Landlocked Fall Chinook Salmon Egg Research Articles

Effects of Two Activated Milt Residence Times on Landlocked Fall Chinook Salmon Egg Survival to the Eyed Stage of Development

AbstractDuring salmonid spawning, the amount of time required for activated milt to successfully fertilize eggs has not been well defined. This study examined the effects of two different activated milt residence times, 20 and 60 s, during production‐scale artificial spawning of 20 landlocked fall Chinook Salmon Oncorhynchus tshawytscha. Mean (SE) survival to the eyed stage of egg development was 29.2% (5.5) in the eggs that were subjected to the 20‐s milt residence time, which was not significantly different from the 32.3% (5.7) survival rate for eggs with the 60‐s residence time. There was considerable variation in egg survival among the individual female spawns, ranging from near 0% to 76.7%. These production‐scale results indicate that activated milt residence times as low as 20 s can be used during the landlocked fall Chinook Salmon spawning, with no significant effect on egg survival to the eyed stage of development.

Landlocked Fall Chinook Salmon Egg Storage for Delayed Fertilization

Delayed fertilization of salmonid eggs can be a useful option to enhance the efficiency of artificial spawning operations. This experiment examined the fertility of landlocked fall Chinook salmon (Oncorhynchus tshawytscha) eggs stored for various times after removal from female broodstock. Fertilization occurred either immediately after spawning or the eggs were stored with oxygen at 11°C and fertilized at 4, 6, 8, 12, or 20 hours post-spawn. Survival to the eyed stage of egg development was significantly greater in the eggs fertilized immediately or after four, six, or eight hours of storage compared to those eggs stored for 12 or 20 hours prior to fertilization (P = 0.024). Survival to hatch was also significantly different (P = 0.018) and followed the same pattern. This study is the first to document the successful fertilization of landlocked fall Chinook salmon eggs after eight hours of storage.

Effect of Activated Milt Residence Time on Landlocked Fall Chinook Salmon Egg Survival

During artificial spawning of salmonids, activated sperm is allowed to remain in contact with eggs for variable durations. This study examined multiple residence times (20, 40, 60, 90, or 120 seconds) for activated sperm on landlocked fall Chinook salmon (Oncorhynchus tshawytscha) eggs during spawning. There was no significant difference in egg survival to the eyed-stage of development or to hatch among any of the treatments, with a mean (SE) percent survival to the eyed stage of 63.9 (5.8). These results indicate that only relatively short residence times of activated milt on eggs during landlocked fall Chinook salmon spawning are needed to ensure egg survival, resulting in potentially substantial reductions in production-level spawning times and associated labor costs.

Impacts of Zebra Mussel Veliger Control Treatments on the Survival of Water-Hardened Landlocked Fall Chinook Salmon Eggs

Several treatment options have been developed to minimize the spread of zebra mussel Dreissena polymorphaveligers (larvae) during fish transportation. However, the effect of these treatments on the survival of newly-fertilized salmonid eggs has not been evaluated. This study examined the survival of water-hardened landlocked fall Chinook salmon Oncorhynchus tshawytscha eggs after one of four different treatments: 1) Control (no chemicals), 2) 100 mg/L formalin for two hours, 3) 750 mg/L of potassium chloride for one hour followed by 20 mg/L formalin for two hours, and 4) 750 mg/L of potassium chloride for one hour followed by 20 mg/L formalin for three hours. The 100 mg/L formalin treatment produced complete egg mortality. Survival to hatch was not significantly different among the other three treatments. Based on these results, the use of 750 mg/L potassium chloride for one hour followed by 20 mg/L formalin for three hours is recommended when moving Chinook salmon eggs from waters potentially infested with zebra mussels to hatcheries for incubation.

The Relationship Between Digital Egg Coloration and Egg Survival in Landlocked Fall Chinook

Digital color values were collected from the eggs of 128 spawns from individual landlocked fall Chinook salmon Oncorhynchus tshawytscha females from Lake Oahe, South Dakota, USA, in 2008, 2009, 2015 and 2016. For all spawns, the mean (SE) a* value, a measure of red-green chromaticness, was 10.99 (0.27), and ranged from 3.98 to 18.71. Mean (SE) b* (yellow-green) was 20.27 (0.32), and ranged from 9.28 to 28.50. Mean (SE) L* (white-black) was 20.73 (0.48), and ranged from 3.98 to 18.71. Egg total color index also showed considerable variation, with a mean (SE) of 23.05 (0.37) and range from 11.70 to 31.64. Egg survival to the eyed-stage was weakly, but significantly, correlated to b* (r = 0.206), L* (r = 0.185), Chroma (r = 0.211), and Entire Color Index (r = 0.211). Spawns with no egg survival had eggs with significantly lower a* values compared to spawns where at least some of the eggs survived to the eyed stage. L*, a*, b*, Chroma, and Entire Color Index varied significantly among the years, but Hue and egg survival to the eyed stage did not. The results of this study indicate a possible link between egg color and landlocked fall Chinook salmon egg survival, possibly due to differences in the diets of feral broodstock females or their ability to deposit bodily carotenoids in the developing eggs.

