Temperature effects on size, maturity, and abundance of the squid Illex argentinus (Cephalopoda, Ommastrephidae) on the Patagonian Shelf

Abstract

Cephalopod fisheries have expanded over the last decade. They are characterised by annual uncertainty in yield quantity and quality. This is attributed to changes in environmental conditions such as temperature combined with the semelparous life strategy (one reproductive cycle during life) of the majority of squid species. We determined the effect of environmental temperature on several individual- and population-level characteristics of Illex argentinus, a squid species in the South Atlantic that sustains one of the largest commercial squid resources in the world. The effect of temperature on dorsal mantle length, proportion of mature females, and abundance was determined in the context of the I. argentinus life cycle periods, and migration patterns. This was achieved by performing 520 linear regressions using a 20-year time series of fisheries data and monthly temperature data from the key regions associated with I. argentinus life cycle on the Patagonian Shelf in the Southwest Atlantic. Temperatures above 17.5 °C in the hatching grounds lead to smaller and less mature females in the Falkland Islands waters, during the feeding period. Larger females, a higher proportion of mature and maturing females, and a lower abundance of I. argentinus were found in the Falkland Islands waters when temperatures in the migration areas were higher than 13.5 °C. These findings will aid in the forecasting and assessment for future fishing seasons of this vital squid resource in the Southwest Atlantic.