On the problem of ecological groups formation in European perch Perca fluviatilis populations

Simulation model of the intraseasonal growth dynamics of young-of-the-year European perch Perca fluviatilis has been developed and studied. The model has been constructed based on the principles of bioenergetics and covers all the main physiological utilization processes of energy that come with food, including somatic growth, expenses on metabolism, and partial loss of energy with egestion and excretion. It is assumed that there are two space-separated biotopes called “inshore” and “pelagial” with different feeding conditions. Fish move from inshore to pelagial as the amount of food in the inshore biotope gets lower, provided that the actual ration is reduced down to the predetermined threshold level. It is demonstrated that the combined distribution of fish specimens belonging to one generation according to weight by the end of their growth period mainly depends on the intensity of exchange process between the biotopes. The ratio between the abundance values of young fish localized in different biotopes is determined by the threshold ration level, which motivates fish to move, as well as the duration of spawning, and, accordingly, length of hatching period.     

A bioenergetics model for an air-breathing fish, Channa striatus

Food consumption, standard metabolism, and growth of juvenile snakehead, Channa striatus, a cannibalistic and air-breathing fish were measured at 24–26 °C under controlled laboratory condition. Snakehead weighing 3.2–29.5 g were evaluated, and were fed smaller snakehead. Based on our observations, we determined bioenergetics relationships between specific food consumption, metabolic rates, and body weight. These values, along with other published parameter values allowed us to construct a bioenergetics model for snakehead. We then verified our model with growth and food consumption measurements from an independent feeding trial. Predicted fish growth closely matched observed growth. Our model underestimated cumulative food consumption when a constant activity value was used, but consumption estimates improved when we used non-constant activity values (1-5 times of standard metabolism). Predicted fish maintenance ration was 1.7% of body weight per day. Food conversion efficiency was greatest (0.59) when fed 2% body weight daily, but declined when daily consumption exceeded 6% body weight. This model provides a useful approach for assessing food requirements of snakehead under controlled condition. This revised version was published online in July 2006 with corrections to the Cover Date.     

Application of a bioenergetics model to roach

A new set of bioenergetic parameters for adult roach (Rutilus rutilus) was fitted to the Wisconsin bioenergetics model (Fish Bioenergetics 3.0). These parameters describing rates of maximum food consumption, routine metabolism, egestion and excretion were derived from laboratory studies with adult roach over a wide range of fish sizes (1.2–300 g) and water temperatures (5–20°C). The new parameter set was compared with the only previously published set for adult roach, where parameters were taken from different life stages and compiled from different studies. In both a simulation and a field study, the new set resulted in a smaller increase of energy losses and a larger increase of energy intake with temperature compared with the previous set. The intermodel differences were most distinct at high (>20°C) and low (<10°C) temperatures, and can be mainly explained by differences in the temperature dependence of the respiration rate between the two sets. At moderate temperatures, the two parameter sets gave similar results.     

Lazy males? Bioenergetic differences in energy acquisition and metabolism help to explain sexual size dimorphism in percids

1. Differences in energy use between genders is a probable mechanism underlying sexual size dimorphism (SSD), but testing this hypothesis in the field has proven difficult. We evaluated this mechanism as an explanation for SSD in two North American percid species--walleye Sander vitreus and yellow perch Perca flavescens. 2. Data from 47 walleye and 67 yellow perch populations indicated that SSD is associated with the onset of maturation: typically, males of both species matured smaller and earlier and attained a smaller asymptotic size than females. Males also demonstrated equal (perch) or longer (walleye) reproductive life spans compared with females. 3. To examine whether reduced post-maturation growth in males was due to lower energy acquisition or higher reproductive costs we applied a contaminant mass-balance model combined with a bioenergetics model to estimate metabolic costs and food consumption of each sex. Mature males exhibited lower food consumption, metabolic costs and food conversion efficiencies compared with females. 4. We propose that slower growth in males at the onset of maturity is a result of decreased feeding activity to reduce predation risk. Our finding that SSD in percids is associated with the onset of maturity is supported by laboratory-based observations reported elsewhere, showing that changes in growth rate, consumption and food conversion efficiency were elicited by oestrogen (positive effects) or androgen (negative effects) exposure in P. flavescens and P. fluviatilis. 5. Researchers applying bioenergetic models for comparative studies across populations should use caution in applying bioenergetic models in the absence of information on population sex ratio and potential differences between the sexes in energetic parameters.     

