Yield and Gel Strength of Gelatin Extracted from Smoked Salmon (Salmo salar) Skins

The gelatin yield and gel strength of gelatin extracted from the skins of smoked salmon were determined. The skins had a crude protein content of 43.5 ± 1.2% and an estimated collagen content of 23.6 ± 1.0%. Following an alkali extraction process under varying extraction conditions, the protein content varied from 2.78% to 32.1%, and the gelatin yield ranged from 2.23% to 22.4% of the initial skin weight. The gelatin purity (gelatin/protein) ranged from 55.4% to 100%, with the highest Hyp/protein sample arbitrarily designated as being 100% pure, i.e., an assumption of pure gelatin. Statistical analysis showed that HCl concentration, pretreatment temperature, and extraction temperature significantly affected the protein yield and gelatin yield. The wide range of gel strengths indicates that the gelatin might have been hydrolyzed to different extents during the different extraction and cooling processes. Statistical analysis did not show that any of the factors studied affected the gel strength. However, the data indicated that low NaOH concentrations and HCl concentrations might not prevent hydrolysis during the extraction process. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS–PAGE) showed that the gelatins contained α- and β-chains and that the gelatins composed of higher concentrations of larger molecular weight polypeptide chains had higher gel strengths.     

Evaluation of Commercial‐scale Approaches for Cryopreservation of White Crappie,Pomoxis annularis,Sperm

Crappie, Pomoxis spp., are popular game fish throughout North America and are produced by public and private hatcheries. However, production is limited by a lack of information on tank culture and induced spawning methods. Development of techniques for storage of sperm and in vitro fertilization would increase flexibility in spawning. Therefore, techniques for sperm cryopreservation were examined in white crappie, Pomoxis annularis. Sperm from adult wild white crappie were used to evaluate sperm extender, cryoprotectant agent and concentration, and cooling technique based on post‐thaw sperm motility. Percent egg fertilization was also compared between sperm stored in the two best cryopreservation protocols and two different osmotic activator solutions. Sperm were cryopreserved using treatment combinations of two extenders (350 mOsmol/kg Hanks' balanced salt solution [HBSS] and 350 mOsmol/kg Ca²⁺free HBSS) and two cryoprotectants (dimethyl sulfoxide [DMSO] and methanol) at concentrations of 5, 10, and 15% that were cooled at four different rates: 5, 10, 20, and 40 C/min. Post‐thaw sperm motility and fertilization rates indicated white crappie sperm can be cryopreserved using either extender, cryoprotectants of either 5% DMSO or 10% methanol, and cooling at 40 C/min. A follow‐up experiment demonstrated sperm in suspensions on ice retained viability after overnight transport.     

Content of synthetic astaxanthin in escaped farmed Atlantic salmon, Salmo salar L., ascending Norwegian rivers

Abstract  Isomeric ratios of astaxanthin in eggs and alevins of Atlantic salmon, Salmo salar L., have proven useful in identifying female spawners of farmed origin, but the method underestimates the proportion of fish of farmed origin. The rate of underestimation was studied by analysing astaxanthin content in tissue of 55 farmed Atlantic salmon ascending two Norwegian rivers in the autumn of 1991. The astaxanthin content fell into two distinct classes. Fifty-one per cent of the adult escaped salmon had isomeric ratios similar to salmon fed synthetic astaxanthin, whereas all the remaining fish had ratios similar to wild fish. Discriminant analysis classified 96.4% of the fish with known astaxanthin content into the correct astaxanthin class on basis of tail-fin erosion, length, weight and gill-cover damage. This discriminant function was used to estimate the astaxanthin classification of 1017 farmed salmon caught in nine rivers during 1989–1991. The classification success varied among years from 52 to 64%. Corresponding numbers for females and males were 45–48% and 54–70%, respectively. Thus, estimates of spawning rates of farmed female salmon via astaxanthin content in eggs or alevins from redds should be adjusted accordingly. The observed isomeric ratios of astaxanthin in the escaped farmed salmon and the relationship with morphology indicates that a significant proportion of the escapees ascending rivers have spent more than 1 year in the wild after escape.     

Iron status and dietary levels of iron affect the bioavailability of haem and nonhaem iron in Atlantic salmon Salmo salar

The absorption of haem iron and nonhaem iron in 155-g Atlantic salmon Salmo salar was studied by simultaneous labelling of the two forms of iron with ⁵⁹Fe or ⁵⁵Fe, respectively. Iron absorption was measured after incorporation of this element into blood and tissue 2 days after oral administration. Fish with a low iron status showed a significantly greater absorption of both haem and nonhaem iron than iron-loaded fish. The low-iron group distributed a larger proportion of the iron to kidney and spleen than the iron-loaded or control fish. Absorption of both forms of iron increased with higher doses administered, but absorption relative to dose administered decreased. There was a trend suggesting that increased levels of dietary haem iron resulted in the reduced uptake of nonhaem iron, but not vice versa . The results of the present study suggest that factors affecting bioavailability of haem and nonhaem iron in Atlantic salmon are similar to those of other vertebrates.     