Iodine Concentrations Prior to Initial Incubation Do Not Impact the Bacterial Communities of Landlocked Fall Chinook salmon Eggs at the Eyed Stage of Development

Iodine Concentrations Prior to Initial Incubation Do Not Impact the Bacterial Communities of Landlocked Fall Chinook salmon Eggs at the Eyed Stage of Development

Increasing Iodine Concentrations during Landlocked Fall Chinook Salmon Egg Disinfection Decrease Bacterial Numbers with No Impact on Egg Survival

AbstractEgg disinfection is an important practice that prevents potential disease transfer, but currently allowable disinfection regimes do not completely eliminate external egg membrane microbes. In this experiment, newly fertilized and water‐hardened landlocked fall Chinook Salmon Oncorhynchus tshawytscha eggs were submersed for 10 min in povidone‐iodine solutions containing 0, 100, 200, and 400 mg/L active iodine. External egg bacterial numbers (CFUs) were quantified after each disinfection treatment, and egg survival (%) was calculated at the eyed stage. All of the disinfection treatments significantly reduced CFUs compared with untreated controls. However, eggs from the 400‐mg/L iodine treatment had significantly lower CFUs (2.20 ± 0.59 [mean ± SE]) than the 100‐mg/L (10.43 ± 8.01) and 200‐mg/L (8.10 ± 1.51) treatments. Percent survival was not significantly different among any of the treatments; survival was 18.86 ± 5.17%, 19.17 ± 4.76%, and 20.16 ± 5.27% in the eggs subjected to 100 mg/L, 200 mg/L, and 400 mg/L iodine, respectively. These results indicate that 10‐min treatments of 400 mg/L active iodine on landlocked fall Chinook Salmon eggs provide the most microbial reduction with no effect on subsequent egg survival.

Incubation of Landlocked Fall Chinook Salmon Eggs in Petri Dishes

AbstractThe use of production‐sized incubators for experiments on eggs from fish populations that have limited egg numbers can be problematic because of the risks associated with potentially hazardous treatments on large numbers of eggs. This study evaluated the technique of incubating small numbers of eggs from landlocked fall Chinook Salmon Oncorhynchus tshawytscha in petri dishes from shortly after fertilization through hatch. In the first experiment at 9°C, each dish held 10 eggs. Three water change intervals were used before the eyed stage: every day, every 3 d, and every 7 d. After egg eye‐up, each original water treatment was divided into water changes of either every day or every 3 d, creating a total of six water change treatments. Water change treatments were the same in the second experiment, but each dish held 15 eggs and the water temperature was 11°C. No significant differences among the treatments were observed in survival to the eyed egg stage or to hatch in either of the experiments. The start of hatching was 55 incubation days in the first experiment at 9°C and 46 d in the second experiment at 11°C. The results from this study indicate that 10 and 15 landlocked fall Chinook Salmon eggs incubated at temperatures of 9°C and 11°C, respectively, can be successfully hatched in petri dishes with water changes of every 7 d before eye‐up and every 3 d after eye‐up, making this a viable technique for use with future experimentation.

Landlocked Fall Chinook Salmon Egg Survival during Jar and Tray Incubation at a Production Hatchery

This study compared the survival of landlocked fall Chinook salmon Oncorhynchus tshawytscha eggs incubated in either upwelling jars, either with or without daily formalin treatments, or vertically-stacked trays treated daily with formalin in a production hatchery. In the first year of the study, survival to the eyed-egg stage was significantly greater in eggs incubated in jars without formalin compared to trays, but there was no significant difference in survival to hatch between the treatments. In the second year, there were no significant differences in eggs incubated in trays, in jars without formalin treatments, and in jars with formalin treatments. In the final year, there was no significant difference in eyed-egg survival between eggs incubated in trays and jars without formalin, but survival to hatch was significantly greater in the eggs incubated in jars. Jar incubation is recommended to maximize the survival of landlocked fall Chinook salmon eggs.