Factors influencing nitrogen and phosphorus excretion rates of fish in a shallow lake

Summary 1. Fish excretion can be an important source of nutrients in aquatic ecosystems. Nitrogen (N) and phosphorus (P) excretion rates are influenced by many factors, including fish diet, fish growth rate and fish size. However, the relative influence of these and other factors on community‐level excretion rates of fish is unknown. 2. We used bioenergetics modeling to estimate excretion rates of eight fish species in a shallow, Minnesota (U.S.A.) lake over four months in both 2004 and 2005. Excretion rates of each species were summed for community‐level N and P excretion rates, as well as the N : P ratio of excretion. We then used a model‐selection approach to assess ability of independent variables to predict excretion rates, and to identify the most parsimonious model for predicting N : P excretion ratios and P and N excretion rates at the community scale. Predictive models were comprised of the independent variables water temperature and average fish density, fish size, fish growth rate, nutrient content of fish and nutrient content of fish diets at the community scale. 3. Fish density and nutrient content of fish diets (either N or P) were the most parsimonious models for predicting both N and P excretion rates, and explained 96% and 92% of the variance in N and P excretion, respectively. Moreover, fish density and nutrient models had 1400‐fold more support for predicting N and 21‐fold more support for predicting P excretion relative to models based on fish density only. Water temperature, fish size, fish growth rates and nutrient content of fish showed little influence on excretion rates, and none of our independent variables showed a strong relationship with N : P ratios of excretion. 4. Past work has focused on the importance of fish density as a driver of fish excretion rates on a volumetric basis. However, our results indicate that volumetric excretion rates at the community scale will also change substantially in response to changes in relative abundance of fish prey or shifts in relative dominance of planktivores, benthivores, or piscivores. Changes in community‐scale excretion rates will have subsequent influences on algal abundance, water clarity, and other ecosystem characteristics.     

The estimation of food consumption in larval and juvenile fish: experimental evaluation of bioenergetics models

The two most commonly used methods for estimating the food consumption of fish are based on either the evacuation rate of food or the energy budget of an individual fish. In this study, both of those methods were used to estimate the food consumption of fish under experimental conditions. Bioenergetics models of vendace Coregonus albula , smelt Osmerus eperlanus , roach Rutilus rutilus and perch Perca fluviatilis were reconstructed based on experimental data and published values. The precision of the bioenergetics estimates for food consumption was evaluated under experimental conditions. The modelling efficiency (EF) of the bioenergetics model was 0.90, 0.97 and 0.93 for coregonids, roach and perch, respectively, which indicated good agreement between observed and predicted values. Under our experimental conditions, the bioenergetics model estimated food consumption better than the evacuation rate model.     

Application of a bioenergetics growth model for European anchovy (<Emphasis Type="Italic">Engraulis encrasicolus</Emphasis>) linked with a lower trophic level ecosystem model

A bioenergetics model is implemented for European anchovy (Engraulis encrasicolus) and applied to the north-eastern Aegean Sea (eastern Mediterranean Sea). The model reproduces the growth of anchovy in a one-way linked configuration with a lower trophic level (LTL) ecosystem model. The LTL model provides densities for three zooplankton functional groups (heterotrophic flagellates, microzooplankton and mesozooplankton) which serve as available energy via consumption for the anchovy model. Our model follows the basic structure of NEMURO.FISH type models (North Pacific Ecosystem Model for Understanding Regional Oceanography for Including Saury and Herring). Several model parameters were specific for the Mediterranean or the Black Sea anchovy and some others were adopted from related species and NEMURO.FISH due to lack of biological information on E. encrasicolus. Simulation results showed that the fastest growth rate occurs during spring and the slowest growth rate from August to December. Zooplankton abundance during autumn was low implying that decreased prey density lead to a reduction in anchovy weight, especially for the age-3 class. Feeding parameters were adjusted to adequately fit the model growth estimates to available weight-at-age data. A detailed sensitivity analyses is conducted to evaluate the importance of the biological processes (consumption, respiration, egestion, specific dynamic action, excretion and egg production) and their parameters to fish growth. The most sensitive parameters were the intercept and exponent slope of the weight-dependent consumption and respiration process equations. Fish weight was fairly sensitive to temperature-dependent parameters.     

