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Conservation hatcheries are becoming a tool in rebuilding salmonid populations, but their contributions are strongly debated. Most studies focus on genetic, morphological, and behavioural, issues and less is known of the importance of infectious agents. The Living Gene Bank (LGB) program of the British Columbia Ministry of the Environment is a recent effort to restore collapsed steelhead trout (Oncorhynchus mykiss) populations on the east coast of Vancouver Island. Our study describes the change in macro- and microparasitic profiles of LGB-hatchery-produced juveniles after they leave the hatchery and enter the natural river environment and also compares them with a limited wild smolt sample. We found that the hatchery was successful in raising parr free of infectious agents, but once introduced into the river environment, the hatchery fish quickly took on a diverse profile of infectious agents. The high numbers of fish released from the hatchery and the existence of hatchery fish that stay in the...

Conservation biologists mostly agree on the need to identify and protect biodiversity below the species level but have not yet resolved the best approach. We addressed 2 issues relevant to this debate. First, we distinguished between the abstract goal of preserving the maximum amount of unique biodiversity and the pragmatic goal of minimizing the loss of ecological goods and services given that further loss of biodiversity seems inevitable. Second, we distinguished between the scientific task of assessing extinction risk and the normative task of choosing targets for protection. We propose that scientific advice on extinction risk be given at the smallest meaningful scale: the elemental conservation unit (ECU). An ECU is a demographically isolated population whose probability of extinction over the time scale of interest (say 100 years) is not substantially affected by natural immigration from other populations. Within this time frame, the loss of an ECU would be irreversible without human intervention. Society's decision to protect an ECU ought to reflect human values that have social, economic, and political dimensions. Scientists can best inform this decision by providing advice about the probability that an ECU will be lost and the ecological and evolutionary consequences of that loss in a form that can be integrated into landscape planning. The ECU approach provides maximum flexibility to decision makers and ensures that the scientific task of assessing extinction risk informs, but remains distinct from, the normative social challenge of setting conservation targets.

We document the invasion of Chinook salmon (Oncorhynchus tshawytscha) to southern South America providing historical, current and future perspectives. We conducted field sampling, angler surveys, and analyzed all written records, and found evidence of reproductive populations in more than ten Andean (and many more coastal) watersheds draining mainly to the Pacific Ocean in Chile (39°–53° S), but also to the Atlantic Ocean in Argentina (50° S). Invasion begun ∼25 years ago apparently from a few point sources of introduction by ocean ranching operations using spring-run Chinook salmon originated from tributaries of the lower Columbia River, USA. The rapid spread suggests that Chinook salmon were pre-adapted to their novel marine and freshwater environments because of similarities to equivalent North Pacific habitats, and invasion may have been facilitated by low ecological resistance. Preliminary data suggest that populations express a latitudinal gradient in juvenile migration life histories equivalent to that in their native range. Parallels to the only other establishment of anadromous Chinook salmon outside their native range, New Zealand, suggests a predictable invasion rate. In South America, the invasion is ongoing in southern areas, yet we deem unlikely colonization of rivers north of the range reached thus far. This is the first anadromous salmon species to have invaded such a large range in South America, and it raises many evolutionary, ecological, environmental and socioeconomic issues, with several discussed here.

Fluctuating asymmetry (FA), the small random deviations from perfect morphological symmetry that result during development, is ubiquitous throughout the animal kingdom. In many species, FA seems to play a role in mate choice, perhaps because it signals an individual's genetic quality and health. However, the relationship between an individual's FA and behaviour is generally unknown: what do more asymmetric individuals do about their own asymmetry? We now show for the first time that individuals respond behaviourally to their own morphological FA in what appears to be an adaptive manner. During courtship, male guppies exhibiting high FA in ornamental colour, bias their displays towards their more colourful body side, thus potentially increasing their attractiveness by exaggerating the quantity of their orange signal. This appears to be a strictly behavioural male response to cues provided by females, as it does not occur when males court a non-reactive model female. Whether inferior males realize any mating advantage remains uncertain, but our study clearly demonstrates a behavioural response to random morphological asymmetries that appears to be adaptive. We propose that the tendency to show or otherwise use a ‘best side’ is common in nature, with implications for sexual signalling and the evolution of more pronounced asymmetries.

Canadian salmon are now eligible for protection under a federal Species at Risk Act proclaimed in June 2003 and fully implemented in June 2004. The act has four major steps dealing with species at risk of extinction: (1) an independent scientific committee assesses biological status and designates those at risk, (2) Federal Cabinet decides, following consideration of socioeconomic implications, which species to add to the legal list of species at risk, (3) legal protection, and (4) recovery planning and implementation. The committee has designated five distinct populations of salmon as endangered—one Atlantic salmon (Salmo salar), one coho salmon (Oncorhynchus kisutch), two sockeye salmon (O. nerka), and one Chinook salmon (O. tshawytscha). Only the Atlantic salmon is currently listed under the act; Cabinet decided not to list the two sockeye after considering socioeconomic implications and decisions on listing coho and Chinook are pending socioeconomic assessment. Both the Species at Risk Act in...

