In situ target strength measurements of Peruvian anchovy (Engraulis ringens) from data collected by a commercial echosounder during fishing operations

Santivañez-Yuffra M.; Pereira-Letona N.; Vasquez-Paredes C. · Fisheries Research (2025) · DOI: 10.1016/j.fishres.2025.107534

Resumen

Although fishing vessels have been used as opportunistic scientific platforms in the last two decades, target strength (TS) studies based on industry-collected data are still scarce. Here we present an in situ TS estimation of Peruvian anchovy (Engraulis ringens) from data recorded by a 120 kHz Simrad ES60 commercial echosounder mounted on the purse-seiner “Maru” in May-July 2017 during its fishing operations on North-Center stock area. TS-length (L) relationships (TS=a Log10 (L)+b, with b= b20 when a= 20) were estimated from pooled data using a curve fitting method. Influence of depth (Z) on TS was also investigated. Mean TS of 10–16.5 cm individuals was −54.2 dB (±0.2 dB) with corresponding a, b and b20 values of 22.2, −79.5 dB and −77 dB. TS showed strong dependence with depth following Boyle's law: TS= 20Log10(L)-6.4Log10(1-Z/10)-73.3 dB (r2=0.8). Our TS and b20 estimates are in line with existing values for E. ringens in Perú but are lower than those published for the same species in Chile and from other members of the Engraulis genus. Results reported here can be used for biomass estimation during periods not covered by systematic surveys, helping to achieve near-real time monitoring of stocks.