TY - JOUR AU - Buscaglia Solé, M. AU - Sielfeld, W. AU - Aguayo Lobo, A. PY - 2021/12/31 Y2 - 2024/03/28 TI - Relative abundance and density of dolphins (Mammalia: Delphinidae) between 18° and 25°S in the Humboldt Current System, northern Chile JF - Anales del Instituto de la Patagonia JA - AIP VL - 49 IS - SE - DO - 10.22352/AIP202149019 UR - https://analesdelinstitutodelapatagonia.cl/article/view/993 SP - AB - <p>Relative abundances and relative densities of dolphins in Northern Chile (18°30'S-70° 27'W; 25°23'S-72°53'W) between March and December 2000, are informed using 99 fringe transects (length 31.7-162.4 km; mean 95.26 ± 22.14 km).&nbsp; During the study 5841 individuals corresponding to 8 species were sighted.</p><p>The relative abundance of species in general, presented a main peak between 23°-23°59´S (0.48 ind/km) and a secondary peak at 19°-19°59´S (0.21 ind/km). The relative density for the total area was 0.13 ind/km<sup>2</sup> (standard error 0.03) and the highest relative density was recorded between 23°-23°59´S (0.254 ind/km<sup>2</sup>; standard error 0.129). The 18°-18°59´S sector showed the lowest relative density (0.04 ind/km<sup>2</sup>). At the species level, the relative abundances were less than 0.1 ind/km, except <em>Lissodelphis peronii</em> (0.33 ind/km), restricted to the 22°-24°S sector, and <em>Tursiops truncatus</em> (0.12 ind/km) at 22°-23°S.</p><p>In the oceanic sector (west of 71°W) <em>T. truncatus</em> was more abundant between 22°-23°9´S (0.085-0.110 ind/km), and in the neritic sector (east of 71°W) it was between 19°-21°59´S (0.140-0.244 ind/km). <em>Globicephala macrorhynchus</em> and <em>Grampus griseus</em> were mainly oceanic, with a main maximum (0.04 ind/km) between 18°-18°59´S and a secondary maximum (0.02 ind/km) at 22°-22° 59´S. In the neritic sector these species were only present between 21°-21°59´S, and with very low representation (0.005 ind/km).</p><p><em>Tursiops truncatus</em> was the most abundant species and the only one with a constant presence throughout the study period (100% of monthly periods) and present in 17.2% of the transects. For the entire study area it presented an estimated mean relative density of ??0.45 ind/km<sup>2</sup> (standard error = 0.0157; coefficient of variation = 3.399).</p><p>The information is discussed in the context of previous studies in the area, and its importance in the design and implementation of conservation and ecosystem management.</p> ER -