affected smolt development and their subsequent growth in seawater until slaughter during commercial production. The results demonstrated that smoltification and growth in freshwater were only slightly modulated by the photoperiod treatment and were instead much more affected by the limiting effect of the low water temperature during that period. In seawater, the growth rate was the highest in the same groups, which had, however, experienced a delay in growth when in freshwater, and consequently, no differences in the final body weight between the eight treatments were found. Such compensatory growth in the sea was probably enhanced by the increasing smolt quality, which could allow for better performance in seawater. A significant link between the weight at slaughter and weight at transfer was observed only in the groups with a lower smolt quality (LL-Feb, LDN-Feb and LDN-Mar), which suggests that larger individuals could cope better with a saline environment. In contrast, smaller smolts probably suffered greater osmotic stress that hindered their performance at sea. Afterwards, as smolt quality increased in the subsequent transfer groups, the relevance of this size effect decreased. This means that the industry may benefit from transferring larger smolts to seawater, especially if these are suspected of having developed suboptimal seawater tolerance. Those individuals are likely to cope better with saline conditions than smaller smolts. Future research should focus on the possible long-term effects of freshwater-rearing regimes on smolt performance in the seawater phase.publishedVersio

Interaction of temperature and feed ration on male postsmolt maturation of Atlantic salmon (Salmo salar L.)

Early maturation of Atlantic salmon male postsmolts is undesirable in aquaculture due to its negative impact on growth, welfare and seawater adaptation, however it is an increasing problem under intensive rearing conditions. The effect of temperature and feeding ration on sexual maturation during the induction of smoltification was tested with a 3 × 2 factorial design including three temperatures (8, 12.5 and 18 °C) and two feeding rations (100% and 67%), from 28 October 2018 to 30 May 2019. Fish in the six resulting treatments (1800 parr, initial mean weight 23.1 ± 7.2 g) were reared in flow-through under continuous light (LD24:0) except for a 5-week winter signal (LD12:12) introduced on 4 February 2019 to induce smoltification. A major effect of temperature determining the life history pattern of each group was observed. At 18 °C, a majority of the males were maturing in May under both rations (100% males in 18–100% and 88.9% males in 18–67%). Fish at 18 °C experienced an early activation of the BPG (Brain-Pituitary-Gonad) axis and displayed very poor signs of smoltification. At 12.5 °C, early maturation was also present, although at lower proportion than at 18 °C and more dependent upon feed ration (40% of males maturing in 12.5–100%, 8.6% in 12.5–67%). Salmon at 12.5 °C displayed the best growth within each feed regime, some early signs of smolting but subsequent low Na+, K+- ATPase activity after the winter signal. At 8 °C, salmon showed best signs of smoltification and lowest growth, while no males matured. The feed restriction had a minor effect on maturation at 18 °C but a greater impact at 12.5 °C, evidenced by significant differences between 12.5–100% and 12.5–67% in gonadosomatic index, plasma 11-ketotestosterone, insulin-like growth factor-I, and pituitary fshb (follicle stimulating hormone β-subunit gene) transcription. Onset of maturation was associated with the photoperiod change from short to long daylength, which probably also induced a slight activation of the BPG axis in non-maturing groups. Our results suggest that postsmolt producers must be cautious when using sustained high water temperatures, or the risk of early maturation and poor hypo-osmoregulatory performance will increase significantly. In addition, reducing the feeding ration will not help decrease incidence of maturation without significantly affecting growth.publishedVersio

The effect of photoperiod manipulation on Atlantic salmon growth, smoltification and sexual maturation: A case study of a commercial RAS

The effect of photoperiod manipulation on growth, smoltification and maturation was assessed in Atlantic salmon through an observational study performed in a commercial RAS facility from June (25.0 ± 11.0 g) to October 2018 (151.1 ± 25.5 g). Half of the commercial cohort 721 was raised in continuous light LD24:0 (LL) while the other received a 6-week LD12:12 winter signal (WS) for smoltification from 12 August to 21 September. Parameters related to growth (body weight, gene expression of pituitary gh1 and gh2, and liver ghr1, igf1 and igfbp1a), smoltification (condition factor, plasma sodium and cortisol, gill NKA activity and nka1a, nka1b and nkcc1a expression) and maturation (GSI and pituitary fshb and lhb expression) were analysed. Afterwards, a multivariate analysis was performed on production data from five commercial cohorts raised in the facility (including 721) to identify variables potentially linked to early maturation in RAS. Results from the observational study indicated weak compensatory growth and slightly better smoltification in WS, although signs of size-induced smoltification were present in LL. Smoltification indicators were poor in both treatments, suggesting that smolts may not be yet ready for seawater. No maturation was observed in any photoperiod treatment; however, the multivariate assessment suggested that such lack of maturation might be rather linked to the low mean temperature and SGR experienced by our cohort.publishedVersio

