Trait changes in a harvested population are driven by a dynamic tug-of-war between natural and harvest selection.
(17/35)
Selective harvest of large individuals should alter natural adaptive landscapes and drive evolution toward reduced somatic growth and increased reproductive investment. However, few studies have simultaneously considered the relative importance of artificial and natural selection in driving trait changes in wild populations. Using 50 years of individual-based data on Windermere pike (Esox lucius), we show that trait changes tracked the adaptive peak, which moved in the direction imposed by the dominating selective force. Individual lifetime somatic growth decreased at the start of the time series because harvest selection was strong and natural selection was too weak to override the strength of harvest selection. However, natural selection favoring fast somatic growth strengthened across the time series in parallel with the increase in pike abundance and, presumably, cannibalism. Harvest selection was overridden by natural selection when the fishing effort dwindled, triggering a rapid increase in pike somatic growth. The two selective forces appear to have acted in concert during only one short period of prey collapse that favored slow-growing pike. Moreover, increased somatic growth occurred concurrently with a reduction in reproductive investment in young and small female pike, indicating a tradeoff between growth and reproduction. The age-specific amplitude of this change paralleled the age-specific strength of harvest pressure, suggesting that reduced investment was also a response to increased life expectancy. This is the first study to demonstrate that a consideration of both natural selection and artificial selection is needed to fully explain time-varying trait dynamics in harvested populations. (+info)
Predator-induced morphology enhances escape locomotion in crucian carp.
(18/35)
Fishes show a remarkable diversity of shapes which have been associated with their swimming abilities and anti-predator adaptations. The crucian carp (Carassius carassius) provides an extreme example of phenotypic plasticity in body shape which makes it a unique model organism for evaluating the relationship between body form and function in fishes. In crucian carp, a deep body is induced by the presence of pike (Esox lucius), and this results in lower vulnerability to gape-limited predators, such as pike itself. Here, we demonstrate that deep-bodied crucian carp attain higher speed, acceleration and turning rate during anti-predator responses than shallow-bodied crucian carp. Therefore, a predator-induced morphology in crucian carp enhances their escape locomotor performance. The deep-bodied carp also show higher percentage of muscle mass. Therefore, their superior performance in escape swimming may be due to a combination of higher muscle power and higher thrust. (+info)
Accumulation of some heavy metals in Raphidascaris acus (Bloch, 1779) and its host (Esox lucius L., 1758).
(19/35)
Concentrations of some heavy metals (Fe, Zn, Cu, Mn and Cr) in liver of pike (Esox lucius L., 1758) and its endoparasite [Raphidascaris acus (Bloch, 1779)] inhabiting Isikli Lake (Turkey) were analyzed using atomic absorption spectrophotometry. Only Fe and Zn were detected in R. acus and liver of fish, while levels of Cu, Mn and Cr were below detection limit (<0.028). The Fe and Zn level in R. acus were 68.4 and 86.9 times higher than in the liver. Nematodes could provide reliable information about the heavy metal pollution of the lakes. (+info)
The inner ears of Northern Canadian freshwater fishes following exposure to seismic air gun sounds.
(20/35)