The recruitment dynamics of the nylon shrimp Heterocarpus reedi, effects of climate and predation off Chile

Climate variability and predation influence the fluctuations in the recruitment of exploited marine populations. This study analyses the dynamics of the recruitment of the nylon shrimp (Heterocarpus reedi Bahamonde 1955) over the period 1968 and 2015, considering the influence of climate variability and the biomass of hake (Merluccius gayi), as a proxy for predation in its distribution area. We collected the Humboldt Current Index (HCI) and Southern Oscillation Index (SOI) time series as climate variables and estimates of recruitment and spawning biomass of nylon shrimp, as well as biomass of hake. Annual deviations in nylon shrimp recruitment showed increased sensitivity to climate variability and hake biomass, expressed through a significant cumulative correlation over time. The recruitment drives the spawning biomass, implying an environmentally driven shrimp recruitment dynamic. Generalized Linear Models showed that hake biomass and climate indices affect negative and positively the shrimp recruitment during the recruitment year, respectively. A path diagram with Structural Equation Models showed that SOI impacted HCI, negatively impacting the hake stock. Hake negatively affected the shrimp stock biomass and recruitment, and SOI either directly or indirectly, through its effect on the hake. The hake impact on the shrimp's spawning stock and recruitment is due to predation under concurrent climate variability on longer-term periods.