Impact of long-term fasting on the stomach-hypothalamus appetite regulating genes in Atlantic salmon postsmolts

Atlantic salmon will experience periods of fasting during its lifecycle. In nature, prolonged fasting periods occur owing to seasonal fluctuations in available feeds, migration or in relation to reproduction. In a culture setting, salmon is fasted mainly as part of planned operational handling prior to vaccination, delousing, transfer etc., and where fasting may last up to nine days. The mechanisms regulating the appetite during long-term fasting may vary among fish species. Here, we studied the impact of long-term fasting on neuro-endocrine regulation of appetite through the stomach-hypothalamic axis in Atlantic salmon post smolts (1.2 kg, ∼46 cm), reared in two experimental conditions (Fed and Fasted; triplicated tanks), and sampled after 4 weeks and 6 weeks of fasting. Fasted fish showed lower condition factor and hepatosomatic index at both sampling points compared to Fed group. In qPCR analysis, hypothalamic relative mRNA expression of agouti-related protein 1 (agrp1) was upregulated in fasted group at both sampling points. Among neuropeptide Y (npy) paralogs, only npya1 at 4 weeks was upregulated by fasting. As for cocaine- and amphetamine-regulated transcripts (cart), cart2a was elevated at 4 weeks, and cart2b at both 4 and 6 weeks in fasted group, while cart3a and cart4 showed no response to fasting. The pro-opiomelanocortin (pomc) a1, a2 and melanocortin-4 receptor (mc4r) a2 increased only after 6 weeks of fasting, while mc4rb1 did not respond to fasting. In stomach, 6 weeks of fasting resulted in a decrease of ghrelin1 (ghrl1), while expression of mboat4 was unaffected. The elevated levels of hypothalamic agrp1 and npya1 in fasted group support orexigenic roles for these neuropeptides. In addition, upregulation of cart2a, cart2b, pomca1 and pomca2 indicate that these play vital roles in appetite regulation and that fasting may halt and/or counteract hunger signals (agrp1 and npya1) to save energy from foraging search activities during catabolic conditions. Another possibility is that these neuropeptides play a role in fasting-induced stress. Based on the drop in mRNA expression of ghrl under catabolic conditions, we hypothesize that Ghrl might return as hunger signal once feed becomes available. We also propose that agrp1 is a potential appetite biomarker gene under feed deprived conditions.publishedVersio

ANALISIS KEMAMPUAN BERFIKIR ALJABAR DI KELAS VII SMP NEGERI 1 KRANGKENG KABUPATEN INDRAMAYU (Studi Survei di Kelas VII Tahun Akademik 2012/2013)

