Was historical cisco Coregonus artedi yield consistent with contemporary recruitment and abundance in Lake Superior?

Abstract

Historically, cisco Coregonus artedi Lesueur was the predominant prey fish and target of commercial fisheries throughout Lake Superior, but most spawning stocks collapsed by the mid‐1900s. Stocks partially recovered by the early 1990s, but contemporary abundance is considered to be below historical levels and driven by intermittent recruitment. Stochastic, age‐structured simulation models were used to determine whether historical (pre‐1955) cisco yield in Lake Superior was consistent with contemporary (1992–2015) abundance, life‐history characteristics and recruitment dynamics. When compared to contemporary stocks, the findings suggest historical stocks had: (1) similar recruits per spawner at low spawning stock sizes; (2) lower rates of compensatory density dependence; (3) similar or lower recruitment variation depending on the area and (4) higher median adult and age‐1 density. These findings are consistent with the hypothesis that eutrophication during the historical period supported greater recruitment and adult abundance and that re‐oligotrophication during the contemporary period may be limiting full recovery.

How Many Ciscoes Are Needed for Stocking in the Laurentian Great Lakes?

“…Total phosphorus (TP) levels in Lake Superior were about 3-5-fold greater during the 1950s (~ 10 µg/L TP in 1953; Beeton et al 1959) than now (~ 2-3 µg/L TP; Dove and Chapra 2015). This suggests the potential to support greater coregonine abundance historically (e.g., Rook et al 2021). Recent trophic convergence in Lakes Superior, Huron, Michigan, and Ontario (e.g., Dove 2009;Barbiero et al 2012) suggests that contemporary estimates of abundance and stock-recruit parameters from Cisco populations in Lake Superior can be used to estimate stocking rates for most other Great Lakes.…”

“…Lake Superior now contains the most abundant and well-studied Cisco populations in the Great Lakes, and most importantly, previous estimates of historical and contemporary Cisco stock-recruit parameters (Rook et al 2021) are available to estimate numbers of hatchery fish needed for stocking at the fry, fall fingerling, and age-1 life stages in other Great Lakes.…”

“…Remnant Cisco populations persisted in Lakes Superior, Huron, Michigan, and Ontario, but with the exception of Lake Superior, contemporary populations are small and isolated (Eshenroder et al 2016). Cisco partially recovered in Lake Superior after the 1980s (Bronte et al 2003), but contemporary abundance is likely below historical levels (Rook et al 2021), and driven by highly variable and sporadic recruitment, with few strong year-classes produced since 1977 (Bronte et al 2003;Stockwell et al 2009;Rook et al 2012Rook et al , 2013.…”

“…To that end, lake-specific estimates of natural mortality could be used with existing stock-recruit models for Ciscoes in Lake Superior (e.g., Rook et al 2021) to inform stocking targets for other Great Lakes (Bronte et al 2017). Workshop participants also recognized the importance of identifying historically important Cisco spawning and rearing areas (hereafter "habitat area" or "habitat areas"; Figure 3) to prioritize for stocking given limited coregonine production capacity in hatcheries (Bronte et al 2017).…”

Effects of warming winter embryo incubation temperatures on larval cisco (Coregonus artedi) survival, growth, and critical thermal maximum

“…Lake Superior stocks partially recovered by the early-1990s (Stockwell et al, 2009), but contemporary abundance is considered to be below historical levels (Rook et al, 2021). Present Lake Superior cisco population abundance is hypothesized to be limited by reduced and inconsistent survival of fish to age-1 due to climatic warming over the past two decades (Van Cleave et al, 2014) and lower overall ecosystem productivity due to reduced phosphorus inputs as compared to 1900-1970 (Rook et al, 2021). Variable and weak year-class strength of coregonines has been observed worldwide over the past several decades and has been associated with annual variations in lake ice formation and winter-spring thermal conditions (Anneville et al, 2015; Karjalainen et al, 2015; Marjomäki et al, 2004; Nyberg et al, 2001).…”