Biological Invasion Theory: Darwin's Contributions from The Origin of Species

Support for this work was provided by (1) a Federal Aid in Sport Fish Restoration Project F-69-P (to R. A. Stein), administered jointly by the US Fish and Wildlife Service and Ohio Department of Natural Resources-Division ofWildlife, (2) the Department of Evolution, Ecology and Organismal Biology at The Ohio State University (OSU), and (3) a Presidential Fellowship awarded to S. A. Ludsin by OSU

First-Year Recruitment of Largemouth Bass: The Interdependency of Early Life Stages

Four early life events (i.e., hatching, the ontogenetic diet shift to piscivory, fall lipid accumulation, and the first winter) are conceptualized as being critical to 1st-yr recruitment success of largemouth bass (Micropterus salmoides) via cause-and-effect associations among them. Toward this end, we conducted a multiple life-stage investigation of largemouth bass to examine the functional dependency and significance to recruitment of these temporally separated early life events. Specifically, we quantified growth and survival of two largemouth bass year-classes in six Alabama ponds from hatching to the end of the first winter. The first winter was an important survival bottleneck with lower largemouth bass survival in ponds with smaller largemouth bass (high-density ponds), relative to ponds with larger fish (low-density ponds). While cannibalism was not important, we found sizedependent first-winter mortality to be regulated directly by lipid reserves (i.e., triglycerides) accumulated during fall, and indirectly by both hatch date and the ontogenetic diet shift to piscivory during summer. Early-hatched largemouth bass attained an initial length advantage, remaining large relative to late-hatched fish, despite the relatively higher growth rate of late-hatched fish during their first month of life. Enhanced size permitted earlyhatched fish to become piscivorous before late-hatched fish, increasing their access to fish prey (i.e., sunfishes) during fall. This in turn elevated their fall lipid accumulation and winter survival above that of late-hatched fish. Our results indeed suggest that 1st-yr recruitment of largemouth bass in southern systems is governed by several functionally dependent critical events. Because each is likely vital to understanding recruitment variability, we suggest that future recruitment studies should adopt a more synthetic (i.e., multiple life-stage) approach.This research was supported in part by National Science Foundation grants DEB-9108986 and DEB-9410323, and Federal Aid in Fish Restoration Project F40-R administered by the Alabama Game and Fish Division to DRD

Life After Death in Lake Erie: Nutrient Controls Drive Fish Species Richness, Rehabilitation

We explored the recent (1969–1996) dynamics of fish communities within Lake Erie, a system formerly degraded by eutrophication and now undergoing oligotrophication owing to phosphorus abatement programs. By merging bottom trawl data from two lake basins of contrasting productivity with life-history information (i.e., tolerances to environmental degradation, diet and temperature preferences), we examined (1) the relationship between system productivity and species richness, (2) whether fish communities are resilient to eutrophication, and (3) whether oligotrophication necessarily leads to reduced sport and commercial fish production. Reduced phosphorus loading has led to fish community rehabilitation. In the productive west basin, six species tolerant of eutrophy (i.e., anoxia, turbidity) declined in abundance, whereas the abundance of three intolerant species increased through time. In the less productive central basin, although only one tolerant species declined, four species intolerant of eutrophic conditions recovered with oligotrophication. These differential responses appear to derive from dissimilar mechanisms by which reduced productivity alters habitat and resource availability for fishes. Specifically, enhanced bottom oxygen, combined with reduced biogenic turbidity and sedimentation, likely drove the loss of tolerant species in the west basin by reducing detrital mass or the ability of these species to compete with intolerant species under conditions of improved water clarity. In contrast, reduced bottom anoxia, which enhanced availability of cool- and cold-water habitat and benthic macroinvertebrate communities, appears important to the recovery of intolerant species in the central basin. Ultimately, these productivity-induced shifts caused species richness to decline in Lake Erie’s west basin and to increase in its central basin. Beyond confirming that unimodal models of productivity and species diversity can describe fish community change in a recovering system, our results provide optimism in an otherwise dismal state of affairs in fisheries management (e.g., overexploitation), given that many recovering intolerant species are desired sport or commercial fishes.Support for this work was provided by (1) Federal Aid in Sport Fish Restoration F-69-P (to R. A. Stein), administered jointly by the U.S. Fish and Wildlife Service and ODNR-ODW, (2) the Department of Evolution, Ecology, and Organismal Biology at The Ohio State University, and (3) a Presidential Fellowship awarded to S. A. Ludsin by The Ohio State University

Evidence of hypoxic foraging forays by yellow perch ( Perca flavescens ) and potential consequences for prey consumption

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91146/1/FWB_2753_sm_fS1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/91146/2/j.1365-2427.2012.02753.x.pd

