Protein degradation and protease activity of chum salmon (Oncorhynchus keta) muscle during spawning migration

Sarcoplasmic protein content decreased significantly and myosin heavy chain was degraded gradually during spawning migration of chum salmon (Oncorhynchus keta). Acid and neutral proteinase activities increased significantly during spawning migration. These proteinase activities were higher in females than in males. High levels of acid proteinase were not caused by the injury of lysosomal membranes. Considering the physiological states of chum salmon, neutral proteinase activity might be related to the degradation of muscle protein. As the changes in serum sex steroids were similar to those in the protease activities during spawning migration, it was considered that high levels of protease activity during spawning migration were closely related to the serum levels of androgens.     

Immunoreactive somatolactin cells in the pituitary of young,migrating, spawning and spent chinook salmon,Oncorhynchus tshawytscha

Immunocytochemical techniques using an antiserum to cod somatolactin (SL) demonstrated the presence of SL cells in the intermediate lobe of the pituitary in Oncorhynchus tshawytscha. The cells were small in yearling fish. Two groups of maturing fish were studied. In the spring run salmon collected in April and May during the upstream migration, the SL cells appeared stimulated. In September, during spawning, SL cell stimulation was maximal with indices of hypertrophy and degranulation often more marked in females than in males. In the other group, salmon of the fall run collected in the Pacific Ocean in August had well developed gonads, large gonadotropes and abundant SL cells. In spawning salmon (September) the SL cells were stimulated, mainly in females. However, the final stimulation was less intense than in spring run spawning fish. The SL cells were smaller, without evident granule release, but still abundant in spent salmon of the fall run caught at the end of November. Various factors (time spent in rivers before spawning, starvation, decalcification, stress, hypothalamic influences) were considered which might explain differences between spring and fall run salmon. These observations suggest that SL may play a role in the control of gonadal maturation in chinook salmon as it may also do in sockeye and chum salmon previously studied, and that SL cells may be sensitive to the ambient salinity.     

Lipid transport in female Fundulus heteroclitus during the reproductive season

Lipid transport during the reproductive cycle of seasonally spawning teleosts has been well described. However, there is little information on lipid transport in a multiple spawning teleost. We examined lipid transport during the reproductive cycle in Fundulus heteroclitus, a teleost that spawns in a semilunar fashion. Plasma levels of triglycerides more than double prior to spawning events and then drop off sharply around the time of spawning. Plasma levels of total cholesterol also changed throughout the spawning cycle, but those changes were not so pronounced. The fraction of lipid carried by very low density lipoprotein (VLDL) and low density lipoprotein (LDL) was greatest prior to spawning events, while high density lipoprotein (HDL) carried the greatest portion of lipid during the spawning period. Vitellogenin (Vtg) was detected prior to spawning events, but it never represented more than 5% of total plasma lipid, making it very unlikely that Vtg is responsible for the changes in plasma lipids that we observed. It is also unlikely that Vtg is solely responsible for transport of lipid to growing ovaries because it carries only a very small portion of plasma lipid. This is the first study we are aware of, that tracks changes in plasma lipids of a multiple spawning teleost with a great enough sampling frequency to resolve single spawning events. This revised version was published online in August 2006 with corrections to the Cover Date.     

Transport of alpha-tocopherol in Atlantic salmon (Salmo salar) during vitellogenesis

The transport of α-tocopherol was studied during vitellogenesis in Atlantic salmon that were fed diets with two levels of α-tocopherol. α-Tocopherol levels were measured in the flesh, liver, ovary and serum, and in the serum the α-tocopherol levels in the very low density lipoprotein (VLDL), low density lipoprotein (LDL), high density lipoprotein (HDL) and very high density lipoprotein (VHDL or vitellogenin) were also measured. Atlantic salmon store α-tocopherol mainly in their flesh because the muscle mass comprises 50% or more of live weight. During vitellogenesis the α-tocopherol content declined to about 10% of the level prior to maturation. The relative range of level of α-tocopherol in the lipoproteins was: HDL> LDL> VLDL> VHDL, irrespective of dietary levels of α-tocopherol. From the recent knowledge on lipid transport during vitellogenesis and the present data, we hypothesize that α-tocopherol is transported from peripheral tissues to liver by HDL and further transported from liver to ovary by LDL. Vitellogenin appears to play a minor role in the transportation of vitamin E to the ovary.     

