Application of a bioenergetics growth model for European anchovy (Engraulis encrasicolus) linked with a lower trophic level ecosystem model

Abstract

A bioenergetics model is implemented for European anchovy (Engraulis encrasicolus) and applied to the north-eastern Aegean Sea (eastern Mediterranean Sea). The model reproduces the growth of anchovy in a one-way linked configuration with a lower trophic level (LTL) ecosystem model. The LTL model provides densities for three zooplankton functional groups (heterotrophic flagellates, microzooplankton and mesozooplankton) which serve as available energy via consumption for the anchovy model. Our model follows the basic structure of NEMURO.FISH type models (North Pacific Ecosystem Model for Understanding Regional Oceanography for Including Saury and Herring). Several model parameters were specific for the Mediterranean or the Black Sea anchovy and some others were adopted from related species and NEM-URO.FISH due to lack of biological information on E. encrasicolus. Simulation results showed that the fastest growth rate occurs during spring and the slowest growth rate from August to December. Zooplankton abundance during autumn was low implying that decreased prey density lead to a reduction in anchovy weight, especially for the age-3 class. Feeding parameters were adjusted to adequately fit the model growth estimates to available weight-at-age data. A detailed sensitivity analyses is conducted to evaluate the importance of the biological processes (consumption, respiration, egestion, specific dynamic action, excretion and egg production) and their parameters to fish growth. The most sensitive parameters were the intercept and exponent slope of the weight-dependent consumption and respiration process equations. Fish weight was fairly sensitive to temperature-dependent parameters.

Trophodynamics of anchovy in a non-upwelling system: direct comparison with sardine

“…To our knowledge, this is the first time that consumption estimates for juvenile European anchovy have been provided in the literature, even though such information is very important for the development of fish bioenergetics models (e.g. Politikos et al 2011). Adult consumption estimates in summer were similar to those reported for the western Mediterranean during the spawning period (Catalan Sea: 3.9% TW; Tudela & Palomera 1995, Gulf of Lions: 4% TW; Plounevez & Champalbert 2000).…”

“…In recently developed small pelagic fish bioenergetics models, plankton consumption has been modeled as a function of prey density alone, without accounting for any predator density effects (e.g. Politikos et al 2011). However, Arditi & Ginzburg (1989 argue that, more basically the dependence of the predator-prey functional response should be on the ratio of prey density to predator density, thus introducing the 'ratio-dependent' functional response model.…”

Seasonal changes in growth and condition of anchovy late larvae explained with a hydrodynamic-biogeochemical model simulation

“…Additional information on the mean oceanographic conditions in the study area during the period that the larvae were growing (recent environmental history) was obtained by outputs of a 3D coupled hydrodynamic−biogeochemical model (Politikos et al 2011, Tsiaras et al 2012) simulation in the North Aegean Sea over the same period.…”

“…The biogeochemical model is based on the European Seas Ecosystem Model (ERSEM, Baretta et al 1995) and was adopted by Petihakis et al (2002) after further calibration/validation against available remote sensing and in situ data , Politikos et al 2011. ERSEM is a comprehensive 'functional' type model that describes pelagic and benthic ecosystem dynamics, taking into account all of the important processes operating both at the physiological and community level, such as growth, respiration, lysis, excretion, mortality and grazing.…”

“…in spring), current measurements may not be representative of the actual conditions that the fish experienced during their development and that may have ultimately determined the mean growth rate in the larval/juvenile sample. In addition to using in situ collected environmental information, we also explored the use of a 3D coupled hydro dynamic−biogeochenical model implemented in the North Aegean Sea (Politikos et al 2011, Tsiaras et al 2012 to assess the environmental conditions that the larvae may have experienced during their development and provide a better understanding of the causes of seasonal changes in mean growth rate and somatic condition.…”