Sexual dimorphism of vertical bar patterning along the ontogenetic gradient was investigated in the South European toothcarp Aphanius fasciatus through the analysis of field samples collected from four different Venice Lagoon sites. Results suggested that, after controlling for site effect, vertical bar number and density were more correlated with size in females than in males, yielding a higher number of less spaced bars in females than in males. Results are discussed with regard to the interplay between natural and sexual selection acting on vertical bar dimorphism, suggesting a role of disruptive colouration in females and a more pronounced role of sexual selection in males.

This study reports the first bicephalic embryo of smalltail shark Carcharhinus porosus, which was removed from a pregnant female in coastal waters of the tropical eastern Pacific Ocean. The observation suggested that although the individual's body was well formed, the malformation of the head would have affected it survival.

The otolith was used to investigate the variability between Aphanopus carbo and Aphanopus intermedius inhabiting the north-eastern Atlantic Ocean. The results indicate a high degree of morphological affinity between species and areas; a noticeable metabolic change in the otolith shape was noted in the specimens of A. carbo, which may be related to migrations of individuals from shallow water (closer to the continental coast) to deeper water (archipelagos of Madeira and the Canary Islands). The results suggest a single population for both species in the north-eastern Atlantic Ocean, although not conclusively.

Approximately 6% of the freshwater living northern straight-mouth nase Pseudochondrostoma duriense in two Spanish rivers had attached post-metamorphic sea lamprey Petromyzon marinus. Minimum prey size was 16·1 cm fork length and 56·3 g mass. The condition factor of attacked P. duriense was 16% lower than that of unattacked conspecifics.

This study demonstrates inducible transgenic expression in the exceptionally short-lived turquoise killifish Nothobranchius furzeri, which is a useful vertebrate model for ageing research. Transgenic N. furzeri bearing a green fluorescent protein (Gfp) containing construct under the control of a heat shock protein 70 promoter were generated, heat shock-induced and reversible Gfp expression was demonstrated and germline transmission of the transgene to the F1 and F2 generations was achieved. The availability of this inducible transgenic expression system will make the study of ageing-related antagonistically pleiotropic genes possible using this unique vertebrate model organism.

To assess the correlation between four visual morphological types based on body colour and shape (fario trout, FT; shiny fario, SFT; presmolt trout, PST; typical smolt ST) of juvenile brown trout Salmo trutta during downstream spring migration and the biological form at the adult stage (river or sea), mark-recapture experiments were carried out over a period of 23 years. Evidence is provided that the visual SFT type is not a relevant one, while objective colorimetric measurements using a black basin are the best way to determine the morphological type in migrating juveniles.

The effects of nuptial colour, parasites and body size on reproductive success were examined in a natural population of three-spined stickleback Gasterosteus aculeatus. Reproductive males were collected, with the contents of their nests, during the embryo-guarding stage from Lynne Lake (Cook Inlet, Alaska, U.S.A.), and nuptial colour, infection status and body size were recorded. Regression analysis revealed that male body size was the only predictor, of those measured, of reproductive success in nature.

The last of 12 brown trout Salmo trutta stocked in a small pond in south-east Norway in 1979 were caught in July 2011. These fish represent a curiosity regarding longevity and growth pattern, and ageing from otoliths was consistent with the known life history of this specimen. Despite almost total stagnation in growth since the age of 16 years, the testes were fully developed.

Lamprey-induced scarring of the nationally rare Coregonus lavaretus, a known host of a freshwater-resident population of European river lamprey Lampetra fluviatilis, was found to have declined precipitously since the establishment of several non-native fishes in Loch Lomond. Evidence presented in this study points to the possibility that L. fluviatilis in this lake may have altered its trophic ecology in response to the negative impact that non-native species, in particular ruffe Gymnocephalus cernuus, have had on their favoured host.

The diel activity patterns of fishes in a temperate New Brunswick stream were studied during the summer over 5 years. Young-of-the year Atlantic salmon Salmo salar and blacknose dace Rhinichthys atratulus were more active during the day than at night, whereas lake chub Couesius plumbeus, brook trout Salvelinus fontinalis and adult white suckers Catostomus commersonii were more active at night than during the day. Because fishes were as likely to be nocturnal as diurnal, the data suggest that more night-time sampling is needed to provide an unbiased view of fish community structure in temperate streams.