Prespawning migratory behaviour of wild and farmed Atlantic salmon, Salmo salar L, in a north Norwegian river

The migration patterns of wild and released farmed Atlantic salmon, Salmo salar L., were studied by radio-telemetry during migration from entering a river to after spawning. The wild salmon were caught during return migration in bagnets and the farmed salmon were produced in a near by fish farm. Both groups were tagged and released at sea near the river mouth of the River Alta, North Norway. A pronounced individual variation in migration pattern was observed. No significant differences was found between wild and farmed salmon in the distance from entering the river mouth to the place of the first stop (recorded in the same pool for 5 days or longer) and the days from entering the river mouth to arrival at the first stop. For both wild and farmed salmon, mean migration speed was 2.6 km day¹, varying from 0.4 to 11.0 km day^-1. A larger proportion of farmed salmon distributed to the upper part of the river at spawning; mean distances from the river mouth were 30.1 and 19.1 km. respectively. Farmed salmon spent a significantly longer time from entering the river to reaching the area occupied during spawning.     

Energy use in spawning Atlantic salmon

Abstract – We studied some of the factors that might influence energy use in spawning Atlantic salmon (Salmo salar). Single females were placed into an experimental channel with either one or three males, after which spawning was monitored continuously. Male status was confirmed using genetic parentage analysis. Daily fat loss was monitored with the Torry Fish Fatmeter and validated through biochemical analyses. Several comparisons were in the expected direction but not statistically significant and therefore require further study: daily fat loss appeared higher for dominant males relative to subordinate males and in the three‐male treatment relative to the one‐male treatment. Most of the variation among individuals remained unexplained, suggesting that several as yet unknown factors strongly influence fat loss in spawning salmon. A large and significant effect was that daily fat loss was higher for females than for males, a difference that might contribute to the shorter spawning duration typical of females.     

Influence of dietary fatty acids on the lipid composition of lipoproteins in farmed Atlantic salmon (Salmo salar)

The dietary influence on the fatty acid composition of neutral lipids and phosphatidylcholine of very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL) of Atlantic salmon (Salmo salar) was studied, using soybean oil, capelin oil and sardine oil as lipid sources in the diets. The fish had a mean weight of 3 Kg and had been fed the experimental diets for 24 months. The results show that the fatty acid composition in the feed are important for the composition of the core lipids as well as the surface components of the lipoproteins.     

Growth promoting effects of carp serum components on goldfish culture cells

ABSTRACT:   The growth promoting effect of carp Cyprinus carpio serum was investigated in a medium for goldfish Carassius auratus cell culture. The cell growth rate was decreased in the L-15 medium containing carp serum free from low molecular weight (LMW) fraction of less than 10 000. The addition of this fraction to the medium recovered the original growth rate, whereas the fraction itself did not enhance cell growth. Similar experiments were carried out with carp serum lipoprotein and albumin-like protein fractions. The high density lipoprotein (HDL) fraction containing apolipoprotein (apo) A-I and apoA-II enhanced cell growth at 20°C and 35°C when added with the above-mentioned LMW fraction. A good proliferation was observed at both 20°C and 35°C with the HDL fraction at 0.58 mg/mL. Carp albumin-like protein fraction, mainly containing a 71 kDa-component, also enhanced goldfish cell growth with the LMW fraction at the two temperatures. These results suggest that HDL and albumin-like proteins play an important role in the goldfish cell growth cooperatively with LMW substances contained in carp serum.     

Serum lipoproteins in haddock, Melanogrammus aeglefinus L.