Unstable release strategies in reared Atlantic salmon, Salmo salar L.

The effects of year, size, sexual maturity and release date on the probability of recapture of tagged Atlantic salmon, Salmo salar L., released from a Swedish hatchery in the Baltic Sea were examined. The probability of recapture varied among years for individuals which were juvenile when released (1988, 13.5%; 1989, 4.4%; 1990, 1.2%) or previously mature males (1988, 1.9%; 1989, 0.5%; 1990, 0.4%). Body size was positively associated with the probability of recapture in each release year for both life-history types. Inter-annual changes in recapture rates were similar for both large and small smolts. There was a significant effect of life-history type on recapture rates in 1988 and 1989, but not in 1990. There was a significant effect of release date on recapture rates in 1988 and 1990, but not in 1989. The maximum recapture rates were associated with different release dates in each year, i.e. 27 May 1988, 6 June 1989 and 21 June 1990.     

Digestibility of diets with precooked rye or wheat by Atlantic salmon, Salmo salar, L.

Four extruded diets, differing in grain supplementation, were fed to triplicate groups of Atlantic salmon ( Salmo salar , L.) with a mean weight of 0.5 kg in a digestibility trial. The diets contained 100 or 150 g kg⁻¹ of precooked rye or wheat, replacing fish meal. There were no significant differences in apparent digestibility coefficients (ADC) of protein, fat or starch which could be related to dietary carbohydrate source or inclusion level. The ADC of dry matter and energy were higher for the diets with wheat than for those with rye, and higher for the diets with wheat than for those with rye, and higher for the diets with 100 g precooked grain kg⁻¹ than for those with 150 g kg⁻¹. The mean ADC of starch was 52% for rye, and 53% for wheat.     

Target spawning requirements for Atlantic salmon, Salmo salar L., in Newfoundland rivers

Abstract In recent years, there has been increasing pressure from user groups in Newfoundland and Labrador, Canada, to manage Atlantic salmon, Salmo salar L., on a river-specific basis. The requirement to maximize benefits to users while ensuring that conservation goals are met has resulted in an initiative to develop river-specific target spawning requirements. In Newfoundland, anadromous juvenile Atlantic salmon make widespread use of lacustrine habitat for rearing. Depending on the river, lacustrine habitat can account for a substantial proportion of total production. Therefore, target spawning requirements for a number of rivers in several management areas were derived in terms of the contribution of both riverine and lacustrine habitats. The approach adopted, and derivations of associated parameter values, are reviewed, and limitations and research needs are discussed.     

Nutritive value of partially dehulled and extruded sunflower meal for post-smolt Atlantic salmon (Salmo salar L.) in sea water

This study determined the digestibility of protein in partially dehulled sunflower meal (SFM) and then, as the main goal, the nutritive value of high‐temperature extruded (≤149°C) partially dehulled SFM (SFM_EX) for post‐smolt Atlantic salmon Salmo salar in sea water. The digestibility study was conducted using the settling column approach (‘Guelph system’) for faeces collection as described by Hajen, Higgs, Beames and Dosanjh. In the nutritive value study, triplicate groups of 50 salmon (mean weight ～116 g) in 4000‐L outdoor fibreglass tanks supplied with 25–40 L min^?1, filtered, oxygenated (dissolved oxygen, 7.0–8.5 mg L^?1), 11–12°C sea water (salinity, 29–31 g L^?1), were fed twice daily to satiation one of five steam‐pelleted dry diets that contained 422 g of digestible protein (DP) kg^?1 and ～16.4 MJ of digestible energy (DE) kg^?1 on a dry weight basis for 84 days. Low‐temperature‐dried anchovy meal (LT‐AM) comprised 68.2% of the basal diet protein whereas in four test diets, SFM_EX progressively replaced up to 33.0% of the DP provided by LT‐AM in the basal diet (SFM_EX≤271 g kg^?1 of dry matter). Sunflower meal had 87.9% DP. Diet treatment did not significantly affect specific growth rate (1.39–1.45% day^?1), feed efficiency (1.19–1.26), percentage of dietary protein retained (45.8–47.5), gross energy utilization (46.5–49.4%), per cent survival (96.0–99.3) or terminal whole body and muscle proximate compositions. We conclude that SFM_EX can comprise ≥271 g kg^?1 of the dry diet or ≥22.7% of the digestible dietary protein of post‐smolt Atlantic salmon in seawater without any adverse effects on their performance.     

