Recent Salmon Declines: A Result of Lost Feeding Opportunities Due to Bad Timing?

As the timing of spring productivity blooms in near-shore areas advances due to warming trends in global climate, the selection pressures on out-migrating salmon smolts are shifting. Species and stocks that leave natal streams earlier may be favoured over later-migrating fish. The low post-release survival of hatchery fish during recent years may be in part due to static release times that do not take the timing of plankton blooms into account. This study examined the effects of release time on the migratory behaviour and survival of wild and hatchery-reared coho salmon (Oncorhynchus kisutch) using acoustic and coded-wire telemetry. Plankton monitoring and near-shore seining were also conducted to determine which habitat and food sources were favoured. Acoustic tags (n = 140) and coded-wire tags (n = 266,692) were implanted into coho salmon smolts at the Seymour and Quinsam Rivers, in British Columbia, Canada. Differences between wild and hatchery fish, and early and late releases were examined during the entire lifecycle. Physiological sampling was also carried out on 30 fish from each release group. The smolt-to-adult survival of coho salmon released during periods of high marine productivity was 1.5- to 3-fold greater than those released both before and after, and the fish's degree of smoltification affected their downstream migration time and duration of stay in the estuary. Therefore, hatchery managers should consider having smolts fully developed and ready for release during the peak of the near-shore plankton blooms. Monitoring chlorophyll a levels and water temperature early in the spring could provide a forecast of the timing of these blooms, giving hatcheries time to adjust their release schedule

The non-specific immune system and innate disease resistance in different strains of teleost fish

Evidence for genetic differences in innate disease resistance in fish have been demonstrated, but the mechanisms responsible for these differences are not well understood. This thesis tested the hypothesis that the non-specific immune system plays a significant role in the innate disease resistance of fish. The experimental approach was to compare the activity of the non-specific immune system in different strains of fish, and to investigate correlations between this activity and innate disease resistance Significant strain differences in the activity of the non-specific immune system were observed for chinook salmon {Oncorhynchus tshawytscha), Nile tilapia (Oreochromis niloticus), and coho salmon (O. kisntch). Disease challenges performed on two strains of coho salmon, showed that the disease resistant strain (highest survival) had a more active and sustained internal cellular and humoral non-specific immune response following the challenge. Further coho salmon strain comparisons showed significant differences in innate disease resistance, thought to be associated with the differences in the external non-specific immune system. When compared with other strains, the most disease resistant strain showed higher mucus bactericidal activity, which appeared to be partially due to increased mucus lysozyme activity and hemolytic activity. A bactericidal cationic peptide appeared to be present in the mucus and is reported for the first time in coho salmon. The strain comparisons reported in this thesis demonstrate the genetic variation of innate disease resistance and non-specific immunity in fish. Strain differences were most apparent in the internal non-specific immune system of infected fish, while strain differences in the activity of the external non-specific immune system were seen in healthy uninfected fish. The external and internal non-specific immune system appeared to have a significant role in preventing infections and subsequent disease-related mortality in fish. Increased activity in both the external and internal non-specific immune system was seen in the strains exhibiting the greatest innate disease resistance.Land and Food Systems, Faculty ofGraduat

Use it or lose it? Sablefish, Anoplopoma fimbria, a species representing a fifth teleostean group where the βNHE associated with the red blood cell adrenergic stress response has been secondarily lost

