What factors constrain walleye recruitment? And how? And where?
Understanding the drivers of recruitment enables effective fisheries management and allows us to predict how fish will respond to environmental change
How environmental factors, stock size, and other biological drivers regulate fish recruitment and how their influence varies spatiotemporally is a key knowledge gap in most ecosystems. We synthesize existing knowledge both conceptually and quantitatively to identify drivers of walleye recruitment and how they vary or are similar across systems.
Phase 1: Conceptual model of walleye recruitment
With the support of the Great Lakes Fishery Commission, we synthesized expert knowledge of the drivers of walleye recruitment across North American walleye populations. We then explored how and why the drivers of walleye recruitment vary spatiotemporally within and among walleye stocks. This assessment brought together a diverse group of professionals with relevant expertise in fisheries. Participants discussed the state of the science and contributed ideas to develop a conceptual model of the key drivers of walleye recruitment. Together, we then developed a conceptual model for the key drivers of walleye recruitment, and identified relevant datasets to be compiled for a subsequent quantitative synthesis.
Phase 2: A quantitative assessment of drivers of walleye recruitment across North America
Using the data identified in Phase 1, we then quantify variability in walleye productivity across Great Lakes and inland lake walleye populations for which stock and recruitment time-series data exist. Such data are available for many Great Lakes walleye stocks (e.g., Lake Erie, Saginaw Bay, Bay of Quinte, Green Bay, Black Bay), as well as for inland lake populations in Ontario, Minnesota, New York, and Wisconsin. We then use stock-recruitment models to evaluate temporal and spatial patterns in walleye productivity. Finally, we examine relationships between walleye recruitment and potential environmental drivers across populations through time. We evaluate interactions among physical drivers and incorporate predictive outputs such that our final unified model of walleye recruitment can be used to inform management approaches into the future.
Conceptual diagram of hypothesized Walleye recruitment drivers for Lake Erie (left) and small inland lakes (right). Vertical bars (top) represent Walleye life stages over time. The top panel depicts the cohort survival (blue; log10 scale), with primary mortality sources (predation, starvation, and abiotic sources) indicated by color. Finally, larger-scale environmental drivers (i.e., secondary causes) that can regulate mortality rates through a variety of mechanisms are represented by violin plots (bottom panels) and directly correspond to the life stages indicated in the survival/mortality diagram above. Secondary mortality causes are shown relative to their degree of influence (violin width) in regulating primary mortality causes over different life stages (x-axis). Violin plot color corresponds to the primary mortality causes influenced by variation in each secondary factor; some factors appear multiple times due to their relationships with multiple primary causes of mortality.
Published in Krabbenhoft et al., 2023. Synthesizing Professional Opinion and Published Science to Build a Conceptual Model of Walleye Recruitment.
