Ages at Migration of Atlantic Salmon (Salmo salar) in Miramichi River

1935 ◽  
Vol 1 (3) ◽  
pp. 159-169
Author(s):  
A. A. Blair

In 1,557 fish examined, the groups, based upon years in the sea and spawning marks, were:—grilse or 1+, 2 and 2+, 3 and 3+, and 1 S.M. and 2 S.M. groups. The 2 and 2+ form 85.1 per cent of the total (grilse excluded), and S.M. 12.8 per cent, and the 3 and 3+, 2.1 per cent. Of fish with one spawning mark, 68.3 per cent first spawned as grilse, 29.9 per cent after two sea winters, and 1.8 per cent after three sea winters. The S.M. group had 11 per cent return to river in less than a year after first spawning, the remainder in little better than a year. Most of the fish with two spawning marks had the same length of absence on both occasions. Only four smolt ages were found:—3 (78.1 per cent), 2 (15.1 per cent), 4 (6.6 per cent) and 5 (0.2 per cent).

1975 ◽  
Vol 32 (4) ◽  
pp. 559-563 ◽  
Author(s):  
James D. McCleave ◽  
Kristin A. Stred

Effects of three different-sized, internally placed dummy ultrasonic transmitters and one size externally placed dummy radio transmitter on swimming performance of Atlantic salmon (Salmo salar) smolts were determined. Critical swimming speeds were similar for fish in control groups and two of the groups tagged with internal transmitters. The widest internal dummy tag (19 mm long × 10 mm diameter) caused a significant (P < 0.05) decrement in swimming performance; the size representing the smallest available transmitters (33 mm long × 8 mm diameter) did not. Linear regression analysis of this latter group demonstrated that larger smolts carried the transmitter better than smaller smolts. Results indicated that fish longer than about 20 cm can successfully be tagged with the available transmitter. Externally placed dummy radio transmitters caused a highly significant (P < 0.01) decrease in swimming speed compared with that of controls.


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.


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