A key to selected rockfishes (Sebastes spp.) based on mitochondrial DNA restriction fragment analysis

Larval and juvenile rockfishes (Sebastes spp.) are difficult to identify using morphological characters. We developed a key based on sizes of restriction endonuclease fragments of the NADH dehydrogenase-3 and -4 (ND3/ND4) and 12S and 16S ribosomal RNA (12S/16S) mitochondrial regions. The key makes use of variation in the ND3/ND4 region. Restriction endonuclease Dde I variation can corroborate identifications, as can 12S/16S variation. The key, based on 71 species, includes most North American taxa, several Asian species, and Sebastolobus alascanus and Helicolenus hilgendorfi that are closely related to rockfishes. Fifty-eight of 71 rockfish species in our database can be distinguished unequivocally, using one to five restriction enzymes; identities of the remaining species are narrowed to small groups: 1) S. polyspinis, S. crameri, and S. ciliatus or variabilis (the two species could not be distinguished and were considered as a single species) ; 2) S. chlorostictus, S. eos, and S. rosenblatti; 3) S. entomelas and S. mystinus; 4)S. emphaeus, S. variegatus, and S. wilsoni; and 5) S. carnatus and S. chrysomelas

Genetic and morphological identification of pelagic juvenile rockfish collected from the Gulf of Alaska

Pelagic juvenile rockfish (Sebastes spp.) collected in surveys designed to assess juvenile salmonids and other species in the Gulf of Alaska in 1998 and 2000–2003 provide an opportunity to document the occurrence of the pelagic juveniles of several species of rockfish. Often, species identification of rockfish is difficult or impossible at this stage of development (~20 to 60 mm), and few species indigenous to Alaska waters have been described. Use of mitochondrial DNA markers for rockfish species allowed unequivocal identification of ten species (S. aleutianus, S. alutus, S. borealis, S. entomelas, S. flavidus, S. melanops, S. pinniger, S. proriger, S. reedi, and S. ruberrimus) in subsamples from the collections. Other specimens were genetically assignable to groups of two or three species. Sebastes borealis, S. crameri, and S. reedi were identified using morphological data. Combining genetic and morphological data allowed successful resolution of the other species as S. emphaeus, probably S. ciliatus (although S. polyspinis cannot be totally ruled out), and S. polyspinis. Many specimens were initially morphologically indistinguishable from S. alutus, and several morphological groups included fish genetically identified as S. alutus. This paper details the characteristics of these pelagic juveniles to facilitate morphological identification of these species in future collections. (PDF file contains 32 pages.

Extent of DNA homology in some distantly and intimately related fishes

An attempt was made to differentiate between runs of steelhead by comparing the reassociations of their DNA. Conditions for the reassociation were studied using E. coli DNA, and observations were made spectrophotometrically. Of the five buffers examined, 1.0 molar sodium perchlorate plus one-hundredth molar tris-HCl, pH 7.1, at 60° or 70°C produced the fastest reassociation rates of 40,000 psi sheared DNA, over ten times faster than that of 0.12 molar sodium phosphate, pH 6.8. The rate increase was necessary for observation of the very slowly reassociating DNA. The genomes of the chinook jack, steelhead, and starry flounder were characterized and compared with respect to the composition of repeated sequences, similarity in base sequencing, and the amount of information in the nonrepeated sequences. The steelhead has a large, highly repeated fraction, sequences repeated at many intermediate frequencies, and a nonrepeated portion comprising 20-40% of the total and having a complexity greater than 2x10⁹ nucleotide pairs. Chinook DNA was quite similar but had distinct differences in the base sequencing of the less repeated region. Flatfish DNA differed greatly from that of the steelhead. The amount of the nonrepeated DNA was two thirds of the total while the complexity was only 1x10⁹. There was no significant amount of DNA repeated at intermediate frequencies, and there were no measurable sequence similarities. The DNA from the Rogue River, the Siletz River, and Sashin Creek steelhead had no differences measurable by the techniques used

Stock Composition of Some Sockeye Salmon, Oncorhynchus nerka, Catches in Southeast Alaska, Based on Incidence of Allozyme Variants, Freshwater Ages, and a Brain-Tissue Parasite

