Assessment of feeding patterns of the mottled scorpionfish (Pontinus clemensi) in the Galapagos Marine Reserve

Abstract

The mottled scorpionfish (Pontinus clemensi) is a species of high economic, cultural and ecological value in the archipelago, which is exposed to possible overexploitation for local consumption. Trophic information is essential not only to provide insights into their role in the ecosystem but also provides a theoretical basis for the management of these resources. We determined the feeding patterns of P. clemensi applying complementary techniques of stomach content analysis (SCA) and stable isotope analysis (SIA). Sampling was conducted at four sites of fishing importance within the Galpagos Marine Reserve (GMR) between November 2017 and April 2018, obtaining 105 stomachs and muscle samples. The Prey-specific Index of Relative Importance (%PSIRI) determined Anchoa ischana as the most important prey, with differences (p < 0.05) in its consumption between seasons, sex, and life stages. However, the δ¹³C values did not show differences (p > 0.05) between sexes and life stages, suggesting the use of the same feeding areas. The δ¹⁵N values showed differences (p < 0.05) between seasons and life stages, pointing towards the consumption of prey from different trophic levels depending on the seasonality and size of the individual. A specialist-type feeding strategy was determined in most categories (Bi < 0.6) except for juveniles that display a possible generalist tendency (Bi = 0.64). The calculated trophic level (TL) places it as a tertiary-secondary consumer (SCA = 4.26, SIA = 3.72), characterized by consuming prey of similar trophic position (OI = 0.14), which led to a high isotopic overlap between groups. Our results constitute baseline information on the feeding patterns of P. clemensi in the GMR and highlights the value of ecological studies in the ecosystem-based fisheries management.