Assessment of economic loss caused by the illegal extraction of seeds of Peruvian scallop Argopecten purpuratus in Independencia Bay (14°15’S) during the 2015-2017 warm period

Abstract

The SST in Independencia Bay (14°15’S), between 2015 and 2017, was characterized by positive thermal anomalies, which peaked at +3.0 °C in January 2016. This condition favored the population growth of Peruvian scallop (Argopecten purpuratus) in its natural banks. Although it is an illegal activity, the availability of their seeds generated expectations for their extraction. given the significant demand for seeds to be used in enclosures, within and outside the bay. A total of 3.32 t, with a mean height of 22.4 mm, was landed in Laguna Grande in March 2016, then landings increased to 20.77 t in June of the same year. By the end of the year, the total amount was 59.665 t. The availability of seeds was low in 2017, with landings in September amounting to 0.13 tons; practically all the natural banks were exhausted. We estimated, based on landings and individual weights, an extraction of 19,691 million seeds, which generated a marketing value of 1,026 million soles (about US$ 309 million in that time). Their projected sizes at 12 months (K = 0.5 year-1, L∞ = 118 mm, t0 = 0), when the scallops reach their commercial size, would correspond to a value of 9.846 million soles (about US$ 2,857 million in that time). This estimation allows us to determine an economic loss higher than 8 million soles, in addition to the population loss of the resource caused by this illegal activity, since warm conditions favor the frequency of the reproductive activity (repeated spawning events) that supply new cohorts to the population. Thus, the illegal extraction of scallops’ seeds affected the yields of the natural banks of Independencia Bay during the 2017 coastal El Niño, impacting the species natural cycle.