Perceptual models of animal vision have greatly contributed to our understanding of animal-animal and plant-animal communication. The receptor-noise model of color contrasts has been central to this research as it quantifies the difference between two colors for any visual system of interest. However, if the properties of the visual system are unknown, assumptions regarding parameter values must be made, generally with unknown consequences. In this study, we conduct a sensitivity analysis of the receptor-noise model using avian visual system parameters to systematically investigate the influence of variation in light environment, photoreceptor sensitivities, photoreceptor densities, and light transmission properties of the ocular media and the oil droplets. We calculated the chromatic contrast of 15 plumage patches to quantify a dichromatism score for 70 species of Galliformes, a group of birds that display a wide range of sexual dimorphism. We found that the photoreceptor densities and the wavelength of maximum sensitivity of the short-wavelength-sensitive photoreceptor 1 (SWS1) can change dichromatism scores by 50% to 100%. In contrast, the light environment, transmission properties of the oil droplets, transmission properties of the ocular media, and the peak sensitivities of the cone photoreceptors had a smaller impact on the scores. By investigating the effect of varying two or more parameters simultaneously, we further demonstrate that improper parameterization could lead to differences between calculated and actual contrasts of more than 650%. Our findings demonstrate that improper parameterization of tetrachromatic visual models can have very large effects on measures of dichromatism scores, potentially leading to erroneous inferences. We urge more complete characterization of avian retinal properties and recommend that researchers either determine whether their species of interest possess an ultraviolet or near-ultraviolet sensitive SWS1 photoreceptor, or present models for both.

No abstract

Aquaculture practices continuously seek to improve efficiency to produce larger fish at lower cost. Selective breeding within brood stocks can result in undesirable effects, promoting hatcheries to use outbreeding to increase or maintain genetic diversity. This practice however, could result in the introduction of wild behavioural phenotypes unable to adapt to captive-living conditions. Using four hatchery first-generation hybrid crosses and two fully domesticated stocks of Chinook salmon (Oncorhynchus tshawytscha) in British Columbia, we examined behavioural responses to common aquaculture practices such as abrupt environmental change and novel feed types in juvenile fish. Controlling for mass, we found crosses varied in their behaviours to a novel setting and preferences for natural versus commercial diets. These differences were furthermore associated with rearing environment and stock-level growth rate and body size. Our results suggest selecting for phenotypes that behaviourally exhibit better coping mechanisms and greater flexibility in response to change is possible, and when in combination with growth metrics, should be an integral part of producing the desired farmed fish. Behaviours that allow commercial anadromous fish to easily transition to captive environmental conditions can benefit production and also animal welfare.

Alternative reproductive tactics are widespread in fishes. In Pacific salmon, males either become a competitive hooknose, or a sneaker jack, which is undesirable in aquaculture when overabundant. Juveniles often experience accelerated growth prior to becoming jacks, potentially caused by increased competitiveness. We tested the behaviour of hatchery-reared Chinook salmon (Oncorhynchus tshawytscha), in fresh water and after one year in salt water. We also tested the effects of freshwater rearing density (100, 50 or 35 fish per 200 L), food ration (high or low), sire (jack or hooknose) for jacks, hooknoses, and females with and without confirmed jack siblings. Sisters of jacks were further identified to test whether females closely related to jacks also showed behavioural differences. Overall, jacks did not behave as predicted; rearing conditions were the strongest determinant of behaviour, and jack sisters behaved differently than jacks and other females. Our study underscores the complexities of jack behaviour, and of females closely related to jacks, at all development stages, and supports the use of behavioural screenings to regulate jacking rates in hatcheries by identifying jack sisters.