Madison S. Powell

Population Structure of Columbia River Basin Chinook Salmon and Steelhead Trout

The population structure of chinook salmon and steelhead trout is presented as an assimilation of the life history forms that have evolved in synchrony with diverse and complex environments over their Pacific range. As poikilotherms, temperature is described as the overwhelming environmental influence that determines what life history options occur. The different populations represent ecological types referred to as spring-, summer-, fall, and winter-run segments, as well as stream- and ocean-type, or stream- and ocean-maturing life history forms. However, they are more correctly described as a continuum of forms that fall along a temporal cline related to incubation and rearing temperatures that determine spawn timing and juvenile residence patterns. Population structure of chinook salmon and steelhead in the Columbia Basin, therefore, is the reflection of the genetic composition of the founding source or sources within the respective region, shaped by the environment, principally temperature, that defines life history evolutionary strategy to maximize fitness under the conditions delineated. The key in developing an effective recovery program for chinook salmon and steelhead is to recognize that measures taken must address the genetic and biological requirements of the population unit within the environmental template identified.

Effect of starvation on transcriptomes of brain and liver in adult female zebrafish (Danio rerio)

We used microarray and quantitative real-time PCR (qRT-PCR) analyses in adult female zebrafish (Danio rerio) to identify metabolic pathways regulated by starvation in the liver and brain. The transcriptome of whole zebrafish brain showed little response to 21 days of starvation. Only agouti-related protein 1 (agrp1) significantly responded, with increased expression in brains of starved fish. In contrast, a 21-day period of starvation significantly downregulated 466 and upregulated 108 transcripts in the liver, indicating an overall decrease in metabolic activity, reduced lipid metabolism, protein biosynthesis, proteolysis, and cellular respiration, and increased gluconeogenesis. Starvation also regulated expression of many components of the unfolded protein response, the first such report in a species other than yeast (Saccharomyces cerevisiae) and mice (Mus musculus). The response of the zebrafish hepatic transcriptome to starvation was strikingly similar to that of rainbow trout (Oncorhynchus mykiss) and less similar to mouse, while the response of common carp (Cyprinus carpio) differed considerably from the other three species.

Metabolism, Swimming Performance, and Tissue Biochemistry of High Desert Redband Trout (Oncorhynchus mykiss ssp.): Evidence for Phenotypic Differences in Physiological Function

Redband trout (Oncorhynchus mykiss ssp.) in southeastern Oregon inhabit high‐elevation streams that exhibit extreme variability in seasonal flow and diel water temperature. Given the strong influence and potential limitations exerted by temperature on fish physiology, we were interested in how acute temperature change and thermal history influenced the physiological capabilities and biochemical characteristics of these trout. To this end, we studied wild redband trout inhabiting two streams with different thermal profiles by measuring (1) critical swimming speed (Ucrit) and oxygen consumption in the field at 12° and 24°C; (2) biochemical indices of energy metabolism in the heart, axial white skeletal muscle, and blood; and (3) temperature preference in a laboratory thermal gradient. Further, we also examined genetic and morphological characteristics of fish from these two streams. At 12°C, maximum metabolic rate (Mo2 max) and metabolic power were greater in Little Blitzen redband trout as compared with those from Bridge Creek (by 37% and 32%, respectively). Conversely, Bridge Creek and Little Blitzen trout had similar values for Mo2 max and metabolic power at 24°C. The Ucrit of Little Blitzen trout was similar at the two temperatures (61 ± 3 vs. 57 ± 4 cm s−1). However, the Ucrit for Bridge Creek trout increased from 62 ± 3 cm s−1 to 75 ± 3 cm s−1 when water temperature was raised from 12° to 24°C, and the Ucrit value at 24°C was significantly greater than for Little Blitzen fish. Cost of transport was lower for Bridge Creek trout at both 12° and 24°C, indicating that these trout swim more efficiently than those from the Little Blitzen. Possible explanations for the greater metabolic power of Little Blitzen redband trout at 12°C include increased relative ventricular mass (27%) and an elevation in epaxial white muscle citrate synthase activity (by 72%). Bridge Creek trout had 50% higher lactate dehydrogenase activity in white muscle and presumably a greater potential for anaerobic metabolism. Both populations exhibited a preferred temperature of approximately 13°C and identical mitochondrial haplotypes and p53 gene allele frequencies. However, Bridge Creek trout had a more robust body form, with a relatively larger head and a deeper body and caudal peduncle. In summary, despite the short distance (∼10 km) and genotypic similarity between study streams, our results indicate that phenotypic reorganization of anatomical characteristics, swimming ability at environmentally pertinent temperatures and white axial muscle ATP‐producing pathways occurs in redband trout.

