Daniel Boisclair

Applications of Bioenergetics Models to Fish Ecology and Management: Where Do We Go from Here?

Abstract Papers and panel discussions given during a 1992 symposium on bioenergetics models are summarized. Bioenergetics models have been applied to a variety of research and management questions relating to fish stocks, populations, food webs, and ecosystems. Applications include estimates of the intensity and dynamics of predator–prey interactions, nutrient cycling within aquatic food webs of varying trophic structure, and food requirements of single animals, whole populations, and communities of fishes. As tools in food web and ecosystem applications, bioenergetics models have been used to compare forage consumption by salmonid predators across the Laurentian Great Lakes for single populations and whole communities, and to estimate the growth potential of pelagic predators in Chesapeake Bay and Lake Ontario. Some critics say that bioenergetics models lack sufficient detail to produce reliable results in such field applications, whereas others say that the models are too complex to be useful tools for ...

Testing Assumptions of Fish Bioenergetics Models by Direct Estimation of Growth, Consumption, and Activity Rates

Abstract We tested the hypothesis that activity rates can represent a large and variable component of a fishs energy budget. We executed five experiments between July 15 and August 2, 1991, to estimate growth, consumption, and activity rates of five young-of-the-year brook trout Salvelinus fontinalis kept in field enclosures. Mean fish wet weight decreased from 3.47 to 2.89 g during our study. This represented a total loss of 3,544 cal (all fish combined). Consumption rates averaged 0.18 g dry·100 g wet–1·d–1. The total quantity of food consumed by the fish inside the enclosure ranged from 112.9 to 188.8 cal·d–1. Median swimming speed ranged from 3.9 to 7.9 cm·s–1. Energetic costs associated with spontaneous swimming (all fish combined) ranged from 94.0 to 498.1 cal·d–1. Spontaneous activity metabolic rate (standard metabolism + net activity rate) represented 1.6–3.8 times the costs associated with standard metabolism. Our study supported the hypothesis that activity rates can be a large and variable com...

The influence of spatial heterogeneity on the study of fish horizontal daily migration

Abstract We described the spatial and short term temporal heterogeneity of fish abundance in the perimeter of four lakes characterized by different levels of abundance in pelagic predators. Fish relative abundance was estimated by acoustically sampling 25 to 100% of the complete contour of the lakes at 4 h intervals during 24 h. During hydroacoustics, the transducer was installed on the side of a boat and directed towards the littoral such that the axis of the acoustic beam was set parallel to the surface of the lake. Maximum values of average fish relative abundance in the pelagic zone ranged from 6 to 209 targets/100 m 3 . Fish relative abundance varied among segments by factors ranging from 3 to 84. Coefficient of variation of fish relative abundance ranged from 64 to 523% and supported the hypothesis that fish are more heterogeneously distributed in lakes containing pelagic piscivores. Our work suggests that the presence of pelagic piscivorous fish may affect the sampling design required to estimate fish abundance and distribution patterns in lakes.

Day-to-day variation in fish horizontal migration and its potential consequence on estimates of trophic interactions in lakes

Abstract We assessed the day-to-day variation in fish horizontal migration by acoustically sampling a small oligotrophic lake at 4-h intervals during 15 consecutive days. Hydroacoustics was performed by directing a 200-kHz transducer from a floating platform situated in the middle of the lake towards the littoral zone such that the longitudinal axis of the acoustic beam was parallel to the surface of the lake. Fish horizontal migration displayed a qualitatively regular daily pattern. Fish relative abundance in the pelagic zone increased at dusk, peaked during the night (up to an average of 62 targets/100 m 3 ), and decreased at dawn. However, fish relative abundance in the pelagic zone varied by up to 12-fold at peak of daily migration. On specific days, fish stayed in the pelagic zone for a time period that ranged from 4 to 24 h, and ventured in the pelagic zone at distances from the hydroacoustic shore that ranged from 7 to 16 m. Simulations indicated that one strategy to minimize the influence of among-day variation of the characteristics of fish horizontal migration at the temporal scale we studied would be to sample the lakes at 4-day intervals.

Relationships between species feeding traits and environmental conditions in fish communities: a three-matrix approach

Understanding the relationships between species biological traits and the environment is crucial to predicting the effect of habitat perturbations on fish communities. It is also an essential step in the assessment of the functional diversity. Using two complementary three-matrix approaches (fourth-corner and RLQ analyses), we tested the hypothesis that feeding-oriented traits determine the spatial distributions of littoral fish species by assessing the relationship between fish spatial distributions, fish species traits, and habitat characteristics in two Laurentian Shield lakes. Significant associations between the feeding-oriented traits and the environmental characteristics suggested that fish communities in small lakes (displaying low species richness) can be spatially structured. Three groups of traits, mainly categorized by the species spatial and temporal feeding activity, were identified. The water column may be divided in two sections, each of them corresponding to a group of traits related to the vertical distribution of the prey coupled with the position of the mouth. Lake areas of low structural complexity were inhabited by functional assemblages dominated by surface feeders while structurally more complex areas were occupied by mid-water and benthic feeders. A third group referring to the time of feeding activity was observed. Our work could serve as a guideline study to evaluate species traits x environment associations at multiple spatial scales. Our results indicate that three-matrix statistical approaches are powerful tools that can be used to study such relationships. These recent statistical approaches open up new research directions such as the study of spatially based biological functions in lakes. They also provide new analytical tools for determining, for example, the potential size of freshwater protected areas.