Setiati Rahayu, 2013. Analisis Kemampuan Berfikir Aljabar di Kelas VII di SMP Negeri 1 Krangkeng Kab. Indramayu (Studi Survei di Kelas VII Tahun Akademik 2012/2013) Untuk mengukur kemampuan berfikir aljabar seorang siswa diperlukan beberapa indikator. Terdapat beberapa indikator untuk memahami aljabar diantaranya memahami pengertian koefisien variabel suku sejenis, kemampuan melakuakan operasi hitung, kemampuan mengggunakan simbol matematika, kemampuan menggunakan bahasa sehari-hari, kemampuan menyederhanakan operasi aljabar, kemampuan menyatakan berbagai hubungan, kemampuan menggunakan diagram alur dan memahami konsep aljabar invers. Tujuan dalam penelitian ini untuk menganalisis kemampuan berfikir aljabar di kelas VII yang ditinjau dari operasi aljabar, penggunaan aljabar, masalah aljabar, dan pemahaman konsep aljabar saat menjawab soal-soal aljabar. Kemampuan siswa dalam memahami aljabar merupakan suatu kondisi yang terdapat dalam sekolah SMP tersebut. Aljabar adalah suatu cabang ilmu matematika yang menggunakan tandatanda dan huruf-huruf yang mewakili angka-angka. Banyaknya indikator yang menjadi indikator kemampuan aljabar, maka akan ada beberapa indikator yang akan menjadi komponen utama dalam kemampuan aljabar. Untuk mengetahui kemampuan siswa dalam memahami aljabar, tidak perlu semua indikator pada\ud materi aljabar diujikan dalam tes. Mengetahui sangat pentingnya komponen utama dalam materi aljabar untuk mengukur kemampuan berfikir aljabar seorang siswa maka peneliti mencoba menganalisis kemampuan berfikir aljabar siswa kelas VII di SMPN 1 Krangkeng. Teknik pengumpulan data yang digunakan dalam penelitian ini adalah tes. Populasi dalam penelitian ini adalah Kelas VII yang berjumlah (160 siswa). Sampel diambil dari kelas VIIB cluster random sampling. Untuk uji coba dilakukan di kelas VIIA yang berjumlah 32. Dari hasil penelitian diperoleh hasil sebagai berikut: 1) Aljabar di SMP N 1 Krangkeng cukup baik hal ini ditunjukan dengan nilai rata-rata 75. 2) Indikator kemampuan berfikir aljabar secara mekanisme dan indikator Kemampuan terbesar yang dicapai oleh siswa kelas VII SMP Negeri 1 Krangkeng tahun ajaran 2012/2013 dalam memahami aljabar adalah pada pengertian koefisien, variabel, konstanta, faktor, suku sejenis adalah sebesar 89.58% dan kemampuan yang kurang dikuasai oleh siswa kelas VII SMP Negeri 1 Krangkeng tahun ajaran 2012/2013 dalam memahami aljabar adalah memahami invers adalah sebesar 85.94%. 3) Dari delapan indicator kemampuan berfikir aljabar ada tiga komponen yang dominan yaitu menggunakan diagram alur, pengertian koefisien variable konstanta, faktor suku sejenis, dan menyederhanakan operasi aljaba

The effect of continuous light at low temperatures on growth in Atlantic salmon reared in commercial size sea pens

The aim of this study was to investigate the effect of continuous light of different duration, applied from late autumn to spring in the second year of the production cycle, on the production performance of Atlantic salmon in Northern Norway. The underlying hypothesis is that the introduction of continuous light (LL) superimposed on the natural light before December (the preferred continuous light regime in Northern Norway) could enhance growth and inhibit maturation in the subsequent year. To test this, two large, commercial scale experiments were performed [Experiment 1 in 2014 at 69.47°N, 18.26°E, and Experiment 2 in 2015 at 69.80°N, 19.42°E] where salmon of initial size of 1–1.5 kg were subjected to LL at different time points during the period between 11 November and 13 December, and reared under LL until 31 March the following year. In Experiment 1 the water temperature at 6 m depth ranged between 6.7 °C in November and 3.6 °C in March and in Experiment 2 the water temperature at 6 m depth ranged between 8.3 °C in November and 3.6 °C in March and 6.8 °C in May 2016. Before and after the period with LL, all fish were reared under natural light. Growth was improved by 13–20% in the early exposed groups (15 Nov and 11 Nov) compared to the late exposed groups (13 Dec.). No maturation was seen in the experimental groups at slaughter (Exp. 1: July–September 2015, Exp. 2: May 2016). Vertebra deformities did not differ between the early and late exposed groups suggesting that continuous light promotes growth at lower temperatures, while supporting normal vertebra development. Only minor differences in flesh texture (measured as differences in cathepsin L + B activity) were found in both experiments. It is concluded that a considerable growth benefit may be achieved by exposing Atlantic salmon to continuous light from early November in their first year in seawater, i.e. one month earlier than presently used by the salmon farming industry in Northern Norway

High fish density delays wound healing in Atlantic salmon (Salmo salar)

In this study, we look closer at how high fish densities influence wound repair mechanisms in post-smolt Atlantic salmon. The fish were wounded with a 5 mm skin punch biopsy needle and stocked at two different densities, a high fish density (100 kg/m3) treatment and a low fish density treatment (20 kg/m3) serving as the control. The healing wounds were followed for 57 days with samples taken 1, 3, 7, 14, 36, 43 and 57 days post wounding. The transcriptomic analysis suggests that high fish density enhance inflammation and represses cell proliferation, tissue secretion and collagen synthesis in the healing wounds. The histological analysis further showed delayed epidermal and dermal repair in the high fish density treatment compared to control. The overall wound contraction was also altered by the treatment. In conclusion, high fish density enhances immune responses and delay tissue repair, which ultimately results in delayed wound healing.High fish density delays wound healing in Atlantic salmon (Salmo salar)publishedVersio