Our understanding of parental care behavior can be significantly advanced through the application of Williams’s Principle, which states that reproduction has not only a benefit but also a cost to lifetime fitness. My laboratory has formalized Williams’s Principle into the relative value theorem and found that its application to fishes, the taxa with the most diverse patterns of parental care, can help to explain which sex provides care and how much. In fishes, it is often the male that provides parental care, not because the male obtains greater benefits from this care, but probably because he pays fewer costs. Fish dynamically adjust their investment into parental care according to the number of offspring in their brood, past investment, genetic relatedness, and alternative mating opportunities, all of which affect the value of current offspring relative to potential future offspring. These results may also help us understand the joy and the challenges of parental care in humans.

Although alternative mating tactics are found in males of many species, little is known about tactic-specific adaptations to sperm competition and the mechanism by which fertilization success is obtained. We now report on the sperm investment patterns of males that use alternative mating tactics in bluegill sunfish (Lepomis macrochirus). Bluegill males are characterized by three alternative mating tactics: parentals, sneakers, and satellites. Parentals delay maturation and adopt a courting and guarding tactic, whereas sneakers and satellites mature precociously and, respectively, use sneaking and female mimicry to steal fertilizations from parentals. We found differences among the tactics in testes weight, sperm longevity, and ejaculate sperm density and competitiveness. Parentals had the largest testes, but the smallest relative to their body weight. Satellites had intermediate-sized testes, and sneakers had the smallest testes, but the largest relative to their body weight. Within each tactic, there was a positive relationship between testes weight and body weight, but the exact relationship differed among the tactics and could not be attributed solely to allometry. Parentals had longer-lived sperm compared with that of both sneakers and satellites. Ejaculate sperm density was greatest in sneakers, satellites were intermediate, and parentals had the lowest. Competition experiments involving equal volumes of ejaculate showed that fertilization success increased linearly with sperm number, consistent with a rafflelike process. However, independent of sperm number, parental sperm were superior at fertilizing eggs. We interpret these sperm investment patterns in relation to differences in sperm competition risk, number of mating opportunities, and alternative investment options. Copyright 2003.

We analyze published data from 592 AC microsatellite loci from 98 species in five vertebrate classes including fish, reptiles, amphibians, birds, and mammals. We use these data to address nine major questions about microsatellite evolution. First, we find that larger genomes do not have more microsatellite loci and therefore reject the hypothesis that microsatellites function primarily to package DNA into chromosomes. Second, we confirm that microsatellite loci are relatively rare in avian genomes, but reject the hypothesis that this is due to physical constraints imposed by flight. Third, we find that microsatellite variation differs among species within classes, possibly relating to population dynamics. Fourth, we reject the hypothesis that microsatellite structure (length, number of alleles, allele dispersion, range in allele sizes) differs between poikilotherms and homeotherms. The difference is found only in fish, which have longer microsatellites and more alleles than the other classes. Fifth, we find that the range in microsatellite allele size at a locus is largely due to the number of alleles and secondarily to allele dispersion. Sixth, length is a major factor influencing mutation rate. Seventh, there is a directional mutation toward an increase in microsatellite length. Eighth, at the species level, microsatellite and allozyme heterozygosity covary and therefore inferences based on large-scale studies of allozyme variation may also reflect microsatellite genetic diversity. Finally, published microsatellite loci (isolated using conventional hybridization methods) provide a biased estimate of the actual mean repeat length of microsatellites in the genome.

We have recently presented models to estimate parentage in breeding systems with multiple mating and incomplete sampling of the candidate parents. Here we provide formulas to calculate the statistical confidence and the optimal trade-off between the number of loci and offspring. These calculations allow an understanding of the statistical significance of the parentage estimates as well as the appropriate sampling regime required to obtain a desired level of confidence. We show that the trade-off generally depends on the parentage of the putative parents. When parentage is low, sampling effort should concentrate on increasing the number of loci. Otherwise, there are similar benefits from increasing the number of loci or offspring. We demonstrate these methods using genetic data from a nest of the bluegill sunfish ( Lepomis macrochirus ).

Many breeding systems include 'multiple mating' in which males or females mate with multiple partners. We identify two forms of multiple mating: 'single-sex', where the next-generation individuals (NGIs) are the product of multiple mating by one sex; and 'two-sex', where the NGIs are the product of multiple mating by both sexes. For both mating systems we develop models that estimate the proportion of NGIs that is fathered (paternity) or mothered (maternity) by the putative parents. The models only require genetic data from the parent or parents in question and the sample of NGIs, as well as an estimate of population allele frequencies. The models provide unbiased estimates, can accommodate loci with many alleles and are robust to violations of their assumptions. They allow researchers to address intractable problems such as the parentage of seeds found on the ground, juvenile fish in a stream, and nestlings in a communal breeding bird. We demonstrate the models using genetic data from a nest of the bluegill sunfish Lepomis macrochirus, where the NGIs may be from multiple females that have spawned with multiple males from different life histories (cuckolder and parental).

