Inventario, abundancia y distribución espacial de mamíferos marinos y aves en las Islas Galápagos durante el Crucero Oceanográfico (Bae Orión) en abril 2009: Implicaciones para conservación

Abstract

Field surveys to determine the species, relative abundance and spatial distribution of marine mammals and sea birds were conducted during theoceanographic cruise onboard the BAE Orion around the Galapagos Islands and the Ecuadorian coast on April 02-23, 2009. A total of 90 sightings ofmarine mammals, including eleven species identified, were performed. Among the cetaceans, the following species and mean group size (mean ±SD, n) were recorded: Blue Whale, Balaenoptera musculus (1, n=1); Pilot Whale, Globicephala macrorhynchus (from 24 ± 22.6 to 29 ± 29.7, n =2);Sperm Whale, Physeter macrocephalus (4 ± 4.24, n=2); Fraser’s Dolphin, Lagenodelphis hosei (300, n=1); Stripped Dolphin, Stenella coeruleoalba(60, n=1); Pantropical Spotted Dolphin, Stenella attenuata (from 175 ± 35.4 to 200 ± 70.7, n=2); Short-beaked Common dolphin, Delphinusdelphis (119 ± 65, n=5); and, Bottlenose Dolphin, Tursiops truncatus (102 ±172, n=7). The two endemic species Galapagos pinnipeds, the Galapagossea lion (Zalophus wollebaeki), and the Galapagos fur seal (Arctocephalus galapagoensis), were also reported. Furthermore, sixteen species of sea birds from 460 sightings (1,490 birds) were identified, including two species critically endangered (CR) under the IUCN-threatened categories: the Galapagos albatross (Phoebastria irrorata), and the Galapagos Petrel (Pterodroma phaeopygia). The major sea bird species and relative abundance (number of birds) throughout the cruise track were, Galapagos/Waved albatross, P. irrorata (15); Galapagos Petrel, P. phaeopygia (24); Galapagos Shearwater, Puffinus subalaris (123); Cape Petrel, Daption capense (1); Parkinson’s Petrel, Procellaria parkinsoni (5); Pink-footed Shearwater, Puffinus creatopus (1); Wedge-rumped Storm Pertrel, Oceanodroma tethys tethys (144); Swallow-tailed Gull, Larus furcatus (119); Blue-footed Booby, Sula nebouxii excisa (46);The Nazcabobby, Sula granti (797); Red-footed Booby, Sula sula websteri (200); Magnificent Frigatebird, Fregata magnificens magnificens (11); Red-billedTropic Bird, Phaethon aethereus (11); and, Brown Pelican, Pelecanus occidentalis urinator (1). The Nazca bobby was the most abundant speciesaccounting for 51% of the total abundance of sea bird species. Most of the sightings of sea birds and marine mammal species were abundant andaggregated in places southwestern Galapagos (0º–2ºS; 94–91ºW), where generally nutrient-enriched, upwelling areas are found. However, during thecruise the areas showing the highest values of primary productivity (0.46- 0.50 mg/m3) were detected southeast of the Galapagos around 2–3ºS and88ºW, where a high abundance of sea birds was also observed. These observations underline the potential use of these warm- blooded, marinevertebrates as eco-markers of primary productivity. Several sea birds and marine mammals, including threatened species, were recorded in foragingareas off the Galapagos Marine Reserve (GMR) boundaries, implying the risk of by catch due to long-line fisheries, gillnets and other anthropogenicimpacts in these unprotected areas