Exponential rates of digestion are described for brown trout and whitefish for July, October, December (1969), and April (1970). The slope of the line fitted to the digestion data from each month was defined as the instantaneous rate of digestion and applied to an exponential growth model to determine the instantaneous consumption rate. The digestion and consumption rates were applied to field measurements of percent fullness to determine the amount of food material ingested during a 24 hour period. Brown trout consumed 127, 24, 19, and 84 mean percent of their stomach capacity in the July, October, December, and April studies. Whitefish consumed 74, 21, 46, and 51 mean percent of their stomach capacity in the same respective study periods. Mean daily ration from four major collection periods was calculated on fish in the 50 gram to BOO gram size range. Brown trout daily ration varied between 1.35 percent and 2.59 percent. Whitefish daily ration varied between 0.44 percent and 0.83 percent. Brown trout diets were quite variable with 44 percent of their caloric intake comprised of terrestrial invertebrates in October, 55 percent of the December calories comprised of fish eggs, and 39 percent of the April calories made up of Leptoceridae larvae. Emerging imagoes were important items in the brown trout diets, contributing as much as 62 percent and not less than 11 percent of the numeric intake for one collection period. Whitefish did not rely upon emerging imagoes as a significant food source. Their stomachs consistently contained mayflies, chironomids, and caddis larvae. Both fish species occasionally consumed substantial amounts of the large stonefly, Pteronarcys.

This thesis presents an automatic animation system for jellyfish that is based on a physical simulation of the organism and its surrounding fluid. Our goal is to explore the unusual style of locomotion, namely jet propulsion, which is utilized by jellyfish. The organism achieves this propulsion by contracting its body, expelling water, and propelling itself forward. The organism then expands again to refill itself with water for a subsequent stroke. We endeavor to model the thrust achieved by the jellyfish, and also the evolution of the organism's geometric configuration. <p> We restrict our discussion of locomotion to fully grown adult jellyfish, and we restrict our study of locomotion to the resonant gait, which is the organism's most active mode of locomotion, and is characterized by a regular contraction rate that is near one of the creature's resonant frequencies. We also consider only species that are axially symmetric, and thus are able to reduce the dimensionality of our model. We can approximate the full 3D geometry of a jellyfish by simulating a 2D slice of the organism. This model reduction yields plausible results at a lower computational cost. From the 2D simulation, we extrapolate to a full 3D model. To prevent our extrapolated model from being artificially smooth, we give the final shape more variation by adding noise to the 3D geometry. This noise is inspired by empirical data of real jellyfish, and also by work with continuous noise functions from the graphics community. <p> Our 2D simulations are done numerically with ideas from the field of computational fluid dynamics. Specifically, we simulate the elastic volume of the jellyfish with a spring-mass system, and we simulate the surrounding fluid using the semi-Lagrangian method. To couple the particle-based elastic representation with the grid-based fluid representation, we use the immersed boundary method. We find this combination of methods to be a very efficient means of simulating the 2D slice with a minimal compromise in physical accuracy.

This thesis presents an automatic animation system for jellyfish that is based on a physical simulation of the organism and its surrounding fluid. Our goal is to explore the unusual style of locomotion, namely jet propulsion, which is utilized by jellyfish. The organism achieves this propulsion by contracting its body, expelling water, and propelling itself forward. The organism then expands again to refill itself with water for a subsequent stroke. We endeavor to model the thrust achieved by the jellyfish, and also the evolution of the organism's geometric configuration. <p> We restrict our discussion of locomotion to fully grown adult jellyfish, and we restrict our study of locomotion to the resonant gait, which is the organism's most active mode of locomotion, and is characterized by a regular contraction rate that is near one of the creature's resonant frequencies. We also consider only species that are axially symmetric, and thus are able to reduce the dimensionality of our model. We can approximate the full 3D geometry of a jellyfish by simulating a 2D slice of the organism. This model reduction yields plausible results at a lower computational cost. From the 2D simulation, we extrapolate to a full 3D model. To prevent our extrapolated model from being artificially smooth, we give the final shape more variation by adding noise to the 3D geometry. This noise is inspired by empirical data of real jellyfish, and also by work with continuous noise functions from the graphics community. <p> Our 2D simulations are done numerically with ideas from the field of computational fluid dynamics. Specifically, we simulate the elastic volume of the jellyfish with a spring-mass system, and we simulate the surrounding fluid using the semi-Lagrangian method. To couple the particle-based elastic representation with the grid-based fluid representation, we use the immersed boundary method. We find this combination of methods to be a very efficient means of simulating the 2D slice with a minimal compromise in physical accuracy.