Microsatellite multiplexing is a powerful technique that can increase the productivity of genetic studies in fisheries biology. We review multiplexing methods and present an optimized and detailed protocol for microsatellite multiplexing that is specifically tailored for use with radioisotopes. The protocol can significantly reduce the cost associated with microsatellites and provides high polymerase chain reaction (PCR) fidelity and band resolution. Comparing three radioisotopes, we find that end labeling with 33P provides the highest resolution. We also present a quick and inexpensive DNA isolation protocol that is successful with fish larvae. Finally, we find that PCR fidelity depends on the quality of the DNA template, and we therefore review preservation and isolation methods specific to various fish tissue types. Together, these microsatellite multiplexing and DNA isolation protocols can significantly reduce the time and expense associated with genetic analyses in fish.

We describe 10 microsatellite loci from bluegill (Lepomis macrochirus) and discuss their evolution within the Centrarchidae. All of the loci exhibit Mendelian inheritance and are unlinked. While six loci are conserved within the Centrarchidae (found also in pumpkinseed (Lepomis gibbosus) and largemouth bass (Micropterus salmoides)), four have origins outside the family and two predate it by 65-150 million years. The persistence of these loci in fish may be due to a slow rate of sequence divergence within their flanking sequences, estimated at 0.14-0.83% per million years. We examine the number of alleles, heterozygosity, range, modes, and the frequency of the most common allele and find that a two-phased model (TPM) or an infinite alleles-model (IAM) best describes the results, while a stepwise mutation model (SMM) is rejected. Therefore, population differentiation analyses utilizing these microsatellite loci should consider parameters based on the IAM (e.g., FST) and not the SMM.

The conditional strategy is a theoretical framework that explains the existence within populations of individuals that express alternative behavioral, physical or life history tactics (phenotypes). An example is fighters and sneakers in many animal mating systems. In the conditional strategy the alternative tactics are chosen by individuals based on their state, for example large or small bodied. Since state is often heritable, due for example to additive genetic variance, the alternative tactics may also have inheritance. As the tactics do not have equal fitnesses, it is generally believed that any such inheritance would prevent the evolutionary stability of the conditional strategy. However, in previous work we introduced an Inheritance Theorem and were able to prove that a conditional strategy with tactic inheritances can have a unique equilibrium proportion of the tactics. We now prove a second property of our Inheritance Theorem, namely the stability of the equilibrium. This means that if the tactics are perturbed from their equilibrium proportions, they will return across generations to their equilibrium proportions. An example is provided in mites. We have therefore established an Inheritance Theorem which includes both the existence of an equilibrium and its stability for alternative tactics in a conditional strategy.Copyright 1998 Academic Press Limited

This paper examines two areas to be considered in developing conservation plans for Atlantic salmon (Salmo salar): goal statements and the general framework for the implementation of a conservation plan. From a biological perspective, the appropriate conservation unit for Atlantic salmon is the Evolutionary Significant Unit (ESU). As conservation decisions will rarely be based solely on biological information, the Operational Conservation Unit (OCU) is defined as resulting from the interplay between biological requirements and socio-economic issues. A multi-scale habitat inventory of Atlantic salmon rivers to know what their status is relative to historical conditions is the first step in a functional conservation plan. The viability of salmon populations may be assessed according to 6 variables: abundance, resilience, age and size structure, sex ratio, spatial and geographical distribution. A genetically viable population possesses the species' evolutionary legacy and the genetic variation on which future evolutionary potential depends. Four factors important to monitoring changes in a population's genetic health are genetic diversity, effective population size, genetic bottlenecks and founder effects and gene flow. Implementation of a conservation plan must be proactive to maintain the quality of the OCUs. Commercial and recreational fisheries need to be limited and several case studies are reviewed. The importance of avoiding the introduction of exotics and minimizing the impact of sampling methodology, as well as the pitfalls of planting eggs, fry, or parr, are addressed. Finally, the importance of fostering public awareness of the value of conservation is essential to apply the political pressure necessary to preserve natural resources.

We characterized the morphology of mature cuckolder and mature parental male bluegills Lepomis macrochirus from Lake Opinicon, Ontario. By rearing bluegill larvae to maturity in experimental ponds in Illinois we also examined whether morphological differences between males of the two reproductive life histories were conserved across widely varying environmental conditions. Cuckolder and parental males collected in Lake Opinicon differed in their size-adjusted body shape. They also differed in their pattern of mass allocation to testis versus somatic tissue. Cuckolder males allocated significantly more of their total body mass to testes compared to parental males. Body shape and testis:somatic ratio differences between male types reared in experimental ponds in Illinois were nearly identical to those observed in bluegills from Lake Opinicon. This divergence between male types remained consistent even when bluegills were reared over a 10-fold variation in growth rate. Average growth rate within pon...