Functional models for growth and food consumption of Atlantic salmon parr, Salmo salar, from a Norwegian river

1. The chief objectives were to analyse and model experimental data for maximum growth and food consumption of Atlantic salmon parr (Salmo salar) collected from a cold glacier fed river in western Norway. The growth and feeding models were also applied to groups of Atlantic salmon growing and feeding at rates below the maximum. The growth models were validated by comparing their predictions with observed growth in the river supplying the experimental fish.
2. Two different models were fitted, one originally developed for British salmon and the other based on a model for bacterial growth. Both gave estimates for optimum temperature for growth at 18–19 °C, somewhat higher than for Atlantic salmon from Britain. Higher optimal temperature for growth in salmon from a cold Norwegian river than from British rivers does not concur with predictions from the thermal adaptation hypothesis.
3. Model parameter estimates differed among growth groups in that the lower critical temperature for growth increased from fast to slow growing individuals. In contrast to findings for brown trout (Salmo trutta), the optimum temperature for growth did not decrease with decreasing levels of food consumption.
4. A new and simple model showed that food consumption (expressed in energy terms) peaked at 19.5–19.8 °C, which is similar to the optimal temperature for growth. Feeding began at a temperature 1.5 °C below the lower temperature for growth and ended about 1 °C above the maximum temperature for growth. Model parameter estimates for consumption differed among growth groups in a manner similar to the growth models. Maximum consumption was lower for Atlantic salmon than for brown trout, except at temperatures above 18 °C.
5. By combining the growth and food consumption models, growth efficiency was estimated and reached a maximum at about 14 °C for fast growing individuals, increasing to nearly 17 °C for slow growing ones, although it was lower overall for the latter group. Efficiency also declined with increasing fish size. Growth efficiency was generally higher for Atlantic salmon than for brown trout, particularly at high temperature.     

Energy allocation in larval and juvenile Coregonus lavaretus: validation of a bioenergetics model

Food consumption and energy allocation of larval and juvenile whitefish Coregonus lavaretus L. were studied by conducting respirometry experiments at 10, 12 and 15° C. Results from these experiments were compared with those predicted by a bioenergetics model that used observed growth as the major input. The data were used to assess the performance of the model, and evaluate its suitability for estimation of food consumption by whitefish. The mean absolute % error (ɛ) between observed and predicted food consumption was 16·3%, and the modelling efficiency (M_E) was 0·90, indicating that the model was reasonably robust. Linear regression analysis of predicted v. observed food consumption values gave a slope slightly above unity, indicating a tendency for the model to overestimate consumption at higher values. ɛ and M e were also calculated for total metabolic rate (RT), and they equalled 13·0% and 0·85, respectively. Despite some deficiencies, it is concluded that the model can be used for prediction of food consumption by highly active, planktivorous fish such as whitefish.     

Evaluation of a Mysis bioenergetics model

Direct approaches for estimating the feeding rate of the opossumshrimp Mysis relicta can be hampered by variable gut residencetime (evacuation rate models) and non-linear functional responses(clearance rate models). Bioenergetics modeling provides analternative method, but the reliability of this approach needsto be evaluated using independent measures of growth and foodconsumption. In this study, we measured growth and food consumptionfor M. relicta and compared experimental results with thosepredicted from a Mysis bioenergetics model. For Mysis rearedat 10°C, model predictions were not significantly differentfrom observed values. Moreover, decomposition of mean squareerror indicated that 70% of the variation between model predictionsand observed values was attributable to random error. On average,model predictions were within 12% of observed values. A sensitivityanalysis revealed that Mysis respiration and prey energy densitywere the most sensitive parameters affecting model output. Byaccounting for uncertainty (95% CLs) in Mysis respiration, weobserved a significant improvement in the accuracy of modeloutput (within 5% of observed values), illustrating the importanceof sensitive input parameters for model performance. These findingshelp corroborate the Mysis bioenergetics model and demonstratethe usefulness of this approach for estimating Mysis feedingrate.     

Ingestion,egestion, excretion,growth, and conversion efficiency for the mummichog, Fundulus heteroclitus (L.)

