An improved prioritization framework for selecting new finfish mariculture candidates for research and development in Indonesia

Aquaculture, particularly marine‐based production, is one of the fastest growing industries in Indonesia. Indonesia's competitiveness in the trade of aquaculture products is constrained by a lack of research and development (R&D) of new aquaculture species candidates. Mariculture has the greatest potential due to Indonesia's vast marine resources and archipelagic geography. Although there are over 3,000 species of marine fish in Indonesia, only 14 species have been widely cultured, largely finfish. Production is dominated by shrimp, groupers and milkfish. Traditionally, candidate species for mariculture in Indonesia and elsewhere have often been selected on their market value before their biological suitability for culture has been established leading to partially successful R&D efforts or even failure. The present study developed a framework for selecting marine fish species to support mariculture R&D in Indonesia based on an improved analytic hierarchy process (AHP). The approach combined various quantitative and qualitative data and involved different R&D stakeholder groups in the selection process. Ten species that had not been previously researched for their aquaculture potential were identified. The modified approach addressed the interaction complexity of criteria and different preferences across the stakeholders. The involvement of different stakeholders in the selection process not only ensured acceptance of the selected species for further research, but also tested the validity and consistency of the method used in this study. The methodology has relevance for mariculture globally given that efficient candidate selection can help focus efforts and investment in mariculture R&D.     

中国水产养殖种类组成、不投饵率和营养级

根据1950–2014年水产养殖种(类)有关统计和调研数据,并在对养殖投饵率、饲料中鱼粉鱼油比例、各类饵料(配合饲料、鲜杂鱼/低值贝类/活鱼、天然饵料等)营养级等基本参数进行估算的基础上,研究分析了中国水产养殖种类组成、生物多样性、不投饵率和营养级的特点及其变化。结果表明:中国水产养殖结构相对稳定,变化较小,其显著特点是种类多样性丰富、优势种显著、营养层次多、营养级低、生态效率高、生物量产出多。其中:(1)养殖种类296个、品种143个,合计为439个。种类组成区域差异明显,淡水养殖鱼类占绝对优势,如2014年草鱼、鲢鱼、鳙鱼、鲤鱼、鲫鱼和罗非鱼排名前6个种类的养殖占淡水养殖产量69.6%,其次为甲壳类、其他类、贝类及藻类,而海水养殖则以贝藻类为主,如2014年牡蛎、蛤、扇贝、海带、贻贝和蛏6个种(类)的养殖占海水养殖产量71.3%,其次为甲壳类、鱼类及其他类;(2)养殖种类多样性特征显著,与世界其他主要水产养殖国家相比,独为一支,具较高的多样性、丰富度和均匀度,发展态势良好;(3)由于养殖方式从天然养殖向投饵养殖转变,不投饵率呈明显下降趋势,从1995年90.5%降至2014年53.8%(淡水35.7%,海水83.0%),但与世界平均水平相比,仍保持较高的水准;(4)与世界相比,营养级低且较稳定。由于配合饲料的广泛使用及其鱼粉鱼油使用量减少,近年营养级略有下降,从2005年较高的2.32降至2014年2.25(淡水2.35,海水2.10)。营养级金字塔由4级构成,以营养级2为主,近年占70%,表明其生态系统有较多的生物量产出。中国水产养殖未来发展需要遵循绿色、可持续和环境友好的发展理念,探讨适宜的、特点各异的新生产模式,发展以养殖容量为基础的生态系统水平的水产养殖管理,建设环境友好型的水产养殖业,为保障国家食物安全、促进生态文明建设作出更大贡献。     

