Great Lakes Fishery Commission

Updated 2024-11-22 14:22:05

Lake Superior -> 2.0 Prey Species -> Age-1 Cisco Catch Rate

2.1.3 5-Year reporting period average age-1 cisco catch rate is greater than 4.17 fish/ha

The biomass trend of cisco in Lake Superior is largely influenced by the frequency and magnitude of recruitment events. The index of age-1 cisco abundance from the USGS bottom trawl survey is strongly correlated with the age compositions of adult fish captured years later by commercial and assessment fisheries. Therefore, the USGS bottom trawl survey is thought to be a good index of cisco year-class strength (i.e., recruitment). Catches of age-1 cisco during 1978-2022 (year-classes 1977-2021) range from 0.01-743.43 individuals/ha. The average index of year-class strength during 5-year reporting periods ranges 2.22-169.44 individuals/ha and the 50^th percentile of the 5-year averages is 4.17 individuals/ha. The average index of year-class strength for the 2017-2021 reporting period is 2.22 individuals/ha which is the lowest of the time-series and less than the 50^th percentile of the 5-year averages.

Figure 1. Mean index of cisco year-class strength by 5-year reporting period. Horizontal line indicates the 50th percentile. Note: year ranges indicate year-classes, not sample years.