The food conversion efficiency of Fundulus heteroclitus (L.) was measured in terms of calories and nitrogen for three diets: Palaemonetes sp., Nereis sp., and Uca pugnax. Fish were allowed to feed ad libitum for 30–60 min each day. Growth, ingestion, egestion, and excretion were measured for fish fed each diet. The growth rates of Fundulus heteroclitus fed two of the single item diets of invertebrates were higher than growth rates previously estimated for mummichogs from the natural population in Canary Creek marsh. In comparison with other fish species, F. heteroclitus was found to have a higher than average assimilation efficiency ($\text{X}\text{?}\text{= 87\%}$ for all three diets) and a lower than average gross growth efficiency (≈12% for two of the diets). Metabolic costs accounted for an average of 69% of ingested energy. Excretion rates were also large, with excretion accounting for more energy than egestion in two of the three diets.     

Surfacing frequency as an index of bioenergetics components of air breathing fishes

Surfacing frequency (Sf) in obligatory air-breathing fishes is a behavioural index of O₂ uptake; as both are interrelated, there is a possibility of predicting one from the other. From the point of cause and effect relationship, feeding (C) is regarded as the cause and Sf and O₂ uptake as its effects. Hence, the last two are predictable from the cause. A pathway for predicting the bioenergetics components, feeding (C), metabolism (M) and growth (P) from a behavioural index of surfacing frequency has been proposed. In this model, C occupies the focal point connecting on the horizontal plane Sf on one side and P on the other side and M vertically. The developed multiple regression models predict the bioenergetics components of the fishes,Macropodus cupanus andChanna striatus of different weight classes ex-posed to different rations and temperatures; the percentage of variation accounted for by the equations is over 90. The pathway can also be followed for predicting bioenergetics components of gill-breathing fishes, if feeding rate alone is known. On application of the relevant part of the pathway toSalmo trutta, the percentage of variation accounted by the equations is 95.     

Seasonal variation in the thermal performance of juvenile Atlantic salmon (Salmo salar)

1. Experimental data on the maximum growth and food consumption of winter‐acclimatised Atlantic salmon (Salmo salar) juveniles from three Norwegian rivers situated at 59 and 70°N were compared with predictions from published models of growth and food consumption of summer‐acclimatised fish from the same populations. 2. All winter‐acclimatised fish maintained positive growth and a substantial energy intake over the whole range of experimental temperature (1–6 °C). This contrasted with predictions from growth models based on summer acclimatised Atlantic salmon, where growth and energy intake ceased at approximately 5 °C. 3. Growth and food consumption varied significantly among populations. Winter‐acclimatised fish from a Northern population had a higher mass‐specific growth rate, higher energy intake and higher growth efficiency than southern populations, which is contrary to predictions from models developed using summer‐acclimatised salmon, where fish from the Northern population had the lowest growth efficiency. 4. The experiment provides evidence that thermal performance varies seasonally and suggests adaptation to the annual thermal regime.     

Feeding modes in stream salmonid population models: is drift feeding the whole story?

Drift-feeding models are essential components of broader models that link stream habitat to salmonid populations and community dynamics. But is an additional feeding mode needed for understanding and predicting salmonid population responses to streamflow and other environmental factors? We addressed this question by applying two versions of the individual-based model inSTREAM to a field experiment in which streamflow was varied in experimental units that each contained a stream pool and the adjacent upstream riffle. The two model versions differed only in the feeding options available to fish. Both versions of inSTREAM included drift feeding; one also included a search feeding mode to represent feeding in which food availability is largely independent of streamflow, such as feeding from the benthos, or feeding from the water column or the water’s surface in low water velocities. We compared the abilities of the two model versions to fit the observed distributions of growth by individual rainbow trout (Oncorhynchus mykiss) in the field experiment. The version giving fish the daily choice between drift or search feeding better fit observations than the version in which fish fed only on drift. Values for drift and search food availability from calibration to the individual mass changes of fish in experimental units with unaltered streamflow yielded realistic distributions of individual growth when applied to experimental units in which streamflow was reduced by 80 %. These results correspond with empirical studies that show search feeding can be an important alternative to drift feeding for salmonids in some settings, and indicate that relatively simple formulations of both processes in individual-based population models can be useful in predicting the effects of environmental alterations on fish populations.     

