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Preseason forecasts depend on data and history

How many salmon will return in this year's summer fisheries? Preseason forecasters look back before they look forward.

by | March 8, 2024

Fisheries technicians remove salmon otoliths.
Fisheries technician Shawna Tilly takes otoliths from sockeye salmon harvested in Resurrection Bay for cost recovery. Lisa Ka’aihue, CIAA

Looking for the 2024 numbers? Jump to the forecasts.

How do we know how many salmon will return to our hatcheries and release sites in any given year? The answer is data and knowledge of the salmon life cycle. These factors help us make preseason forecasts that help us plan the year’s hatchery operations. The forecasts also help fisheries managers project common property and cost-recovery fishing opportunities. 

Gathering data for preseason forecasts

We pull together information from many different data sources to create forecasts for the next fishing season. We look at numbers from the following sources:

  • Hatcheries
  • Smolt and adult enumeration field camps
  • Harvests
  • Otolith analysis 

These factors all come together to evaluate returns in past years and help us predict future returns. The more samples, more counts, and the longer the program has been in place, the better the forecasting will be. 

How preseason forecasts begin

To build a forecast, we first look at the number of salmon released or smolts migrating from the watershed. For release numbers, we depend on reports from our hatcheries. Depending on the release program, we also determine fish numbers either by weight or by subtracting mortalities from the best-known number, usually eyed eggs. 

Some release programs have smolt traps that provide more information on the success of a release program by counting fish leaving the system. This helps us determine what is called 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 downstream to continue their journey to the ocean. 

We use simple traps, like the one used at Hidden Lake, to more elaborate, permanent traps, like the year-round structure at Bear Creek Weir. 

How many salmon survive to adulthood?

The sports fishery at Resurrection Bay near Seward.
A typical day of anglers catching sockeye salmon from the shores of Resurrection Bay. These fish are CIAA hatchery fish and the sport fish harvest is estimated each year by the Alaska Department of Fish and Game. Choiz M. Sagliba

Our next step is to figure out how many salmon fry or smolts survive to adulthood. We get this information by determining the total return of adults for a particular year class, which means all of the salmon that return from a specific spawning year.

This is particularly important when we are looking at species like sockeye salmon that may return to spawn at different ages.  Sockeyes can spend one-to-four years in fresh water and one-to-three years in the ocean before returning to spawn.

There may be varying year classes returning in any one year. The total adult return for any release program is the sum of fish caught in the common property and cost recovery fisheries. We add to this number any fish used for broodstock and escapement. 

Overall, we can arrive at a pretty accurate result from the different fish harvests, although we rely on estimated sport fish harvests provided by fisheries managers. Sport fish harvests, such as those in Resurrection Bay, rely on a  voluntary survey that is sent out to anglers each year. We suspect the estimates are conservative at best. 

The role of weirs

Hidden Creek salmon weir
A simple smolt trap is installed temporarily across Hidden Creek to allow CIAA fisheries technicians to count smolt leaving Hidden Lake. Lucas Chorba, CIAA

At some locations, CIAA counts adult returns using a weir, which produces fairly accurate escapement numbers. We also factor in the ages of the fish we count to determine how fish will return in a specific year. This is because some species, such as sockeyes, can return over more than one year.

We can tell the age of salmon by analyzing their otoliths, tiny bones in their ears. We do otolith analysis on salmon caught at our weirs and also in common property and cost recovery harvests.

Sometimes our forecasts may fall short or exceed our expectations. With in-season monitoring at many of our sites, fishery managers can restrict or liberalize common property fishing accordingly.  

The 2024 preseason forecast

This table shows the forecasted CIAA hatchery returns for the 2024 season. A portion
of these returns will be available for common property fishing. Other portions will be
available for cost-recovery harvests, broodstock collection, and
escapement.

SpeciesReturn SiteTotal Return
SockeyeResurrection Bay111,500
SockeyeTutka Bay Lagoon42,000
SockeyeChina Poot and Hazel lakes29,000
SockeyeKirschner Lake30,300
SockeyeHidden Lake16,300
CohoBear Lake9,700
PinkTutka Bay Lagoon281,000
PinkPort Graham Bay454,000

Where’s the data?

When the numbers flow in, CIAA posts them to the website. Check past records and up-to-the-minute counts at Data and Reports.

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