Testing new electronic archival tags in Alaska salmon

Objective 1

Raise hatchery coho to a minimum size of 150 mm prior to smoltification. 

Outdoor raceways

Coho salmon (Ship Creek stock) are raised in outdoor raceways at ADF&G’s  Fort Richardson Fish Hatchery, located in Anchorage, Alaska for approximately 1.5 years. Coho are released each spring into Ship Creek in late May or early June.  After spending 14 - 18 months at sea, adults return each season to spawn.

Fish in outdoor raceway

Approximately 1,000,000 coho are being raised by ADF&G in outdoor raceways at Fort Richardson.

Feeding juvenile fish

Hatchery employees feed fish by hand year round on daily and seasonal feed programs.  Indoor raceways use a pre-set automatic feeding system. Fort Richardson Hatchery species include; coho salmon, king salmon, arctic grayling, arctic char, rainbow trout, and lake trout.

Indoor circular holding tanks

Coho pre-smolt were brought in from the outdoor raceway to begin the process of accelerated growth for tagging.  Water temperature was slowly raised from 3 degrees Celsius to 14 degrees Celsius over a couple days.  This increase in water temperature and establishment of a hardy feed schedule will accelerate the growth of the coho pre-smolt to adequate tagging size of 180 mm to 250 mm by early spring.  With a dramatic increase in growth, a large proportion of the coho post-smolts released each spring will return in late summer and fall as Jacks (pre-mature adult males).

U.S.G.S. Fisheries biologist, Derek Wilson, keeps a close watch on water quality with in the coho holding tank.  Dissolved oxygen and other gases are monitored and recorded to maintain minimal stress levels and overall health of the coho population.

 

Coho on a measuring board

Each coho is initially weighed (g) and measured (mm) and every 2 weeks length and weight are taken from a sub-sample of the population to monitor growth rate and condition factor.  A comparison will be made with growth rate before and after tagging.  Prior to release, final weight and length will be taken from each coho in the study population.

Initial average fish measurements (January 12, 2001), taken from a subset of Fort Richardson Hatchery coho selected at random were 109.63 mm fork length (FL) and 15.85 g wet weight.  By introducing the study population to an indoor climate consisting of warmer water (11.9 ^oC), increased food supply (0.47g/fish/day), and less crowding, we were able to reach our goal of accelerating the growth of the coho to reach adequate tagging size.  Final average fish measurements (May 22, 2001) were 182.42 mm (FL) and 78.05 g.

The 2002 season began by randomly selecting 500 coho pre-smolt from the Fort Richardson outdoor raceways in November 2001 and introduced them to an indoor holding tank climate of 9^oC water and fed daily to satiation. The accelerated growth program was started earlier due to a cooler indoor water supply in order to reach a minimum tagging size of 180 mm by May 2002.  Initial average measurements (November 27, 2001) were 98.35 mm (FL) and 12.41 g wet weight.

(continued to Objective 2)

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