Manipulation of the energetic state of Atlantic salmon Salmo salar juveniles and the effect on migration speed

2018 ◽  
Vol 92 (4) ◽  
pp. 961-978 ◽  
Author(s):  
L. Persson ◽  
K. Leonardsson ◽  
A. Alanärä
2018 ◽  
Vol 75 (8) ◽  
pp. 1177-1184 ◽  
Author(s):  
Riina Huusko ◽  
Pekka Hyvärinen ◽  
Mikko Jaukkuri ◽  
Aki Mäki-Petäys ◽  
Panu Orell ◽  
...  

Connectivity problems in fish migration in regulated rivers have been widely studied, but few studies have rigorously compared parallel migration success between regulated and free-flowing rivers. Here, survival and migration speed of downstream migrating radio-tagged Atlantic salmon (Salmo salar) smolts were studied in two large neighboring rivers in the northern Baltic Sea area: one without and one with dams. Both rivers have a free-flowing upper section, where the survival and migration speed of salmon smolts were similar. Survival along the lower section of the free-flowing river was about six times higher than in the lower part of the regulated river with five hydropower plants. Migration speed of smolts was also significantly faster in the river without dams. These severe problems in downstream connectivity in the regulated river pose challenging tasks for restoration of salmon populations.


2012 ◽  
Vol 69 (12) ◽  
pp. 1981-1993 ◽  
Author(s):  
Anssi Vainikka ◽  
Riina Huusko ◽  
Pekka Hyvärinen ◽  
Pekka K. Korhonen ◽  
Tapio Laaksonen ◽  
...  

Since food availability is known to affect both the precocious maturation and start of feeding migration in wild juvenile salmonids, we examined if a reduction in otherwise plentiful feeding in hatcheries could improve migration tendency and the subsequent survival of released Atlantic salmon (Salmo salar) smolts. A reduction in diet lipid content and feed ration (FR) the previous spring and in FR in the winter prior to release proved efficient; spring-diet treatment halved the proportion of mature males in the autumn prior to release, and a reduction in FR in the winter prior to release decreased latency before leaving the stocking site. In addition, a reduction in FR in winter affected the onset of migration, improved migration speed, and defined the direction of migration downstream in controlled experiments. However, diet manipulations neither affected the swimming endurance nor improved the generally poor tag recapture rates. We conclude that reduced FR at specific times could be used to reduce both precocious male maturity and improve the migration tendency of released salmon.


2001 ◽  
Vol 32 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Sjofn Sigurgisladottir ◽  
Margret S. Sigurdardottir ◽  
Helga Ingvarsdottir ◽  
Ole J. Torrissen ◽  
Hannes Hafsteinsson

2005 ◽  
Vol 68 (7) ◽  
pp. 1336-1339 ◽  
Author(s):  
L. L. NESSE ◽  
T. LØVOLD ◽  
B. BERGSJØ ◽  
K. NORDBY ◽  
C. WALLACE ◽  
...  

The objective of our experiments was to study the persistence and dissemination of orally administered Salmonella in smoltified Atlantic salmon. In experiment 1, salmon kept at 15°C were fed for 1 week with feed contaminated with 96 most-probable-number units of Salmonella Agona per 100 g of feed and then starved for 2 weeks. Samples were taken from the gastrointestinal tract and examined for Salmonella 1, 2, 8, 9, 15, and 16 days after the feeding ended. In experiment 2, Salmonella Agona and Montevideo were separately mixed with feed and administered by gastric intubation. Each fish received 1.0 × 108, 1.0 × 106, or 1.0 × 104 CFU. The different groups were kept in parallel at 5 and 15°C and observed for 4 weeks. Every week, three fish in each group were sacrificed, and samples were taken from the skin, the pooled internal organs, the muscle, and the gastrointestinal tract and examined for the presence of Salmonella. The results from the two experiments showed that the persistence of Salmonella in the fish was highly dependent on the dose administered. Salmonella was not recovered from any of the fish that were fed for 1 week with the lowest concentration of Salmonella. In the fish given the highest dose of Salmonella, bacteria persisted for at least 4 weeks in the gastrointestinal tract as well as, to some extent, the internal organs. The present study shows that under practical conditions in Norway, the risk of Salmonella in fish feed being passed on to the consumer of the fish is negligible.


2021 ◽  
Vol 9 (4) ◽  
pp. 703
Author(s):  
Deborah Vargas ◽  
Eva Vallejos-Vidal ◽  
Sebastián Reyes-Cerpa ◽  
Aarón Oyarzún-Arrau ◽  
Claudio Acuña-Castillo ◽  
...  

Piscirickettsia salmonis, the etiological agent of the Salmon Rickettsial Septicemia (SRS), is one the most serious health problems for the Chilean salmon industry. Typical antimicrobial strategies used against P. salmonis include antibiotics and vaccines, but these applications have largely failed. A few years ago, the first attenuated-live vaccine against SRS (ALPHA JECT LiVac® SRS vaccine) was released to the market. However, there is no data about the agents involved in the activation of the immune response induced under field conditions. Therefore, in this study we evaluated the expression profile of a set of gene markers related to innate and adaptive immunity in the context of a cellular response in Atlantic salmon (Salmo salar) reared under productive farm conditions and immunized with a live-attenuated vaccine against P. salmonis. We analyzed the expression at zero, 5-, 15- and 45-days post-vaccination (dpv). Our results reveal that the administration of the attenuated live SRS LiVac vaccine induces a short-term upregulation of the cellular-mediated immune response at 5 dpv modulated by the upregulation of ifnα, ifnγ, and the cd4 and cd8α T cell surface markers. In addition, we also registered the upregulation of il-10 and tgfβ. Altogether, the results suggest that a balanced activation of the immune response took place only at early times post-vaccination (5 dpv). The scope of this short-term upregulation of the cellular-mediated immune response against a natural outbreak in fish subjected to productive farm conditions deserves further research.


Sign in / Sign up

Export Citation Format

Share Document