The lipoprotein and lipid composition of the serum in postabsorptive haddock was characterized. A low level of very low density lipoproteins (VLDL; <50 mg dL^?1) was observed in serum. High density lipoprotein (HDL) was the predominant lipoprotein class followed by low density lipoproteins (LDL). Of the lipoprotein classes, the highest proportions of triacylglycerol (28%) and phospholipid (64%) were observed in the lipid of VLDL and HDL, respectively. Serum lipid (48%), phospholipid (50%) cholesterol ester (65%) and HDL (51%) contained a high level of polyunsaturated FA, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Serum triacylglycerol (38%) and VLDL (36%) contained a lower proportion of polyunsaturated fatty acid. The phospholipid, triacylglycerol, cholesterol ester and cholesterol contents of the whole serum were 739, 214, 201 and 141 mg dL^?1 respectively. On the basis of total acyl carbon number, the 38C (36%) and 36C (24%) molecules were the predominant phospholipids. The 50C (11%), 52C (17%), 54C (21%), 56C (21%) and 58C (15%) molecules were the major triacylglycerols. High molecular weight apo B‐like proteins were observed in the VLDL, LDL and intermediate density lipoprotein (IDL) fractions. An apo AI‐like protein was predominant in the HDL fraction. The prevalence of enlarged fatty livers in cultured gadoid fish (i.e. haddock and cod) is a major constraint to their commercialization and has been associated with the level of dietary lipid. Information on lipid (triacylglycerol) transport out of the liver through the serum as lipoproteins (VLDL) has implications for our understanding of fatty liver development in cultured gadoid fish. The low level of VLDL triacylglycerol (<12 mg dL^?1) circulating in the serum of postabsorptive haddock suggests either a low level of lipid transport out of the liver as triacylglycerol or relatively rapid turn over of VLDL.     

Migratory behaviour of adult wild and escaped farmed Atlantic salmon, Salmo salar L., before, during and after spawning in a Norwegian river

The migratory behaviour of adult wild and escaped farmed Atlantic salmon, Salmo salar L., before, during after spawning in the River Namsen, Norway, was analysed using radio telemetry. The fish were caught, radio tagged and released into the fjord between 7 and 25 km from the river mouth. A significantly higher proportion of wild (74%) than farmed (43%) salmon was subsequently recorded in the river. Wild salmon (33%) were more frequently captured in the sea and in rivers than farmed salmon (14%). The migration speed from release to passing a data logger 11 km upstream from the river mouth was not significantly different between wild (20.6 km day^?1) and farmed (19.8 km day^?1) salmon. Wild salmon tagged when water flow in the river was increasing had a significantly higher migration speed than wild salmon tagged when water flow was decreasing. This was not true for farmed salmon. Farmed salmon were distributed significantly higher up the river than wild salmon during spawning, although both types of fish were found together in spawning areas. Thus, there was no geographical isolation to prevent spawning between wild and escaped farmed salmon. Farmed salmon had significantly more and longer up- and downstream movements than wild salmon during the spawning period. Unlike farmed salmon, the number of riverine movements by wild salmon increased significantly when variation in water flow increased. A smaller proportion of wild (9%) than farmed (77%) salmon survived through the winter after spawning.     

Interactions between naturalised exotic salmonids and reintroduced Atlantic salmon in a Lake Ontario tributary

Abstract – Atlantic salmon (Salmo salar) was once native to Lake Ontario, however, its numbers rapidly declined following colonisation by Europeans and the species was extirpated by 1896. Government agencies surrounding Lake Ontario are currently undertaking a variety of studies to assess the feasibility of reintroducing Atlantic salmon. We released hatchery‐reared adult Atlantic salmon into a Lake Ontario tributary to examine spawning interactions between this species and fall‐spawning exotic salmonids found in the same stream. Chinook salmon, coho salmon and brown trout were observed interacting with spawning Atlantic salmon in nearly one‐quarter of our observation bouts, with chinook salmon interacting most frequently. Whereas a previous investigation found that chinook salmon caused elevated agonistic behaviour and general activity by spawning Atlantic salmon, the present study found that interspecific courtship was the most common form of exotic interaction with spawning Atlantic salmon. In particular, we observed precocial male Chinook salmon courting female Atlantic salmon and defending the female against approach by male Atlantic salmon. We discuss the potential implications of these interactions on the Lake Ontario Atlantic salmon reintroduction programme.     