We tested the hypothesis that larger individuals in a temperate fish population emerge from winter in better energetic condition than do smaller individuals. We sampled adult male bluegills Lepomis macrochirus in Lake Opinicon, Ontario, after spring ice break and just before active feeding began. By extracting neutral and membrane-bound polar lipids. we estimated the energetic condition of each individual. We found that both the mass of lipids and the lipids per gram of body weight were significantly and positively correlated with body size. These results are attributed to the allometric relationships between body size and energy reserves and between body size and metabolic rate. Body size, therefore, profoundly affects energetic state, which may explain why individuals of different size vary in their reproductive behavior and survivorship.

Variable microsatellite DNA markers are powerful tools to study parentage and gene flow in fish populations. In this work, we cloned and characterized 60 (GT) repeat microsatellite sequences from the bluegill sunfish (Lepomis macrochirus) genome. We report the frequency distribution, the lengths, and the proportions of the repeat classes for comparison with microsatellites isolated from other teleost, mammal, and invertebrate genomes. Bluegill microsatellites are similar to those of other fish, strengthening previous reports of significant differences in the organization of microsatellites between teleosts and mammals. Primers for polymerase chain reaction amplification were designed for 17 bluegill microsatellite loci. The allele frequencies, the degree of polymorphism, and heterozygosities were estimated using bluegill from Lake Opinicon, Ontario. Seven loci are potentially highly informative for fingerprinting studies of parentage. A preliminary paternity analysis using two of these loci on brood from a natural nest revealed their potential utility at estimating relative success of the two reproductive life histories, parental and cuckolder, characteristic of male bluegill. Cross-amplification using these microsatellite markers on related fish species showed some degree of locus conservation among taxa, potentially allowing DNA fingerprinting of a variety of centrarchids.

We quantified divergence in phenotype of sea-ranched, farmed, and wild Atlantic salmon (Salmo salar) of a common genetic stock (River Imsa, Norway). These first-generation fish were also contrasted with a fifth-generation farmed population (Norwegian commercial strain) and with wild and multigeneration sea-ranched populations of coho salmon (Oncorhynchus kisutch). In comparisons using mature Atlantic salmon male parr, cultured juveniles had smaller heads and fins and narrower caudal peduncles and could be distinguished from wild juveniles with 100% accuracy. When juveniles were reared to adulthood in the natural marine environment, some environmentally induced differences due to juvenile hatchery rearing persisted but many disappeared. This was particularly true for head and trunk morphology. Greater adult divergence from the wild state was observed in multigeneration sea-ranched coho salmon, suggesting that evolutionary changes may accumulate with time. Continued farming of salmon juveniles through adulthood increased environmentally induced phenotypic divergence considerably. Both rayed-fin sizes and body streamlining decreased. Fifth-generation Norwegian farmed salmon showed the greatest morphological differences. Both the proportion of a fish's life history and number of generations spent in culture are thus probably important determinants of phenotypic divergence of cultured fish from their wild state.

In colonies of bluegill Lepomis macrochirus, some males provide parental care for broods in nests, whereas other males steal fertilizations and do not provide parental care. Using experimental pond populations of bluegill of known genotype (determined through protein electrophoresis), we demonstrate that cuckolder males successfully fertilize eggs in parental male nests. Using electrophoretic techniques to assess the fertilization success of nesting parental male bluegill in Lake Opinicon, Ontario, we demonstrate that paternity of these males ranges from 41% to 100% among four colonies studied. This difference among colonies is related to the density of cuckolder males.

In the breeding system of Pacific salmon, females compete for oviposition territories, and males compete to fertilize eggs. The natural selection in females and sexual selection in males likely has been responsible for their elaborate breeding morphologies and the dimorphism between the sexes. We quantified direct-selection intensities during breeding on mature coho salmon (Oncorhynchus kisutch), measured for seven phenotypic characters, including three secondary sexual characters. Wild and sea-ranched hatchery coho were used to enhance the range of phenotypes over which selection could be examined. The fish were allowed to breed in experimental arenas where we could quantify components of breeding success as well as estimate overall breeding success. We found that without competition, natural selection acts only on female body size for increased egg production; there is no detectable selection on males for the phenotypic distribution we used. Under competition, the opportunity for selection increased sixfold among females. Natural selection favored female body size and caudal-peduncle (tail) depth. Increased body size meant increased egg production and access to nesting territories. The caudal peduncle, used in burst swimming and nest digging, influenced both successful egg deposition and nest survival. Increasing density increased competition among females, though it did not significantly intensify natural selection on their characters. In males, competition increased the opportunity for selection 52-fold, which was nine times greater than for females. Sexual selection favored male body size and hooked snout length, both characters directly influencing male access to spawning opportunities. Selection on male body size was also affected significantly by breeding density. The ability of large males to control access to spawning females decreased at higher densities reflecting an increase in the operational sex ratio. Further, the relative success of small males, which could sneak access to spawning females, appeared to increase as that of intermediate-sized males decreased. Such disruptive selection may be responsible for the evolution of alternative reproductive tactics in salmon.

