Curriculum: Compare Egg Survival – Natural vs Hatchery – Issaquah Ck

Compare Egg Survival Rate: Natural vs. Hatchery-Raised Chinook Salmon

For Issaquah Creek Fall Run Chinook

Naturally-Produced Issaquah Creek fall Chinook

  • Adults enter the Ballard Locks from Puget Sound in July-August, then swim through and hold in the deeper, cooler waters of Lake Union and Lake Washington as their bodies transform to spawning stage.
  • Adults continue up the Sammamish River and through Lake Sammamish and into Issaquah Creek in late August and early September, with the end-of-summer rains.
  • In late September and early October, adults search for suitable spawning gravel with adequate water supply and pair up with a suitable mate for spawning.
  • In November-December, fry hatch and remain in gravel.
  • Fry emerge in February-March and fish spend approximately 3-4 months in fresh water before migrating downstream to the ocean.
  • Estimated survival of naturally produced salmon (egg to smolt): Less than 5 percent.

Chart:

Diagram - Compare Egg Rate Survival - Natural vs. Hatchery
Click to enlarge

Hatchery-Produced Issaquah Creek fall Chinook

  • Adults enter the Ballard Locks from Puget Sound in July-August, then swim through and hold in the deeper, cooler waters of Lake Union and Lake Washington as their bodies transform to spawning stage.
  • Adults continue up the Sammamish River and through Lake Sammamish and into Issaquah Creek in late August and early September, with the end-of-summer rains.
  • The adults are diverted out of the stream at the weir and jump up the 11 steps of the fish ladder to hatchery holding ponds, where they are protected against predators.
  • Starting in late September and continuing through the first half of October, hatchery staff and volunteers randomly select salmon pairs and spawn them manually.
  • Eggs are treated to control fungus and placed in incubators in the hatchery building.
  • In the spring, fry are transferred to the outdoor rearing ponds (raceways). (2-3 percent loss at this point).
  • Fingerlings are protected from predators by fences and netting, given intensive feeding and provided disease control treatment. Adipose fin-clipping is accomplished both with automated machinery and by hand. Fish reared to smolts and released in early summer.
  • Estimated survival of hatchery produced salmon (egg to smolt): 90-95 percent.