Experimental Design To examine how sensory cues affect ontogenetic dietary shifts, we will be exposing pumpkinseeds (Lepomis gibbosus) to three treatments of bluegill (Lepomis macrochirus) sensory cues as well as a control. The different types of sensory cues will include visual only, chemical only, and a combination of visual and chemical cues, and no cues in a flow-through mesocosm. For an assay, a mesocosm will be stocked with a single bluegill (used for sensory cues donor) upstream, a single pumpkinseed downstream, with three food choices (macrophytes, snails, and crayfish). Video recordings of pumpkinseed behavior will be used to determine time spent foraging and time spent near each food choice. Comparisons on foraging behaviors will be based on pumpkinseed responses to these variables. A total of 120 trials will be run with an n=30 Fish Collection and Husbandry: 40 bluegill (Lepomis macrochirus) and 120 pumpkinseed (Lepomis gibbosus) will be collected from fish farms. All fish will be stored in separate steel cattle tanks (200 x 60 x 60 cm: l x w x d). Unfiltered water from the Maple River will flow into the tank from a PVC delivery and exit the tank via a standpipe which will allow the water depth to stay at approximately 60 cm. To mitigate fish from jumping out of the cattle tanks, screen mesh will be placed over the tanks and clipped to the sides. Bluegills will be fed standard measurements of Tetramin tropical flake food daily. Pumpkinseeds will be fed Tetramin tropical flake food if they are not going through a trial, otherwise, the pumpkinseed will be fed with three food options (elodea, snails, and crayfish) during behavioral assays. Mesocosm Design Four flow through stream mesocosms (160 x 40 14 cm l x w x d) will be framed with cinderblocks and lined with 0.1 mm thick plastic sheeting. Each mesocosm will consist of two sections each measuring 80 x 40 x 24 cm (l x w x d). The upstream section will house a single bluegill and the downstream section will contain the focal animal, a single pumpkinseed. This same set up has been successful in previous experiments (Wagner & Moore, 2022; Wood et al., 2018; Wood & Moore, 2020). One 208 1 plastic drum will serve as constant head tank for the four mesocosms and will be filled with water from the east branch of the Maple River. Both bluegill and pumpkinseed are found in the Maple River. Water will enter the drum via a PVC pipe (7.6 cm diameter) that will be covered with nylon stockings to prevent excess detritus and/or macroinvertebrates from entering the mesocosm. This plastic drum will feed all four mesocosms with water from one 10 mm diameter garden house per mesocosm (flow rate = 0.086 ± 0.003 1 s-1 [mean ± SEM]. For the control, chemical and the combined visual and chemical treatments, water will first flow into the upstream bluegill section of the mesocosm before flowing through a screened opening (28 x 12 cm opening with 1 x1 mm screening) in a partial wall into the downstream pumpkinseed section (Figure 1A). The water will exit the mesocosm from the downstream end of the mesocosm through another screened opening. For the visual treatment, the mesocosm will have a drain on the side of the bluegill section and another drain on the pumpkinseed section (Figure 1 B). This will mitigate the odor cue from the bluegills flowing into the pumpkinseed section. Each section will have its own hose. Food Collection and Storage Macrophytes Samples of American waterweed (Elodea canadensis) and muskgrass (Chara spp.) will be collected from North Fishtail Bay of Douglas Lake, in Cheboygan County, Michigan, USA (45.5618° N, 84.6762 ° W). A macrophyte sampling rake will be cast into mats of submerged vegetation to collect the aquatic plants. Macrophytes that are collected will be stored in a flow through stream filled with water from the east branch of the Maple River. The plant storage stream will be lined with sand and located in open sunlight to mimic a nature environment. A surplus of plant samples will be maintained for the duration of the experiment. Pointed-Campeloma Three hundred Campeloma snails (Campeloma decisum) will be collected from Douglas Lake in Cheboygan County, Michigan (45.5770° N, 84.6929° W) prior to the start of the experiment. Snails will be collected by kicking up sediment along the lakeshore to uncover buried snails. All snails found will be placed into a bucket and carried back to the University of Michigan Biological Station (UMBS) Stream Research Facility. Snails will be placed into a 37.85 liter (10 gallons) aquarium filled with unfiltered river water from the east Branch of the Maple River. The bottom of the tank will contain a sand substrate layer for snails to burrow. Two air hoses will be placed within the tank to provide oxygen and water will be replaced once a week. Replacing the water will ensure water evaporation is kept to a minimum along with providing more detritus for snails to feed on. Crayfish One hundred rusty crayfish (Faxonius rusticus) will be captured by using hand nets from Maple Bay in Burt Lake, in Cheboygan County, MI (45.48° N, 84.70° W). All crayfish chelae will be banded and placed into a steel cattle trough (200 x 60 x 60 cm: l x w x d). with unfiltered river water from the east Branch of the Maple River (45.5280° N, 84.7738° W) fed through PVC pipes (7.6 cm diameter). Water will be able to exit the holding tank through a standpipe which will keep the water depth at approximately 60 cm. The crayfish will be able to feed on naturally occurring detritus contained within the river water. Crayfish will be housed outside under natural daylight:darkness cycle and natural temperature. Ethical Approval Bluegill and pumpkinseed will be maintained and handled following established animal care and use procedures. The use of vertebrate animals has been approved by the Institutional Care and Use Committee at University of Michigan (Protocol #) and by the Institutional Care and Use Committee at Bowling Green State University (Protocol #). Experimental Protocol Each trial will run for 1 hour. The trial will begin at 0730 by selecting plant samples from the plant storage streams. The plant sample selected will weigh approximately 1 gram. Each plant sample will be dried with a salad spinner before being weighed. After being weighed, plant samples will be placed into a mesh bag. Next, five snails will be selected, measured (length and width in mm) and placed into a separate mesh bag. Lastly, five crayfish will be selected, the post orbital carapace length and maximum carapace width in mm) and placed into a third mesh bag. Each mesh bag will allow water to flow through them. The mesh bags will be held down by placing a rock inside them. Once the food choices are placed within the respective treatments, one bluegill and one pumpkinseed will be selected and measured before being placed into their respective sections of the mesocosms. Beginning at 0830 an automatic light timer will activate the red lights illuminating the mesocosms. At 0845, the cameras above the mesocosms will begin recording the foraging behavior of the pumpkinseeds. The cameras will shut down one hour later at 0945 when behavioral recordings are finished. After exposure to each treatment, fish will be placed into a steel cattle tank (200 x 60 x 60 cm: l x w x d) labeled used to separate pre-exposed and exposed fish. Plant, snail, and crayfish samples will be taken out of the mesocosm and placed back into their respective holding tanks. The mesocosms will be flushed overnight (at least 12-hours) before a new trial begins the next morning. During the flushing period, water within the mesocosms will be replaced approximately 24 times.