中国深远海养殖发展方式研究

在渔业转型发展进程中,发展深远海养殖是突破生态环境和自然资源约束性挑战,实现新时期中国海水养殖业可持续发展的战略方向。基于联合国粮食及农业组织(FAO)关于深远海养殖发展的定义,结合中国海水养殖业发展水平和海域条件,对中国深远海养殖概念进行了界定。提出养殖品种选择、养殖系统构建、养殖海域规划是关系深远海养殖产业稳步有序发展的重要因素。在养殖品种选择方面,应重点考虑经济潜力、适应水温和养殖技术;在养殖系统构建上,分析比较了不同养殖系统应用于深远海养殖的适宜性、安全性和经济性;在养殖海域规划方面,应重点考虑养殖排放、环境承载力和海域条件。     

The suitability of anadromous Arctic charr as host and vector of the monogenean Gyrodactylus salaris

Abstract –  In 2000, the Atlantic salmon ( Salmo salar L.) stock in the river Signaldalselva, North Norway was found to be infected with the monogenean Gyrodactylus salaris (Malmberg). This river system has a multispecies fish community of nine species in total. Low densities of Atlantic salmon parr were found during electrofishing in October (2003) with a prevalence of 94% and a mean abundance of 848 G. salaris. This watercourse also holds a riverine stock of anadromous Arctic charr ( Salvelinus alpinus ), which is not common in Norway. Among the parr of Arctic charr, 64% were infested with an abundance of 23 parasites per fish. The most heavily infected 0+ and 1+ juvenile Arctic charr had 469 and 534 parasites, respectively, indicating that the parasites are able to reproduce on Arctic charr in the wild. There was little variation in the rates of infestation of Arctic charr along the studied stretch of the river, even in areas with very low densities of Atlantic salmon parr. The parr of anadromous Arctic charr seem to be suitable as long-term hosts for G. salaris . Moreover, a few (22%) infested adult sea-running Arctic charr were captured after ascending the river in the autumn, which shows that large fish may also act as carriers of G. salaris . However, no parasites were recorded on potential anadromous Arctic charr before descending during early spring (April 2003 and April 2004). Thus, it is still not clear whether anadromous Arctic charr are able to disperse the parasite between watercourses. So far, it is uncertain whether G. salaris may increase the mortality rates of Arctic charr and thereby be a threat to these unusual occurring riverine anadromous Arctic charr stocks.     

Foraging mode variation in three stream‐dwelling salmonid fishes

Despite long‐standing interest in foraging modes as an important element of animal space use, few studies document and compare individual foraging mode differences among species and ecological conditions in the wild. We observed and compared foraging modes of 61 wild Arctic charr, Salvelinus alpinus, 42 brown trout, Salmo trutta, and 50 Atlantic salmon, Salmo salar, in their first growing season over a range of habitats in 10 Icelandic streams. We found that although stream salmonids typically sit‐and‐wait to ambush prey from short distances, Arctic charr were more mobile during prey search and prior to prey attack than Atlantic salmon, whereas brown trout were intermediate. In all three species, individuals that were mobile during search were more likely to be moving when initiating attacks on prey, although the strength and the slope of this relationship differed among species. Arctic charr also differed from salmon and trout as more mobile individuals travelled longer distances during prey pursuits. Finally, coupled with published data from the literature, salmonid foraging mobility (both during search and prior to attack) clearly decreased from still water habitats (e.g., brook charr), to slow‐running waters (e.g., Arctic charr) to fast‐running waters (e.g., Atlantic salmon). Hence, our study suggests that foraging mode of young salmonids can vary distinctly among related species and furthers our understanding of the behavioural mechanisms shaping the geographical distribution of wild salmonids.     