The role of past investment in parental-care behaviour has often been controversial. Some researchers have argued that organisms basing present investment on past investment are committing the 'Concorde fallacy'. Others have incorporated life history theory to suggest that investing according to past investment is one component of investing according to expected future reproductive success: a parent can use past investment as well as other information, such as brood size, to make its optimal parental-investment decisions. Although parental-investment research is still in its infancy, the incorporation of life history theory suggests that the Concorde fallacy is a misleading concept.

Increased disease and parasitism are a well-documented cost of group living for colonial birds and mammals, but we now show that disease in offspring of fish may be reduced by nesting in colonies. The aquatic fungusSaprolegnia sp., which is a common cause of egg mortality among freshwater fishes, is more prevalent in the nests of solitary than colonial male bluegill sunfish (Lepomis macrochirus). Moreover, fungal infection decreases with nest density in colonies. This may be due in part to a behavioural advantage since colonial males can devote less time to defending eggs and more time to fanning them, which reduces fungal infection. In addition, we demonstrate experimentally that solitary nests become infected at higher rates than colonial nests, even in the absence of parental males. This suggests that colonies are encountered by spores at a lower rate and/or that the large number of nests in colonies dilutes the number of fungal spores per nest. Through one or all of these mechanisms, egg mortality in colonial nests is lowered significantly. Therefore, in some cases, disease may select for group living.

Recent models of sexual selection suggest that females may prefer males that provide heritable benefits (`good genes9) for offspring development or survival. We tested this possibility with a three-generation experiment using Trinidadian guppies, Poecilia reticulata, a species of livebearing freshwater fish. First, we show that female guppies were attracted to larger-bodied males. Areas of various colour pigments had no effect on female preference in this population. Second, male size had significant father-son heritability. Third, large fathers sired both sons and daughters with higher growth rates. Finally, the higher growth rates of daughters resulted in large reproductive output, attributable to their larger body size. Female mate preferences may therefore have important effects on the inheritance of life history traits by offspring. The results are consistent with the `good genes9 theory of sexual selection but they also illustrate some of the pitfalls inherent in distinguishing among alternative theories.

We report an experimental study that contrasts the reproductive behavior of wild to hatchery coho salmon (Oncorhynchus kisutch). The hatchery fish had completed four generations of sea-ranching, which involves artificial breeding and juvenile rearing but natural growth to adulthood in the sea. Mature males and females were individually tagged, measured and placed into three experimental arenas in a stream channel. One arena contained isolated pairs of fish, thus providing data on reproductive behavior in the absence of competition. A second arena contained male and female hatchery fish and a third arena contained male and female wild fish. In the latter two arenas the fish were free to compete among themselves for breeding opportunities. Three variables significantly influenced reproductive behavior and breeding sucess: (1) competition; (2) body weight; and (3) hatchery versus wild origin. In the absence of competition, both hatchcry and wild fish bred readily. However, competition delayed spawning, reduced nest numbers, increased body wounding, increased egg loss through retention and nest superimposition, and increased variance in breeding success. Body weight was an important determinant of success in the competitive environment. Small females were delayed in spawning and experienced greater egg losses, and small males had reduced access to spawning females. As a group, the hatchery fish differed from the wild fish in breeding behavior and potential. Hatchery females had larger egg masses but smaller fecundities than wild females due to their larger egg size. Hatchery males had larger testes than wild males, but were less aggressive, exhibited less spawning behavior and were generally less active than wild males. These results imply significant differences in the reproductive potential of hatchery relative to wild fish during competition.

The Society for Conservation Biology (SCB) can enhance conservation of biodiversity in North America by increasing its engagement in public policy. Toward this end, the North America Section of SCB is establishing partnerships with other professional organizations in order to speak more powerfully to decision makers and taking other actions--such as increasing interaction with chapters--geared to engage members more substantively in science-policy issues. Additionally, the section is developing a North American Biodiversity Blueprint, which spans the continental United States and Canada and is informed by natural and social science. This blueprint is intended to clarify the policy challenges for protecting continental biodiversity, to foster bilateral collaboration to resolve common problems, and to suggest rational alternative policies and practices that are more likely than current practices to sustain North America's natural heritage. Conservation scientists and practitioners can play a key role by drawing policy makers' attention to ultimate, as well as proximate, causes of biodiversity decline and to the ecological and economic consequences of not addressing these threats.

