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Featured researches published by Chris J. Foote.


Fisheries Research | 1999

Stocks and chameleons: the use of phenotypic variation in stock identification

Douglas P Swain; Chris J. Foote

Phenotypic variation in morphological characters like body shape or meristic count has long been used to delineate stocks of fish. It is now well known that there may be both environmental and genetic components to this variation. Genetic studies often fail to support the population differentiation suggested by morphological variation. This may reflect environmental induction of the morphological differences, or rapid genetic change in the morphological characters due to selection. Patterns of morphological variation that conform to those expected in response to selection are sometimes taken as evidence of genetic divergence. However, controlled rearing of suspected stocks in a common environment is needed to confirm genetic differentiation. Even then, phenotypic differences do not guarantee genetic differences because morphological differences in offspring can reflect environmental differences experienced by parents before fertilization. In many cases, controlled rearing has confirmed the morphological differences that point to differentiation into separate stocks adapted to different environments. In some cases, controlled rearing has revealed that phenotypic similarity among groups of fish hides genetic differentiation that compensates for differences between stocks in environmental influences. In other cases, widespread patterns that were assumed to reflect genetic responses to selection have been revealed by controlled rearing experiments to be environmentally-induced. This raises the possibility that phenotypic plasticity may itself be adaptive, allowing stocks, like chameleons, to shift their appearance to match their ecological circumstances.


Evolution | 1996

Evidence for sympatric genetic divergence of anadromous and nonanadromous morphs of sockeye salmon (Oncorhynchus nerka).

Chris C. Wood; Chris J. Foote

Anadromous and nonanadromous morphs of the Pacific salmon Oncorhynchus nerka spawn in close physical proximity in tributaries to Takla Lake, British Columbia, yet differ in morphology, gill raker number, allozyme allele frequencies, and reproductive traits. Both morphs are semelparous typically maturing at age four, the anadromous morph (sockeye) at fork lengths of 38–65 cm and the nonanadromous morph (kokanee) at 17–22 cm. When reared together, pure and hybrid morphs also exhibited different growth rates and maturity schedules. Collectively, these large differences between the morphs confirm that sockeye and kokanee exist as reproductively isolated populations. Average gene flow (m) was estimated to be 0.1–0.8% between morphs, 1.7–3.7% among tributaries for kokanee, and 0.3–5.6% among tributaries for sockeye. We conclude that divergence has occurred in sympatry and examine potential isolating mechanisms.


Behaviour | 1988

The role of male choice in the assortative mating of anadromous and non-anadromous sockeye salmon (Oncorhynchus nerka).

Chris J. Foote; Peter A. Larkin

Assortative mating between the anadromous (sockeye salmon) and non-anadromous (kokanee) forms of Oncorhynchus nerka was documented in Pierre Creek, Babine Lake, British Columbia. Sockeye males of all sizes mated almost exclusively with sockeye females. Only a small proportion of the smallest sockeye males (acks) were observed courting kokanee females. Kokanee males either courted kokanee females or acted as sneaks to sockeye pairs. We experimentally tested the hypotheses that assortative mating occurred because of: a) male intrasexual competition for the largest (sockeye) females; b) male choice dependent on male size; and c) male choice dependent on form. Our results demonstrated male competition was not the cause of assortative mating as has previously been suggested. Kokanee males only preferred sockeye over kokanee females when direct access to kokanee females was denied. Male choice was dependent on male size as has previously been demonstrated within kokanee, but appeared to also involve a form component. Kokanee males preferred kokanec females over the much larger and fecund sockeye females. The evolution of assortative mating between sockeye and kokanee fits models of sympatric speciation. An initial degree of assortative mating between forms is predicted by their environmentally induced great size difference. This promotes genetic divergence between the forms, which has been documented, accompanied by the evolution of premating isolating mechanisms. However, behavioural divergence is not complete in Pierre Creek. Kokanec males restricted from direct access to kokanee females prefer to sneak on sockeye pairs over kokanee pairs.


Behaviour | 1990

An experimental comparison of male and female spawning territoriality in a Pacific salmon

Chris J. Foote

The spawning territoriality of male and female non-anadromous sockeye salmon, Oncorhynchus nerka, was examined experimentally by comparing the resources sought after, the behaviours used in intrasexual competition, and the correlates of success in intrasexual competition for each sex. Females expressed territorial behaviour both in the presence and absence of males, defending specific, repeatedly selected, spawning sites. In contrast, males exhibited clear territorial behaviour only in the presence of females, defending access to specific females and positions over time. Size was a factor in determining which females established territories within preferred areas, but this advantage was largely negated by prior residency. Size was a major factor in determining which males gained closest access to individual females, with smaller males adopting subordinate, sneak, positions. Prior residence was also a significant factor in determining the outcome of contests for access to females, with the weight of this factor dependent on the relative sizes of competing males. The behavioural differences between sexes appear to arise from differences both in the resources defended and the relative costs of potential losses for each sex.


