The invariance of production per unit of food consumed in fish populations.
The amount of biomass production per unit of food consumed (P/Q) represents an important quantity in ecosystem functioning, because it indicates how efficient a population transforms ingested food into biomass. Several investigations have noticed that P/Q remains relatively constant (or invariant) across fish population that feed at the same food-type level (carnivorous/herbivorous). Nevertheless, theoretical explanation for this invariant is still lacking. In this paper, we demonstrate that P/Q remains invariant across fish populations with stable-age distribution. Three key assumptions underpin the P/Q invariant: (1) the ratio between natural mortality M and von Bertalanffy growth parameter k (M/k ratio) should remain invariant across fish populations; (2) a parameter defining the fraction of ingested food available for growth needs to remain constant across fish that feed at the same trophic level; (3) third, the ratio between length at age 0 ([Formula: see text]) and asymptotic length ([Formula: see text]) should be constant across fish populations. The influence of these assumptions on the P/Q estimates were numerically assessed considering fish populations of different lifespan. Numerical evaluations show that the most critical condition highly relates to the first assumption, M/k. Results are discussed in the context of the reliability of the required assumption to consider the P/Q invariant in stable-age distributed fish populations.
Center for Applied Ecology and Sustainability (CAPES), Pontificia Universidad Católica de Chile, Avenida Libertador Bernardo O'Higgins 340, Santiago, Chile. rodrigo.wiff@gmail.com.
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Wiff
Instituto de Matemáticas, Pontificia Universidad Católica de Valparaíso, Blanco Viel 596, Cerro Barón, Valparaiso, Chile.
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Barrientos
Modelización y análisis de recursos naturales (MAREN), CURE Rocha, Universidad de la República, Ruta 9 km 210, 27000, Rocha, Uruguay.
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Comisión de Investigaciones Científicas de la Provincia de Buenos Aires, La Plata, Argentina.|Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), Paseo Victoria Ocampo No. 1, 7600, Mar del Plata, Argentina.
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D000818:Animals; D001522:Behavior, Animal; D018533:Biomass; D017753:Ecosystem; D005247:Feeding Behavior; D005399:Fishes / Q000502:physiology*; D016014:Linear Models; D008954:Models, Biological; D015203:Reproducibility of Results; D013045:Species Specificity
Biomass production; Food consumption; Invariance; Life history theory; Von Bertalanffy