The incidence of four discrete characters of individual sockeye salmon -two genetically inherited proteins (PGM-1*and PGM-2*), freshwater age at migration, and the presence of the brain-tissue parasite Myxobolus arcticus-in weekly samples from two Alaskan fisheries (Noyes Island in 1986 and Sumner Strait in 1987) were used to infer stock composition of the catches based on corresponding character samples from 73 Alaskan and Canadian stocks. Estimated contributions of 13 stock groups, formed on the basis of character similarity of their members, were roughly consistent with expectations from tagging experiments, knowledge of stock magnitudes, and similar assessments from scales. Imprecision of the estimated contributions by the 13 stock groups limited their practical value; but variability was much reduced for combined estimated contributions by two inclusive categories, namely stock groups whose members had either high or low brainparasite prevalence. Noyes Island catches consisted predominantly of unparasitized fish, most of which were probably of Canadian origin. The majority of Sumner Strait catches consisted of parasitized fish, whose freshwater origins may have been in Alaska or Canada. (PDF file contains 27 pages.

Potentially adaptive mitochondrial haplotypes as a tool to identify divergent nuclear loci

1. Genetic tools are commonly used for conservation and management of at-risk species. Individuals are often sampled from mixtures that are composed of many populations, which creates a need to assign individuals to their source. This can be problematic when the genetic divergence among source populations is weak but can be improved using adaptive genetic loci, which should show stronger levels of divergence. 2. We previously reported a signature of positive selection in the mitochondrial-encoded ND5 subunit of complex I in diverse taxa. The respiratory machinery of the mitochondria in salmonids is composed of more than 80 nuclear genes and there is substantial interaction between nuclear and mitochondrial expressed gene products. Recent studies report adaptive variation in mitochondrial function as well as co-evolution between mitochondrial and nuclear genomes. We used potentially adaptive ND5-based mitochondrial haplotypes to identify nuclear loci that would display increased levels of genetic divergence compared to neutral nuclear loci in chum salmon (Oncorhynchus keta). Populations in a geographic area the size of France have previously demonstrated weak genetic divergence even after substantial discovery efforts by multiple laboratories for allozymes, microsatellites and SNPs over the last two decades. 3. We used RAD-based next-generation sequencing and identified a nuclear-encoded subunit of mitochondrial complex I that was a significant FST outlier and 14 other divergent nuclear markers that improve genetic assignment of individuals to their population of origin relative to assignments based on neutral markers alone. 4. This work demonstrates how a known adaptive marker can be leveraged to increase the probability of identifying divergent markers for applied genetics tools that may be biologically linked to it

Evolutionary effects of alternative artificial propagation programs: implications for viability of endangered anadromous salmonids

Most hatchery programs for anadromous salmonids have been initiated to increase the numbers of fish for harvest, to mitigate for habitat losses, or to increase abundance in populations at low abundance. However, the manner in which these programs are implemented can have significant impacts on the evolutionary trajectory and long-term viability of populations. In this paper, we review the potential benefits and risks of hatchery programs relative to the conservation of species listed under the US Endangered Species Act. To illustrate, we present the range of potential effects within a population as well as among populations of Chinook salmon (Oncorhynchus tshawytscha) where changes to major hatchery programs are being considered. We apply evolutionary considerations emerging from these examples to suggest broader principles for hatchery uses that are consistent with conservation goals. We conclude that because of the evolutionary risks posed by artificial propagation programs, they should not be viewed as a substitute for addressing other limiting factors that prevent achieving viability. At the population level, artificial propagation programs that are implemented as a short-term approach to avoid imminent extinction are more likely to achieve long-term population viability than approaches that rely on long-term supplementation. In addition, artificial propagation programs can have out-of-population impacts that should be considered in conservation planning

Positive Darwinian Selection in the Piston That Powers Proton Pumps in Complex I of the Mitochondria of Pacific Salmon

The mechanism of oxidative phosphorylation is well understood, but evolution of the proteins involved is not. We combined phylogenetic, genomic, and structural biology analyses to examine the evolution of twelve mitochondrial encoded proteins of closely related, yet phenotypically diverse, Pacific salmon. Two separate analyses identified the same seven positively selected sites in ND5. A strong signal was also detected at three sites of ND2. An energetic coupling analysis revealed several structures in the ND5 protein that may have co-evolved with the selected sites. These data implicate Complex I, specifically the piston arm of ND5 where it connects the proton pumps, as important in the evolution of Pacific salmon. Lastly, the lineage to Chinook experienced rapid evolution at the piston arm