Abstract – In natural systems, prey frequently interact with multiple predators and the outcome often cannot be predicted by summing the effects of individual predator species. Multiple predator interactions can create emergent effects for prey, but how those change across environmental gradients is poorly understood. Turbidity is an environmental factor in aquatic systems that may influence multiple predator effects on prey. Interactions between a cruising predator (largemouth bass Micropterus salmoides) and an ambush predator (muskellunge Esox masquinongy) and their combination foraging on a shared prey (bluegill Lepomis macrochirus) were examined across a turbidity gradient. Turbidity modified multiple predator effects on prey. In clear water, combined predators consumed in total more prey than expected from individual predator treatments, suggesting risk enhancement for prey. In moderately turbid water, the predators consumed fewer prey together than expected, suggesting a risk reduction for prey. At high turbidity, there were no apparent emergent effects; however, the cruising predator consumed more prey than the ambush predator, suggesting an advantage for this predator. Understanding multiple predator traits across a gradient of turbidity increases our understanding of how complex natural systems function. 相似文献
This study evaluated the apparent digestibility coefficients (ADCs) of dry matter, protein, lipid, energy, calcium, phosphorus, and essential and non‐essential amino acid availability of animal and plant protein sources in practical diets for the carnivorous fish, largemouth bass Micropterus salmoides (8.0±0.5 g; 10.0±0.3 cm). Fish were conditioned to accept artificial feed and those stocked in plastic cages were fed pelleted test diets. Diets contained 30% of the ingredient tested mixed with 70% of a reference ration (RD) containing 40 g 100 g?1 of crude protein, 19.85 kJ g?1 crude energy, and 0.5% of chromic oxide. Cages were then transferred to cylindrical, conical‐bottomed aquaria (200 L) where the faeces were collected by sedimentation in a refrigerated container. All the tested ingredients had high ADCs for protein and lipid; ADCs of amino acids of varying protein sources showed significant differences (P<0.01). Plant protein sources did not significantly influence the ADCs of diets. The results allow the inference that the availability of amino acids in plant and animal protein sources varies considerably. 相似文献
Abstract Variation in brood abandonment was explored by conducting partial brood removals from smallmouth bass, Micropterus dolomieu Lacepède, nests in two north temperate lakes. In both lakes, percent of the brood removed had no effect on nest failure rates. Nest failure prior to offspring swim‐up was more common, but unrelated to brood size after removal, in the lake with higher post‐spawning mortality and lower growth and fecundity. Brood size after removal was negatively related to nest failure in the lake with high survival, growth and fecundity. Nests guarded by young males failed more frequently than those of old males, and young broods failed more frequently than old broods. Dynamic programming and logistic regression models developed to predict nest fate worked better for the lake with selective pressures that theoretically favoured abandonment (e.g. high post‐spawning mortality). Both models identified male age and brood age as important factors in predicting nest fates. Because nest success is related to the age of the parent, this could have consequences for overall nest success for populations with different demographics. 相似文献