The macroscopic and microscopic diversity of potential food items available in the nests of plainfin midshipman Porichthys notatus were quantified and compared with items that were found in the stomach and intestine (digestive tract) of the guarding males. In this species, males occur as one of two possible reproductive morphs: guarder males that care for young and sneaker males that parasitize the courtship and care of guarde...

Juvenile Atlantic salmon Salmo salar from three allopatric populations ( LaHave , Sebago and Saint‐Jean) were placed into artificial streams with combinations of four non‐native salmonids: brown trout Salmo trutta , rainbow trout Oncorhynchus mykiss , Chinook salmon Oncorhynchus tshawytscha and coho salmon Oncorhynchus kisutch . Non‐additive effects, as evidenced by lower performance than predicted from weighted summed two‐spe...

This study examined the effect of dietary carotenoid availability on carotenoid and retinoid concentrations in the flesh, plasma, skin and eggs of female Chinook salmon Oncorhynchus tshawytscha . Carotenoid concentrations in all tissues were closely related to dietary availability. Early in the breeding season, carotenoids were stored primarily in the muscle, with a flesh carotenoid concentration of 9·9 µg g −1 in fish fed a h...

The genetic architecture of fitness at the class IIB gene of the major histocompatibility complex (MHC) in the guppy Poecilia reticulata was analysed. Diversity at the MHC is thought to be maintained by some form of balancing selection; heterozygote advantage, frequency‐dependent selection or spatially and temporally fluctuating selection. Here these hypotheses are evaluated by using an algorithm that partitions the effect of...

Multilocus heterozygosity, aggressive and feeding behaviour, plasma cortisol levels and growth rate were evaluated among three groups of juvenile Chinook salmon Oncorhynchus tshawytscha : diploid, triploid and mixed groups of diploid and triploid fish. There was no difference between diploid and triploid fish in measurements of heterozygosity calculated using seven microsatellite loci, and these measurements did not correlate...

African Great Lake cichlid populations are divided into thousands of genetic subpopulations. The low gene flow between these subpopulations is thought to result from high degrees of natal philopatry, heavy predation pressure, and a patchy distribution of preferred habitats. While predation pressure and habitat distribution are fairly straightforward to assess, data on dispersal distances and rates are scarce. In fishes, direct...

The allometric relationship between body mass and gonad mass in males of 23 fish species from 11 families was examined. There was no evidence of a single allometry for all fishes. A cross species analysis suggested a scaling coefficient of 1·04, which was significantly different from a previous study that reported a scaling coefficient of 0·904. A within species analysis generated scaling coefficients from 0·68 to 3·90. Furthe...

A single‐sex model is presented that calculates the probability of detecting multiple mating ( PrDM ) given genetic data from the single genetic parent and a sample of its offspring. The model incorporates the effects of numbers of loci, alleles, offspring and genetic parents contributing to the multiple mating, all of which effect PrDM . The model is used to determine the actual number of loci and offspring that are required...

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 requir...

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 (pa...