Managing Somass Mi’aat: Assessing the Resource

mi'aat (sockeye salmon)

The arrival of mi’aat (sockeye salmon) to Nuu-chah-nulth territories marks the beginning of a season that has always been important for Nuu-chah-nulth people. In traditional times, a Nation’s Ha’wilth would appoint advisors long before the sockeye returned, to help care for the run and ensure a good outcome for his people. These advisors included beach keepers and stream-keepers (or tsa-tsa-thluk) whose job it was to protect and manage the resources in a sustainable manner.

Today fisheries management may look different, but Nuu-chah-nulth chiefs and their advisors still play an important role on the management team for Somass fisheries. In the case of Somass sockeye (sockeye produced from Sproat and Great Central Lakes) local First Nations work with the Department of Fisheries and Oceans, Uu-a-thluk, and the recreational and commercial fishing sectors to provide information that helps manage the fishery. They fulfill these roles both before and during the sockeye fishing season.

Given its complexity, management of the Somass sockeye fishery can be grouped in to two distinct, but linked parts: fishery assessment and planning. This article will focus on fishery assessment. A future article will discuss fishery planning.


Forecasting the Return:

Well before mi’aat return to the Somass River system, Department of Fisheries and Oceans (DFO) staff develop a pre-season forecast to estimate the number of returning sockeye. To do this, they use six different production models and a mix of environmental and biological information. The result is a range of possible run size estimates.

Because all model predictions are not perfect, it would be poor management to go with any pre-season prediction on face value. Instead, DFO biologists use the model predictions to determine a single management forecast for adults returning to the Somass system. The objective of this management forecast is to provide an initial run size to start the season, balancing escapement needs with fishing opportunities.

This year, the management forecast is 600,000.

Gathering Information In-Season:

To manage sockeye fisheries effectively, fisheries managers also require high quality in-season information. Catch information from all fisheries, the age of returning adults, escapements to each lake (Sproat and Great Central) and estimates of how many sockeye are holding in Alberni Inlet is required weekly.

DFO’s test boat works two days a week using sonar to identify schools of sockeye in Barkley Sound and Alberni Inlet. At standard locations, the boat uses a seine net to sample for fish size, age, gender, and DNA. The samples also provide the test boat captain with more information about how many sockeye they are seeing on the sonar.

Each day, Hupacasath Fisheries staff use automatic counters to collect escapement data as fish enter Sproat and Great Central Lakes. They also collect additional biological samples weekly from these sites, providing all information to DFO. Catch information and more biological samples are collected from all fisheries as they occur.

Putting it All Together:

The management team uses all the above information to track the run and determine if any adjustments to the pre-season management forecast are needed. A technical committee made up of DFO, Uu-a-thluk, Tseshaht and Hupacasath technical staff reviews the weekly assessment information and develops a run profile. The run profile looks at the ages and the total number of fish that can be accounted for up to that week.

The total accounting is then matched up with a run-timing curve, which provides an estimate of what percentage of the run has returned by a certain date. In simple terms, if 500,000 sockeye can be accounted for by the catch, escapement, and inlet data on July 7th, and on average 50% of the run has returned by that date, then the total run size estimate would be 1 million.

Unfortunately, it’s not that simple. The early portion of the Somass sockeye run (generally the first two months) is highly variable and not very useful for predictions. As a general rule, by the first week of July, the size, age groupings, and timing of the run becomes clearer allowing adjustments to the run size if appropriate. Further adjustments to the run-size will be made in subsequent weeks if supported by the available information.

Collection of assessment information continues long after sockeye fisheries have ended for the season. Daily escapement counts to the lakes and weekly biosampling continue until the run has ended, usually by the first week of November. Together, all this information contributes to fisheries assessment in the Somass River system.


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