Diet Composition and Ecological Role of Argentine Shortfin Squid Illex argentinus in Energy Accumulation: A Review

Abstract

The Argentine shortfin squid Illex argentinus is a pelagic neritic cephalopod species found in the southwest Atlantic Ocean. The squid is characterized by a short lifespan, fast growth, and semelparous reproduction. The squid is one of most important targeted species in global cephalopod fisheries and plays a key role as transient "biological pumps" in the southwest Atlantic ecosystem. The squid is a highly migratory species and can migrate hundreds or even thousands of miles between its spawning and feeding ground to complete its life cycle. The squid adopts a mixed income-capital breeding strategy, where the reproduction is mainly supported by energy acquired and mobilized rapidly during the breeding season, coupled with using energy reserves when energy demands for reproduction are robust. The squid shows spatial differences in feeding habits and also shift diets as they grow, leading to different trophic niches. In general, the squid diet shifts from crustaceans to fish and cephalopods as they mature. Given the fact that species in a higher trophic position have greater energy content, a diet shift to fish and cephalopods is expected to meet the energy demands for reproduction. In the present review, we summarized the characteristics of energy accumulated in soma and reproductive systems for I. argentinus, which shows a dramatic increase in energy in the reproductive tissues when the squid reaches maturation. In addition, we compiled previous studies that focused on diet composition and trophic roles in the southwest Atlantic ecosystem, where the squid feeds voraciously on many prey species and plays a key role as prey item for many top predators, including marine mammals. Notably, squid changes diets in relation to energy demands and resource availability. However, future research is still needed to address the functional mechanisms of the shifting dietary habits with growth. To justify the mechanism, we suggest the following priorities in the near future studies: (1) evaluate the relationships between energy acquisition and migratory habits; (2) clarify feeding strategies that potentially maximize the energy gain; and (3) address the potential effect of the ongoing global climate change and fishery activity on the role of energy transfer in the southwest Atlantic ecosystem. Such research would advance our understanding of the species and support the sustainability of resource exploitation.

Keywords

• illex argentinus
• energy accumulation
• diet composition
• ecological niche
• cephalopod