Ecologists are increasingly interested in how organisms respond to altered environments. This interest is stimulated in part by the rapid change that human activities are bringing upon the planet. One mechanism for relatively rapid responses may be "conditional strategies" recently documented by behavioral ecologists (Maynard Smith 1982, Parker 1984, Gross 1991). These strategies allow individuals to decide between alternative phenotypic "tactics," depending on the situation. For example, in mate competition a small male may employ a behavioral tactic that involves sneaking, while a larger male employs a behavioral tactic that involves fighting. The decision is based on relative body size, which in turn determines the success likely from either tactic. If the decision is reversible, such as employing sneaking or fighting behavior, the same individual may switch tactics under different circumstances. If the decision is irreversible, as is the case with precocious vs. delayed maturity, the alternatives represent differences in individual life history. In both cases the conditional strategy allows an individual to facultatively adjust its phenotype to maximize its lifetime reproductive success. This paper will illustrate how alternative life-history and behavioral tactics in a conditional strategy may respond to environmental changes caused by humans. Our example will be the conditional strategy of male salmon. Male salmon have two life-history tactics: maturing precociously at a small body size, or delaying maturity until a larger body size is reached. These small and large males in salmon are known by various names, respectively: as precocious parr and adult in Atlantic salmon (Mills 1989), and jack and hooknose in Pacific salmon (Gross 1984). Males also employ two behavioral tactics for gaining access to females on the breeding grounds: small males usually sneak while larger males fight. Before considering how human perturbations to the environment may affect the conditional strategy of male salmon, we first need to review the

This study provides empirical evidence in a wild population for frequency-dependent sexual selection between alternative male reproductive strategies. The bluegill sunfish ( Lepomis macrochirus ) has two male reproductive strategies, cuckolder or parental, used by different males to compete in fertilizing the same eggs. As the density of cuckolders in colonies of parental males increases, the average mating success of cuckolders initially peaks but then declines. The cuckolder density at which their success peaks is determined by ecological characteristics of each colony. A theoretical analysis assuming random and omniscient cuckolder distributions among ecologically different colonies shows that cuckolders will fertilize decreasing proportions of eggs, relative to parental males, as cuckolders increase in frequency in the population. This supports evolutionary models that assume negative frequency-dependent selection between the competing strategies. Cuckolder and parental strategies may therefore have evolved as an Evolutionarily Stable State (ESST).

The hormonal mechanisms underlying parental care behavior in fish are poorly understood. This study investigates the effects of bromocriptine, a specific dopamine receptor agonist that inhibits secretion of prolactin from the pituitary, on parental care behaviors of nesting male bluegills. Parental male bluegills (Lepomis macrochirus) exhibit a complex set of reproductive behaviors including the construction of nests in colonies and courtship of females. After spawning, these males then alone remain to fan and guard the eggs and larvae from predators. Compared with control males, males implanted with bromocriptine showed significantly less defense of their broods and spent significantly more time rim circling their nests, a behavior typical of prespawning males. Because there were no significant differences among male groups in the levels of 11-ketotestosterone (11KT) or testosterone (T), the observed behavioral alterations cannot be ascribed to androgenic effects of bromocriptine. Instead, we suggest tha...

Mate choice in noneconomic mating systems has been considered paradoxical because, relative to economic systems, females were thought to have "highly developed" preferences, despite males' having little to offer. Efforts to resolve this paradox have generally searched for genetic benefits of choice through either "good genes" or "runaway" coevolution. In this paper, we emphasize natural selection acting directly on females and their offspring. We argue that, although females are expected to pay lower costs in noneconomic mating systems, this need not translate into examining fewer males or spending less time in this activity. Furthermore, various direct (nongenetic) benefits may accrue. In species in which males offer benefits that are more variable, such as territories or parental care, females should evolve toward greater investment in mate choice, especially when these resources cannot be shared among females. Any tendency for females to be more selective in noneconomic mating systems, despite lower be...

The latitudinal variation in clutch size found in many animal species, including Pacific salmon, has been an enigmatic problem in ecology. We analyze egg number and egg size of 17 populations of coho salmon (Oncorhynchus kisutch) distributed over a latitudinal gradient in North America. These populations have a significant latitudinal increase in their egg number. But this increase is accompanied by a significant latitudinal decrease in their egg size. The total biomass of eggs produced also declines with latitude. Thus, the positive latitudinal trend in egg number cannot be explained by latitudinal variation in the total investment in eggs. This suggests that local optima in egg size may result in latitudinal clines in egg number. This reasoning, that egg number evolves around selection for egg size, is in fact predicted by life history theory and may explain the clutch size patterns observed in many organisms. See full-text article at JSTOR

We review the evidence for fisheries-induced evolution in anadromous salmonids. Salmon are exposed to a variety of fishing gears and intensities as immature or maturing individuals. We evaluate the evidence that fishing is causing evolutionary changes to traits including body size, migration timing and age of maturation, and we discuss the implications for fisheries and conservation. Few studies have fully evaluated the ingredients of fisheries-induced evolution: selection intensity, genetic variability, correlation among traits under selection, and response to selection. Most studies are limited in their ability to separate genetic responses from phenotypic plasticity, and environmental change complicates interpretation. However, strong evidence for selection intensity and for genetic variability in salmon fitness traits indicates that fishing can cause detectable evolution within ten or fewer generations. Evolutionary issues are therefore meaningful considerations in salmon fishery management. Evolutionary biologists have rarely been involved in the development of salmon fishing policy, yet evolutionary biology is relevant to the long-term success of fisheries. Future management might consider fishing policy to (i) allow experimental testing of evolutionary responses to exploitation and (ii) improve the long-term sustainability of the fishery by mitigating unfavorable evolutionary responses to fishing. We provide suggestions for how this might be done.

