A stochastic bioenergetics model-based approach to translating large river flow and temperature into fish population responses: the pallid sturgeon example

Abstract

In managing fish populations, especially at-risk species, realistic mathematical models are needed to help predict population response to potential management actions in the context of environmental conditions and changing climate while effectively incorporating the stochastic nature of real world conditions. We provide a key component of such a model for the endangered pallid sturgeon (Scaphirhynchus albus) in the form of an individual-based bioenergetics model influenced not only by temperature but also by flow. This component is based on modification of a known individual-based bioenergetics model through incorporation of: the observed ontogenetic shift in pallid sturgeon diet from marcroinvertebrates to fish; the energetic costs of swimming under flowing-water conditions; and stochasticity. We provide an assessment of how differences in environmental conditions could potentially alter pallid sturgeon growth estimates, using observed temperature and velocity from channelized portions of the Lower Missouri River mainstem. We do this using separate relationships between the proportion of maximum consumption and fork length and swimming cost standard error estimates for fish captured above and below the Kansas River in the Lower Missouri River. Critical to our matching observed growth in the field with predicted growth based on observed environmental conditions was a two-step shift in diet from macroinvertebrates to fish.Bioenergetics models can be used in fish life-history models to help partition energy intake based on the laws of thermodynamics, where the energy consumed by a fish must balance the energy required by physiological processes and growth (Enders & Scruton 2006). A bioenergetics model provides an approach of estimating the consumed energy that is partitioned into three basic components: metabolism, waste loss and growth. This modelling framework accounts for the energy cost experienced by the fish and is used to solve for the level of consumption consistent with the observed growth, integrating the array of environmental conditions experienced by the fish (Moss 2001). Essentially, bioenergetics models are used to understand the relationship between growth and feeding rates under different environmental conditions. Over the last few decades, bioenergetics models have been used widely as a tool in fisheries management and the agricultural industry to address issues related to management of sport fish populations (Chipps & Wahl 2008).One well-known bioenergetics modelling approach used in fisheries is known as the Wisconsin model (Kitchell et al. 1977); its application has been reviewed by Hanson et al. (1997). The Wisconsin model refers to an approach that incorporates maximum feeding rates (C max ) and P values (% of C max ) as a way to explore consumption patterns. The P values are meant to put consumption estimates into context (i.e. a fish feeding at 40% or 95% of C max ). As part of the Wisconsin approach, consumption is equated to the sum of metabolic cost, waste loss and net gain in weight, wi...

Subtle physiological and morphological differences explain ecological success of sympatric congeners

“…This is supported by other modeling approaches in which a shift to higher quality prey fish by pallid sturgeon was necessary to attain growth rates observed in the field (Wildhaber et al. ). Moreover, fish prey comprises the majority of large (>50 cm) juvenile pallid sturgeon diets, indicating that young pallid sturgeon depend more on higher quality prey than shovelnose sturgeon (Gerrity et al.…”

Range-wide assessment of pallid sturgeonScaphirhynchus albus(Forbes & Richardson, 1905) relative condition

“…Pallid sturgeon shift their diet from macroinvertebrates to fish between lengths of 500 and 700 mm, and are completely piscivorous by 700 mm (Gerrity et al., ; Grohs et al., ; Winders & Steffensen, ). Juvenile pallid sturgeon readily feed on diptera, ephemeroptera, decapoda, and trichoptera (Grohs et al., ; Winders & Steffensen, ), which have a mean caloric density of 3065.8 J/g compared to a caloric content of 4473.5 J/g (Wildhaber et al., ). To consume the caloric equivalent of a single, small‐bodied fish, a juvenile pallid sturgeon feeding on macroinvertebrates likely needs a longer forage period.…”

Hierarchical stochastic modelling of large river ecosystems and fish growth across spatio-temporal scales and climate models: the Missouri River endangered pallid sturgeon example

“…A substantial focus of this study was the development of a stochastic bioenergetics model for fish growth. Specifically, to translate water velocity and temperature into fish growth, we implement a daily time step, individual-based, bioenergetics model for the endangered pallid sturgeon based on a basic pallid sturgeon bioenergetics model (Chipps et al 2008), combined with swimming energetics described for other sturgeon species (Geist et al 2005); a general description is given below (details of the model can be found in Wildhaber et al 2015). The parameters of the bioenergetics model were estimated through field study of pallid and other sturgeon species, extrapolated across different size classes or kept constant throughout the population (Tetzlaff et al 2011).…”

“…Our bioenergetics model (as originally described by Kitchell et al 1977) (Wildhaber et al 2015) is fundamentally based on the following simple relationship that conserves energy input and output:…”