Use of stable isotopes to distinguish farmed from wild Atlantic salmon, Salmo salar

Abstract –  Stable isotopes of carbon and nitrogen ( δ ¹³C and δ ¹⁵N) were examined in wild and aquaculture origin Atlantic salmon, Salmo salar , to evaluate their utility to identify escaped farmed fish. Samples of muscle tissue obtained from wild Conne River, Newfoundland, salmon were significantly more enriched in nitrogen ( δ ¹⁵N: mean = 12.75; SD ± 0.38‰) but depleted in lipid corrected carbon ( δ ¹³C': mean = −20.51; SD ± 0.23‰) by comparison with aquaculture specimens obtained from Bay d'Espoir, Newfoundland ( δ ¹⁵N = 10.96 ± 0.19‰;  δ ¹³C' = −19.25 ± 0.17‰) resulting in a complete separation of the two groups. Aquaculture specimens differed in δ ¹³C' from analyses of commercial salmon diet by 0.24‰, within the enrichment range associated with trophic transfers, while the δ ¹⁵N values in salmon muscle were enriched by 5.01‰. Although differences occurred in direct comparisons of white muscle and adipose tissue ( N  = 49), the average δ ¹³C' and δ ¹⁵N signatures varied in absolute amounts by only 0.5‰, supporting the use of adipose tissue as a nonlethal means to determine isotopic signatures of Atlantic salmon.     

Habitat utilization of juvenile Atlantic salmon (Salmo salar L.), brown trout (Salmo trutta L.) and Arctic charr (Salvelinus alpinus (L.)) in two lakes in northern Norway

Abstract— Habitat utilization of juvenile Atlantic salmon, brown trout and Arctic charr was investigated in two lakes in northern Norway during the icefree season. Both the vertical distribution and the distribution among different habitat types were studied by gillnetting with small mesh sized gillnets (8-15 mm) in different habitats. Salmon and trout were predominantly caught in the littoral and sublittoral zones (0-6 m depth). Access to shelter seemed to be the most important factor determining the horizontal distribution of small salmon and trout. Most of these fish were caught in stony or vegetated habitats, while few salmon and trout were caught on sandy locations or in the pelagic zone. In one of the lakes, there were significantly higher catch rates of salmon than of trout in the stony littoral (0-3 m), while in the other lake there were no significant differences in spatial distribution between these two species. Charr were primarily found in the profundal, sublittoral or pelagic zones of the lakes.     

Differences in the time of river entry of Atlantic salmon,Salmo salar L., spawning in different parts of the River North Esk

Abstract Spawning adult Atlantic salmon, Salmo salar L., were sampled in five tributaries of the River North Esk, Scotland, during the winters 1989/90 and 1990/91. The fish furthest upriver had higher sea- and smolt-ages and the one-sea-winter fish were smaller and more coloured than those spawning further downstream. These differences indicate that the uppermost tributaries are populated by fish which enter the river early in the year and the lowest tributaries by fish entering late in the year. Exactly why such a structure exists is not clear, but it is suggested that these differences may be adaptive and that selection effects may continually be modifying these populations.     

Retained levels of dietary α-, γ- and δ-tocopherol in tissues and body fluids of Atlantic salmon, Salmo salar, L.

The purpose of this study was to describe the relationship between dietary supplementation and concentration of γ- and δ-tocopherol (TOH) in tissues of Atlantic salmon, Salmo salar , L., when α-TOH was fed at a constant level. Post-smolt Atlantic salmon (230 g) in duplicate tanks were fed a fish-meal-based diet with 250 g kg⁻¹ lipid. Different combinations of RRR -tocopherylacetate preparations were added to give the following levels of TOH (mg kg⁻¹) in diets 1–4, respectively: 150α; 150α+ 100δ; 150α+ 50γ+ 50δ; 150α+ 100γ+ 100δ. The concentrations of γ- and δ-TOH in most tissues were directly proportional to the feed concentrations. Exceptions were γ-TOH in erythrocytes, spleen and kidney and δ-TOH in heart muscle, where the intercept with the y -axis was significantly different from zero. The relative retained levels of α-, γ- and δ-TOH in most tissues were similar to their biological activities in mammals. An exception was muscle and adipose tissue, where γ- and δ-TOH were retained at rates of 70–90% and 20–35% compared with α-TOH, respectively. α-TOH was retained to a greater extent when α-TOH was fed alone than when γ- and δ-TOH were added to the diet. Fish growth was significantly correlated to total dietary TOH concentration. The data suggest that turnover of tocopherols in Atlantic salmon is similar to that in mammals, i.e. that discrimination between the tocopherols is mediated through competition for a tocopherol-binding protein in the liver, and consequently that α-TOH is preferentially secreted in very low density lipoprotein. Muscle and adipose tissue appear to be supplied with tocopherols from chylomicrons that have not yet been exposed to the hepatic discrimination mechanism.     

