Acoustic biomass estimation and uncertainty of Pacific hake and Humboldt squid in the Northern California current in 2009.

Abstract

The population of Humboldt squid (Dosidicus gigas) has seen an explosion in the Eastern North Pacific over the last several years. The species has gone from being rarely seen in the waters off OR, WA, and BC to becoming a major predator in the marine food web in this area. This population explosion has the potential to cause large impacts in major fish stocks. The biennial 2009 Joint U.S.-Canada Pacific hake (Merluccius productus) acoustic trawl survey also noted large amounts of Humboldt over much of the survey area. Because Humboldt squid could be acoustically confused with Pacific hake, and because the presence of Humboldt squid disrupted the normal shoaling pattern of hake, an estimated depth threshold was used to help distinguish Humboldt squid from hake. Accordingly, the biomass estimate of Pacific hake for 2009 was less certain. Several methods were explored to quantify the uncertainty and assess the reliability of the hake biomass estimate.