How do we know how many salmon are going to return to our hatcheries and release sites in any given year? We use a lot of data and our knowledge of the salmon life cycle to help us make preseason forecasts. These forecasts are important to help not only with our own hatchery operations, but for fisheries managers to plan for common property and cost recovery fishing opportunities.
Forecasting for the next fishing season relies on a culmination of different data sources. Information gathered from the hatcheries, smolt and adult enumeration field camps, harvest data, and otolith analysis all come together to not only provide an evaluation of past years’ performance but to predict what might happen for future returns. The more samples, more counts, and the longer the program has been in place, the better the forecasting will be.
Forecasting begins with migration
The basis for forecasting the adult return starts with the number of salmon released or smolts migrating from the watershed. For release numbers, the information provided by the hatcheries is key. Depending on the release program, we determine fish numbers either by biomass weighing or by subtracting mortalities from the best known number — usually eyed eggs.
Some release programs have smolt traps that provide further information on the success of release program by providing an enumeration of the fish leaving the system in question (fry-to-smolt survival). A smolt trap uses a weir, like a fence, placed across a stream. There is a gate to the trap that allows juvenile fish to swim in. Our fisheries technicians can then count the smolts in the trap, before releasing them back into the stream to continue their journey to the ocean.
Next comes survival
Next, information relating to the survival from fry-to-adult or smolt-to-adult is needed. We get this information by determining the total return of adults for a particular year class. Different species mature at varying ages. For example, sockeye salmon can spend one to four years in fresh water and one to three years in the ocean before returning to spawn. Other species, such as pink salmon, have a short life cycle of just two years.
The total adult return for any release program is the sum of fish that were caught in the common property and cost recovery fisheries, plus any fish used for broodstock and escapement. Overall, a good number can be generated from the different fish harvests, although sport fish harvests generally are estimated because actual numbers are not known or lag behind by a couple of years.
At locations where CIAA is able to count the adult return by using a weir, escapement numbers are readily available and fairly accurate. Besides the counts, the age contribution of the population is crucial to determine how fish will return in any specific year (multiple return year species only). This information is determined by analyzing otoliths from fish sampled at the weir and/or through cost recovery/common property harvests.
Sometimes our forecasts may fall short or exceed our expectations. With inseason monitoring at many of our sites, fishery managers are able to restrict or liberalize common property fishing accordingly.
2025 Forecast
Lauren Deal, Hatchery Operations Manager, sums up the 2025 forecasted returns as follows:
Sockeye returns have multiple age groups of fish return in a given year. In 2025, fish are returning from eggs collected in 2021, 2022, and 2023 (called the “parent class”). For Resurrection Bay, these three parent classes each have a historical survival of 4.3% to 4.9%, which is considered average. For the Lower Cook Inlet fish, historical survivals are correlated to their release site.
At Tutka Bay Lagoon, sockeye parent classes have historical survivals of 7.7% to 10.9%, which is considered good. At Leisure and Hazel Lakes sockeye parent classes have survivals of 2.2% to 5.3%, which is considered fair. At Kirschner Lake, sockeye parent classes have survivals of 8.2% to 11.9%, which is considered excellent. Overall, the predicted sockeye returns to Resurrection Bay and Lower Cook Inlet are expected to be good in 2025.
Pink salmon return on an odd-year, even-year cycle, with odd-year fish historically being more abundant. The prediction for this odd-year’s return is based on the past five odd-year survivals (2023, 2021, 2019, 2017, and 2015), which had a 2.07% average survival from fry release to adult return. In 2024 Tutka Bay Lagoon Hatchery released 42.9 million fry from eggs collected from adults that returned in 2023. Overall, the pink return is expected to be good in 2025 with a total return of 883,800.
And the fall fish, coho salmon, will also be returning to Bear Lake this year. Based on the average survival of the last four parent classes (2021, 2018, 2015, and 2012) at 2.5%, the return is considered fair, with a total return of 2,060.
