Anchoveta (Engraulis ringens) Biomass in the Peruvian Marine Ecosystem Estimated by Various Hydroacoustic Methodologies during spring of 2019

The Hydroacoustic Pelagic Resources Assessment survey (Cruise 1909-11) was conducted along the Peruvian coast (03°23'S-18°21'S) between 29 September and 15 November 2019 with the participation of three scientific research vessels from the Peruvian Marine Research Institute (Instituto del Mar del Peru, IMARPE), the R/V José Olaya Balandra, the R/V Flores Portugal and the R/V Humboldt. Using the acoustic data collected by the three scientific vessels we estimated the anchoveta biomass using seven hydroacoustic methodologies by applying the following three types of techniques in the processing and subsequent analysis of the eco-acoustic records for the frequencies of 120 and 38 kHz: stratification by isoparalitoral areas; stratification by transects; and by geostatistics. The three best anchoveta biomass estimates were 8.37 million tons obtained with the method of stratification by isoparalitoral areas using the 120 kHz acoustic frequency data; 8.47 million tons obtained with the transect stratification method using data from the 38 kHz frequency; and 8.22 million tons obtained with the geostatistical delta method using the 120 kHz frequency data with coefficients of variation of 5.44%, 13.71%, and 33.21%, respectively. Special attention was paid in the analyzes of the size distribution, in the length-weight relationship of the anchovy obtained in the survey 1909-11 and the use of the Target Strength (TS) equations, taking into account the great influence these may have on the population biomass estimates irrespective of the hydroacoustic technique being used. Based on the results obtained, we conclude that the anchoveta population in the Peruvian marine ecosystem is in an abundant and healthy state, although its abundance and in particular its distribution pattern may be affected by anomalous climatic events.