Fisheries restoration is increasingly used to recover populations and improve food web function. Despite widespread application, the ability to evaluate restoration success is often limited without system-specific information, including the original drivers of fish population decline. In this dissertation, I present the trajectory of two planktivorous fishes: introduced alewife (Alosa pseudoharengus) and extirpated cisco (Coregonus artedi), the focal species of a reintroduction effort in Keuka Lake, New York. I first investigated the collapse of alewife by the mid-2010s across two lakes, Keuka Lake and Otsego Lake, New York, testing both top-down and bottom-up hypotheses for population decline. A data-driven approach across trophic levels revealed multiple pathways to alewife collapse, with common ecosystem consequences including a pelagic prey fish void left vacant in both lakes over a decade later. Next, I evaluated subsequent cisco reintroductions to Keuka Lake beginning in 2018 to restore a native prey fish base, using acoustic telemetry and environmental DNA (eDNA) technologies to monitor outcomes. Results from a whole-lake acoustic telemetry experiment revealed high post-release mortality, information useful for adapting management practices to improve survival of stocked juvenile fish. In addition, a field assessment validated that eDNA-based methods successfully detected cold-water, pelagic schooling fish like cisco at coarse spatial scales. Yet, fine-scale comparisons revealed that deep lake currents, empirically measured with drifter devices, could transport cisco eDNA up to 3.3 km over 24 hours, complicating spatial interpretation. Finally, I believe insights from the past are important to inform the future: results from population modeling were used to assess the viability of future restoration scenarios. By incorporating in situ cisco life history parameters from Keuka Lake, outcomes from a population viability analysis indicated that cisco re-establishment is unlikely with current stocking practices and lake conditions. Although Keuka Lake is oligotrophic, has abundant zooplankton and mysid (Mysis diluviana) prey, and lacks alewife, an ecosystem state more representative of historical cisco habitat, the still abundant top predator lake trout (Salvelinus namaycush) population that caused alewife collapse may similarly hinder cisco recovery. Combined, this integrated approach provided opportunity to evaluate fisheries restoration in Keuka Lake with application to cold-water lake ecosystems.