Like most teleosts, sablefish (Anoplopoma fimbria Pallas 1814) blood exhibits a moderate Root effect (~35% maximal desaturation), where a reduction in blood pH dramatically reduces O₂ carrying capacity, a mechanism important for oxygenating the eye and filling the swim bladder (SB) in teleosts. Although sablefish lack a SB, we observed a well-defined choroid rete at the eye. The adrenergically mediated cell swelling typically associated with a functional red blood cell (RBC) β-adrenergic Na⁺/H⁺ exchanger (βNHE), which would normally protect RBC pH, and thus O₂ transport, during a generalized acidosis, was not observed in sablefish blood. Neither isoproterenol (a β-agonist) nor 8-bromo cAMP could elicit this response. Furthermore, RBC osmotic shrinkage, known to stimulate NHEs in general and βNHE in other teleosts such as trout and flounder, resulted in no significant regulatory volume increase (RVI), further supporting the absence of a functional RBC βNHE. The onset of the Root effect occurs at a much lower RBC pH (6.83–6.92) than in other teleosts, and thus RBC βNHE may not be required to protect O₂ transport during a generalized acidosis in vivo. Phylogenetically, sablefish may represent a fifth group of teleosts exhibiting a secondary reduction or loss of βNHE activity. However, sablefish have not lost the choroid rete at the eye (unlike in the other four groups), which may still function with the Root effect to oxygenate the retina, but the low pH onset of the Root effect may ensure haemoglobin (Hb)-O₂ binding is not compromised at the respiratory surface during a general acidosis in the absence of RBC βNHE. The sablefish may represent an anomaly within the framework of Root effect evolution, in that they possess a moderate Root effect and a choroid rete at the eye, but lack the RBC βNHE and the SB system

Concurrent injection of a rhabdovirus-specific DNA vaccine with a polyvalent, oil-adjuvanted vaccine delays the specific anti-viral immune response in Atlantic salmon, Salmo salar L.

Vaccines are commonly used in salmonid aquaculture as a method of disease prevention. Although there is a substantial amount of published research regarding the immunological and physiological effects following the injection of different polyvalent vaccines and DNA vaccines, there are no published reports examining the physiological and immunological effects of concurrent vaccine injection, which is the situation encountered in aquaculture. Using key immunological parameters such as lysozyme activity and specific antibody titres we examined the short-term activation of the immune response of cultured Atlantic salmon (Salmo salar L.) following concurrent injection with a traditional, polyvalent, oil-adjuvanted vaccine (AV) and an IHNV-specific DNA vaccine (DV). Our results indicate that different aspects of the innate and adaptive immune responses are influenced in either a positive or negative manner. While concurrent vaccine injection elicited an increase in lysozyme activity, changes in antibody titre (Ab) were antigen specific. The production of anti-Aeromonas salmonicida Abs was significantly greater in the combined vaccine group at 296 degree days post-vaccine injection (dd pvi), while the production of anti-Listonella anguillarum Abs was significantly greater at 106 dd pvi in the combined vaccine group. Of even greater interest was the apparent delay in production of IHNV-specific neutralizing antibodies (NAb) when the DV was injected concurrently with the polyvalent AV. The results indicated that concurrent injection of a polyvalent oil-AV and a DV can be beneficial to the production of antibodies; however, the specific anti-viral response may be delayed

The mean stomach fullness of wild and hatchery coho salmon smolts in the Campbell River estuary and near-shore area from 2007 to 2009, with standard error.

<p>The mean stomach fullness of wild and hatchery coho salmon smolts in the Campbell River estuary and near-shore area from 2007 to 2009, with standard error.</p

Zooplankton, phytoplankton, and return rates of coho salmon jacks (red bars) and adults (blue bars) released during 2007 and 2008.

<p>Zooplankton, phytoplankton, and return rates of coho salmon jacks (red bars) and adults (blue bars) released during 2007 and 2008.</p

Zooplankton, phytoplankton and temperature in Discovery Passage during the 2009 monitoring period.

<p>Zooplankton, phytoplankton and temperature in Discovery Passage during the 2009 monitoring period.</p

Acoustically tagged wild (W) and hatchery (H) coho salmon released at the Quinsam Hatchery (Rel 2006) and Seymour Hatchery (Rel 2007), including the number released (N Rel) and the number and proportion of smolts detected in the respective estuaries (N Est, % Est).

<p>Acoustically tagged wild (W) and hatchery (H) coho salmon released at the Quinsam Hatchery (Rel 2006) and Seymour Hatchery (Rel 2007), including the number released (N Rel) and the number and proportion of smolts detected in the respective estuaries (N Est, % Est).</p