Effect of rearing temperatures on the growth and maturation of Arctic charr (Salvelinus alpinus) during juvenile and on‐growing periods

The effect of rearing temperature on the growth and maturation of Arctic charr (Salvelinus alpinus) was investigated. Arctic charr juveniles were reared for 6 months (phase I, October–April, size range 20–500 g) at constant temperatures of 9, 12 and 15 °C and according to two temperature‐step groups (T_step) i.e. fish transferred from 15 to 12 °C or from 12 to 9 °C. All the previous treatments were then reared either at 7 °C or at 12 °C for an additional 4 months (phase II, size range 300–1000 g) and then slaughtered in August 2008. The overall growth rate was the highest at a constant temperature of 15 °C for the first 6 months of the trial, with the fish in this group being 44% and 78% heavier than the fish reared at a constant temperature of 12 or 9 °C respectively. Arctic charr showed a negative response in terms of the growth rate when transferred from higher to lower temperatures, especially for groups previously reared at 15 °C. There was a trend for higher gonadosomatic index values at the end of the experiment for groups of fish that were exposed to higher rearing temperatures during the juvenile phase i.e. 4.18% (±0.79) and 7.29% (±0.89), for the temperature groups of 12 and 15 °C, respectively, compared with 2.49% (±0.74) for the 9 °C group. Our results suggest that for the production of fish >1000 g, moderate or low temperatures (here 9 °C) should be applied during the juvenile phase in order to reduce the negative effects arising from maturation. Farmers with access to heat sources should accordingly choose more moderate rearing temperatures during the juvenile stage, especially if the fish is to be moved down in the temperature regime during the on‐growing period.     

Modelling the life-history variation of Arctic charr

Abstract –  A model based on proximate considerations of life histories of Atlantic salmon, Salmo salar , was examined for its applicability to fit the variation in life-history of wild Arctic charr, Salvelinus alpinus , based on a qualitative assessment of information related to growth and lipid dynamics of Arctic charr. The original salmon model is discussed in context of modifications required to account for added complexities in the life history of Arctic charr in relation to anadromy versus residency. A study from North Norway shows that individual charr that emigrate from the lakes to the sea, maintain a high growth rate in the lake in late summer and early autumn compared with resident fish. Their relatively low lipid level in autumn combined with a high rate of change of lipid during winter was associated with postponement of maturation in the anadromous individuals. Individuals that remain resident in the lake arrested growth in autumn. Their high lipid level in autumn combined with a low rate of change of lipid during winter was associated with maturation the following summer, without emigration from freshwater. Results from this and other related studies show similarities with the model derived from lipid and growth dynamics of Atlantic salmon. The adjusted charr model illustrates possible proximate explanations for the high variation in life-history strategies of Arctic charr. However, the model does not account for the characteristic return migration of immature charr into freshwater several weeks after their entry to the sea. The proximate physiological stimulus for this movement of immature fish is not entirely clear.     

Temperature–growth patterns of individually tagged anadromous Arctic charr Salvelinus alpinus in Ungava and Labrador,Canada

Individual measurements of annual, or within‐season growth were determined from tag‐recaptured Arctic charr and examined in relation to summer sea surface temperatures and within‐season capture timing in the Ungava and Labrador regions of Eastern Canada. Differences between two years of growth (2010–2011) were significant for Ungava Bay Arctic charr, with growth being higher in the warmer year. Growth of Labrador Arctic charr did not vary significantly among years (1982–1985). Regional comparisons demonstrated that Ungava Arctic charr had significantly higher annual growth rates and experienced warmer temperatures than Labrador Arctic charr. The higher annual growth of Ungava Bay Arctic charr was attributed to the high sea surface temperatures experienced in 2010–2011 and the localised differences in nearshore productivity as compared to Labrador. Within‐season growth rates of Labrador Arctic charr peaked in June, declined towards August and were negatively correlated with the length of time spent at sea and mean experienced sea surface temperatures. A quadratic model relating growth rate to temperature best explained the pattern of within‐season growth. Collectively, results suggest that increases in water temperature may have profound consequences for Arctic charr growth in the Canadian sub‐Arctic, depending on the responses of local marine productivity to those same temperature increases.     

