SALMON AQUACULTURE: LARGER COMPANIES AND INCREASED PRODUCTION

Salmon farming is among the most successful aquaculture industries with a production growth that is substantially higher than aggregate aquaculture production in recent decades. It is well known that innovations and productivity growth are the main sources for this development. In this article we look closer at two potentially important factors in production growth, development of farm size and company size directly through economies of scale and indirectly through capacity in R&D, innovation, sales and marketing. In Norway, production per license has increased from 26 tons in 1980 to 1,130 tons in 2010, suggesting a substantial intensification in the industry. In all five leading salmon producing countries, the degree of concentration has increased and the large firms have become bigger over time.     

BIOECONOMICS OF CAPTURE-BASED AQUACULTURE OF COD (GADUS MORHUA)

This study formulates and parameterizes a bioeconomic model of capture-based aquaculture (CBA) of cod (Gadus morhua). The model is solved for the optimal harvest pattern and calculates economic profit and net present value for a model farm. The biological sub-model incorporates knowledge from interviews with existing farmers, research trials and existing cod aquaculture literature. Economic components are obtained from interviews and sales statistics from exporters. A farm of the modeled scale is likely to influence market prices, hence sales prices were estimated assuming a supply response based on the price elasticity. Taking into account the opportunity cost of selling the fish directly, NPV is found to be marginally positive. Sensitivity analysis revealed that profitability is sensitive to changes in several parameters. Hence, further research is valuable and care should be taken when considering investments in cod CBA.     

Growth performance of European whitefish [Coregonus lavaretus (L.)] under a constant light and temperature regime

Growth, feed intake and maturation were monitored in a fast‐growing benthivore morph of European whitefish [Coregonus lavaretus (L.)] held under constant light (LD 24:0) and temperature conditions (10°C) for 415 days. Their growth was best described by polynomial regression model and no indication of seasonal patterns (e.g. winter depression) in growth rates was found. There was no significant difference in food conversion ratio (FCR) between periods during the experiment and the FCR was favourable (0.84). Furthermore, there were no differences in growth between males and females. None of the fish became sexually mature by the time the experiment was terminated, although they had reached a mean size of about 444 g. The European whitefish seems to be a promising aquaculture species as the growth rate was relatively high with a remarkable homogenous growth performance between individual fish within each experimental unit, a relatively favourable FCR, a low degree of agonistic behaviour and negligible growth depression due to internal biological rhythms or gonad maturation. These results were obtained at relatively low temperatures that should be beneficial for sustainable cost‐effective farming conditions in cold climate condition in northern Scandinavia.     

Reduction of early sexual maturation in male S0 Atlantic salmon (Salmo salar L.) by dietary supplementation of tetradecylthioacetic acid (TTA)

Effects of dietary tetradecylthioacetic fatty acid (TTA) on muscle fat, development of gonads and early sexual maturation in S0 Atlantic salmon during the first year in sea were investigated. TTA (0.5% w/w) was added to the feeds for 8 weeks in the spring. In May, at the end of the TTA‐feeding period, the fish in the TTA group had significantly (P < 0.05) less fat (10.1%) stored in muscle compared with the control group (10.8%). In September, mean male gonadosomatic index (GSI) in maturing fish in the TTA group was found to be lower compared with the maturing fish in the control group (P = 0.05). On the basis of GSI values, male sexual maturation in September was 10.0% vs. 14.4% for the TTA and the control group respectively. Thus, relative to the control group, the incidence of male sexual maturation in the TTA group was reduced by about 1/3 (P = 0.002). Production data was not affected by dietary supplementation of TTA. This study reveals that TTA significantly reduces the incidence of male sexual maturation in S0 Atlantic salmon. A significant elimination model of TTA in fish muscle that takes into account, the growth rate of the fish was further developed in this study.     

