El Niño costero 2017

impact on population of Tagelus dombeii (Lamarck, 1818) and community structure of macrobenthos in the Isla Blanca-ENAPU, Peru

Abstract

Information from two population assessments of Tagelus dombeii in the Isla Blanca-ENAPU natural bank (El Ferrol Bay) in June 2016 (before EN) and June 2017 (after EN) was analyzed. Changes in the macrobenthos structure are described. For population estimation, the area of the bank evaluated was considered, as well as mean density and biomass per depth stratum; for mortality, double valves in “vital position” (recent deaths) per 1 m2 were counted. For the macrobenthos community structure, richness, Pielou’s equity, Shannon diversity, Simpson dominance, and biological value index were analyzed. The decrease in population was 92.3% in June 2017 as compared to June 2016, resulting from the high temperatures of February (25.6 °C) and March (26.8 °C), which were above the maximum tolerance of 25.1 °C determined for the species. In 2016, the catches varied from 14 to 17 t/station, maintaining those levels throughout the year; in 2017, the catches in summer and autumn were 22.1 and 6.5 t, respectively, and they decreased 61% in autumn 2017 as compared to autumn 2016. Species richness declined after the effects of El Niño in the summer of 2017. The dominance of species in June 2016, represented by T. dombeii, Nassarius gayii and Pagurus villosus, was replaced in June 2017 by N. gayii for having a greater survival strategy, mobility and ability to vary or combine their eating habits from predator to necrophagus. T. dombeii, as a target species, went from being an abundant and frequent species in June 2016 to an intermediate common species in June 2017.