The marine temperature and depth preferences of Arctic charr (Salvelinus alpinus) and sea trout (Salmo trutta), as recorded by data storage tags

Eleven Arctic charr (Salvelinus alpinus) (370–512 mm) and eight sea trout (Salmo trutta) (370–585 mm in length) were tagged externally or internally with depth‐ and temperature‐measuring data‐storage tags (DST) before they were released into the sea in the Alta Fjord in north Norway in June 2002. All sea trout were recaptured after they spent 1–40 days at sea, while all Arctic charr were recaptured after 0.5–33 days at sea. On average, trout preferred water about 0.6 m deeper and 1.3°C warmer than Arctic charr. Arctic charr spent >50% of their time between 0 and 1 m depth, while trout spent >50% of their time between 1 and 2 m depth. Both species spent >90% of their time in water no deeper than 3 m from the water surface. However, sea trout dove more frequently and to greater depths (max. 28 m) than Arctic charr (max. 16 m), and these deep dives were most frequently performed at the end of the sea migration. Arctic charr demonstrated a diel diving pattern, staying on average about 0.5 m deeper between 08:00 hours and about 15:00 hours than during the rest of the 24 h, even though there was continuous daylight during the experiments. When comparing data obtained from the DSTs with temperature measurements within the fjord system, the two species were observed to select different feeding areas during their sea migration, the sea trout choosing the inner and warmer parts of the fjord, in contrast to the Arctic charr that preferred the outer, colder parts of the fjord. The observed differences in migration behaviour between the two species are discussed in relation to species preferences for prey and habitat selection, and their optimal temperatures for growth.     

Apparent digestibility of macro‐nutrients and phosphorus in plant‐derived ingredients for Atlantic salmon,Salmo salar and Arctic charr,Salvelinus alpinus

Alternative protein sources for aquafeeds need to be indentified in order to increase the efficiency of production. Many studies have examined terrestrial plant meals/protein concentrates as alternatives. Recently the focus has turned to aquatic protists and plants as well as by‐products from other industries, such as breweries. Atlantic salmon, Salmo salar, and Arctic charr, Salvelinus alpinus, were fed diets containing canola meal, soybean meal, corn gluten meal, soy protein concentrate, barley protein concentrate, and solar dried algae included at 30% of the test diet. Barley protein concentrate had the highest apparent protein digestibility values for both species (96.3% for Atlantic salmon and 85.1% for Arctic charr), followed by corn gluten meal. Algae had the highest organic matter digestibility value for arctic charr (80.1%) while corn gluten meal had the highest organic matter digestibility value for Atlantic salmon (88.4%). Algae had a high energy apparent digestibility coefficient (82.4 salmon, 82.7 charr) along with corn gluten meal (78.5 salmon, 82.7 charr) for both species. In general, Atlantic salmon had higher apparent digestibility coefficients compared to Arctic charr for most of the tested ingredients. Both corn gluten and barley protein concentrate appear good candidates as alternative protein sources with both species.     

Is the winter period a severe bottleneck of anadromous riverine Arctic charr parr?

Abstract –  Winter growth and survival of wild individually tagged juvenile Arctic charr (1+ age) from a riverine anadromous stock, were studied in a small ice-covered (∼6 months) ground water brook (temperature ∼1 °C) connected to Skibotnelva in subarctic northern Norway. The overall winter survival was estimated to be 68% from late October 2005 to early May 2006. The recaptured charr were not significantly different in initial length or weight compared with the nonrecaptured fish suggesting low size-dependent mortality. The majority (98%) of the recaptured charr showed significant increase in size, with a mean increment of 62% from their initial bodyweight and 12% of the charr parr had more than doubled their weight. The mean specific growth rate was calculated to be slightly lower (0.27) than estimated values from a growth model (∼0.35). In addition, the condition factor increased significantly during the field experiment. These results are the first individual growth data on riverine anadromous Arctic charr parr under natural winter conditions, and indicate that charr can grow relatively fast during periods with low temperature and also that ground water brooks can be good over-wintering habitat for juvenile Arctic charr. These results suggest that the winter period is perhaps a less severe bottleneck than previously recognised for the cold-adapted Arctic charr.     

