Faculty Bibliography

Shortnose sturgeon, Acipenser brevirostrum, is a small, endangered species which occurs in 19 estuary systems along the east coast of North America. These populations are considered as separate entities by the U.S. National Marine Fisheries Service although evidence of morphologic or genetic differentiation among populations has not been documented. The purpose of this study was to compare morphological and genetic attributes among shortnose sturgeon collected From the Kennebec and Androscoggin Rivers, Maine, and the Hudson River, New York. Six morphometric and five meristic characteristics were quantified. Multivariate and univariate analyses of covariance and variance were used to assess differences among populations. Our analyses provided evidence for distinct populations in the Androscoggin and Kennebec Rivers, but character differentiation was greater between fish from these two locations and the Hudson River. Analysis of morphometric characters indicated significant differences in fish shape among the three rivers, with Hudson River sturgeon differing from the Maine rivers for the characters of head length, snout length, and mouth width. Significant differences were observed for meristic characters, but pairwise comparisons did not reflect a clear pattern of variability. Sequencing of a portion of the mitochondrial DNA control region revealed 15 haplotypes among 73 total specimens from the three rivers. Shortnose sturgeon from the Kennebec and Androscoggin Rivers were different from each other (p = 0.0260); both differed significantly (p < 0.0001) from the Hudson River collection. Gene flow was estimated at approximately 7 female migrants per generation between the two Maine populations and about 1 per generation between each of the Maine populations and the Hudson River population. Such strong stock structuring among presumably recently established post-Pleistocene (< 10,000 yr) populations suggests that this species occurs in highly discrete units, Morphological and genetic variation observed in this study combined with current knowledge of life history attributes of shortnose sturgeon indicate that conservative management decisions are necessary until the patterns and extent of differentiation among populations species-wide can be investigated further

The Atlantic sturgeon Acipenser oxyrinchus oxyrinchus has a latitudinally broad distribution along the east coast of North America, with extant populations occurring from the Saint Lawrence River to rivers in southern Georgia. This species once supported intensive caviar-based fisheries that resulted in overharvest and sharply reduced population abundances; presently, directed commercial fishing for Atlantic sturgeon is banned in U.S. waters. We sequenced a 203-base-pair section of the mitochondrial DNA (mtDNA) control region of 322 Atlantic sturgeon specimens from 11 river systems across their range to elucidate their stock structure. We found a pronounced latitudinal dine in the number of composite mtDNA haplotypes and in haplotypic diversity, which increased from north to south, from previously glaciated and subsequently recolonized systems to the portion of their range unglaciated during the Pleistocene. The observed number of haplotypes per population ranged from 1 haplotype in each of the two northernmost population samples to 17 in the sample from the Savannah River. Haplotypic diversity ranged from 0.0 to 0.90. The greater genetic diversity within and among southern populations is likely a product of the persistence of these populations through the Pleistocene and to the faster mutation rates associated with their shorter generation times. Of 39 composite mtDNA haplotypes found, 64% were unique to particular populations. Monomorphism of the two Canadian populations suggested a strong founder effect. Three haplotypes unique to northern populations were probably the result of base substitutions that occurred within the past 10,000 years. In contrast with an earlier study, we found stock structure among southern populations and evidence of at least seven generic stocks across this subspecies' range

