Anchoveta (Engraulis ringens) Biomass in the Peruvian Marine Ecosystem Estimated by Various Hydroacoustic Methodologies during Spring of 2019: A Recent Study

The Hydroacoustic Pelagic Resources Assessment survey (Cruise 1909-11) was carried out along the Peruvian coast (03°23'S-18°21'S) between September 29 and November 15, 2019, with the involvement 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. We estimated anchoveta biomass using seven hydroacoustic methodologies based on the acoustic data collected by the three scientific vessels. We used 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 stratification by geostatistics. The three best anchoveta biomass estimates were 8.37 million tonnes acquired with the method of stratification by isoparalitoral areas using the 120 kHz acoustic frequency data; 8.47 million tonnes obtained with the transect stratification technique using data from the 38 kHz frequency; and 8.22 million tonnes obtained with the geostatistical delta method using the 120 kHz frequency data, with coefficients of variation of 5.44 percent, 13.71 percent, and 33.21 percent, respectively. The analyses of the size distribution, the length-weight relationship of the anchovy obtained in the survey 1909-11, and the use of the Target Strength (TS) equations received special attention due to the large influence these may have on population biomass estimates regardless of the hydroacoustic technique used. Based on the findings, we conclude that the anchoveta population in the Peruvian marine ecosystem is abundant and healthy, though its abundance and, in particular, its distribution pattern may be influenced by climatic events.