Comparative growth study of wild- and hatchery-produced Arctic charr (Salvelinus alpinus L.) in a coldwater recirculation system

The growth performance of Arctic charr of wild (W) and hatchery (H) origin was compared in a commercial coldwater recirculation system (Villmarksfisk, Bardu, 68°N, 19°E, Norway). The initial individual body mass was 115 g and similar between groups. The rearing temperature was 9.2 °C and the fish were held under continuous light (24:0 L:D). At the end of the experiment (day 240), the average body mass of the H fish was 451 g compared to 231 g in the W fish. The accumulated mortality of wild Arctic charr was about 40%; 10 times higher than the mortality of hatchery-produced Arctic charr (4%). The difference in growth performance and survival rate impose a great disadvantage of using this wild caught fish as compared to commercially available hatchery-produced Arctic charr in coldwater recirculation system. However, further improvements in the production chain (catching, live transport, quarantine, size grading, etc.) may still make production of wild caught Arctic charr profitable, especially as it demands a higher price in niche markets.     

The ability of carnobacteria isolated from fish intestine to inhibit growth of fish pathogenic bacteria: a screening study

In the present study a microtitre plate assay was used to evaluate antagonistic activity of 157 intestinal bacteria belonging to Carnobacterium isolated from Arctic charr (Salvelinus alpinus L.), Atlantic salmon (Salmo salar L.) and wolf fish (Anarhichas lupus L.) against fish pathogenic bacteria. One hundred and forty‐nine strains isolated from Arctic charr fed; (a) different lipid levels and (b) different fatty acids were screened for their ability to inhibit growth of the fish pathogen Aeromonas salmonicida ssp. salmonicida strain AL 2020 (the causative agent of furunculosis). Carnobacterium maltaromaticum and Carnobacterium mobile isolated from fish fed a low‐lipid diet inhibited growth of the pathogen, while none of the Carnobacterium divergens isolated from fish fed the high‐lipid diet had this ability. When Arctic charr was fed different fatty acids, was the frequency of antibacterial ability of C. maltaromaticum highest in strains isolated from fish fed 4%α‐linolenic acid (18:3 n‐3) and lowest in strains isolated from fish fed 4% linoleic acid (18:2 n‐6). Extracellular growth inhibitory compounds harvested in exponential and stationary growth phase from eight carnobacteria strains isolated from three fish species were tested for their ability to inhibit growth of six fish pathogens [A. salmonicida, Vibrio splendidus strain VS11, Vibrio salmonicida strain LFI 315, Vibrio anguillarum strain LFI 317, Moritella (Vibrio) viscosa strain LFI 5000 and C. maltaromaticum (piscicola) CCUG 34645]. The highest antibacterial activity was found when cellular extracts of the producer isolate were harvested in stationary growth phase. Scanning electron microscopy (SEM) investigations of A. salmonicida showed that cell morphology was affected by the inhibitory substance produce by strain 8M851, a Carnobacterium inhibens‐like bacteria.     

Size‐dependent stress response in juvenile Arctic charr (Salvelinus alpinus) under prolonged predator conditioning

Predator conditioning can be used to improve post‐release antipredator recognition of hatchery‐reared salmonids. However, possible negative stress‐related effects of prolonged predator conditioning on juvenile fish physiology are poorly understood. We studied the effects of prolonged (91 days) predator odour exposure on whole‐body cortisol level and spleen size in six full‐sib families of juvenile hatchery‐bred Arctic charr (Salvelinus alpinus). Chemical cues from water containing charr‐fed pikeperch (Sander lucioperca) were used as the predator exposure stimuli and lakewater was used as a chemical control. Our study revealed that juvenile body cortisol levels post‐predator conditioning were affected by treatment, fish size and their interaction. Importantly, among the smaller (i.e. slowest growing) charr, the predator‐exposed fish had higher cortisol levels than control fish, while the opposite pattern was true for the larger fish. These results suggest that chemical cues from charr‐fed predators induce a prolonged stress response in juvenile charr. As prolonged predation exposure seems to elevate stress levels in a size‐dependent manner, the larger, faster growing fish could possibly have intrinsically lower stress responses to predation threats than smaller, slower growing fish. Possible coupling between stress sensitivity and growth requires further attention due to the likely implications for the management of unintended domestication among captive‐reared salmonids.     