Evolution | 2001

COUNTERGRADIENT VARIATION AND SECONDARY SEXUAL COLOR: PHENOTYPIC CONVERGENCE PROMOTES GENETIC DIVERGENCE IN CAROTENOID USE BETWEEN SYMPATRIC ANADROMOUS AND NONANADROMOUS MORPHS OF SOCKEYE SALMON (ONCORHYNCHUS NERKA)

J. Kevin Craig; Chris J. Foote

Genetically distinct anadromous (sockeye) and nonanadromous (kokanee) morphs of the Pacific salmon, Oncorhynchus nerka, develop identical, brilliant red color at maturity during sympatric breeding in freshwater streams. The marine and lacustrine environments they occupy prior to maturity, however, appear to differ in the availability of dietary carotenoid pigments necessary to produce red coloration. We tested the hypothesis that kokanee, which occupy carotenoid‐poor lakes, are more efficient at using the dietary pigments than are sockeye, which occupy the more productive North Pacific Ocean. In a 2‐year controlled breeding study, flesh and skin color of mature and immature crosses fed a low‐carotenoid diet were quantified with both a chromameter and by chemical extraction of carotenoid pigments. Results revealed striking countergradient variation in carotenoid use, with kokanee approximately three times more efficient at sequestering the pigments to the flesh musculature than similar age sockeye. This difference translated into virtually nonoverlapping differences between pure crosses in secondary sexual color at maturity, when the pigments are mobilized and transported to the skin. Kokanee crosses turned pinkish red over most of their body, whereas sockeye turned olive green. The olive green was similar to the breeding color of residuals in the wild, the progeny of anadromous sockeye that remain in fresh water and are believed to have given rise to kokanee on numerous independent occasions. Reciprocal hybrids were similar to each other and intermediate to the pure crosses, indicating additive genetic inheritance. Mate choice trials with sockeye males in the wild showed the ancestral morph strongly preferred red over green models. These results suggest a preference for red mates maintained in nonanadromous breeding populations drove the reevolution of the red phenotype in kokanee via more efficient use of dietary carotenoid pigments. This is a novel, yet hidden, mechanism by which sexual selection promotes the genetic differentiation of these sympatric populations.


Molecular Ecology | 1998

Microsatellite analysis of genetic population structure in an endangered salmonid: the coastal cutthroat trout (Oncorhynchus clarki clarki)

John K. Wenburg; Paul Bentzen; Chris J. Foote

The genetic population structure of coastal cutthroat trout (Oncorhynchus clarki clarki) in Washington state was investigated by analysis of variation in allele frequencies at six highly polymorphic microsatellite loci for 13 anadromous populations, along with one outgroup population from the Yellowstone subspecies (O. clarki bouvieri) (mean heterozygosity = 67%; average number of alleles per locus = 24). Tests for genetic differentiation revealed highly significant differences in genotypic frequencies for pairwise comparisons between all populations within geographical regions and overall population subdivision was substantial (FST = 0.121, RST = 0.093), with 44.6% and 55.4% of the among‐population diversity being attributable to differences between streams (FSR = 0.054) and between regions (FRT = 0.067), respectively. Analysis of genetic distances and geographical distances did not support a simple model of isolation by distance for these populations. With one exception, neighbour‐joining dendrograms from the Cavalli‐Sforza and Edwards’ chord distances and maximum likelihood algorithms clustered populations by physiogeographic region, although overall bootstrap support was relatively low (53%). Our results suggest that coastal cutthroat trout populations are ultimately structured genetically at the level of individual streams. It appears that the dynamic balance between gene flow and genetic drift in the subspecies favours a high degree of genetic differentiation and population subdivision with the simultaneous maintenance of high heterozygosity levels within local populations. Results are discussed in terms of coastal cutthroat trout ecology along with implications for the designation of evolutionarily significant units pursuant to the US Endangered Species Act of 1973 and analogous conservation units.


Behaviour | 1988

Male mate choice dependent on male size in salmon

Chris J. Foote

[Non-anadromous sockeye salmon males (kokanee), Oncorhynchus nerka, were tested to determine if they select mates according to their absolute size (fork length) or if male mate choice was governed by the size of the male. In a series of four experiments, involving three size groups of mâles and females, the size of females presented and males tested were systematically varied. The results demonstrated male choice is dependent on male size and not solely on the absolute size of females as previously suggested in salmon and other fishes. Males of all sizes discriminated against females smaller than themselves, but did not discriminate between females of their own size and those larger. Thus, male selectivity increases with male size in salmon. The smallest males are the least selective of mates whereas the largest males arc the most selective, preferring the largest females. This varying selectivity corresponds to the availability of females on the spawning grounds. Small males have the most limited range of potential mates (because of the effects of size in intrasexual competition and female choice) whereas large males have the widest range in potential mates. The experimental results presented are consistent with two observed patterns of association of male and female salmonids on the spawning grounds: a) the number of males aggregated around females increases with increasing female size; and b) pairing between the sexes is assortative by size. Assortative mating by size was demonstrated to be further increased by male intrasexual competition. These results suggest that intrasexual competition and mate choice by the opposite sex can lead to the evolution of varying strategies of mate choice within sexes, just as it can lead to the evolution of varying strategies of seeking mates., Non-anadromous sockeye salmon males (kokanee), Oncorhynchus nerka, were tested to determine if they select mates according to their absolute size (fork length) or if male mate choice was governed by the size of the male. In a series of four experiments, involving three size groups of mâles and females, the size of females presented and males tested were systematically varied. The results demonstrated male choice is dependent on male size and not solely on the absolute size of females as previously suggested in salmon and other fishes. Males of all sizes discriminated against females smaller than themselves, but did not discriminate between females of their own size and those larger. Thus, male selectivity increases with male size in salmon. The smallest males are the least selective of mates whereas the largest males arc the most selective, preferring the largest females. This varying selectivity corresponds to the availability of females on the spawning grounds. Small males have the most limited range of potential mates (because of the effects of size in intrasexual competition and female choice) whereas large males have the widest range in potential mates. The experimental results presented are consistent with two observed patterns of association of male and female salmonids on the spawning grounds: a) the number of males aggregated around females increases with increasing female size; and b) pairing between the sexes is assortative by size. Assortative mating by size was demonstrated to be further increased by male intrasexual competition. These results suggest that intrasexual competition and mate choice by the opposite sex can lead to the evolution of varying strategies of mate choice within sexes, just as it can lead to the evolution of varying strategies of seeking mates.]