Benefits of Turbid River Plume Habitat for Lake Erie Yellow Perch (Perca flavescens) Recruitment Determined by Juvenile to Larval Genotype Assignment

Nutrient-rich, turbid river plumes that are common to large lakes and coastal marine ecosystems have been hypothesized to benefit survival of fish during early life stages by increasing food availability and (or) reducing vulnerability to visual predators. However, evidence that river plumes truly benefit the recruitment process remains meager for both freshwater and marine fishes. Here, we use genotype assignment between juvenile and larval yellow perch (Perca flavescens) from western Lake Erie to estimate and compare recruitment to the age-0 juvenile stage for larvae residing inside the highly turbid, south-shore Maumee River plume versus those occupying the less turbid, more northerly Detroit River plume. Bayesian genotype assignment of a mixed assemblage of juvenile (age-0) yellow perch to putative larval source populations established that recruitment of larvae was higher from the turbid Maumee River plume than for the less turbid Detroit River plume during 2006 and 2007, but not in 2008. Our findings add to the growing evidence that turbid river plumes can indeed enhance survival of fish larvae to recruited life stages, and also demonstrate how novel population genetic analyses of early life stages can contribute to determining critical early life stage processes in the fish recruitment process

Effects of Hypoxia on Consumption, Growth, and RNA:DNA Ratios of Young Yellow Perch

As in various freshwater and coastal marine ecosystems worldwide, seasonal bottom water hypoxia is a recurring phenomenon in Lake Erie’s central basin. While bottom hypoxia can strongly affect sessile benthic animals, its effects on mobile organisms such as fish are less understood. We evaluated the potential for bottom hypoxia to affect the growth rates of yellow perch Perca flavescens, a species of ecological and economic importance in the lake. To this end, we (1) conducted laboratory experiments to quantify the effects of reduced dissolved oxygen on consumption, somatic growth, and RNA : DNA ratios (an index of short‐term growth) of young yellow perch and (2) explored the effects of bottom hypoxia on young yellow perch growth in Lake Erie’s central basin by collecting individuals in hypoxicand normoxic regions of the lake and quantifying their RNA : DNA ratios. Yellow perch consumption and growth in our experiments declined under hypoxic conditions (≤2 mg O2/L). While yellow perch RNA : DNA ratios responded strongly to experimental temperature, nucleic acid ratios were not significantly affected by dissolved oxygen or feeding ration. We did, however, observe a positive correlation between yellow perch growth and RNA : DNA ratios at low temperatures (11°C). The nucleic acid ratios of yellow perch collected in Lake Erie varied spatiotemporally, but their patterns were not consistent with hypoxia. In short, while yellow perch consumption and growth rates respond directly and negatively to low oxygen conditions, these responses are not necessarily reflected in RNA : DNA ratios. Moreover, in central Lake Erie, where yellow perch can behaviorally avoid hypoxic areas, the RNA : DNA ratios of yellow perch do not respond strongly to bottom hypoxia. Thus, this study suggests that there is no strong negative effect of bottom hypoxia on the growth of young yellow perch in Lake Erie.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141858/1/tafs1574.pd

Indirect consequences of hypolimnetic hypoxia on zooplankton growth in a large eutrophic lake

Diel vertical migration (DVM) of some zooplankters in eutrophic lakes is often compressed during peak hypoxia. To better understand the indirect consequences of seasonal hypolimnetic hypoxia, we integrated laboratory-based experimental and field-based observational approaches to quantify how compressed DVM can affect growth of a cladoceran, Daphnia mendotae, in central Lake Erie, North America. To evaluate hypoxia tolerance of D. mendotae, we conducted a survivorship experiment with varying dissolved oxygen concentrations, which demonstrated high sensitivity of D. mendotae to hypoxia (≤2 mg O2 l−1), supporting the field observations of their behavioral avoidance of the hypoxic hypolimnion. To investigate the effect of temporary changes in habitat conditions associated with the compressed DVM, we quantified the growth of D. mendotae, using a 3 (food quantity) × 2 (temperature) factorial design laboratory experiment. Neither food quantity nor temperature affected short-term growth in body length of D. mendotae. However, D. mendotae RNA content (an index of short-term condition) decreased under starvation, indicating an immediate response of short-term feeding on condition. We further evaluated the effect of hypoxia-induced upward shifts in vertical distribution by quantifying the RNA content of D. mendotae from central Lake Erie before and during peak hypoxia. Despite high temperature and food quantity in the upper water column, RNA content in field-collected D. mendotae remained low during peak hypoxia. Furthermore, D. mendotae collected during peak hypoxia consisted of only small-bodied