Bioen Maintenance

Maintenance

The mobilized energy $E_M$ fuels all metabolic processes starting in priority with the costs of maintenance of existing tissues $E_m$, which is often referred to as the standard metabolic rate in ecophysiology literature. Here, we include in maintenance costs also routine activities of individuals including foraging and digestion, so that they might be compared to routine metabolic rate in the ecophysiology literature. The maintenance costs are explicitly modeled to describe the share of mobilized energy between maintenance and the production of new tissues (CTW01, HJorgensen14, MEBR10), with precedence of the former over the latter, as well as to link mechanistically starvation mortality to energetic starvation when neither mobilized energy nor gonad energy reserves can cover the costs of maintenance (see next section New tissue production for more details).

The maintenance energy rate $E_m$ scales with individual’s somatic mass $w(i,t)$ with the same exponent as maximum ingestion rate. Thus, for a given temperature, the production of new tissues, and notably somatic growth, is not limited by disproportionately increasing maintenance costs relative to ingestion rate as somatic mass increases (LMN17, LMN18). In addition, the maintenance rate also increases with the temperature $T(i,t)$ experienced by individuals (GCW+02) and can be described as

$$ E_m(i,t) = C_m w(i,t)^{\beta} \varphi_m(T(i,t)) $$

with $C_m$ the mass-specific maintenance rate and $varphi_m$ the Arrhenius function describing the effect of temperature on $E_m$, defined as:

$$ \varphi_m(T(i,t)) = e^{\dfrac{-\varepsilon{}_m}{k_B T}} $$

with $\varepsilon{}_m$ the activation energy for maintenance rate increase with temperature.

---

CTW01 Eric L Charnov, Thomas F Turner, and Kirk O Winemiller. Reproductive constraints and the evolu- tion of life histories with indeterminate growth. Proceedings of the National Academy of Sciences, 98(16):9460–9464, 2001.

HJorgensen14 Rebecca E Holt and Christian Jørgensen. Climate warming causes life-history evolution in a model for atlantic cod (gadus morhua). Conservation Physiology, 2(1):cou050, 2014.

MEBR10 Fabian M Mollet, Bruno Ernande, Thomas Brunel, and Adriaan D Rijnsdorp. Multiple growth-correlated life history traits estimated simultaneously in individuals. Oikos, 119(1):10–26, 2010.

LMN17 Sjannie Lefevre, David J McKenzie, and Göran E Nilsson. Models projecting the fate of fish popula- tions under climate change need to be based on valid physiological mechanisms. Global Change Biology, 23(9):3449–3459, 2017.

LMN18 Sjannie Lefevre, David J McKenzie, and Göran E Nilsson. In modelling effects of global warming, invalid assumptions lead to unrealistic projections. Global change biology, 24(2):553–556, 2018.

GCW+02 James F Gillooly, Eric L Charnov, Geoffrey B West, Van M Savage, and James H Brown. Effects of size and temperature on developmental time. Nature, 417(6884):70–73, 2002.