Transactions of The American Fisheries Society | 2000

Disturbance of Small-Stream Habitat by Spawning Sockeye Salmon in Alaska

Douglas P. Peterson; Chris J. Foote

Abstract We examined how the spatially and temporally predictable disturbance caused by a spawning run of native sockeye salmon Oncorhynchus nerka temporarily affected benthic and invertebrate drift communities of two small streams in southwestern Alaska. Surface gravel size temporarily increased as a consequence of this mechanical disturbance, and periphyton biomass decreased in one stream. The postspawning rise in periphyton biomass in Bear Creek (larger sockeye salmon run) likely reflects nutrient release by decomposing sockeye salmon. Total benthic invertebrate and larval chironomid density decreased during spawning in one stream, but most invertebrate taxa in both streams did not exhibit clear spawning-related impacts. In contrast, invertebrate drift almost always increased during daylight hours when sockeye salmon were present, but it was difficult to separate mechanical effects of sockeye salmon acting via redd construction versus swimming. Total daytime drift density during spawning was four times...


Evolutionary Applications | 2008

Recurrent evolution of life history ecotypes in sockeye salmon: implications for conservation and future evolution

Chris C. Wood; John W. Bickham; R. John Nelson; Chris J. Foote; John C. Patton

We examine the evolutionary history and speculate about the evolutionary future of three basic life history ecotypes that contribute to the biocomplexity of sockeye salmon (Oncorhynchus nerka). The ‘recurrent evolution’ (RE) hypothesis claims that the sea/river ecotype is ancestral, a ‘straying’ form with poorly differentiated (meta)population structure, and that highly structured populations of lake‐type sockeye and kokanee have evolved repeatedly in parallel adaptive radiations between recurrent glaciations of the Pleistocene Epoch. Basic premises of this hypothesis are consistent with new, independent evidence from recent surveys of genetic variation in mitochondrial and microsatellite DNA: (1) sockeye salmon are most closely related to pink (O. gorbuscha) and chum (O. keta) salmon with sea‐type life histories; (2) the sockeye life history ecotypes exist as polyphyletic lineages within large drainages and geographic regions; (3) the sea/river ecotype exhibits less genetic differentiation among populations than the lake or kokanee ecotypes both within and among drainages; and (4) genetic diversity is typically higher in the sea/river ecotype than in the lake and kokanee ecotypes. Anthropogenic modification of estuarine habitat and intensive coastal fisheries have likely reduced and fragmented historic metapopulations of the sea/river ecotype, particularly in southern areas. In contrast, the kokanee ecotype appears to be favoured by marine fisheries and predicted changes in climate.


Transactions of The American Fisheries Society | 2000

Selection on Morphology of Spawning Wild Sockeye Salmon by a Gill-Net Fishery

Troy R. Hamon; Chris J. Foote; R. A. Y. Hilborn; Donald E. Rogers

Abstract Human activities can cause artificial selection in wild animals. To examine the effects of gill-net selectivity on locally differentiated populations of sockeye salmon Oncorhynchus nerka in Bristol Bay, Alaska, we completed a three-part study: (1) We showed differentiation in the body form of mature sockeye salmon spawning in beach and stream habitats that were separated by less than 300 m. (2) Because gill-net selection acts directly on the girth of immature sockeye salmon, we correlated girth at capture with the morphological characters distinguishing locally differentiated populations on the spawning grounds. By tagging individual fish and measuring them both when immature and when mature, we found morphology at maturity to be highly correlated with girth during immaturity. (3) Using selection regimes from the fishery catch and escapement data for 1994, we examined the effects of gill-net selectivity on populations of mature adults. We showed that although populations of mixed ocean age-classe...

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Chris C. Wood

Fisheries and Oceans Canada

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Troy R. Hamon

University of Washington

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Gayle S. Brown

Fisheries and Oceans Canada

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W.Craig Clarke

Fisheries and Oceans Canada

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Andrew H. Dittman

National Oceanic and Atmospheric Administration

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