Atlantic Salmon Salmo Salar Fry Research Articles

Reducing mortality associated with opportunistic infections in Atlantic salmonSalmo salarfry using hydrogen peroxide and peracetic acid

Developing efficacious protocols for applying water disinfectants to reduce opportunistic pathogen-associated mortalities during the Atlantic salmon Salmo salar fry stage would be highly beneficial for producers. Atlantic salmon fry (0.47 g ± 0.02) were exposed to daily stressors over four weeks while providing daily 30-min bath treatments of 15 mg/L hydrogen peroxide (H2O2), 0.2 mg/L peracetic acid (PAA) or 0.5 mg/L PAA. Survival was tracked, and skin and gill samples were collected at 2 and 4 weeks for histopathology. Moribund fish were regularly assessed via wet-mount microscopy, with organisms resembling Saprolegnia spp. routinely observed on gills of affected fish. Tanks treated with H2O2 had significantly (p < 0.05) higher survival (83.7% ± 1.7) compared to controls (69.5% ± 5.2) while no significant differences were observed between either PAA treatments (76.6% ± 0.6 and 77.4% ± 3.0 survival in the 0.2 mg/L and 0.5 mg/L PAA groups, respectively) and controls. Interestingly, no significant differences were noted among treatments for waterborne Saprolegnia spp. concentrations through qPCR quantification. Lower total suspended solids (TSS) were observed in both PAA treatment groups; no other water quality differences were noted. No treatment impacts were observed through histopathology at either sampling point. These results suggest that, at the dosage and treatment regime tested, H2O2 can be a safe and efficacious water treatment for reducing Atlantic salmon fry opportunistic infection-associated mortality during periods of physical and environmental stress. Assessments of alternative PAA treatment regimens should also be considered in future research aimed at reducing early life-stage mortality in Atlantic salmon.

Evidence of Atlantic salmon Salmo salar fry movement between fresh water and a brackish environment.

This study reports descent of Atlantic salmon Salmo salar fry from their natal streams to brackish waters of the Baltic Sea and their use of this environment as an alternative rearing habitat before ascending back to freshwater streams. To the authors' knowledge, residency in a brackish environment has not previously been demonstrated in S. salar fry. Recruitment success and evolutionary significance of this alternative life-history strategy are presently not known.

Maladaptation and phenotypic mismatch in hatchery-reared Atlantic salmon Salmo salar released in the wild.

Changes in body shape, fluctuating asymmetry (FA) and crypsis were compared among Atlantic salmon Salmo salar fry kept as controls in captivity and those released and subsequently recaptured in the wild according to a before-after-control-impact (BACI) design. Hatchery fish that survived in the wild became more cryptic and displayed a much lower incidence of fin erosion and of asymmetric individuals than control fish kept in captivity. Significant differences in body shape were also apparent, and survivors had longer heads, thicker caudal peduncles and a more streamlined body shape than hatchery controls as early as 20 days following stocking, most likely as a result of phenotypic plasticity and non-random, selective mortality of maladapted phenotypes. Hatchery-reared fish typically perform poorly in the wild and the results of this study indicate that this may be due to phenotypic mismatch, i.e. because hatcheries generate fish that are phenotypically mismatched to the natural environment.

Growth hormone transgenesis does not influence territorial dominance or growth and survival of first-feeding Atlantic salmon Salmo salar in food-limited stream microcosms

This study explored the relative competitive ability and performance of first-feeding growth hormone (GH) transgenic and non-transgenic Atlantic salmon Salmo salar fry under low food conditions. Pair-wise dominance trials indicated a strong competitive advantage for residents of a contested foraging territory. Transgenic and non-transgenic individuals, however, were equally likely to be dominant. Similarly, in stream environments with limited food, the transgene did not influence the growth in mass or survival at high or low fry densities. Fry in low-density treatments, however, performed better than fry in high-density treatments. These results indicate that, under the environment examined, the growth performance of GH-transgenic and non-transgenic S. salar may be similar during first feeding, an intense period of selection in their life history. Similarities in competitive ability and growth performance with wild-type fish suggest that the capacity of transgenic S. salar to establish in natural streams may not be inhibited during early life history.

