Matthew A. Cronin

The Controversy about Salmon Hatcheries

Abstract The use of hatcheries has been a subject of lengthy debate in the management of salmon and trout resources in the Pacific Northwest. The problem has resulted in part from the wide distribution of hatchery fish in circumstances where natural populations were disadvantaged by management policy involving hatchery fish and the confusion of the effects of management with the effects of artificial propagation. Recently, the controversy has been epitomized by the recommendations to fisheries management agencies that excess hatchery fish should not be allowed to spawn in the wild, and hatchery fish should be excluded from salmon populations listed under the Endangered Species Act. The authors of the present article disagree with those recommendations and conclude that hatchery fish have an important role in recovery and supplementation of wild stocks. The present article is an attempt to help give balance to the discussion by providing a different perspective on hatchery fish and the literature pertainin...

Variation in Mitochondrial DNA and Microsatellite DNA in Caribou (Rangifer tarandus) in North America

Abstract Genetic variation of caribou (Rangifer tarandus) at 18 microsatellite DNA loci and the cytochrome-b gene of mitochondrial DNA (mtDNA) was quantified in 11 herds of 3 North American subspecies: Alaskan barren ground caribou (R. t. granti), Canadian barren ground caribou (R. t. groenlandicus), and woodland caribou (R. t. caribou). Phylogenetic analysis of 1,194 nucleotides of cytochrome-b sequence resulted in a clade of 52 genotypes in R. t. granti, R. t. groenlandicus, and in 1 herd of R. t. caribou, and a clade of 7 genotypes in R. t. caribou. mtDNA sequence divergence is approximately 1% between these clades and 0.3–0.6% within these clades. The subspecies do not have monophyletic mtDNA, but do have different frequencies of mtDNA genotypes. Microsatellite allele frequencies also are differentiated between the woodland (R. t. caribou) and barren ground (R. t. granti and R. t. groenlandicus) subspecies. An exception is the George River herd in Labrador, which is classified as R. t. caribou but has mtDNA and microsatellite allele frequencies intermediate between the other herds of R. t. caribou and R. t. groenlandicus. Within subspecies, there is relatively low differentiation of microsatellite allele frequencies and mtDNA genotypes among herds of R. t. granti and R. t. groenlandicus, and relatively high differentiation of microsatellite alleles and mtDNA genotypes among herds of R. t. caribou in 4 geographically separate areas in Canada. The extent of differentiation of mtDNA genotype frequencies and microsatellite allele frequencies within and among each subspecies reflects past and present gene flow among herds. Issues related to subspecies, populations, ecotypes, and herds are discussed.

Genetic differentiation of sockeye salmon subpopulations from a geologically young Alaskan lake system

Abstract The Tustumena Lake drainage in southcentral Alaska is glacially turbid and geologically young (<2,000 years old). Previous field studies identified at least three subpopulations of sockeye salmon Oncorhynchus nerka at Tustumena Lake, based on the distribution and timing of spawners. The subpopulations included early-run salmon that spawned in six clearwater tributaries of the lake (mid August), lake shoreline spawners (late August), and late-run fish that spawned in the lakes outlet, the Kasilof River (late September). Our objective was to determine the degree of genetic differentiation among these subpopulations based on restriction enzyme analyses of the cytochrome b gene of mitochondrial DNA and analyses of four polymorphic allozyme loci. Mitochondrial DNA haplotype frequencies for outlet-spawning sockeye salmon differed significantly from those of all other subpopulations. The most common (36%) haplotype in the outlet subpopulation did not occur elsewhere, thus suggesting little or no gene f...

Northern Alaska oil fields and caribou : A commentary

Abstract We discuss the status of caribou, Rangifer tarandus, herds relative to oil field development in the Prudhoe Bay region of Alaska. The Central Arctic caribou herd, which spends June and July in and around oil fields in the Prudhoe Bay region, has increased since the inception of oil field development and has demographics similar to those of adjacent herds which are not near oil fields. Although oil field development may impact individual caribou through disturbance or impedance of movements, herd-level impacts of the oil fields are not apparent. Caribou populations characteristically fluctuate dramatically, and differentiating human and non-human impacts is difficult or impossible. The herd is the unit of management, and management objectives are being met. The experience in northern Alaskas oil fields indicates resource extraction and wildlife populations can be compatible when managed properly.

A Proposal to Eliminate Redundant Terminology for Intra-Species Groups

Abstract Many new terms have come into use for intra-species groups of animals defined with genetic criteria including subspecies, evolutionarily significant units, evolutionary units, management units, metapopulations, distinct population segments, populations, and subpopulations. These terms have redundant meanings and can lead to confusion for biologists, managers, and policy makers. I propose that for wildlife management we can simplify intra-species terminology and use only the terms subspecies, populations, and subpopulations. These 3 terms have roots in evolutionary and population biology and can incorporate genetic, demographic, and geographic considerations.

RABIES AND CANINE DISTEMPER IN AN ARCTIC FOX POPULATION IN ALASKA

Two oil field workers were attacked by a rabid arctic fox (Alopex lagopus) in the Prudhoe Bay oil field (Alaska, USA) prompting officials to reduce the local fox population. Ninety-nine foxes were killed during winter 1994. We tested foxes for prevalence of rabies and canine distemper. Exposure to rabies was detected in five of 99 foxes. Of the five, only one fox had rabies virus in neural tissue as determined by the direct fluorescent antibody test. The other four foxes had been exposed to rabies, but had apparently produced antibodies and did not have an active infection. No evidence of canine distemper was detected as determined by the absence of distemper antibodies in serum and distemper virus in neural tissue.

