Merluccius productus : Evidence of a Specialized Predator in the Gulf of California Ecosystem

ABSTRACT Merluccius productus , commonly referred to as the Pacific Hake, is well known as a relevant species in the structure and functioning of its marine food web networks, acting as a foraging species. Additionally, it represents an important resource for the fishing industry. Nevertheless, little is known about its feeding habits. Therefore, this work describes the diet of the Pacific hake inhabiting the Gulf of California. Samples were obtained from six exploratory fishing research trips conducted between 2014 and 2017. The Prey‐Specific Index of Relative Importance (%PSIRI) was used to quantify the dietary components of the Pacific hake. Additionally, to determine its feeding strategy, a similarity analysis was conducted and the Levin's Index and Morisita–Horn Index were calculated. The sampling included 1772 organisms with sizes ranging from 13.3 to 98.4 cm TL. The analysis of 39.2% of stomachs revealed the presence of different prey items, allowing the identification of 23 distinct prey types grouped into three categories: bony fish, crustaceans, and mollusks. The Prey‐Specific Index of Relative Importance indicated that the diet is mainly composed of Solenocera mutator (25.2%), fish remains (24.9%), Nyctiphanes simplex (18.7%), and Benthosema panamense (8.3%), collectively accounting for 77.1% of the diet composition. The low Levin's index value (Bi = 0.19) classified the Pacific hake as a specialized predator, while the Morisita–Horn index indicated a moderate level of dietary overlap (Cλ = 0.42). The temporal similarity analysis revealed an overall similarity of 60%, allowing the identification of three distinct groups. Notably, Group B, composed of stomach contents from F‐2014 and C‐2014, exhibited a higher similarity of 76.1%. The highest contribution to the similarity of this group was represented by the euphausiids N. simplex (41.03%). Our results suggest that M. productus primarily feeds on highly abundant and available prey species in its environment, predominantly pelagic crustaceans, performing vertical migration to feed. The high frequency of crustaceans such as S. mutator and N. simplex , along with the fish B. panamense , further supports the classification of M. productus as a specialized predator.