Rapid, Efficient Growth Reduces Mercury Concentrations in Stream‐Dwelling Atlantic Salmon

Mercury (Hg) is a potent toxin that biomagnifies in aquatic food webs. Large fish generally have higher Hg concentrations than small fish of the same species. However, models predict that fish that grow large faster should have lower Hg concentrations than small, slow-growing fish due to somatic growth dilution (SGD). We examined the relationship between Hg concentrations and growth rate in fish using a large-scale field experiment. Atlantic salmon (Salmo salar) fry hatched under uniform initial conditions were released at eighteen sites in natural streams, collected after one growing season, and Hg concentration and growth measured. As expected for Hg accumulation from food, mercury concentrations in salmon tracked Hg concentrations in their prey. Nonetheless, large, fast-growing salmon had lower Hg concentrations than small, slow-growing salmon, consistent with SGD. While prey Hg concentration accounted for 59% of the explained variation in salmon Hg concentration across sites, salmon growth rate accounted for 38% of the explained variation independent of prey Hg concentration. A mass-balance Hg accumulation model shows that such SGD occurs when fast growth is associated with high growth efficiency. Fish growth is tremendously variable and sensitive to anthropogenic impacts, so SGD of Hg has important implications for fisheries management.

Evaluation of a new semi‐natural incubation technique for Atlantic salmon Salmo salar fry

The incubation environment had a significant effect on fork length (L(F)) and body mass (M) of Atlantic salmon Salmo salar fry at the time of emergence. Fry that were incubated in a new incubator design, that mimics the conditions in a natural redd (the Bamberger-Box), achieved significantly greater and attained a significantly higher M than those reared in conventional hatchery troughs for control. Fewer fry from the Bamberger-Boxes had visible deformities compared with those from the hatchery troughs. Results were consistent for five consecutive seasons using both wild and domesticated broodstock from genetically different origins. Survival from the eyed embryo stage in the Bamberger-Boxes and hatchery troughs was >93% during normal climatic conditions. Only larvae reared in Bamberger-Boxes, however, survived abnormally high water temperatures during one test season. The results demonstrate that the Bamberger-Box is an effective alternative to the conventional incubation technology.

Predator‐induced hyperventilation in wild and hatchery Atlantic salmon fry

Following exposure to a predator stimulus (a brown trout Salmo trutta), the opercular rate of Atlantic salmon Salmo salar fry increased by 35·3 ± 11·0%(mean ± 95% CI). The time taken for opercular rate to decline to baseline levels depended upon the occurrence of any associated locomotory activity. Opercular rates of fish that dashed when exposed remained elevated for 38·2 ± 20·6 min, whereas those of individuals that did not move (‘freezers’) recovered within 7·2 ± 2·9 min. The duration that opercular rate remained elevated was positively correlated with the magnitude of the elevation, which was higher in ‘dashers’ than freezers. The maximum opercular rate in ‘freezers’ was similar between wild fry and hatchery‐reared fry (from wild parents). There was a significant delay, however, in hatchery compared with wild fry in the time until peak ventilatory response and onset in the decline phase. This difference in opercular response suggests that hatchery fish were slower to realize fully the potential danger from the predator. Any delay in response could be directly attributed to the effect of hatchery‐rearing environment, rather than domestication or hatchery selection effects.

A Comparison of Atlantic Salmon Embryo and Fry Stocking in the Salmon River, New York

Abstract To assess the feasibility of restoring an extirpated species, it is crucial to identify the method of reintroduction that optimizes juvenile survival and growth so that adequate adult populations may be established. Because Atlantic salmon Salmo salar fry are relatively expensive to rear, we compared the efficacies of two embryo-stocking methods and one fry-stocking method in producing age-0 Atlantic salmon parr in the Salmon River, New York. As measured by resulting parr densities, there were no differences in survival rates between embryos stocked with and without protective hatching boxes; the mean survival of embryo-stocked fish to late summer was less than 0.01%. Fry stocking produced significantly greater densities of late-summer parr than did embryo stocking, with site-specific survival ranging up to 8%; the mean survival of fry was 2%. Considering the hatchery costs of rearing each life stage, the labor involved in stocking, and the resulting late-summer parr abundances, we recommend plan...

