Joshua K. Raabe

Raabe JK, VanDeHey JA, Zentner DL, Cross TK, Sass GG. 2019. Walleye inland lake habitat: considerations for successful natural recruitment and stocking in North Central North America. Lake Reserve Manage. XX:XX–XX. Walleye (Sander vitreus) occur naturally or through extensive introductions in many inland lakes (i.e., non-Laurentian Great Lakes) throughout North Central North America. Persistence of walleye in these systems is influenced by factors including habitat, species interactions, exploitation, and stocking. Managers have expressed concerns about recent declining walleye recruitment and abundance in many inland populations, despite various conservation efforts (e.g., stocking, regulations). Therefore, we synthesized the scientific literature to provide information on how habitat influences successful natural recruitment and stocking. Historical and more recent studies indicate walleye are most successful in coolwater, mesotrophic, intermediate-to-large (>100 ha) lakes and that they spawn close to shore, in shallow water, and predominately over gravel and cobble substrates. Recent studies suggest that age-0 recruitment bottlenecks are likely occurring between hatching and midsummer. Relatedly, survival of stocked walleye tends to be higher for large fingerlings over fry or small fingerlings. Modeling studies indicate walleye declines may be attributed to warmer water and increasing water clarity, especially in smaller lakes or those with higher Centrarchidae or northern pike (Esox lucius) abundance. Important future walleye research includes connecting spawning habitat quality and quantity with hatching and recruitment success and continued evaluation of influential factors in the first year and later life stages. Management should focus on identifying and protecting high quality lakes and important habitats (e.g., spawning), along with understanding habitat and biological factors to determine whether walleye populations can be improved (e.g., habitat projects, stocking, regulations) or in some cases not managed for altogether (e.g., too warm).

Nature‐like fishways are engineered to be low maintenance, aesthetically pleasing, and able to pass a diversity of species. However, evaluations of nature‐like fishways are limited, especially on large rivers and for anadromous species. Therefore, we studied a nature‐like “rock arch rapids” rock ramp fishway constructed in 2012 at the most downstream of three locks and dams (LDs) on the Cape Fear River, North Carolina. We evaluated upstream fish passage effectiveness and time until passage through the LD‐1 (river kilometer [rkm] 97) fishway and via locking procedures at LD‐2 (rkm 149) and LD‐3 (rkm 186) from March to early July for three consecutive years, 2013–2015. We used stationary acoustic telemetry receivers to evaluate tagged anadromous American Shad Alosa sapidissima and Striped Bass Morone saxatilis and introduced potamodromous Flathead Catfish Pylodictis olivaris. For American Shad, raw upstream passage efficiency at the LD‐1 fishway was similar to that for LD passage via locking procedures in this and previous studies (53–65%), but passage rates were considerably lower for Striped Bass (19–25%). Duration downstream prior to upstream passage averaged 14.7 d for American Shad (SD = 10.2) and 11.6 d for Striped Bass (SD = 17.1). The raw upstream passage efficiency of Flathead Catfish at LD‐1 was variable (13–80%), and certain individuals passed multiple times in a season and spent extended durations downstream prior to passage (mean = 17.4 d; SD = 20.8), potentially foraging. The rock arch rapids LD‐1 fishway passed each species upstream in all years, but anadromous fish passage was delayed for some individuals and the fishway did not meet predetermined success criteria (80% passage efficiency), indicating that design modifications may be necessary to improve overall effectiveness.