Recently, PWSAC has updated the egg-take systems at AFK, CCH, and WNH with the electroanesthesia technology and mechanized the system. This has increased the efficiency of the operation (more eggs/hour, less manpower) and eliminated the wear and tear on hatchery technicians by reducing the handling of live adult salmon.
The top left picture shows the CCH egg-take raceway where a fish culturist is operating the hydraulic raceway crowder, fish lift, and electroanesthesia unit. This egg-take step took a total of nine people with the old system. The top right picture shows the operation of lifting the fish out of the raceway and into the electroanesthesia unit. Once the fish are anesthetized they slide into the egg-take room through an opening in the wall just past the window. Another person (lower left picture) then sorts the fish by sex.
Once in the egg-take room and sorted, the fish slide to one of four fish culturists who extract the gametes as shown in the lower right picture. The eggs and sperm slide into a common trough that empties into a single bucket.
Fertilization of the eggs occurs once water is added to the bucket in the rinse tank. Fertilization is instantaneous but the fish culturists allow the eggs to stay in the rinse tank for 30 seconds just to make sure. The excess sperm, ovarian fluid, and blood are then rinsed and the eggs are gently poured into the incubator.
Egg fertility samples can be taken approximately 10 hours after fertilization depending on the temperature of the incubation water. The left picture shows a fish culturist examining the blastodisc of an egg (white spot). A fertilized egg will have a developed blastodisc that will have divided into four cells looking somewhat like a shamrock where an unfertilized egg will have a blastodisc that will be a smooth circle. Fertility sampling during the egg-takes acts as a quality control measure that can give the hatchery managers feedback on the egg-take operation. Normal pink salmon egg-take fertilities range from 95-100%.
The stream environment is duplicated in an incubator by the constant upwelling flow of fresh water which supplies oxygen and washes away waste. Often, incubator trays are filled with small, plastic, saddle-shaped pieces of artificial gravel called substrate. The substrate provides hundreds of thousands of hiding spaces where the alevin may remain undisturbed, using most of their yolk material for body development. The right picture shows an incubator with pink salmon eggs at CCH.
Eggs continue to develop into the fall months. The pink and chum salmon eggs reach the "eyed egg stage" starting in October. At this stage, a distinct eye is visible through the egg shell and the early formation of otoliths are under way. The otoliths are part of the salmon's inner ear equilibrium system. Otoliths are made up of protein and calcium carbonate which grows from the inside out, much like the rings of a tree. The pictures above are a cross-sectional view of CCH and WNH pink salmon from the 1997 brood year. The white area is the calcium carbonate and the dark rings are the protein layer. By manipulating the incubation water temperature, fish culturists can lay down protein rings (otolith marks) that look somewhat like a bar-code. This can be done in mass to 100% of the population. This is an extremely valuable fisheries management tool as the adults return. The picture on the left is a CCH pink salmon ( ||| ||| ) compared to the picture on the right ( |||||||| ) a WNH pink salmon. For more information on otoliths and/or otolith marking visit our friends at the ADF&G Otolith Lab .
Between November and January, the eggs hatch into alevin (fry with yolk sacs attached). The alevin continue to develop using the yolk material for growth. During this period, the young salmon are very sensitive to light, so the incubation room is kept dark as much as possible. By March, the alevin have absorbed most of their yolk sacs and their bellies have "buttoned-up". At this point the fry begin to emerge from the incubation substrate. Incubator outmigration begins in late March and extends into May.
After the fry emerge from the incubators they are, depending on their species and the needs of the hatchery, either directly released into local waters, or held in captivity and fed a commercially manufactured fish food. Often, fry are moved to saltwater rearing pens and fed prior to release. The fry imprint to the various chemical characteristics of the surrounding environment. It is this imprinting process that enables the fish to instinctively return to their release site as mature adults to spawn.
Several factors determine how long the fish are fed in the net pens before they are released. In order to enhance the survival rate, a key target size and release time is selected. But often, critical factors, such as the occurrence of "plankton blooms" in the receiving waters which will provide natural feed for the fry upon their release, also influence the decision as to when to release the fry.
The fertilization and incubation process of culturing the four species of salmon are basically the same. Pink and chum salmon are biologically adapted to living in saltwater immediately after they have emerged from incubators. However coho, and sockeye salmon must remain in freshwater until they have reached a stage of development known as "smolt", which allows them to physiologically adapt to saltwater. Because these smolts have been reared for sometime in freshwater, they are bigger than pink and chum salmon fry and generally have a better chance of surviving in the wild and eventually returning as adult fish. Some coho salmon are remote-released for the sport fishery.
A major phase of a PNP hatchery operation is to "harvest" a portion of the returning adults for broodstock or for sale to recover operating costs, "cost recovery". The picture on the left shows the contract seiner making a set in front of the AFK hatchery brood enclosure. The cost recovery fish are pumped directly from the seiner's net onto a processor's tender (right picture). During the harvest period, fish culturists sample the returning adults for average weight, sex ratio, and stage of maturity.
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