Ecosystem-based modeling of Pacific hake (Merluccius productus) in the Gulf of California: Evidence of potential functional redundancy and fisheries implications

Understanding the ecological role of exploited species requires evaluating abundance and food – web interactions. Pacific hake ( Merluccius productus ) is an important demersal fishery resource in the northern Gulf of California, but its ecosystem role remains poorly understood. This study used Ecopath with Ecosim (EwE) to evaluate the trophic role of Pacific hake, examine trophic patterns consistent with potential functional redundancy, and assess biomass responses under alternative fishing - effort scenarios. The model included 23 functional groups and represented juvenile and adult hake separately to account for ontogenetic differences in trophic interactions. An exploratory temporal comparison indicated that simulated CPUE broadly reproduced the overall pattern of observed Pacific hake CPUE. Juvenile and adult hake differed in trophic position, omnivory, and trophic interactions, supporting the ecological relevance of representing life stages separately. Neither life stage was identified as a keystone species according to the selected index; instead, Pacific hake was embedded within multiple trophic pathways, a pattern consistent with potential functional redundancy in the modeled food web. The highest keystone index value corresponded to benthic macroinvertebrates, highlighting the importance of lower trophic-level components. Ecosim simulations showed progressively greater declines in Pacific hake biomass as fishing effort increased. Incorporating life-stage structure provided additional ecological resolution in the ecosystem model. Although Pacific hake was not identified as a keystone species, its position within multiple trophic pathways provides structural evidence consistent with potential functional redundancy. These findings support ecosystem-based management of the demersal fishery in the northern Gulf of California.