About 20,000 Chinook salmon ( Oncorhynchus tshawytscha) from Lake Ontario enter the Credit River, Ontario, Canada every fall to spawn and die. In this study, samples of muscle and eggs collected from female Chinook salmon entering the Credit River contained total PCBs, DDT compounds and other organochlorine (OC) compounds at μg/kg concentrations. Semi-permeable membrane devices (SPMDs) were deployed at a reference site above the spawning grounds and at two downstream sites at intervals over a 14-month period that spanned two spawning runs. There was an increase in the concentrations of total PCBs, total DDT and other classes of OCs in the SPMDs deployed at the two downstream sites during and after both spawning runs; indicating that the decay of salmon releases contaminants into the river. Based upon the concentrations of contaminants in the salmon tissues, approximately 75 g of total PCBs and 35 g of total DDT compounds would be transported annually into the Credit River from this source.

We develop fractional allocation models and confidence statistics for parentage analysis in mating systems. The models can be used, for example, to estimate the paternities of candidate males when the genetic mother is known or to calculate the parentage of candidate parent pairs when neither is known. The models do not require two implicit assumptions made by previous models, assumptions that are potentially erroneous. First, we provide formulas to calculate the expected parentage, as opposed to using a maximum likelihood algorithm to calculate the most likely parentage. The expected parentage is superior as it does not assume a symmetrical probability distribution of parentage and therefore, unlike the most likely parentage, will be unbiased. Second, we provide a mathematical framework for incorporating additional biological data to estimate the prior probability distribution of parentage. This additional biological data might include behavioral observations during mating or morphological measurements known to correlate with parentage. The value of multiple sources of information is increased accuracy of the estimates. We show that when the prior probability of parentage is known, and the expected parentage is calculated, fractional allocation provides unbiased estimates of the variance in reproductive success, thereby correcting a problem that has previously plagued parentage analyses. We also develop formulas to calculate the confidence interval in the parentage estimates, thus enabling the assessment of precision. These confidence statistics have not previously been available for fractional models. We demonstrate our models with several biological examples based on data from two fish species that we study, coho salmon (Oncorhychus kisutch) and bluegill sunfish (Lepomis macrochirus). In coho, multiple males compete to fertilize a single female's eggs. We show how behavioral observations taken during spawning can be combined with genetic data to provide an accurate calculation of each male's paternity. In bluegill, multiple males and multiple females may mate in a single nest. For a nest, we calculate the fertilization success and the 95% confidence interval of each candidate parent pair.

Theories of parental care evolution predict that genetic relatedness will be an important variable in the amount of care a parent provides. However, current inferences of relatedness–based parental investment from studies in humans and birds remain challenged. No study has yet demonstrated parental care adjustment in a manner uncomplicated by life–history correlates or experimental design. We now present a unique test that controls for individual life histories and demonstrates paternity–related dynamic adjustments in parental care. Brood–rearing male bluegill sunfish ( Lepomis macrochirus ) that are cuckolded to a varying degree will either increase or decrease their parental investment in response to changing information on paternity during brood development. Specifically, as parental males detect paternity lost to cuckolders and, hence, a reduction in the value of their brood, they adaptively lower their level of parental care. Conversely, if they detect that their paternity is higher than previously assessed, they adaptively raise their level of parental care. This dynamic adjustment during brood rearing indicates the importance of genetic relatedness in parental investment decisions and provides needed empirical support for theoretical predictions.

Sperm competition is a major force in sexual selection, but its implications for mating-system and life-history evolution are only beginning to be understood. The well-known sneak-guard model predicts that sneaks will win in sperm competition. We now provide empirical confirmation of this prediction. Bluegill sunfish (Lepomis macrochirus) have both sneak (cuckolder) and guard (parental) males. Guards make nests, court females and provide solitary parental care for the embryos. Sneaks include small cuckolders, which are termed 'sneakers', that dart in and out of nests in order to ejaculate between the spawning pair and larger cuckolders, which are termed 'satellites', that mimic females in order to ejaculate between the spawning pair. Using field behavioural data, genetic data and new mathematical models for paternity analyses, we show, for the first time to the authors' knowledge, that sneaks fertilize more eggs than guards during sperm competition. In addition, we show that sneakers are superior to satellites in sperm competition and, thus, that even among sneaks there are tactic-specific differences in competitive success.

A proof is presented to show that, when fitnesses from alternative tactics within a population depend on both their frequency and the phenotypic condition of individuals, there will be a unique ESS switchpoint s* that determines both the condition at which an individual will switch between tactics and the resulting frequency of the tactics in the population. For an individual at the ESS s*, the fitnesses of the alternative tactics will be equal. When fitness is averaged over the population, however, the average fitnesses of the alternative tactics will not be equal.

