Collecting and Fertilizing Eggs
PWSAC utilizes electroanesthesia technology and a mechanized system to increase the efficiency of gamete (eggs / sperm) collection. This system eliminates handling lively adult salmon. Therefore reducing wear and tear on hatchery staff.
Hatchery staff operates a hydraulic raceway crowder, fish lift, and electroanesthesia unit. As the fish are anesthetized they slide into the egg-take room through the use of a conveyor system. After that the fish are sorted by sex.
In the egg-take room, gametes and sperm are extracted by hand. The eggs and sperm are collected in a common trough that feeds into a bucket. Water is added to the eggs and sperm to induce fertilization. The excess sperm, ovarian fluid, and blood are rinsed away. The fertilized eggs are gently poured into an incubator tray.
Egg fertility samples are taken approximately 10 hours after fertilization. Time intervals will vary depending on the temperature of the incubation water. The blastodisc of an egg (whitespot) is examined to determine fertilization success. A fertilized egg will have a developed blastodisc divided into four cells, looking somewhat like a shamrock. An unfertilized egg has a blastodisc shaped like a smooth circle.
Fertility sampling during egg-take operations is used as a measure of quality control. The information gathered allows hatchery managers to determine the successful fertility from a completed egg-take operation. Typical pink salmon egg-take fertility ranges from 95-100%.
Incubating the Eggs
The incubator rooms at each facility are designed to mimic a natural stream environment. There is a constant upwelling flow of fresh water to supply oxygen and wash away waste. Incubator trays are filled with small, plastic, saddle-shaped pieces that act as artificial gravel (called substrate). The substrate also provides hiding spaces where hatched young salmon (alevin) can remain undisturbed until they have absorbed their yolk material for body development. Alevin are very sensitive to light, so the incubation areas are kept as dark as possible.
Salmon embryos develop inside their protective egg until the “eyed-egg” stage. Pink and chum salmon reach the”eyed-egg” stage around October. In November and January, salmon begin to hatch out of their eggs as alevin (fry with yolk sacs attached). By March, the alevin have absorbed their yolk sacs and their bellies have”buttoned-up.” At this point the fry emerge from the incubation substrate. Fry leave the incubators (outmigration) beginning in late March and are reared until late May.
The otolith is a part of the salmon’s inner ear equilibrium system. Otoliths are comprised of protein and calcium carbonate which grow like the rings of a tree. The white area is calcium carbonate and the dark rings are protein layers. At the “eyed-egg” stage, a distinct eye is visible through the egg shell and indicates the early formation of otoliths.
By manipulating incubation water temperatures, protein rings are created (otolith marks) to look somewhat like a bar-code. This can be done in mass to 100% of the population. These barcodes are extremely valuable fisheries management tools. Each barcode is specific to a hatchery the salmon was raised at. When the adult salmon are ready to return for spawning, they return in mass as a mixed stock fishery. The otolith marking will identify if an adult salmon was raised at a hatchery. CCH pink salmon have two bands of comprised of three rings each (||| |||). WNH pink salmon have one band of eight rings (||||||||).
Feeding the Fry
As fry emerge from incubators, they are either are directly released into local waters or held in captivity and fed a commercially manufactured fish food. Most fry are moved to saltwater rearing net pens and fed prior to release. When introduced to salt water, the fry imprint to the various chemical characteristics of the surrounding environment. This imprinting process 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. To increase the survival rate, a key target size and release time is selected. But often, critical factors, such as the occurrence of “zooplankton blooms” in the receiving waters, which provide natural feed for the fry upon their release, also influence the decision as to when to release the fry.
Pink and chum salmon are biologically adept to live in saltwater immediately after emerging from incubators. Coho, sockeye, and Chinook salmon remain in freshwater for a year until they have reached a stage of development known as smolt. Smolt reared in freshwater are bigger than pink and chum salmon fry. The size advantage gives a better chance of marine survival when released. Most of the coho and Chinook salmon reared are released remotely (away from the hatchery) for the sport fishery.
PNP hatchery operations allow for harvest of a portion of the returning adults for broodstock and/or licensing a portion of the returning salmon to seafood processors. The licensing provides seafood processors the opportunity to catch and sell the fish for “cost recovery.” The processing companies often send large boats (seiner) to make sets in front of the hatchery brood enclosure to capture a high quantity of fish. The cost recovery fish are pumped from the seiner’s net onto a tender boat for delivery to the processor. During harvest, hatchery staff sample the adults to determine average weight, sex ratio, and stage of maturity.