Sexual dimorphism in hepatic gene expression and the response to dietary carbohydrate manipulation in the zebrafish (Danio rerio)

In this study, we tested for the presence of sexual dimorphism in the hepatic transcriptome of the adult zebrafish and examined the effect of long term manipulation of dietary carbohydrate on gene expression in both sexes. Zebrafish were fed diets comprised of 0%, 15%, 25%, or 35% carbohydrate from the larval stage through sexual maturity, then sampled for hepatic tissue, growth, proximate body composition, and retention efficiencies. Using Affymetrix microarrays and qRT-PCR, we observed substantial sexual dimorphism in the hepatic transcriptome. Males up-regulated genes associated with oxidative metabolism, carbohydrate metabolism, energy production, and amelioration of oxidative stress, while females had higher expression levels of genes associated with translation. Restriction of dietary carbohydrate (0% diet) significantly affected hepatic gene expression, growth performance, retention efficiencies of protein and energy, and percentages of moisture, lipid, and ash. The response of some genes to dietary manipulation varied by sex; with increased dietary carbohydrate, males up-regulated genes associated with oxidative metabolism (e.g. hadhbeta) while females up-regulated genes associated with glucose phosphorylation (e.g. glucokinase). Our data support the use of the zebrafish model for the study of fish nutritional genomics, but highlight the importance of accounting for sexual dimorphism in these studies.

Hybridization and Introgression in a Managed, Native Population of Yellowstone Cutthroat Trout: Genetic Detection and Management Implications

Abstract Since the mid-1920s, the Idaho Department of Fish and Game has cultured Yellowstone cutthroat trout Oncorhynchus clarki bouvieri at Henrys Lake to offset declines in natural production and for use in stocking programs throughout Idaho. Since the mid-1970s, they have also produced F1 hybrids: female Yellowstone cutthroat trout × male rainbow trout O. mykiss. The ability of fishery managers, when selecting broodstock, to visually distinguish returning cutthroat trout from F1 hybrids is, therefore, crucial to avoid accidental introduction of rainbow trout genes into the hatchery-supplemented cutthroat trout population. To evaluate this ability, fish identified by staff as putative cutthroat trout or hybrids (an array of phenotypic characters are used), were sampled during two spawning seasons. Phenotypically identified fish were genetically tested using species-specific restriction fragment length polymorphisms (RFLPs) of nuclear and mitochondrial DNA gene loci and diagnostic allozyme loci. Current ...

A genetic evaluation of relatedness for broodstock management of captive, endangered Snake River sockeye salmon, Oncorhynchus nerka

The use of captive broodstocks is becoming more frequently employed as the number of species facing endangerment or extinction throughout the world increases. Efforts to rebuild the endangered Snake River sockeye salmon, Oncorhynchus nerka, population have been ongoing for over a decade, but the use of microsatellite data to develop inbreeding avoidance matrices is a more recent component to the program. This study used known genealogical relationships among sockeye salmon offspring to test four different pairwise relatedness estimators and a maximum-likelihood (M-L) relatedness estimator. The goal of this study was to develop a breeding strategy with these estimators that would minimize the loss of genetic diversity, minimize inbreeding, and determine how returning anadromous adults are incorporated into the broodstock along with full-term hatchery adults. Results of this study indicated that both the Mxy and RQG estimators had the lowest Type II error rates and the M-L and RR estimators had the lowest Type I error rates. An approach that utilizes a combination of estimators may provide the most valuable information for managers. We recommend that the M-L and RR methods be used to rank the genetic importance of returning adults and the Mxy or RQG estimators be used to determine which fish to pair for spawning. This approach provides for the best genetic management of this captive, endangered population and should be generally applicable to the genetic management of other endangered stocks with no pedigree.

Dietary carbohydrate level affects transcription factor expression that regulates skeletal muscle myogenesis in rainbow trout.