Replacing dietary fish oil with increasing levels of rapeseed oil and olive oil – effects on Atlantic salmon (Salmo salar L.) tissue and lipoprotein lipid composition and lipogenic enzyme activities

Six groups of Atlantic salmon, initial weight 142 ± 1 g, were fed increasing dietary inclusion of rapeseed oil (RO) in a regression design and one group was fed a 50% olive oil/50% capelin oil diet. Fatty acid composition was measured in red and white muscle, liver, and fatty acid and lipid class composition was measured in plasma and in the lipoproteins; very low density lipoprotein, low density lipoprotein, high density lipoprotein and nonlipoprotein fraction after 22 and 42 weeks of feeding. Further, the activities of liver NADH‐isocitrate dehydrogenase (ICDH), malic enzyme, glucose‐6‐phosphate dehydrogenase (G6PDH) and 6‐phosphogluconate dehydrogenase were measured at each sampling point. After 42 weeks of feeding the experimental diets, the tissue and lipoprotein fatty acid composition was highly affected by dietary fatty acid composition. Regressions showed that 22:1n ? 11, 18:1n ? 9, 18:3n ? 3 and 18:2n ? 6 are readily metabolized in all tissues analysed. Further, 20:5n ? 3 seems to be metabolized in muscle and retained in liver. 22:6n ? 3 was selectively retained in all the analysed tissues, and with higher retention in liver and plasma with higher polar lipid/neutral lipid ratio compared to white and red muscle. Liver from salmon fed 100% RO showed decreased G6PDH and increased ICDH activities compared to the other dietary groups; however, no linear relationship related to increased RO inclusion was detected. The amount of plasma lipoproteins, liver monoene fatty acid level and lipogenic enzyme activity decreased from the autumn to the winter sampling with concomitant decrease in temperature.     

Prespawning migratory behaviour and spawning success of sea-ranched Atlantic salmon, Salmo salar L., in the River Gudenaa, Denmark

The migratory behaviour of sea-ranched Atlantic salmon, Salmo salar L., was analysed by radio-telemetry in the River Gudenaa, Denmark. The main objectives were to: (1) estimate mortality of returning adults through the fjord; (2) observe rate of progression and migratory pattern in the fjord and river; and (3) record whether spawning occurs in the river. Forty-two returning salmon (19 males and 23 females of total body length from 60–97 cm) reared and released as smolts, were caught and equipped with external radio transmitters in the outer estuary of the River Gudenaa in 1994 and 1995. Of the tagged salmon, 18 (43%) were caught in the estuary, four (10%) were not recorded after release and 20 (47%) entered the river. The mean rate of progression through the fjord was 7.6 km d−1 (range 1.4–18.2) in 1994 and 5.4 km  d−1 (range 1.6–17.1) in 1995. Eleven salmon were alive at the onset of the spawning period. Eight were retrieved dead from the river during or after the spawning period; four with empty gonads assumed to be successful spawners, and four with intact gonads. In 1994, unsuccessful spawners (found dead with intact gonads) entered the river earlier and had a longer total migration distance in the river compared to successful spawners. This suggests that spawning success of sea-ranched salmon is associated with time of river entry and river migration length.     

Comparison of population dynamics of Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) in a small tributary of the River Scorff (Brittany, France)

The population dynamics of Atlantic salmon (Salmo salar L.) and brown trout (Salmo trutta L.) were compared in a small tributary of the River Scorff (Brittany, France) from spawning time to the beginning of the third growing season. The spawning and fry emergence of the two species took place at approximately the same time. In the first autumn, the densityof 0+ juveniles and settling rate from the egg stage were much higher in trout than in salmon. The emigration rate from 0+ population was much higher in trout than in salmon. The size of resident and migrating fish was always smaller in salmon than in trout, whatever the age. The low level of salmon production in the brook, compared with trout, was the result of low survival from egg to 0+ stage in autumn, combined with the small proportion of juveniles migrating after the first growing season. This was not compensated by a high number of migrants the next year. The role of physical habitat, inter-and intraspecific competition, predation and migration dependence on size and early sexual maturity is discussed. Indications are that small tributaries of the type studied are of great value for recruitment in trout but not very productive for juvenile salmon.     

