{'fraction_non_alphanumeric': 0.01920062695924765, 'fraction_numerical': 0.00039184952978056425, 'mean_word_length': 5.446969696969697, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
SEAPODYM.V2: A SPATIAL ECOSYSTEM AND POPULATION DYNAMICS MODEL WITH PARAMETER OPTIMIZATION PROVIDING A NEW TOOL FOR TUNA MANAGEMENT

An enhanced version of the spatial ecosystem and population dynamics model SEAPODYM is presented to describe spatial dynamics of tuna and tuna-like species in the Pacific Ocean. It includes the modelling of mid-trophic organisms of the pelagic ecosystem with several pelagic mid-trophic functional groups. Parametrization of the dynamics of these components is based on an allometric relationship. Then, a simple energy transfer from primary production is used, justified by the existence of constant slopes in log-log biomass size spectrum relationships. Impacts of vertical behaviour of the organisms and horizontal currents are considered through a system of advection-diffusion equations. Dynamics of tuna populations have been revised. This new version of SEAPODYM includes expanded definitions of habitat indices, movements, and natural mortality based on empirical evidences and first biological principles. A thermal habitat of tuna species is derived from an individual heat budget model. The feeding habitat is computed according to the accessibility of tuna predator cohorts to different vertically migrating and non-migrating micronekton (mid-trophic) functional groups. The spawning habitat is based on temperature and the coincidence of spawning fish with presence or absence of predators and food for larvae. The successful larval recruitment is linked to spawning stock biomass. Larvae drift with currents, while immature and adult tuna can move of their own volition, in addition to being advected by currents. A food requirement index is computed to adjust locally the natural mortality of cohorts based on food demand and accessibility to available forage components. Together these mechanisms induce bottom-up and top-down effects, and intra-(i.e. between cohorts) and inter-species interactions. The model is now fully operational for running multi-species, multi-fisheries simulations, and the structure of the model allows a validation from multiple data sources. In particular, the model includes a rigorous mathematical parameter optimization using catch data and size frequency of catch. Examples of applications are presented to illustrate the interest of the model for management of tuna stocks in the context of climate and ecosystem variability, and to investigate potential changes due to anthropogenic activities including global warming and fisheries pressures and management scenarios.