Josh E. Rasmussen

Ontogeny and sex alter the effect of predation on body shape in a livebearing fish: sexual dimorphism, parallelism, and costs of reproduction

Predation can cause morphological divergence among populations, while ontogeny and sex often determine much of morphological diversity among individuals. We used geometric morphometrics to characterize body shape in the livebearing fish Brachyrhaphis rhabdophora to test for interactions between these three major shape-determining factors. We assessed shape variation between juveniles and adults of both sexes, and among adults for populations from high- and low-predation areas. Shape differed significantly between predation regimes for all juveniles regardless of sex. As males grew and matured into adults, ontogenetic shape trajectories were parallel, thus maintaining shape differences in adult males between predation environments. However, shape of adult females between predation environments followed a different pattern. As females grew and matured, ontogenetic shape trajectories converged so that shape differences were less pronounced between mature females in predator and nonpredator environments. Convergence in female body shape may indicate a trade-off between optimal shape for predator evasion versus shape required for the livebearing mode of reproduction.

Individual Movement of Stream Fishes: Linking Ecological Drivers with Evolutionary Processes

ABSTRACT Movement of organisms is an important activity that has ecological and evolutionary implications, including individual reproductive success and survival, population growth and persistence, local adaptation, and gene flow. Expression of movement behavior has traditionally been termed dispersal and measured relative to home ranges. This simplistic approach belies the complexity of the process. Movement of freshwater stream fish has been at times viewed as predominantly restricted in nature, but recent research challenges this paradigm since some distribution of movement exists in every population. A better research approach is to understand the drivers that promote or limit movement. Drivers of movement can be categorized as extrinsic ecological factors (context dependent), e.g., habitat quality, habitat variability, and the presence of predators, and intrinsic traits of the fish (condition dependent), such as body size and condition. One intrinsic trait that has received relatively little attention is the inherent personality to be sedentary or mobile, and how this interacts with the suite of traits and behaviors to drive movement. Future movement behavior research should focus on the interaction of extrinsic and intrinsic drivers to better understand the evolutionary and ecological implications of movement.

Status of Lost River Sucker and Shortnose Sucker

ABSTRACT. The endangered Lost River sucker (Deltistes luxatus) and shortnose sucker (Chasmistes brevirostris) are endemic to the Upper Klamath Basin, Oregon and California. The once very abundant populations have declined drastically due to a combination of habitat loss and impairment, disruption of reproduction and gene flow, intensive harvest, and loss of entire populations. Spawning populations within Upper Klamath Lake are declining and have not had significant recruitment for over a decade. In addition to habitat loss, these populations are threatened by periodic harmful water conditions resulting from massive algal blooms and entrainment of larvae and juveniles into water delivery systems or hydroelectric structures. Populations of shortnose sucker in Clear Lake appear to be relatively healthy and stable, but recruitment of Lost River sucker appears to be sparse. These populations are affected by drought and water management. Other populations are potentially introgressed with Klamath largescale sucker (Catostomus snyderi) or lack sufficient spawning opportunities to be self-sustaining and therefore function as sink populations. Although genetic and ecological similarities between the species are strong, it is important to better understand the needs of both species individually to assure effectiveness and efficiency in recovery efforts. Determination of the factors limiting juvenile survival and recruitment is vital and should be part of a broader program which includes comparison among populations to understand demography and vital rates. Efforts should also include habitat restoration, improvement of water quality conditions, and reduction of entrainment, as well as monitoring to evaluate effectiveness. Lastly, a controlled propagation program should be considered and/or implemented to conserve unique genetic stocks and provide opportunity for augmentation of wild-spawned populations.

A multivariate approach to the analysis of within lifetime variation in life history

Summary Ecological and environmental gradients create varying selective pressures on organisms that result in differences in optimal life history tactics. Moreover, life histories are inherently multivariate, consisting of a coordinated suite of life history traits that vary over an organisms lifetime. Such variation can be described as a trajectory of phenotypic change through time in multivariate space defined by a set of life history traits. We demonstrate the use of phenotypic trajectory analysis as a multivariate analytical approach for quantifying and comparing phenotypic change in life history throughout an organisms life. Life history trajectories have attributes – magnitude, direction, and shape – that can be quantified and statistically compared. We demonstrate the construction of trajectories using levels characterized by individuals with the same age or similar state, and we show how this approach can be used to evaluate the evolution of life history strategies given predictions from life history theory. We demonstrate the utility of phenotypic trajectory analysis for life histories using two examples. We compare life history trajectories of burying beetles and show that females balance costs of reproduction differently based on resource availability. We also characterize life history trajectories of livebearing fish in different predation environments. We show that females in non-predator environments, but not predator environments, exhibit trajectories consistent with the terminal investment hypothesis. While analysing life history variation in a multivariate framework is not novel, we show that phenotypic trajectory analysis provides a method to statistically test age- and state-based predictions of life history theory.