Previous studies demonstrated reduced survivorship of pink salmon embryos from populations in Prince William Sound, Alaska, USA, that were exposed to Exxon Valdez-released oil compared with populations from matched nonoiled streams. Survivorship was also significantly decreased in embyros from lineages that were oiled in Prince William Sound and reared in clean water under controlled hatchery conditions compared with the descendants of nonoiled lineages. This suggests that the effect of oiling on pink salmon populations was persistent and could be transmitted intergenerationally. However, the ability of environmentally released oil to cause DNA sequence alterations in natural populations has yet to be demonstrated. We used polymerase chain reaction analysis to screen for alterations in the K-ras oncogene in DNA from pink salmon embryos that were exposed under controlled laboratory conditions to weathered Prudhoe Bay crude oil. Polymerase chain reaction and direct DNA sequence analyses were used to identify mutational hotspots within exons 1 and 2 of K-ras, and 3' primer mismatch analysis was used to determine the frequency of mutations in the 40 offspring of two families of pink salmon that were experimentally exposed to oiled or clean gravel. Mutations were only observed at codons 12, 13, and 61 of K-ras, sites that are frequently mutated in animal and human tumors. All mutations resulted in deduced amino acid substitutions. As expected, in all individuals exhibiting mutations, the copy number of the normal allele exceeded that of the mutated allele. The frequencies of mutations in oiled embryos at K-ras exons 1 and 2 were 68 and 41%, respectively. K-ras mutations were not observed in siblings that were exposed to clean gravel or in the parents of the two experimental matings. These results indicate that exposure of pink salmon embryos to weathered Prudhoe Bay crude oil under controlled laboratory conditions can elicit somatic cell mutations in high frequency at mutational hotspots in genes su!

Quantification of cytochrome P4501A1 (CYP1A1) mRNA levels in environmentally exposed Atlantic tomcod (Microgadus tomcod) has revealed significantly induced gene expression in fish from contaminated locales including the Hudson River, New York, and the Miramichi River, New Brunswick. In order to calibrate this response, determine its sensitivity and dose-responsiveness, levels of hepatic CYP1A1 mRNA were quantified in depurated Atlantic tomcod intraperitoneally (i.p.) injected with various concentrations of: beta-naphthoflavone (beta-NF), the PAH benzo[a]pyrene (B[a]P), the non-ortho coplanar PCB congener-3,3',4,4'- tetrachlorobiphenyl (IUP

Populations of marine, estuarine, and freshwater fish from highly urban and industrialized sites in North America often exhibit elevated prevalences of neoplastic, preneoplastic, and nonneoplastic hepatic lesions, and sometimes epidermal neoplasms compared to conspecifics from more pristine reference locales. Positive statistical associations with environmental concentrations of PAHs and other xenobiotics and experimental laboratory studies suggest a chemical etiology to these epizootics. Studies have investigated the expression of carcinogenically relevant genes, the extent of overall DNA damage, somatic cell mutations, germ line polymorphisms, and overall levels of genetic diversity in fish from these populations and other polluted sites. In general, elevated levels of cytochrome P4501A expression have been found in fish from contaminated locales; however, inhibition of gene induction has been seen in hepatic lesions and in normal tissue in fish from the most contaminated sites, perhaps due to genetic adaptation or physiological acclimation. Levels of bulky hepatic DNA adducts, as detected by 32P-postlabeling, are almost always elevated in fish from populations that are exposed to highly contaminated environments. However, levels of DNA adducts were not always predictive of the vulnerability to neoplasia of populations and species from polluted sites. Elevated levels of oxygen radical-induced DNA damage have been observed in hepatic tumors, preneoplastic lesions, and normal livers in a single species of flatfish from contaminated sites; however, the prevalences of these alterations in other species and at other polluted sites has yet to be evaluated. Frequent alterations in the K-ras oncogene have been reported in hepatic neoplasms in several species from highly contaminated sites and also in embryos that were experimentally exposed to oil-contaminated sediments. Studies also suggest that heritable germ line polymorphisms, altered allelic frequencies, and reductions in overall genetic diversity may have occurred in some highly impacted populations; however, the origin and functional significance of altered allelic frequencies have largely yet to be evaluated. In summary, feral fish appear particularly sensitive to DNA alterations from xenobiotics, perhaps due to their unusually high levels of exposure, relatively inefficient DNA repair, and the high frequency of polyploidy in some taxa and provide excellent models to explore the relationships between xenobiotic exposure and altered gene structure and expression

