Application of a bioenergetics model for analysis of growth and food consumption of subarctic whitefish Coregonus lavaretus (L.) in Lake Kilpisjärvi, Finnish Lapland

A bioenergetics model was used to estimate daily food consumption and growth of benthic whitefish Coregonus lavaretus (L.) of age groups 1+ to 10+, in oligotrophic Lake Kilpisjärvi, northern Finnish Lapland. Fish and zooplankton samples and water temperature data were collected twice per month from February to December 1993. Simulation results indicated wide seasonal variations in consumption and growth rates. Growth was in general slow; especially in age-group 6 the net increase in weight was slight. The fit of the model to the weight data was good, and the model was able to follow even rapid seasonal variations in the weight. There were clear changes in the diet during the year. In March, when the food intake was reduced, copepods, mainly adult calanoids, formed the bulk of the food consumed. The most intensive consumption period lasted from June to late September. Chironomid pupae and planktonic cladocerans were the major summer food items. The largest individuals fed mainly on molluscs during summer. Zooplankton survey and consumption estimates did not show directly that the population density of copepodids and adults of Eudiaptomus graciloides were affected by whitefish predation although their population density decreased in spring. Nauplii, showing the maximum population density in April, were not consumed. The role of copepod consumption in the timing of Diphyllobothrium ditremum plerocercoid transmission to whitefish was also discussed. The increased copepod consumption rate during winter results in high energy intake but also an increased risk of food transmitted parasite infection.     

Growth and food consumption of vendace (Coregonus albula (L.)) in Lake Pyhäjärvi,SW Finland: a bioenergetics modeling analysis

Hydrobiologia - We used a bioenergetics model to estimate daily food consumption of young-of-the-year (YOY) and adult vendace in the mesotrophic Lake Pyhäjärvi. Weekly samples of fish and...     

Consumption, growth and evacuation in the Pacific cod, Gadus macrocephalus

Growth of Pacific cod was related to energy consumption (cal g⁻¹ day⁻¹) and was well described by linear equations. Maintenance ration was 11 and 12 cal g⁻¹ day⁻¹ at 4.5 and 6.5° C, respectively. Cod between 200 and 5000 g had similar growth rates when growth was expressed as a function of consumption (cal g⁻¹ day⁻¹). Laboratory consumption of food averaged 0.9 and 1.3% body weight per day at 4.5 and 6.5° C, respectively. At these temperatures growth was 0.34–0.38% body weight day⁻¹.
Maximum stomach volumes equated to approximately 4.7% of body weight with shrimp as prey. At this meal size Pacific cod did not feed the next day. A multiple meal evacuation experiment was used to verify the consumption estimates. A return-to-hunger estimate of the meal size evacuated was 1.5% body weight day⁻¹ at 6.5° C, similar to the 1.3% consumption estimate. For Pacific cod fed a single meal of 1% body weight the estimated instantaneous evacuation rate was 0.63 body weight day⁻¹ at 6.5° C. Meal size markedly affected the evacuation rate.
Measured consumption and growth rates are similar to those of Atlantic cod, Gadus morhua .     

空间直观景观模型的验证方法

空间直观景观模型已是当前景观生态学研究的一大热点。空间景观模型模拟空间格局变化。其模拟结果包含非空间数据和空间数据。空间直观景观模型的验证除进行非空间数据的验证外,还需要进行空间数据的验证。本文回顾了空间直观模型发展历程,总结现有的空间直观模型验证方法。包括主观评价、图形比较、偏差分析、回归分析、假设检验、多尺度拟合度分析和景观指数分析,同时提出今后空间直观景观模型验证方法研究的重点方向。     

An application of a bioenergetics model to Eurasian perch (Perca fluviatilis L.)

A bioenergetics model was developed for Eurasian perch ( Perca fluviatilis L.) by revising an existing model for yellow perch and walleye. Data were gathered from field studies and the literature. Besides adjusting the original parameters of the model, effects of season on consumption and metabolic rates were added. The predictive capability of the revised model was high both concerning the levels of growth and its seasonal development in the Baltic coastal waters to which the model was applied. Perch young-of-the-year attained almost maximum consumption and growth except in the highest temperatures experienced. In larger fish, the model estimated consumption to be about 50 per cent of the maximum possible rate.     