Prespawn mortality in adult spring Chinook salmon outplanted above barrier dams

Keefer ML, Taylor GA, Garletts DF, Gauthier GA, Pierce TM, Caudill CC. Prespawn mortality in adult spring Chinook salmon outplanted above barrier dams.
Ecology of Freshwater Fish 2010: 19: 361–372. © 2010 John Wiley & Sons A/S Abstract – Dams without fish passage facilities block access to much of the historic spawning habitat of spring Chinook salmon (Oncorhynchus tshawytscha) in Oregon’s Willamette River basin. Adult salmon are routinely outplanted above the dams to supplement natural production, but many die before spawning despite extensive suitable habitat. In 2004–2007, we examined prespawn mortality patterns using live detection and carcass recovery data for 242 radio‐tagged outplants. Total prespawn mortality was 48%, but variability was high, ranging from 0% to 93% for individual release groups. Prespawn mortality was strongly condition dependent, consistently higher for females than males and higher for early release groups. Across years, warm water temperature in the migration corridor and at the collection site was associated with sharply higher mortality. Results highlight a need for better evaluations of the effects of adult mortality on population reintroduction and recovery and relationships among prespawn mortality, dam‐related temperature change and salmon life history and behaviour.     

Effects of hemi-castration on plasma steroid levels in two teleost fishes; the three-spined stickleback, Gasterosteus aculeatus, and the Atlantic salmon, Salmo salar

In order to study the possible homeostatic regulation of gonadal steroids in fishes, plasma steroid levels were measured in hemi-castrated and sham-operated nesting male three-spined sticklebacks, Gasterosteus aculeatus, and in mature 2-year old male Atlantic salmon, Salmo salar. Hemi-castration significantly suppressed androgen levels in both species. In sticklebacks, plasma levels of 11-ketotestosterone (11KT) were 56% and levels of testosterone (T) 55% of those found in sham-operated males. In hemi-castrated salmon the levels of 11KT were 63%, and the levels of T were 75% of the levels in sham-operated males. In contrast, levels of 17α,20β-dihydroxy-4-pregnen-3-one (17,20-P) in salmon (not measured in sticklebacks) were not different between hemi-castrated and sham-operated males. The results suggest that, although levels of the steroid 17,20-P were compensated in hemi-castrated salmon, the androgen levels in fish males in full spawning condition are not closely regulated by negative feedbacks. This revised version was published online in July 2006 with corrections to the Cover Date.     

A factorial experimental design for investigation of effects of dietary lipid content and pro- and antioxidants on lipid composition in Atlantic salmon (Salmo salar) tissues and lipoproteins

Sixteen groups of post smolt, Atlantic salmon ( Salmo salar ) (initial weight 148 ± 17 g) were fed diets with different lipid content and composition of pro- and antioxidants (vitamin E, vitamin C, astaxanthin, Fe, Cu and Mn). The composition of the experimental diets was based on a multivariate reduced factorial design (RFD) (2^7–3) with either high (+1) or low (–1) level (within limits of toxicity and requirement) of each of the seven dietary variables. Lipid class and fatty acid (FA) composition was analysed in retina, very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL). Further FA composition was analysed in fillet, liver and plasma. High dietary lipid increased growth, feed efficiency, fillet lipid level and the amount of LDL and HDL in plasma, whereas high dietary copper and high dietary vitamin E decreased the amount of plasma LDL. High dietary vitamin E decreased the amount of lipid and protein in LDL, whereas high dietary lipid increased cholesterol and cholesterol ester levels in plasma and HDL and the amount of lipid in LDL. Dietary astaxanthin and manganese affected retina PE levels. The FA composition did not differ significantly between the 16 diets. Dietary FA composition was reflected in fillet FA composition and gradually less in VLDL, LDL, HDL, plasma, liver and retina FA composition. Dietary lipid content influenced FA composition to some extent in the analysed tissues, i.e. generally high dietary lipid content led to a decreased relative amount of saturated and monoene fatty acids and an increase of the relative amount of polyene fatty acids.     