Comparing correlative and bioenergetics‐based habitat suitability models for drift‐feeding fishes

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The combined effect of feeding time and ration on growth performance and nitrogen metabolism of greenback flounder

Greenback flounder Rhombosolea tapirina ( c. 2 g) fed to satiation had significantly ( P <0·01) higher feed consumption in the evening than in the morning whereas there was no difference between feeding times for flounder fed restricted rations (1 or 2% body weight per day) because they consumed all of the ration. Differences in growth performance were due to feeding time and ration. Carcass moisture, lipid and energy content were significantly ( P <0·001) different between rations; length gain was significantly affected by feeding time ( P <0·05) and ration ( P <0·001); weight gain showed a significant ( P <0·001) interaction between feeding time and ration. The relationship between feed consumption and specific growth rate showed that the exponential gradient was significantly higher ( P <0·01) for the evening fed fish and indicated feed efficiency for evening fed fish increased as feed consumption increased. Urea excretion increased from 12–20 to 58–63% of total nitrogen excretion at the 1 and 3% rations, respectively. Ammonia and urea excretion were significantly affected by ration ( P <0·001) and feeding time ( P <0·05). Fish fed the 2% ration in the evening had higher growth efficiency and significantly ( P <0·01) lower rates of urea excretion than fish fed 2 or 3% ration in the morning. It is suggested that the higher energetic costs associated with differences in ammonia and urea excretion contributed to differences in growth efficiency.     

Effects of angling on feeding by largemouth bass

Angling practice significantly effected the time required for largemouth bass Micropterus salmoides to begin feeding. Mean ± s.e. time until feeding resumed was longest for fish that experienced a simulated tournament (15·6 ± 2·2 h) followed by fish that were caught and released (8·4 ± 2·2 h) and controls (0·3 ± 1·6 h). Effects on feeding related to angling practices were maintained throughout the 48 h observation period. Using multiple logistic regression and bioenergetics simulations, decreased growth in fish subjected to competitive or catch-and-release angling events was predicted. Fish subjected to multiple captures in a pond experiment had greater mass loss than those not captured, supporting model predictions.     

Can filter‐feeding Asian carp invade the Laurentian Great Lakes? A bioenergetic modelling exercise

1. There is much concern that filter‐feeding Asian carp will invade the Laurentian Great Lakes and deplete crucial plankton resources. We developed bioenergetic models, using parameters from Asian carp and other fish species, to explore the possibility that planktonic food resources are insufficient to support the growth of silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis) in the Great Lakes. 2. The models estimated basic metabolic requirements of silver and bighead carp under various body sizes, swimming speeds and reproductive stages. These requirements were then related to planktonic food resources and environmental temperature to predict when and where silver and bighead carp may survive in the Great Lakes, and how far they may travel. 3. Parameter values for respiration functions were derived experimentally in a coordinated study of silver and bighead carp, while consumption parameters were obtained from the literature on silver carp. Other model parameters lacking for Asian carp, such as those for egestion and excretion, were obtained from the literature on other fish species. 4. We found that full‐sized bighead carp required 61.0 kJ d^?1 just to maintain their body mass at 20 °C, approximately equivalent to feeding in a region with 255 μg L^?1 macrozooplankton (dry) or 10.43 μg L^?1 chlorophyll a. Silver carp energy requirements were slightly higher. 5. When applied to various habitats in the Great Lakes, our results suggest that silver and bighead carp will be unable to colonise most open‐water regions because of limited plankton availability. However, in some circumstances, carp metabolism at lower temperatures may be low enough to permit positive growth even at very low rations. Positive growth is even more likely in productive embayments and wetlands, and the modelled swimming costs in some of these habitats suggest that carp could travel >1 km d^?1 without losing biomass. 6. The simulation (and firmly hypothetical) results from this modelling study suggest when and where Asian carp could become established in the Great Lakes. Given the potential consequences to Great Lakes ecosystems if these filter feeders do prove capable of establishing reproducing populations, efforts to keep Asian carp out of the Great Lakes must not be lessened. However, we do encourage the use of bioenergetic modelling in a holistic approach to assessing the risk of Asian carp invasion in the Great Lakes region.