Striped bass, Morone saxatilis, in the Coos River, Oregon, are derived from natural colonists from San Francisco Bay, which in turn were intentionally transplanted from the Hudson River. Because of founder effects, this unusually well-documented colonization sequence should have resulted in diminished genetic variability in the penultimate and ultimate populations, which may have been further compounded in the Coos River population by subsequent drastic reductions in its abundance. To test whether these sequential bottlenecks reduced genetic diversity we surveyed both nuclear DNA (nDNA) and mitochondrial DNA (mtDNA) variation in the Coos River population and in both populations along the historical pathway that led to its founding. There was no evidence of reduced nDNA diversity among these populations at the three loci examined. However, the number of mtDNA haplotypes revealed decreased from 8 in the original Hudson River population, to 5 in the San Francisco Bay population, to only 1 in the Coos River population. This pattern of conserved nDNA diversity and reduced mtDNA diversity is consistent with a recent population bottleneck. Coos River striped bass have shown increasing levels of pathological hermaphroditism. We speculate that the reduced genetic diversity of the Coos River striped bass population may have led to a depensatory cascade involving hermaphroditism that inhibited reproduction and recruitment, followed by in creased levels of inbreeding as the population declined

There is considerable interest in restoring stocks of Atlantic sturgeon (Acipenser oxyrinchus), one of only two dozen extant sturgeons worldwide. Populations of its two subspecies are found in large rivers along the North American coasts of the Atlantic (A. o. oxyrinchus) and the Gulf of Mexico (A. o. desotoi). Although these populations were severely reduced because of overfishing and, in some instances, blockage of spawning runs, their present statuses, vary from those that still support limited fisheries (St. John River, new Brunswick), to a large but apparently declining population (Hudson River), to relict-sized (Delaware River, Mobile River), to apparently extirpated (Maryland tributaries of Chesapeake Bay; St. Johns, river, Florida). There are two primary alternatives for restoring these populations: (1) eliminating harvest and allowing natural recolonization and increase and (2) hatchery-based stocking (reintroduction or supplementation). We performed genetic analyses aimed at guiding restoration efforts. Mitochondrial DNA analysis revealed strong stock structure along both coasts at eh regional and, in some instances, population levels. Estimates of gene flow rates were low and suggested slow natural recolonization rates. Thus, the first alternative avoids the genetic risks of interstock transfer and inbreeding depression that may result from hatchery-based programs, but given the low intrinsic rates of increases and recolonization of Atlantic sturgeon, recovery may take decades to centuries, if it occurs at all. Therefore,it is imperative that the restoration approach be tailored to the particular circumstances and demographics of each population; however, the characteristics of this species and poor funding prospects make this information difficult to obtain. It appears likely that initial Atlantic sturgeon stocking efforts will target systems where they are extinct, as recently occurred in the Nanticoke River of Chesapeake Bay

Striped bass Morone saxatilis populations in drainages along the Gulf of Mexico coast (Gulf) were depleted in the 1950s and 1960s, probably because of anthropogenic influences. It is believed that only the Apalachicola-Chattahoochee-Flint (A-C-F) river system continually supported a naturally reproducing population of Gulf lineage. Striped bass juveniles of Atlantic coast (Atlantic) ancestry were introduced to restore population abundances in the A-C-F from the late 1960s to the mid 1970s and in many other Gulf rivers from the 1960s to the present. We previously identified mtDNA polymorphisms that were unique to approximately 60% of striped bass from the A-C-F and which confirmed the continued successful natural reproduction of striped bass of Gulf maternal ancestry within the system. However, the genetic relatedness of the extant A-C-F population to 'pure' Gulf striped bass was not addressed. In this study, we determined the frequency of a diagnostic mtDNA XbaI polymorphism in samples of 'pure' Gulf striped bass that were collected from the A-C-F prior to the introduction of Atlantic fish, that were obtained from museum collections, and that were originally preserved in formalin. PCR primers were developed that allowed for amplification of a 191-bp mtDNA fragment that contained the diagnostic XbaI restriction site. Using RFLP and direct sequence analyses of the PCR amplicons, we found no significant differences in mtDNA XbaI genotype frequencies between the archived samples and extant A-C-F samples collected over a 15-year period. This indicates that significant maternally mediated introgression of Atlantic mtDNA genomes into the A-C-F gene pool has not occurred. Additionally, we found no evidence of the unique Gulf mtDNA genotype in striped bass from extant populations in Texas, Louisiana and the Mississippi River. These results highlight the importance of the A-C-F as a repository of striped bass to restore extirpated Gulf populations and the potential use of museum collections in retrospective population studies