The divergence of hatchery fish in traits important for reproductive success has raised concerns about their ability to rehabilitate wild populations, and the threat that their inevitable straying poses to biological diversity through introgression. We therefore undertook a study of the breeding competition and success of sea-ranched hatchery fish placed in direct competition with wild fish. Experiments using wild and hatchery coho salmo (Oncorhynchus kisutch) were conducted within a controlled stream channel, allowing selective manipulation of breeding competition and density. Hatchery fish, particularly males, were competitively inferior to wild fish, being less aggressive and more submissive. As a consequence, hatchery males were denied access to ovipositing females; they partook in fewer spawnings, held more distal positions in spawning hierarchies, and attained only an estimated 62% of the breeding success of wild males. By contrast, competition did not appear to inhibit hatchery females as overtly as males. Hatchery and wild females exhibited similar levels of aggressive behavior, however hatchery females did suffer greater delays in the onset of breeding, failed to spawn larger proportions of their eggs, and lost more eggs to nest destruction by other females. They averaged an estimated 82% of the breeding success of wild females. There was thus a sex bias in the breeding disadvantage of hatchery fish, with males suffering more than females. Furthermore, the breeding disadvantage was density dependent with the relative success of hatchery to wild fish declining with increasing density. These results imply that hatchery fish have restricted abilities to rehabilitate wild populations, and may pose ecological and genetic threats to the conservation of wild populations.

1. Escape of cultured organisms into natural ecosystems may threaten wild populations both ecologically and genetically. In the aquaculture industry, farmed Atlantic salmon (Salmo salar L.) often escape and enter the spawning grounds of wild salmon. We report experiments to assess the competitive and reproductive abilities of fifth-generation farmed salmon and their potential impacts upon wild salmon. 2. The farmed and wild females had similar levels of competitive behaviour; however, they differed in reproductive behaviour and success. Farmed females displayed less breeding behaviour, constructed fewer nests, retained a greater weight of eggs unspawned, were less efficient at nest covering, incurred more nest destruction, and suffered greater egg mortality than wild females. As a result, farmed females had less than one-third of the reproductive success of wild females. 3. The farmed males were even less successful than the farmed females in competition with the wild fish. They were less aggressive, courted less, partook in fewer spawnings, and achieved only an estimated one to three percentage of the reproductive success of the wild males. 4. The farmed males exhibited inappropriate mating behaviour, that led to poor fertilization success, even in the absence of competition with wild males. 5. Adult farmed fish are thus likely to be relatively unsuccessful in natural environments due to a competitive and reproductive inferiority apparently resulting from domestication.

In North American sunfishes (Lepomis: Centrarchidae) ♂♂ build nests and provide solitary parental care for the young. In this paper I provide for bluegill (L. macrocbirus) a detailed account of ♂♂ which do not build nests, but steal fertilizations from the nests of other ♂♂. I begin by giving data on the behavior, morphology, and population demography of ♂♂. Next, through an analysis of individual male life-histories, I show that cuckoldry and parenting are discrete alternative reproductive strategies. This is followed by a theoretical analysis and an empirical test of cuckoldry and parental care as evolutionarily stable strategies (a mixed ESS). Several predictions are made concerning how natural selection will influence the life-history dynamics of these strategies. A general theory is then developed for sunfishes, and a first test made on the pumpkinseed (L. gibbosus). Finally, I note the parallels between male cuckoldry in sunfishes and precocial male life-histories in salmon and cichlids.

Since Pacific salmon (Oncorhynchus spp.) die on the breeding grounds after spawning, duration of individual life may affect survival of deposited eggs. In addition, breeding life of both sexes has implications for estimates of size of spawning populations. We therefore examined the contributions of body size, population density, water level, season, and year to length of breeding life in individual coho salmon (O. kisutch). Age 3 breeding males and females lived an average of 9 days (range, 2–30 days), and 2-year-old "jack" males averaged 8 days (range, 2–21 days). Sixteen percent of the variance among age 3 males and 44% of the variance among females could be explained by the variables examined. Density of adults made a significant negative contribution to life-span, while water level, season, and year were insignificant. Body size was the most important variable in explaining breeding life-span, being positively related and accounting for 10% and 36% of the variance in 3-year-old males and females, respectively. In contrast, none of these variables explained the observed variation in jack male breeding life. The differences between the sexes and between 2- and 3-year-old males are consistent with levels of competition on the breeding grounds. We show that the results on individual body size and breeding life span can be used to offset biases in population estimates.

The quality of parental care appears to correlate positively with egg size, both among and within species of fishes. Past models of the trade-off between quantity and quality of offspring have been inadequate in explaining this correlation. Using features of models by Smith and Fretwell (1974), Shine (1978), and Taylor and Williams (1984), we constructed a model to explain continuous covariation between the quality of parental care and egg size. Our model contains three major assumptions about the dependence of offspring survival on egg size: offspring from larger eggs develop more slowly and take longer to resorb their yolk sacs and become juveniles; egg size determines initial juvenile size; and larger juveniles, which hatch from larger eggs, have lower mortalities, experience faster growth, and take less time to become adults. Under these assumptions, as parental care reduces instantaneous egg mortality, the optimal egg size increases. This increase is expected both among and within populations. Thus, ...