Trophic variability of long tail hake Macruronus magellanicus in the Southwestern Atlantic: movements evidenced by stomach content and stable isotope analysis

Abstract

Studying the trophic ecology of marine fishes in their natural habitat provides insights into their behavior, their role in community dynamics, and in energy flow through ecosystems. The long tail hake Macruronus magellanicus Lönnberg, 1907, is distributed from 35°S in the Atlantic Ocean and 33°S in the Pacific Ocean and supports important fisheries around the southern tip of South America. The trophic ecology of this species was evaluated in the Southwestern Atlantic (52°–56°S, 106 to 932 m depth) for the first time. This is the main fishing area in the southern region of its distribution. Stomach contents and C and N stable isotope analysis were used to assess ontogenetic and spatial variability in long tail hake diet. The main prey items identified in the stomach contents varied spatially, differentiating three feeding grounds with euphausiids, Fuegian sprats (Sprattus fuegensis), and squat lobsters (Munida gregaria) as the main prey in each. However, these differences were not reflected in the stable isotope signals of their muscles. Our results suggest that long tail hake move between feeding grounds in a shorter time period than the isotopic turnover rate of muscle (~ 2–5 months). Independent of the feeding grounds, both methodologies showed ontogenetic variability in diet. Our evidence suggests in the southern tip of South America, long tail hake move among grounds to take advantage of the availability of different resources. These results provide valuable information on the trophic ecology of long tail hake to consider in management and conservation policies.