Impact of a new artificial shelter on Arctic charr (Salvelinus alpinus, L.) behaviour and culture performance during the endogenous feeding period

Shelter is of major importance in many species of fish both in the wild and in aquaculture. Sheltering behaviour of Arctic charr has been poorly studied in aquaculture. A new type of shelter made of PVC agricultural drain cut in half was tested on culture performance and behaviour during the endogenous feeding period. This device offered grooves where alevins could position themselves and lie in a vertical position. A first experiment compared fish with and without shelter in incubator compartments. All fish were measured at 122, 158, and 190 days post fertilization (dpf) and observed at 126, 139 and 157 dpf. Fish provided with shelter showed better growth performances, lower mortality and started first exogenous feeding about six days later compared to fish without shelter. These effects from shelter provision were also associated with much less mobility in fish provided with shelter. At 126 dpf, all fish provided with shelter were immobile while other fish displayed horizontal stationary body movement (86%) or swam against the water current (7%). At 157 dpf, 85% of fish without shelter were immobile compared to 95% in fish provided with shelter. Both categories displayed stationary body movements. In most cases, there was one single fish per groove and a stable average value of 2.4 grooves was maintained between two successive fish throughout the study. The second experiment was a preference test where the fish were placed in similar compartments but occupied by a half shelter. We found that 61% of the fish were located under the shelter at 122 dpf while at 157 dpf, 58% were on the shelter and 42% out of the shelter. The present results revealed Arctic charr behavioural characteristics in the presence of a new type of artificial shelter at very early stages of development. This shelter enables the fish to stabilize in a vertical position without producing any movement and to choose by itself its favorite location throughout development. This device could be used to improve Arctic charr growth, performance and fish welfare during the endogenous feeding period.     

Latitudinal variation in growth and otolith‐inferred field metabolic rates of Canadian young‐of‐the‐year Arctic charr

Countergradient variation (CGV) is defined as genetic variation that counteracts the negative influences of the physical environment, minimising phenotypic variability along an environmental gradient. CGV is thought to have relevance in predicting the response of organisms to climate variability and change. To test the hypothesis that growth rate increased with latitude, consistent with CGV, young‐of‐the‐year (YOY) Arctic charr, Salvelinus alpinus, were examined along a ~27° latitudinal gradient in central and eastern Canada. Growth rates were estimated from fork lengths standardised by the thermal opportunity for growth based on experienced water temperatures derived using otolith oxygen stable isotopes. Results demonstrated patterns consistent with CGV, where northern populations demonstrated faster growth rates. A secondary aim was to test for similar geographical patterns in otolith‐inferred metabolic rates, which reflect the energetic costs of standard metabolic rate (SMR) and other processes such as feeding, locomotion, thermoregulation, reproduction and growth. Results demonstrated a significant, positive relationship between otolith‐inferred metabolic rate and latitude, which may reflect an increase in one, or a combination, of the above‐noted physiological processes. The similar latitudinal pattern in growth and otolith‐inferred metabolic rates suggests greater intake of food per unit of time by northern fish. The phenotypic variation in physiological traits observed here demonstrates the significant adaptability of Arctic charr to different thermal regimes with different growing season lengths. Determining the relative contributions of phenotypic plasticity and genetic variation to the observed latitudinal variation will be critical to predicting the responses of Arctic charr to climate change more accurately.     

