Trophic ecology of the squid Doryteuthis gahi in the Southwest Atlantic inferred from stable isotope analysis

The Patagonian longfin squid Doryteuthis gahi has an annual life cycle with two seasonal cohorts (autumn and spring spawners). Previous studies estimated the trophic level of adult squid by stable isotope analysis of their muscle or gladius tissues, but few studies compared different sizes and spawning cohorts. In this study, mixed models were used to compare carbon ( δ 13 C) and nitrogen ( δ 15 N) stable isotope signatures of muscle and gladius tissues of the autumn and spring spawning cohorts and squid of different sizes. A published isoscape model provided δ 15 N baselines to calculate the trophic level of D. gahi . Sampled herbivorous prey such as Euphausiacea, planktonic juveniles Munida gregaria and salps Ihlea supported the trophic level estimates. The autumn spawning cohort had higher δ 13 C values than the spring spawning cohort. δ 15 N values increased with increasing dorsal mantle length, suggesting an ontogenetic change towards larger prey. Muscle tissue was enriched in 15 N but slightly depleted in 13 C compared to gladius tissue. Adult squid had an estimated trophic level of ~3.2, with no significant differences between spawning cohorts. Stable isotope values followed a seasonal trend, with lower δ 15 N values and lower δ 13 C value between July and September. Large individuals of the spring spawning cohort were found to have the least niche overlap with other groups of D. gahi . Our study of the trophic levels and ecology of D. gahi can provide important information on its role in the food chain and can build the basis of studies on interaction with other species, and the impact of environmental changes on their populations. This information can inform the development of management strategies aimed at preserving the balance of the ecosystem and ensuring its sustainable use.

• Publication year

  2023

• Venue

  Estuarine, Coastal and Shelf Science

• Publication date

  2023-03-01

• Fields of study

  Not labeled

• Identifiers
  DOI 10.1016/j.ecss.2023.108300
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar

• No claims are published for this paper.

• No concepts are published for this paper.

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