Characterization of Bacteria Isolated from Landlocked Fall Chinook Salmon Eggs from Lake Oahe, South Dakota

AbstractBacteria were isolated from the eggs of landlocked fall Chinook Salmon Oncorhynchus tshawytscha prior to initial placement in vertical‐flow incubations trays 4 h after spawning and also 27 d later at the early eyed egg stage of development. Bacterial densities on the eggs after iodophor disinfection and just before being placed in trays were very low, and most isolates were gram‐positive, nonfermenting cocci. In contrast, bacterial densities on eggs at incubation day 27 exceeded 1 × 107 CFU/egg and were dominated by slow‐growing, gram‐negative coccobacilli. Pseudomonas spp., as well as Flavobacterium (closely related to F. johnsoniae) were also present. Most Pseudomonas and Flavobacterium isolates produced extracellular proteases, making them candidates for further investigation into their possible contribution to egg mortality.

Parental Male Effects on Landlocked Fall Chinook Salmon Progeny Survival

AbstractThe Lake Oahe, South Dakota, population of landlocked fall‐run Chinook salmon Oncorhynchus tshawytscha is maintained entirely by hatchery propagation and exhibits relatively poor egg survival during hatchery incubation. This study was undertaken to determine the influence of male gametes on embryo survival. Eggs from an individual female were subdivided and subsequently fertilized with milt from four discrete males. This was repeated with three additional females using the milt from the same four males. This entire procedure was then replicated three times, using four new females and four new males each time, for a total of 16 males and 16 females. The eggs from each unique cross were then incubated discretely. There was no significant effect of spawning males on subsequent embryo survival to the eyed stage of egg development. Swim‐up fry length and weight were also not significantly affected by male parentage. In contrast, there was a significant maternal effect on eyed egg survival, and swim‐up fry length and weight, which varied significantly among progeny from individual females. These results suggest that the relatively poor survival exhibited by Lake Oahe landlocked fall Chinook salmon eggs during hatchery incubation is largely a function of initial egg quality from spawning females.

An Evaluation of Two Egg Collection and Two Fertilization Techniques during Landlocked Fall Chinook Salmon Spawning

AbstractIn an attempt to improve embryo survival of landlocked fall Chinook salmon Oncorhynchus tshawytscha, we compared two egg collection techniques and two different egg fertilization (sperm activation) protocols on egg survival to the eyed stage of development. A total of four treatments were used with 13 females: egg collection into a suspended net and fertilization either with or without ovarian fluid and egg collection into a hard plastic pan and subsequent fertilization either with or without ovarian fluid. There was no significant difference in survival to the eyed stage with respect to collection technique. However, the presence of ovarian fluid during sperm activation and fertilization had a small but significantly negative effect on egg survival, decreasing mean eyed egg survival by approximately 4.0%. Overall, eyed egg survival was improved in 10 of the 13 spawns fertilized without ovarian fluid. To maximize embryo survival, removal of ovarian fluid prior to fertilization is recommended for landlocked fall Chinook salmon eggs.

Use of Hydrogen Peroxide during Incubation of Landlocked Fall Chinook Salmon Eggs in Vertical‐Flow Incubators

AbstractSix different hydrogen peroxide treatment regimes were evaluated in a series of three trials with landlocked fall Chinook salmon Oncorhynchus tshawytscha eggs incubated in vertical‐flow incubators. Six daily 15‐min hydrogen peroxide treatment regimes (1,000 mg/L; 1,000 mg/L with a decrease to 500 mg/L during estimated blastopore formation; 2,000 mg/L; 2,000 mg/L with a decrease to 500 mg/L during estimated blastopore formation; 2,500 mg/L; and 2,500 mg/L with a decrease to 500 mg/L during estimated blastopore formation) were compared with daily 15‐min treatments of 1,667 mg/L of formalin. Mortality at egg eye‐up and fry hatch and from eye‐up to hatch was significantly greater in eggs receiving the 2,500‐mg/L hydrogen peroxide treatments throughout incubation and in those receiving 2,500 mg/L hydrogen peroxide with a decrease to 500 mg/L during blastopore formation than in either of the 1,000‐mg/L hydrogen peroxide treatment regimes or the formalin‐treated eggs in the first trial. No significant differences in mortality were observed among any of the treatments in the subsequent two trials with maximum hydrogen peroxide concentrations of 2,000 mg/L. Fungal infestations were observed primarily in the incubation trays treated at either of the 1,000‐mg/L hydrogen peroxide regimens, as well as in those trays whose treatment concentrations were dropped to 500 mg/L during blastopore formation. Infestations were not observed in any of the formalin‐treated trays. If minor fungal infestation is acceptable, then daily hydrogen peroxide treatments of 1,000 mg/L for 15 min would probably provide adequate fungal control compared with formalin usage.