The influence of prey biomass on activity and consumption rates of brook trout

The objectives of this work were (1) to assess the influence of zooplankton biomass on activity and consumption rates of young-of-the-year brook trout ( Salvelinus fontinalis ) and (2) to validate an in situ enclosure approach to quantify energy allocation patterns in fish. These objectives were attained by directly estimating fish growth, consumption and activity rates on 10 occasions characterized by different levels of zooplankton biomass (0.005 to 0.100 mg dry weight 1⁻¹). One enclosure was used to estimate growth and activity rates and five additional enclosures were used to estimate consumption rates. Among-experiment variations of activity rates (sum for five trout = 2.4 to 33.5 calories day⁻¹) were proportionally more important than variations of consumption rates (sum for five trout = 59.5 to 112.7 calories day⁻¹). The results support the existence of a significant positive relationship between fish activity rates and zooplankton biomass. No significant relationship was found between consumption rates and prey biomass. Final size of fish inside the enclosure was within 7.6% of the value estimated using experimentally derived activity and consumption rates. This situation, together with the stability of among-enclosure activity and feeding schedules, suggested that the experimental design was appropriate to estimate fish energy allocation patterns. Combination of our observations with those of a previously published work indicated that small variations of fish size or zooplankton biomass can cause a two-fold variation of fish activity costs.     

Gastric evacuation of horse mackerel. II. The effects of different prey types on the evacuation model

Gastric evacuation experiments were performed on horse mackerel Trachurus trachurus. Discrete meals of different sizes of krill Meganyctiphanes norvegicus, mysids Neomysis integer , brown shrimp Crangon crangon , and herring Clupea harengus were fed to test the effect of prey type on the gastric evacuation. A general evacuation model without meal size as a variable was fitted to the data on dry weights by means of non-linear regression. With the exception of mysid evacuation the estimated parameters for curvature, predator weight effect, and temperature effect of the general evacuation model were very similar for all other food types and also confirmed the results obtained with smelt Osmerus eperlanus. In contrast the evacuation of mysids showed a strong exponential curvature, rather the effect of prey size than of prey type. The prey specific evacuation constants of the model revealed a linear relationship to the energy content. A general consumption model for field estimates is presented that can be used for prey types that have not yet been tested in the experiments, provided the energy content is known.     

Predicting availability to consumers of spatially and temporally variable resources

Ecological dynamics in many aquatic communities are strongly influenced by spatial and temporal variability of key limiting resources, and the extent to which consumers can locate and exploit concentrations of those resources. Intuitively, resource concentrations that are `close' and `long-lived' should typically be more available to consumers than `distant' and `ephemeral' resource concentrations. The speed and accuracy with which consumers can locate concentrations of their resources is in part determined by their movement characteristics and sensory constraints, which vary with taxon, life-history stage, physiological state, environmental conditions, and other factors. This has motivated detailed observation and modelling of individual-level foraging behaviors in a wide variety of taxa. However, our abilities to develop this intuitive concept of availability into empirically-based, quantitative predictions for consumer–resource interactions remain limited, largely due to the complexities of formulating and simulating spatially explicit models of consumer–resource interactions, and the difficulty of understanding how specific simulation results relate to broader ecological situations. This paper presents a non-dimensional index, the Frost number, that provides a simple prediction of availability to consumers of spatially and temporally varying resource concentrations. This index incorporates characteristics of both resource distributions and consumer movement behaviors. When Frost numbers characterizing consumer–resource interactions are much less than unity, resource concentrations are typically unavailable to consumers because travel time to reach them exceeds the longevity of the resource. Conversely, when Frost numbers are much greater than unity, resource longevity exceeds travel time so that resource concentrations are available. The Frost number may provide a preliminary identification of the length and time scales at which resources are available to consumers in complex ecological systems, even when detailed spatial observations and simulations are not available.     

Diet variation of a generalist fish predator,grey snapper Lutjanus griseus,across an estuarine gradient: trade‐offs of quantity for quality?

This study examined diet, prey quality and growth for a generalist fish predator, grey snapper Lutjanus griseus, at five sites across an estuarine gradient in the Loxahatchee River estuary, Florida, U.S.A. Lutjanus griseus diets shifted from dominance by low quality, intertidal crabs upstream to an increased reliance on higher quality shrimp, fishes and benthic crabs downstream. Frequency of L. griseus with empty stomachs was higher at downstream sites. Lutjanus griseus growth rates did not vary among sites. Results indicate that L. griseus may be able to compensate for lower quality prey upstream by consuming more, and thus individuals are able to maintain similar levels of energy balance and growth rates across the estuarine gradient. Elucidating mechanisms, such as compensatory feeding, that enable generalist species to remain successful across habitat conditions are critical to understanding their organismal ecology and may facilitate predictions about the response of generalists to landscape alteration.