Assessing the food web impacts of an anadromous Arctic charr introduction to a sub‐Arctic watershed using stable isotopes

Anadromous Arctic charr, Salvelinus alpinus (L.), was introduced to a sub‐Arctic river–lake system near the village of Kujjuuaq, Nunavik, and the stable isotope values and diets of key resident fish species were used to assess changes in feeding patterns. Stable isotope values for most species did not differ significantly between the pre‐ and post‐introduction periods, with observed shifts being within the bounds of expected natural variation. Lake chub, Couesius plumbeus (Agassiz), were the single species to show a difference between study periods, with a small but significant increase in δ¹⁵N. No significant post‐introduction changes were seen in lake trout, Salvelinus namaycush (Walbaum), omnivory or in any of the assessed quantitative food web metrics. Gut contents of major fish species similarly showed significant temporal overlap between the pre‐ and post‐introduction periods, and there was no significant change in species' weight–length relationships. The minor ecological impact was interpreted in relation to the availability of open niches exploitable by ecological generalists such as Arctic charr. The explanation accords with the known habitat and feeding flexibility of Arctic charr and the ecological immaturity of sub‐Arctic lakes known to have driven adaptive variation among Arctic charr. Findings suggest that anadromous Arctic charr may be introduced at moderate densities to other sub‐Arctic watersheds without major negative food web consequences for other resident fish species.     

Migrations and harvest rates of Arctic charr (Salvelinus alpinus) in a marine protected area

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Putative virulence factors of atypical Aeromonas salmonicida isolated from Arctic charr,Salvelinus alpinus (L.), and European grayling,Thymallus thymallus (L.)

Atypical Aeromonas salmonicida (AAS) causes generalized lethal infections in farmed Arctic charr, Salvelinus alpinus (L.), and European grayling, Thymallus thymallus (L.), and is thus a serious threat for culture of these fish species. Virulence factors were studied among isolates of AAS from Arctic charr (n = 20), European grayling (n = 19) and other fish species (n = 20), of which 48 were of Finnish and 11 of Swedish origin. All isolates produced an A-layer. Extracellular products (ECP) of the AAS isolates did not produce detectable gelatinase and caseinase activity in test assays. Analysis of the same ECP preparations with substrate sodium dodecyl sulphate-polyacrylamide gel electrophoresis showed weak proteolytic activity, indicating the different sensitivity of the detection methods used. The ECP from AAS isolates showed low cytotoxic activity against cultured cells. However, the ECP did not induce mortality in challenged Arctic charr. The results suggest that toxic components, like ECP, secreted by the bacterium may not be the major virulence factor in AAS-infection in Arctic charr and European grayling, and hence the pathogenesis also differs from the pathogenesis of AAS-infection in Atlantic salmon, Salmo salar L.     

Evaluation of growth performance and intestinal barrier function in Arctic Charr (Salvelinus alpinus) fed yeast (Saccharomyces cerevisiae), fungi (Rhizopus oryzae) and blue mussel (Mytilus edulis)

Arctic charr (Salvelinus alpinus) were fed for 99 days on experimental diets with 40% of fish meal replaced, on a crude protein basis, with intact yeast (Saccharomyces cerevisiae) (ISC), extracted yeast (ESC), Rhizopus oryzae fungus (RHO) or de‐shelled blue mussels (Mytilus edulis) (MYE). The fish were evaluated for growth performance, nutrient digestibility and fish intestinal function. Growth performance, retention of crude protein and sum of amino acids were not affected in fish fed diets ISC or MYE compared with those fed the reference (REF) diet. However, fish fed diet ISC displayed decreased digestibility of crude protein and indispensable amino acids and decreased intestinal barrier function compared with fish fed the REF diet. Fish fed diet ESC exhibited decreased growth performance and protein retention, but had comparable digestibility to fish fed the REF diet. Fish fed diets MYE and RHO showed similar performance in terms of growth, nutrient digestibility and intestinal barrier function. Overall, the results indicated that blue mussel and intact S. cerevisiae yeast are promising protein sources for Arctic charr.