Flawed evidence supporting the Metabolic Theory of Ecology may undermine goals of ecosystem-based fishery management: the case of invasive Indo-Pacific lionfish in the western Atlantic

Abstract

Given its ability to yield predictions for very diverse phenomena based only on two parameters—body size and temperature—the Metabolic Theory of Ecology (MTE) has earned a prominent place among ecology’s efficient theories. In a seminal article, the leading proponents of the MTE claimed that the theory was supported by evidence from Pauly’s (On the interrelationships between natural mortality, growth parameters, and mean environmental temperature in 175 fish stocks. Journal Du Conseil International Pour L’Exploration de la mer 39:175–192) dataset on natural mortality, biomass, and environmental temperature for 175 fish stocks spanning tropical, temperate, and polar locations. We demonstrate that the evidence presented by the proponents of the MTE is flawed because it fails to account for the fact that Pauly re-estimated environmental temperatures for polar fish as ‘physiologically effective temperatures’ to correct for their ‘abnormally’ high natural (mass-corrected) mortalities, which on average turned out to be similar to (rather than lower than) the mortalities recorded for temperate fish. Failing to account for these modifications skews the coefficients from MTE regression models and wrongly validates predictions from the theory. It is important to point out these deficiencies given the broad appeal of the MTE as a theoretical framework for applied ecological research. In a recent application, the MTE was used to estimate biomass production rates of prey fish in a model of invasive Indo-Pacific lionfish (Pterois volitans and P. miles) predation in Bahamian reefs. We show that the MTE coefficients may lead to a drastic overestimation of prey fish mortality and productivity rates, leading to erroneous estimations of target densities for ecological control of lionfish stocks. A set of robust mortality-weight coefficients is proposed as an alternative to the MTE.