Metabolic recovery in Atlantic salmon fry and parr following forced activity

Atlantic salmon Salmo salar fry and parr were subjected to 5 min of forced activity and the subsequent changes in oxygen consumption and ammonia excretion rates were evaluated over a 24 h period. In a second experiment, individual Atlantic salmon fry and parr were freeze‐clamped in liquid nitrogen, before, immediately following a 5 min activity period, or after periods of recovery up to 2 h. Samples were analysed for whole body phosphocreatine (PCr), ATP and lactate. Five minutes of forced activity resulted in significant increases in both oxygen consumption and ammonia excretion rates. Changes in the oxygen consumption rates were greater in the parr compared with the fry. In contrast, the post‐exercise ammonia excretion rates were nearly twice as high for the fry compared with the parr. Exercise also caused a marked decrease in PCr levels (c. 47 and 65% in fry and parr, respectively), no change in ATP levels and a significant increase in lactate levels in Atlantic salmon fry and parr. Recovery of PCr occurred quickly (between 15 and 30 min) in fry and parr. Although the post‐activity levels of lactate were lower in fry (c. 3 μmol g−1) compared with parr (c. 14 μmol g−1), lactate levels returned to control levels within 60 min in fry, but it took &gt;2 h for this metabolite to recover in parr. Compared with parr, these findings show that Atlantic salmon fry possess a reduced anaerobic capacity, and these results are consistent with the theoretical and experimental evidence that smaller fish support burst swimming through aerobic processes.

Influence of egg vitamin A status and egg incubation temperature on subsequent development of the early vertebral column in Atlantic salmon fry

The effect of egg vitamin A (VA) status and egg incubation temperature on the development of spinal disorders was investigated in Atlantic salmon Salmo salar fry. Atlantic salmon eggs were sorted into two groups with high VA (3·3 ± 0·1 μg retinol g−1 dry mass) and low VA (2·2 ± 0·3 μg retinol g−1 dry mass) status before fertilization and incubated at high (14° C) or low (8° C) temperature from 133 day degrees until the onset of feeding. High egg incubation temperatures increased the concentration of retinol in the eggs: the high VA and high temperature group displayed a significantly higher retinol concentration than the high VA and low temperature group (P = 0·001). After hatching, all experimental groups increased their retinol concentration. The source of the increased retinol levels was probably retinal, although astaxanthin may also be a VA precursor after hatching. Atlantic salmon fry incubated at high temperatures had increased amounts of notochord tissue. When measuring morphogenic activity in the notochord using the expression of sonic hedgehog (shh, mRNA), however, no significant difference was found between the experimental groups. No clear effect of VA status or incubation temperature could be found on the formation of the early vertebral column although Atlantic salmon fry incubated at low temperatures had less regular constrictions of the prospective vertebral column than fry incubated at high temperatures.

Induction of infectious pancreatic necrosis (IPN) in Atlantic salmon Salmo salar and brook trout Salvelinus fontinalis by bath challenge of fry with infectious pancreatic necrosis virus (IPNV) serotype Sp

DAO Diseases of Aquatic Organisms Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials DAO 28:39-44 (1997) - doi:10.3354/dao028039 Induction of infectious pancreatic necrosis (IPN) in Atlantic salmon Salmo salar and brook trout Salvelinus fontinalis by bath challenge of fry with infectious pancreatic necrosis virus (IPNV) serotype Sp Taksdal T, Stangeland K, Dannevig BH Thirteen week old Atlantic salmon Salmo salar fry and 15 wk old brook trout Salvelinus fontinalis with average weights of 0.19 and 0.17 g, respectively, were bath challenged with infectious pancreatic necrosis virus (IPNV), serotype Sp, N1 strain. The virus had been isolated from a clinical outbreak of infectious pancreatic necrosis (IPN) in Atlantic salmon parr. Cell culture supernatant after a first passage of virus was used as the infective material. Approximately 400 fry of each species were divided into 2 parallel tanks with challenged fish and 2 parallel tanks with non-challenged fish. At 69 d after challenge, cumulative mortalities of Atlantic salmon were 76 and 82% for the challenged groups and 6 and 15% for the non-challenged groups. The corresponding values for brook trout were 42 and 43% for the challenged groups and 8 and 10% for the non-challenged groups. The onset of mortality in challenged Atlantic salmon was delayed compared with the onset in brook trout. IPNV was re-isolated from the fry of all challenged groups. Histological examination of sampled moribund fish showed hepatic degeneration or necrosis and exocrine pancreatic necrosis in fry from all challenged groups. The presence of IPNV in the lesions was demonstrated immunohistochemically. Virological, histological and immunohistochemical examinations of fry sampled prior to challenge and of non-challenged fry gave negative results. This study represents, to our knowledge, the first report of an experimental induction of clinical IPN in Atlantic salmon fry. Infectious pancreatic necrosis · Atlantic salmon · Brook trout Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in DAO Vol. 28, No. 1. Publication date: January 16, 1997 Print ISSN:0177-5103; Online ISSN:1616-1580 Copyright © 1997 Inter-Research.