<Emphasis Type="Italic">Colletotrichum acutatum</Emphasis> occurs asymptomatically on apple leaves

Fungi within the Colletotrichum acutatum species complex occur asymptomatically on plant parts of many different plant species. Leaves from apple orchards in southern Norway were sampled, frozen for five hours and incubated for six days to reveal presence of asymptomatic infections of C. acutatum. Number of leaves (incidence) and leaf area covered (severity) with conidial masses of C. acutatum were assessed biweekly on cv. Aroma from late May to late September during three growing seasons. The first finding of conidial masses occurred in the second half of July, and there was a higher incidence occurring in August and September. Sampling of leaves from fruit spurs and vegetative shoots of cvs. Aroma and Elstar showed that conidial masses of C. acutatum developed on leaves on both shoot types, and there was no difference in incidence between these two types. The fungus was detected on leaves from six of eight commercial orchards of cv. Aroma over three years, with a mean incidence of 5.5 %. After storage, bitter rot was found on apple fruit from all eight orchards. There was no correlation between incidence of conidial masses of C. acutatum on leaves and on fruit. In all orchards and seasons investigated, incidence and severity on leaves varied from 0 to 67 % and 0 to 85 %, respectively. The discovery of apple leaves containing conidial masses of C. acutatum clearly indicate for leaves as a potential source of inoculum for fruit infections.     

Selection in a provenance trial of Norway spruce (Picea abies L. Karst) produced a land race with desirable properties

Selections were made within East European Norway spruce provenances in a provenance trial in northern Sweden and the selected clones were grafted in a Norwegian seed orchard mixed with plus trees of local origin. Full-sib families were generated by controlled crosses, producing sets of both inter- and intraprovenance families, which were planted in two short-term and in long-term trials. Measurements were made of frost damage, tree height, annual shoot growth rhythm and lammas shoots, and genetic parameters were estimated. The intraprovenance families from selected trees of East European origin showed the least variation in all traits and had the lowest heritability values. The variation among the intraprovenance families of local origin was large and with the highest estimates of heritability. The means of the provenance hybrid families were intermediate between those of the intraprovenance families. Strong genetic correlations were present between the growth rhythm traits measured, and in the family group of local origin also between these traits and frost damage, as well as for lammas shoots and height. The progenies of the selected parents of East European origin seem to be a desirable land race with less damage, lower percentage of lammas shoots and less variability in growth capacity.     

Analytical models for splitting capacity of bottom rails in partially anchored timber frame shear walls based on fracture mechanics

Plastic design methods can be used for determining the load-carrying capacity of partially anchored shear walls. For such walls, the leading stud is not fully anchored against uplift and tying down forces are developed in the sheathing-to-framing joints and the bottom rail will be subjected to crosswise bending, leading to possible splitting failure of the rail. In order to use these plastic design methods, a ductile behaviour of the sheathing-to-framing joints must be ensured. In two earlier experimental programmes, the splitting failure capacity of the bottom rail has been studied. Two brittle failure modes occurred during testing: (1) a crack opening from the bottom surface of the bottom rail and (2) a crack opening from the side surface of the bottom rail. In this article, a fracture mechanics approach for the two failure modes is used to evaluate the experimental results. The comparison shows a good agreement between the experimental and analytical results. The failure mode is largely dependent on the distance between the edge of the washer and the loaded edge of the bottom rail. The fracture mechanics models seem to capture the essential behaviour of the splitting modes and to include the decisive parameters.     

Improving production efficiency of farmed Atlantic salmon (Salmo salar L.) by isoenergetic diets with increased dietary protein‐to‐lipid ratio

The effects of isoenergetic diets with high (HP) and low (LP) protein‐to‐lipid ratios on feeding rate (SFR), feed conversion (FCR), growth (TGC) and relative‐ and absolute nutrient retention were investigated using both whole‐body weight (BW) and carcass weight (CW) to assess the production efficiency. Three different feeding trials in seawater were conducted: two large‐scale trials with yearling smolt (S1) and under‐yearling smolt (S0) and one small‐scale with S1 smolt. The initial body weights in the trials were 105, 319 and 978 g, respectively, and the fish were fed and monitored until they reached harvest weights. In all three trials, the dietary HP group attained significantly higher (p < .05) CW at harvest based on fish with equal BW. Also, fish fed the HP diets significantly improved FCR (p < .05) when based on CW. In the small‐scale trial, fish fed HP diet, especially during late autumn and spring, significantly (p < .001) improved FCR_BW and FCR_CW. Improved FCR coincided with significantly higher (p < .05) relative energy retention in the dietary HP group. In all three trials, the HP groups had significantly higher (p < .05) TGC with regard to both BW and CW. Taken together, the present studies indicate that growth performance and feed utilization in modern salmon farming has the potential to be further improved by increasing the dietary protein‐to‐lipid ratio. In addition, dietary influence is more precisely assessed when using carcass as the weight denominator when analysing feed utilization and growth performance.