Habitat‐based polymorphism is common in stream fishes

Morphological differences (size and shape) across habitats are common in lake fish where differences relate to two dominant contrasting habitats: the pelagic and littoral habitat. Repeated occurrence of littoral and pelagic morphs across multiple populations of several lake fish species has been considered as important evidence that polymorphism is adaptive in these systems. It has been suggested that these habitat-based polymorphic differences are due to the temporal stability of the differences between littoral and pelagic habitats. Although streams are spatially heterogeneous, they are also more temporally dynamic than lakes and it is still an open question whether streams provide the environmental conditions that promote habitat-based polymorphism. We tested whether fish from riffle, run and pool habitats, respectively, differed consistently in their morphology. Our test compared patterns of morphological variation (size and shape) in 10 fish species from the three stream habitat types in 36 separate streams distributed across three watersheds. For most species, body size and shape (after controlling for body size) differed across riffle, run and pool habitats. Unlike many lake species, the nature of these differences was not consistent across species, possibly because these species use these habitat types in different ways. Our results suggest that habitat-based polymorphism is an important feature also in stream fishes despite the fact that streams are temporally variable in contrast to lake systems. Future research is required to assess whether the patterns of habitat-based polymorphism encountered in streams have a genetic basis or they are simply the result of within generation phenotypic plasticity.

Multiscale codependence analysis: an integrated approach to analyze relationships across scales.

The spatial and temporal organization of ecological processes and features and the scales at which they occur are central topics to landscape ecology and metapopulation dynamics, and increasingly regarded as a cornerstone paradigm for understanding ecological processes. Hence, there is need for computational approaches which allow the identification of the proper spatial or temporal scales of ecological processes and the explicit integration of that information in models. For that purpose, we propose a new method (multiscale codependence analysis, MCA) to test the statistical significance of the correlations between two variables at particular spatial or temporal scales. Validation of the method (using Monte Carlo simulations) included the study of type I error rate, under five statistical significance thresholds, and of type II error rate and statistical power. The method was found to be valid, in terms of type I error rate, and to have sufficient statistical power to be useful in practice. MCA has assumptions that are met in a wide range of circumstances. When applied to model the river habitat of juvenile Atlantic salmon, MCA revealed that variables describing substrate composition of the river bed were the most influential predictors of parr abundance at 0.4-4.1 km scales whereas mean channel depth was more influential at 200-300 m scales. When properly assessed, the spatial structuring observed in nature may be used purposefully to refine our understanding of natural processes and enhance model representativeness.

Effects of environmental fluctuations on fish metabolism: Atlantic salmon Salmo salar as a case study

Using Atlantic salmon Salmo salar parr as study species, recent findings are summarized on how (1) diurnal variations in water temperature affects standard metabolic rate, (2) shelter may reduce routine metabolic rate and (3) fluctuations of water speed affect the costs of activity. The results suggest that the accuracy of bioenergetics models can be hampered if the effects of environmental fluctuations are omitted. Incorporating environmental fluctuations into estimates and models of fish metabolism will not only improve the accuracy of energy budget calculations, but also have crucial management implications for conservation and improve the capacity to predict effects of climate change.

NSERC's HydroNet: A National Research Network to Promote Sustainable Hydropower and Healthy Aquatic Ecosystems

Abstract NSERCs HydroNet is a collaborative national five-year research program initiated in 2010 involving academic, government, and industry partners. The overarching goal of HydroNet is to improve the understanding of the effects of hydropower operations on aquatic ecosystems, and to provide scientifically defensible and transparent tools to improve the decision-making process associated with hydropower operations. Multiple projects are imbedded under three themes: 1) Ecosystemic analysis of productive capacity offish habitats (PCFH) in rivers, 2) Mesoscale modelling of the productive capacity offish habitats in lakes and reservoirs, and 3) Predicting the entrainment risk of fish in hydropower reservoirs relative to power generation operations by combining behavioral ecology and hydraulic engineering. The knowledge generated by HydroNet is essential to balance the competing demands for limited water resources and to ensure that hydropower is sustainable, maintains healthy aquatic ecosystems and a vibr...

Phylogenetics to help predict active metabolism

This paper shows how to build predictive models involving phylogenetic information to estimate metabolic traits such as active metabolic costs. Fish swimming cost is often estimated from body mass and swimming speed. The parameters of the relationships between these variables and swimming cost vary among species because each species has its own morphology and physiology. It is now widely recognized that traits are phylogenetically structured. Using new statistical approaches, it is possible to both correct swimming cost models for statistical phylogenetic non-independence and use the inherent phylogenetic signal to improve models. With these models one can extend, to a larger set of species, empirical knowledge about traits that are difficult to obtain; swimming cost is one such trait. Swimming cost accounts for a large and variable component of a fish energy budget, yet models have only been developed from observations performed on a few species, thereby constraining the scope of bioenergetic models. Her...