Evaluation of release strategies for captive-reared June sucker based on poststocking survival

ABSTRACT. The recovery program for the endangered June sucker (Chasmistes liorus) relies on population augmentation to overcome recruitment deficits. Successful recruitment of artificially propagated individuals is affected by release timing, release size, and rearing techniques. We examined the effect of release timing and release size (total length [TL] and a relative condition factor [Wr]) on recruitment probability of hatchery-reared June sucker (Utah Division of Wildlife Resources Fisheries Experiment Station [FES]) and captive-reared June sucker (Red Butte Reservoir [RBR] refuge population) stocked across multiple years. Because source and year effects were confounded, we assessed the probability of recruitment individually for each major stocking event (i.e., source × year combination). Successful recruitment occurred if an individual was recaptured or detected at least once during annual spawning runs up Utah Lake tributaries. For stocking events from RBR, probability of recruitment was highest in individuals stocked during spring and early summer but decreased as summer progressed. No difference existed between spring and fall stocking events. June sucker from the FES stocked in October had lower overall probability of recruitment than those stocked in August. The relationships between recruitment probability and TL and Wr for stocking events from RBR were hump shaped, with peaks at approximately 375 mm TL and 100%, respectively. For FES individuals, a positive relationship existed between recruitment probability and TL for individuals stocked during August only; no relationship existed between the recruitment probability and Wr. Release timing and release size affected the recruitment success of captive-reared June sucker; therefore, recovery plans should incorporate these factors in augmentation efforts to maximize augmentation efficiency and success.

Evaluation of endangered lakesucker rearing in tributaries to Upper Klamath Lake by use of X-ray imaging

Abstract. Two species of endangered, primarily lake-dwelling sucker are endemic to the Upper Klamath Basin in southern Oregon: shortnose sucker (Chasmistes brevirostris) and Lost River sucker (Deltistes luxatus). A third unlisted species, Klamath largescale sucker (Catostomus snyderi), also occurs in the basin. Apart from a small group of adult Lost River suckers documented in a tributary to Upper Klamath Lake in the late 1990s, it is generally believed that though the listed sucker species spawn in tributaries, the larvae out-migrate within days of swim-up, and therefore, there is no juvenile residence in the tributaries. We used X-ray imaging and vertebral counts to identify 347 juvenile suckers collected from tributaries to Upper Klamath Lake between 2006 and 2008. We positively identified 13 individuals as Lost River sucker. Our finding of juvenile endangered suckers rearing in tributaries to Upper Klamath Lake challenges the previous finding that larval and juvenile suckers only spend a small portion of their lives in rivers. This finding may have broader implications for future research and management of endangered suckers in the Klamath Basin.

Predation environment affects boldness temperament of neotropical livebearers

Abstract Behavioral traits of individuals are important phenotypes that potentially interact with many other traits, an understanding of which may illuminate the evolutionary forces affecting populations and species. Among the five axes of temperament is the propensity to behave boldly in the presence of a perceived risk. To determine the effect of different predatorial regimes on boldness and fearfulness, we assessed the behavior of individuals in a novel portable swim chamber (i.e., forced open‐field test) by Brachyrhaphis rhabdophora (n = 633). We used an information theoretic framework to compare generalized (logistic) linear fixed‐effects models of predatorial regime (predator‐free [n = 6] and predator [n = 4] sites), sex, and standard length (SL). Fish from predator sites were much more fearful in the novel arena than fish from nonpredator sites. This varied by length, but not by sex. At 48 mm SL, fish from nonpredator sites were 4.9 times more likely to express bold behavior (ambulation) in the novel swim chamber as fish from predator sites. Probabilities of “ambulating” within the swim chamber increased with size for nonpredator sites and decreased with size for predator sites.