Understanding the effects of dietary carbohydrates on transcription factors that regulate myogenesis provides insight into the role of nutrient sensing by satellite cells towards myocyte differentiation. We evaluated the influence of dietary carbohydrate level (0, 15, 25 or 35%) on the temporal mRNA expression patterns (4, 8 or 12 weeks) of transcription factors that regulate satellite cell myocyte addition (MA) in rainbow trout (Oncorhynchus mykiss), a vertebrate with indeterminate growth. Relative to the 0% carbohydrate (NC) diet, 15 (IC-15) and 25% (IC-25) carbohydrate containing diets significantly up-regulate MyoD and Myf5, but not Pax7, after 12 weeks of feeding. Simultaneously, the Pax7/MyoD mRNA expression ratio declined significantly with both the IC diets. Myogenin mRNA expression also increased in rainbow trout (RBT) fed the IC-15 diet. The high carbohydrate (HC) diet (35%) attenuated the increased mRNA expression of these transcription factors. It is of note that the 4 and 8 week samples lacked the promyogenic expression patterns. The myogenic gene expression in fish fed the IC-15 diet for 12 weeks indicate a transcriptional signature that reflects increased satellite cell myogenesis. Our results suggest a potential role for satellite cells in the nutrient sensing ability of a vertebrate with indeterminate skeletal muscle growth.

Incidence of Hybridization between Naturally Sympatric Westslope Cutthroat Trout and Rainbow Trout in the Middle Fork Salmon River Drainage, Idaho

Abstract Introgressive hybridization has been widely reported for westslope cutthroat trout (WCT) Oncorhynchus clarkii lewisi and rainbow trout (RBT) O. mykiss and is often a result of introductions of nonnative RBT into previously allopatric populations of westslope cutthroat trout. The WCT evolved in sympatry with RBT in a portion of its native range. Few studies have evaluated natural hybrid zone structure in sympatric populations or the effects of nonnative introductions within sympatric populations. We used one mitochondrial DNA marker and three co-dominant nuclear DNA markers to examine 17 populations of WCT that were sympatric with native RBT-steelhead (anadromous RBT). As 5 of the 11 sample locations were situated downstream of stocked headwater mountain lakes, we wanted to determine the effects of headwater lake introductions on naturally sympatric populations of WCT and RBT-steelhead below the lakes. Hybrids were found in streams below stocked and unstocked headwater lakes. Our results indicated...

Mitochondrial DNA Analysis of Burbot Stocks in the Kootenai River Basin of British Columbia, Montana, and Idaho

Abstract Differences in mitochondrial haplotype frequency were examined among burbot Lota lota collected from four areas within the Kootenai River Basin of British Columbia, Montana and Idaho. The polymerase chain reaction (PCR) was used to amplify three gene regions of the mitochondrial genome: NADH dehydrogenase subunit 1 (ND1), NADH dehydrogenase subunit 2 (ND2), and NADH dehydrogenase subunits 5 and 6 combined (ND5,6). Amplified DNA was screened for restriction fragment length polymorphisms (RFLPs). Simple haplotypes resulting from RFLPs in a single gene region were combined into composite haplotypes. The distribution of composite haplotypes and their frequencies correspond to areas of the Kootenay River basin above and below a presumptive geographic barrier, Kootenai Falls, Montana, and suggest spatially segregated populations. A test of geographic heterogeneity among haplotype frequency distributions was highly significant (P < 0.001) when a Monte Carlo simulation was used to approximate a χ2 test. ...

Habitat Selection Influences Sex Distribution, Morphology, Tissue Biochemistry, and Parasite Load of Juvenile Coho Salmon in the West Fork Smith River, Oregon

Abstract Given the strong influence of water temperature on salmonid physiology and behavior, in the summers of 2004 and 2005 we studied juvenile male and female coho salmon Oncorhynchus kisutch in two reaches of Oregons West Fork Smith River with different thermal profiles. Our goals were to compare the body morphology, tissue biochemistry, genetics, and parasite load and determine whether sex, tissue biochemistry, and infection with multiple parasite species influence swimming performance. Sex differences in habitat selection distribution were apparent; proportionately more females occupied the cooler, upper reach, and males predominated in the warmer, lower reach. Despite having similar genotypes, fish in the upper reach had deeper bodies and higher condition factors, regardless of sex. These fish also had higher blood lipids and elevated citrate synthase activity in epaxial white muscle, suggesting a greater potential for aerobic metabolism. Critical swimming speeds measured streamside at 18°C and en...