Survival Of Atlantic Salmon Research Articles

The influence of temperature on aqueous aluminium chemistry and survival of Atlantic salmon ( Salmo salar L.) fingerlings

The present study is mainly focusing on the effect of temperature on Al-chemistry and the resulting toxicity to fish. Atlantic salmon ( Salmo salar L.) fingerlings were exposed to water at defined combinations of temperature, pH and Al-concentration, and mortality was recorded. Mortality was correlated to the concentration of inorganic aluminium, and increased systematically with increasing temperature. The degree of ongoing Al-polymerization is thought to be the most important factor for the temperature dependent Al-toxicity observed.

Influence of the timing of initial feeding on the survival and growth of hatchery-reared Atlantic salmon ( Salmo salar L.)

This study investigated the effects of timing of initial feeding on growth and survival of Atlantic salmon ( Salmo salar L.) fry. Food was first presented to triplicate groups of 200 salmon fry at four different stages in development (375, 548, 653, 800 degree-days post-hatching). Alevins fed prior to final yolk resorption were significantly larger and had lower mortalities than those fed after the stage at which the maximum alevin wet weight (MAWW) was achieved (circa 435 degree-days post-hatching). Although the “window” of initial feeding opportunity lasted several weeks, delaying feeding much beyond MAWW reduced absolute growth. A 5-week delay led to mortalities which approached 60%. However, initial feeding can be delayed 1–2 weeks at 10°C without adversely affecting subsequent survival or specific growth rate.

Effects of temperature and feeding on smolting and seawater survival of Atlantic salmon ( Salmo salar)

Atlantic salmon were reared in fresh water at ambient temperature or under conditions of constant 11°C temperature from November to April. One of the ambient temperature groups was not fed during November and December in order to produce small fish for study during the smolting period. Yearling fish were transferred to seawater net-pens as yearlings at the end of April. Survival of the fish in seawater was compared among the groups. For determination of smolt development, gill Na +K +ATPase activity and plasma concentration of thyroid hormones were measured during the spring in fish in fresh water. Gill ATPase activity was elevated in the ambient temperature groups in February compared with the group in heated water. Plasma thyroxine showed an initial peak value in the ambient temperature-fasted group in March. During April and May all groups showed similar changes in ATPase and thyroid hormones, suggesting completion of smolting by the beginning of May. Survival of fish in seawater was greatest in the ambient-fed group and poorest in the heated-fed groups. All groups in seawater showed two periods of increased mortality. The first mortality occurred immediately after seawater entry; a second period of increased mortality occurred between the middle of June and middle of July. It is suggested by these results that warm water temperature in the winter may be detrimental to the subsequent survival of the fish in seawater.

Salmon ranching experiments in the River Imsa: Effect of timing of Atlantic salmon ( Salmo salar) smolt migration on survival to adults

We tested the hypothesis that survival of Atlantic salmon adapted to seawater in the spring does not change with time of release. This was done through successive releases of tagged smolts and post-smolts in the estuary of the River Imsa and at a sea locality 4 km outside the Research Station for Freshwater Fish at Ims, S.W. Norway, where the fish were reared. Based on tag returns it was demonstrated that survival was highest for fish released in the spring, at the same time natural smolts leave the River Imsa. In autumn and winter the survival to adults was poor. Our results suggest that there is a window of migration which gradually closes in late summer. We hypothesise that behaviour of the fish will change with time of release and that this will result in heavy predation at times other than spring.

Vitamin E and selenium prophylaxis against “Hitra disease” in farmed Atlantic salmon — a survival study

Effects of a parenteral administration of selenium, vitamin E or a combination of the two on the survival of Atlantic salmon with subclinical “Hitra disease” were compared using survival curves and related hypotheses-testing methods. The median survival time, i.e. the point when 50% of the individuals are dead, was 34 days in the Se group, 38 days in the vitamin E group, 31 days in the Se+vitamin E group, and 28 days in the control group which received only a placebo. Differences between the groups did not reach statistical significance; even when testing the vitamin E group against the control group the P value was about 15%. Thus, treatments did not prevent mortalities in salmon with subclinical “Hitra disease”.