A Population Genetic Analysis of the Potential for a Crude Oil Spill to Induce Heritable Mutations and Impact Natural Populations

The primary environmental impact following an oil spill typically is acute toxicity to fish and wildlife. However, multigenerational effects through toxicant-induced heritable mutations might also occur. Some polycyclic aromatic hydrocarbon (PAH) components of crude oil are potentially mutagenic, although specific components and doses that induce mutations are poorly known. We applied population genetics concepts to assess the extent of mortality and the persistence of deleterious heritable mutations resulting from exposure to potential mutagens, such as crude oil. If lethal mutations are induced, the population will experience some mortality, but the mutations are quickly removed or reduced to low frequency by natural selection. This occurs within one or a few generations when mutations are dominant or partially recessive. Totally recessive alleles persist in low frequency for many generations, but result in relatively little impact on the population, depending on the number of mutated loci. We also applied population genetics concepts to assess the potential for heritable mutations induced by the Exxon Valdez oil spill in Prince William Sound, Alaska, to affect pink salmon populations. We stress that breeding units (e.g., streams with distinct spawning populations of salmon) must be considered individually to assess heritable genetic effects. For several streams impacted by the oil spill, there is inconsistency between observed egg mortality and that expected if lethal heritable mutations had been induced by exposure to crude oil. Observed mortality was either higher or lower than expected depending on the spawning population, year, and cohort considered. Any potential subtle effect of lethal mutations induced by the Exxon Valdez oil spill is overridden by natural environmental variation among spawning areas. We discuss the need to focus on population-level effects in toxicological assessments because fish and wildlife management focuses on populations, not individuals.

Genetic Variation, Relatedness, and Effective Population Size of Polar Bears (Ursus maritimus) in the southern Beaufort Sea, Alaska

Polar bears (Ursus maritimus) are unique among bears in that they are adapted to the Arctic sea ice environment. Genetic data are useful for understanding their evolution and can contribute to management. We assessed parentage and relatedness of polar bears in the southern Beaufort Sea, Alaska, with genetic data and field observations of age, sex, and mother-offspring and sibling relationships. Genotypes at 14 microsatellite DNA loci for 226 bears indicate that genetic variation is comparable to other populations of polar bears with mean number of alleles per locus of 7.9 and observed and expected heterozygosity of 0.71. The genetic data verified 60 field-identified mother-offspring pairs and identified 10 additional mother-cub pairs and 48 father-offspring pairs. The entire sample of related and unrelated bears had a mean pairwise relatedness index (r(xy)) of approximately zero, parent-offspring and siblings had r(xy) of approximately 0.5, and 5.2% of the samples had r(xy) values within the range expected for parent-offspring. Effective population size (N(e) = 277) and the ratio of N(e) to total population size (N(e)/N = 0.182) were estimated from the numbers of reproducing males and females. N(e) estimates with genetic methods gave variable results. Our results verify and expand field data on reproduction by females and provide new data on reproduction by males and estimates of relatedness and N(e) in a polar bear population.

Caribou distribution near an oilfield road on Alaska's North Slope, 1978-2001

Abstract Previous research in the Milne Point oilfield in northern Alaska showed that the density of caribou (Rangifer tarandus) in the calving period within 1 km of a road was significantly lower after construction than before construction of the road. This was interpreted as displacement from the road and a functional loss of habitat and has been extensively cited as a documented effect of oilfield development on caribou. We continued this study with additional aerial surveys flown during 1991–2001 and compared caribou numbers and density in 6 1-km intervals from the road over 3 time periods: pre-road construction (1978–1981), early post-road construction (1982–1987), and recent post-road construction (1991–2001). During the recent post-road period, the densities of calves and of all caribou were not significantly lower within 1 km of the road than the densities in the pre-road period. In addition, calf density was higher in the interval within 1 km of the road than in the intervals 1–6 km from the road during the recent post-road construction period. The total number of calving caribou observed in the study area has declined since pre-road construction and early post-road periods, but we found no evidence that caribou using the area during calving avoided areas near the road during the recent post-road period. Numbers of caribou in the study area during the post-calving period (after 20 June) during 1991–2001 were highly variable, but generally were higher than during calving. Analyses of relationships between calving and post-calving caribou densities and distance intervals from Milne Point Road suggested that distributions of calves and adult caribou were not strongly influenced by presence of the road.

Hydraulic Sampling Protocol to Estimate Natural Embryo Mortality of Pink Salmon

Abstract Productivity of naturally spawning salmon populations is sometimes estimated by sampling incubating eggs from the spawning grounds to assess survival by pumping water or an air–water mixture into the stream gravel and collecting eggs displaced by the resulting agitation. General knowledge regarding embryo sensitivity to physical shock indicates that this procedure may kill eggs if conducted before embryo development has advanced beyond blastopore closure, which is up to day 12 postfertilization. In 1998, we assessed the impact of sample timing on egg mortality estimates of pink salmon Oncorhynchus gorbuscha in 10 spawning streams in Prince William Sound, Alaska, by hydraulically sampling the same streams in September and again in October. The mean egg mortality was significantly higher in the early sampling period (63.6%) than in the later sampling period (22.8%). Results from examining stage of advancement at the time of embryo death indicate that sampling with hydraulic techniques will elevate ...