Freshwater reconditioning and ranching of Atlantic salmon,Salmo salar L., kelts: growth and reproductive performance

Abstract Artificial reconditioning of Atlantic salmon in fresh water over two successive years produced kelt survival rates of 28% and 55% in years one and two, respectively. Eye damage and failure to identify non-feeders were important factors contributing to high mortalities. Average fecundities of kelts reconditioned for the first (1220 ova kg^-1) and second (1093 ova kg^-1) year were lower than obtained for virgin control fish (1590 and 1728 ova kg^-1 respectively). Average survival to swim-up for progeny of first-year (64.5%) and second-year (71.4%) reconditioned fish were similar to survival of virgin control fish progeny (72.3% and 68.9% respectively). Ranched kelts showed better growth parameters than for freshwater reconditioning but had lower average fecundities (1310 ova kg^-1 compared with 1820 ova kg^-1) and lower average progeny survival to swim-up (60.8% compared with 88.6%) than their control group.     

The effect of feed pigment type on flesh pigment deposition and colour in farmed Atlantic salmon, Salmo salar L.

The characteristic pink colour of salmonid flesh is a result of deposition of naturally occurring carotenoid pigments. Achieving successful pigmentation in farmed salmonids is a vital aspect of fish farming and commercial feed production. Currently commercial diets for farmed salmonids contain either or both of the synthetic pigments commercially available, astaxanthin and canthaxanthin. Atlantic salmon, Salmo salar L. ( = 220 g initial weight) were given feeds where the pigment source was astaxanthin only, canthaxanthin only or a astaxanthin/canthaxanthin mix. The rearing environment was 12 × 3 m tanks supplied with sea water at the EWOS research farm Lønningdal, near Bergen, Norway. As the proportion of dietary canthaxanthin increased, flesh pigment levels also showed an increase; the pigment content in the muscle of canthaxanthin‐only fed fish was 0.4 mg kg^?1 (or 14%) higher than that of the astaxanthin‐only fed fish, with the mixed pigment fed fish being intermediate between the two extremes. Results of cross‐section assessment for Minolta colorimeter redness (a*) values and Roche Salmofan^TM scores also showed an increase in colour with increasing proportions of canthaxanthin in the feed. The data reported clearly indicates that S. salar ( = 810 g final weight) of this size deposit canthaxanthin more efficiently than they do astaxanthin. These results contrast with those obtained by other authors with rainbow trout, Oncorynchus mykiss (Walbaum), and imply that the absorption or utilization of the pigments differs between species.     

Potential impact of climate warming on recreational fishing opportunities for Atlantic salmon, Salmo salar L., in Newfoundland, Canada

Potential impacts of climate warming on recreational fishing opportunities were addressed by assessing the frequency and extent that Atlantic salmon, Salmo salar L., rivers in Newfoundland have been closed over a 25-year period (1975 to 1999) because of warm water temperatures and low water levels. On average, approximately 28% of all salmon rivers were temporarily closed annually, with over 70% affected in some years. This has resulted in a loss of 35–65% of the potential fishing days available in some salmon fishing areas with the collective 1995 to 1999 period being impacted the most over the past two decades. Geographically, west and south-west coastal rivers were affected less from environmental closures than east and some south coast fishing areas. A trend for increased closures of rivers related to environmental reasons could reduce the economic importance of the recreational salmon fishery and also make it more difficult to assess the status of Atlantic salmon stocks, which is a requirement for conservation of the resource.     

Effects of catch and release angling on Atlantic salmon, Salmo salar L., of the Conne River, Newfoundland

The effects of catch and release angling on survival of Atlantic salmon, Salmo salar L., at Conne River, Newfoundland, were investigated by retaining angled ( n =49; experimental group) and trap-caught ( n =20; control group) fish in holding cages for up to 40 days. Samples were obtained from 8 June to 4 July, 2000, and partitioned among four water temperature strata. Apart from not being angled, control fish were handled, tagged, and transferred to holding cages in a manner similar to angled salmon. Water temperatures and discharge were monitored throughout the duration of the study. Overall, 8.2% of salmon caught and released died, but 12% died among salmon angled in water temperatures ≥ 17.9 °C. No control fish died. There were no significant differences in time associated with angling, exposure to air, tagging, transfer to holding cages, nor total handling time between salmon that survived vs. those that died. Results of the study should encourage managers to continue to use catch and release as a viable tool in the management of Atlantic salmon stocks.