Effects of Carlin tagging and fin clipping on survival of Atlantic salmon ( Salmo salar L.) released as smolts

During the period 1976–1979, in total 2567 wild migrating smolts of Atlantic salmon were Carlin-tagged, 2528 were adipose fin-clipped and 2309 individuals were released unmarked into the River Imsa, S.W. Norway. The smolts were caught in a permanent Wolf trap. The adult return rate to the river was highest for unmarked and lowest for Carlin-tagged fish. The main reason for this is probably a mortality of smolts due to handling, anaesthesia and tagging.

Estimating Survival of Atlantic Salmon during the Intragravel Period

Abstract Survival of Atlantic salmon Salmo salar between fertilization and emergence was monitored in Northern Stream, Washington County, Maine. Green eggs were buried in modified Whitlock–Vibert egg boxes and survival was estimated on five occasions–four before emergence and one at emergence. Survival was 74% through hatching, but decreased rapidly after hatching to only 2% at emergence.

Genetic variation in survival of Atlantic salmon during the sea-rearing period

Data from three year-classes of Atlantic salmon were analysed to estimate the heritability for survival during the sea-rearing period. The overall survival for each year-class during 2 years in the sea was 31.8, 51.1 and 25.5%. Haemorrhagic syndrome (“Hitra disease”) was the main cause of death in all year-classes. Heritabilities for survival calculated on the observed scale varied from 0 to 0.21, based on the sire components of variance. Heritabilities for survival were also calculated for two separate parts of the seawater phase. Correlations between sire least square means for survival and body weight, length and condition factor at slaughter were positive in general, but varied from −0.18 to 0.38. Correlations between sire least square means for survival and % immature fish after 1.5 years in the sea were negative in general, but varied from −0.45 to 0.03.

Artificial reconditioning, spawning and survival of Atlantic salmon, Salmo salar L., kelts in salt water and survival of their Fl progeny

. Atlantic salmon kelts were successfully reconditioned in salinities of 16% and 28%o using a moist pellet diet. Two groups of reconditioned kelts were re-acclimated to fresh water in the autumn tu prevent super chitling in salt water during the winter. The feeding response and growth of salmon kelis. both years, was highest when salinities were maintained at 28% during the winter and 16%during the summer. However, other salinities also provided acceptable growth rates. Two-sea-winter salmon kelts reconditioned at a slower rate in all groups than 1-sea-winter salmon kelts. Kelt survival was 93.1% the first year and 82.7% the second year. Gonnd maturation occurred in 17.9% of the female 1-sea-winter kelts and 40.6% of the male 1-sea-winter kelts after the first year. At the end of the second year. 83.3% of the 1-sea-winter female kelts and 96.3% of the l-sea-winter male kelts matured and spawned. Reconditioned salmon kelts with a mean fork length of 68.4 cm produced 7261 eggs per fish with a mean egg diameter of 5.70 mm and a fecundity of 2262 eggs.kg−1, Survival (Fl) from the green egg stage to the alevin and smolt stages was 73.5% and 38.8% respectively. The smolt to adult return rule based on unadjusted tug recaptures was 2.20%.

Growth and survival of Atlantic salmon (Salmo salar) in Llyn Dwythwch, North Wales

SUMMARY. Atlantic salmon fry have been annually stocked into Llyn Dwythwch, North Wales, since 1969, in an attempt to increase the natural stocks of the area. The growth and survival of 1‐ and 2‐year‐old salmon were investigated, and compared with that of other lake‐reared populations and also with salmon in the natural stream environment. Lake‐reared salmon follow the same patterns of slow and rapid growth as found for river fish, but the growth rate was superior in the former. The variation in length – weight relationship with age and sex was investigated. Survival rates in general compared favourably with the survival in rivers, with high mortality rates of salmon in Llyn Dwythwch resulting from predation at spring stocking by the resident brown trout. This was later avoided by stocking larger fish in the autumn.