Metabolic adaptations of oxidative muscle during spawning migration in the Atlantic salmon <Emphasis Type="Italic">Salmo salar</Emphasis> L.

The adaptability/plasticity of the highly oxidative red muscle in Atlantic salmon was demonstrated during spawning migration. Substrate concentrations and the enzymatic pathways of ATP production were examined in red muscle obtained from Atlantic salmon at different sites along their migratory route in the Exploits River, Newfoundland, Canada. Individuals were chronologically sampled from a seawater site, two sites upstream, and at spawning. The 20% decrease in salmon body weight during the later stages of migration was accompanied by large decreases (mg dry weight⁻¹) in both glycogen (P < 0.01) and total muscle lipid (P < 0.01). In contrast, water content and protein concentration (mg dry weight⁻¹) of the red muscle increased by 25 and 34%, respectively, at spawning. Enzymes of the glycolytic pathways demonstrated a significant (P < 0.001) decrease in maximal activity as migration proceeded whereas enzymes of the oxidative phosphorylation pathways, specifically the citric acid cycle enzymes, exhibited an increase (P < 0.001) in maximal activity at spawning. The antioxidant enzyme superoxide dismutase also demonstrated an increase (P < 0.001) in maximal activity during the latter stages of migration. These adaptations imply that the red epaxial muscle of Atlantic salmon has a more efficient means of oxidizing lipids, while minimizing free radical damage, during the later stages of migration and spawning, thereby potentially increasing post spawning survival.     

Temporal spawning migration patterns of landlocked Atlantic salmon (Salmo salar) in a constructed stream

Landlocked Atlantic salmon (ouananiche, Salmo salar) spawning migration timing varies throughout its range and is influenced by a variety of environmental variables. This study examined the spawning migration time of landlocked Atlantic salmon in a small (4 ha) constructed stream linked to a large reservoir (32,600 ha) in Newfoundland, Canada. Salmon use of the stream was passively monitored using Passive Integrated Transponder (PIT) Tags from 2006 to 2012. Of the salmon tagged throughout the reservoir, 48% entered the stream during the spawning season and remained there for 18–36 days from late September to November before they returned to the reservoir. Most fish entered the stream at dusk (32%). The lunar cycle influenced the timing of migration each year. Mean stream discharge (cubic metres per second) influenced migration timing in some years, and water temperature appeared to have minimal impact on migration timing. Twenty per cent of fish migrated to the stream in multiple years and 51% of these individuals appeared to use the stream on a biennial or alternate year cycle. These results demonstrate that small constructed streams can attract salmon from throughout a large reservoir and can provide valuable habitat in areas where spawning habitat is limited.     

Changes in GnRH levels in the brain and pituitary gland during migrations of sockeye salmon and chum salmon

Levels of two moleculer types of gonadotropin-releasing hormone (GnRH), salmon GnRH (sGnRH) and chicken GnRH–II (cGnRH–II) in the various brain regions and pituitary gland of sockeye salmon (Oncorhynchus nerka) and chum salmon (O. keta) during smoltification and spawning migration, respectively, were measured using specific time-resolved fluoroimmunoassay (TR-FIA) systems. Changes in sGnRH levels in different brain regions tended to be specifically synchronized with serum thyroid hormone or pituitary gonadotropin (GTH) levels during smoltification and spawning migration, respectively. In contrast, cGnRH–II levels did not show such synchronized changes. SGnRH and cGnRH–II in various brain regions might have different roles during smoltification and spawning migration of salmonid fishes.