Estrategias de conservación frente a múltiples amenazas: el cormorán moñudo en el Parque Nacional Marítimo Terrestre de las Islas Atlánticas de Galicia

Velando, A. & Munilla, I. Estrategias de conservación frente a múltiples amenazas: el cormorán moñudo en el Parque Nacional Marítimo Terrestre de las Islas Atlánticas de Galicia. En: Proyectos de investigación en Parques Nacionales 2006-2009. 377-395. Organismo Autónomo de Parques Nacionales. (2010).


Este trabajo ha profundizado en el conocimiento de la biología y la ecología de las poblaciones de cormorán moñudo, Phalacrocorax aristotelis, del Parque Nacional marítimo y terrestre de las Islas Atlánticas de Galicia. Se ha estudiado el uso que hacen los moñudos del espacio marítimo, lo que ha permitido establecer que variables físicas como la profundidad y la presencia de fondos de arena son relevantes para explicar su distribución en el medio marino. El análisis de recuperaciones y de los avistamientos de aves marcadas durante el estudio, indican que los cormoranes del Parque Nacional constituyen una unidad de conservación válida. Los censos, efectuados en tres años consecutivos, señalan un fuerte y generalizado descenso de la población nidificante, pues se ha pasado de 2047 parejas en 2004 a 911 en 2009 (-56%). De acuerdo con los criterios de la Lista Roja de la UICN los moñudos del Parque Nacional padecen un grave riesgo de extinción puesto que satisfacen criterios correspondientes a las categorías “En Peligro” y “En Peligro Crítico”. El estudio identificó asimismo los posibles factores responsables de la mala situación que atraviesa el cormorán moñudo en el Parque Nacional: a) Aumento de la mortalidad en artes menores de enmalle (betas, miños y trasmallos); b) Reducción en la provisión de lanzones (Ammodytidae), quizás achacable a los efectos prolongados de la marea negra del Prestige que contaminó los fondos de arena donde viven estos peces, pues se ha puesto de manifiesto una fuerte asociación entre el éxito reproductor de los moñudos del Parque y la importancia del lanzón en su dieta; c) La interferencia de las embarcaciones de recreo, que excluyen a los cormoranes de sus mejores zonas de alimentación y provocan un aumento de la competencia interespecífica; y, d) La reciente aparición de ejemplares de visón americano en las colonias de cría. Al tener en cuenta el efecto de los factores limitantes identificados sobre las variables demográficas, se puso de manifiesto que tan solo mediante la adopción de varias medidas de manejo que combinen la reducción de la mortalidad de adultos y juveniles con un reforzamiento del éxito reproductivo, es posible invertir la tendencia que, desde hace más de 15 años viene arrastrando la población de cormoranes del Parque Nacional. Según los resultados de los modelos demográficos de simulación, los esfuerzos de conservación han de concentrarse en las medidas que inciden en el aumento de la supervivencia de los adultos, pues son las que más atenúan el declive poblacional; por lo tanto, las medidas encaminadas a reducir la mortalidad en artes de pesca y la depredación de los carnívoros terrestres deben ser priorizadas.

Short-term indirect effects of the Prestige’ oil spill on European shags: changes in availability of prey

Velando, A., Munilla, I. & Leyenda, P. M. Short-term indirect effects of the Prestige’ oil spill on European shags: changes in availability of prey. Marine Ecology Progress Series 302, 263–274 (2005).

In 2003, immediately following the ‘Prestige’ oil spill in Galicia, Spain, we studied the reproductive performance of European shags Phalacrocorax aristotelis at Illas Cíes, the main breeding ground for the species in Spain. Over the 10 yr preceding the spill, we monitored the breeding and the dynamics of the Illas Cíes population. We performed 1000 simulations of the population dynamics using the population parameters and their variability for the pre-spill period. The number of breeding
pairs counted in 2003 was lower than any of the values predicted by the simulation models, suggesting that population parameters changed after the ‘Prestige’ wreck. Environmental conditions cannot explain the observed effects because weather conditions were far from severe in 2003. The analysis of shag casualities showed that despite the extensive oiling of Illas Cíes and nearby waters it is unlikely that shags were killed in large numbers. Nevertheless, the shag feeding grounds around Illas Cíes, which are mainly sandy bottoms, were continuously exposed to oil pollution throughout the shag breeding season as revealed by the high levels of pollutants in sediments, plankton, and other organisms. In the pre-spill years, shags showed low seasonal dietary variation, feeding mainly on sandeels. Nevertheless, in 2003, there was a dietary shift with a lower occurrence of sandeel that, together with sandeel fishery data, indicate lower sandeel availability at foraging areas. In addition, reproductive performance in 2003 was significantly lower and chick condition was poorer compared to the pre-spill years. When all this information is taken into account, the picture that emerges strongly suggests that the European Shag population in Illas Cíes is suffering a negative impact of an indirect nature mediated through a reduction on the availability of a highly preferred forage-fish.

Intercolony and seasonal differences in the breeding diet of European shags on the Galician coast (NW Spain)

Velando, A. & Freire, J. Intercolony and seasonal differences in the breeding diet of European shags on the Galician coast (NW Spain). Marine Ecology Progress Series 188, 225–236 (1999).


The seasonal and spatial variations in the dlet of the European shag Phalacrocorax aristotelis were studied during the breeding period, based on the analysis of 202 adults’ pellets (February to June, 1995) and 30 regurgitatons of chicks (April, May and June, 1995 and 1996) taken from 2 colonies located in close proximity to one another ( < l 5 km) on the coast of Galicia (W Spain; Islands of Cies and Ons). The diet of birds from the Cies Islands consisted mainly of sandeels (family Ammodytidae), which make up over 70% of the prey during all months. These fishes went practically unreported in a number of previous studies of fish communities in the region, probably due to the low catchability of trawl nets and the possibility that the habitats of sandeels where shags forage, shallow (<10 to 15 m) sandy bottoms, were not sampled adequately. Seasonal changes were found on the Island of Ons, where in winter (February and March) the diet was based on gobids (family Gobiidae) and sand smelts Atherina presbyter, while In spring the dominant prey were the Ammodytidae (in May and June they made up over 86%). The consumption of sandeels established an increased similarity in diet between the colonies throughout the breeding cycle, and they were the only prey whose abundance was negatively correlated with the diversity of each pellet. This study highlights the high plasticity in prey and feeding habitats (both pelagic and benthic with different types of substrates) used by the European shag. It should be noted, however, that the main prey during chick rearing are sandeels. Differences were found in the mean sizes of the different prey consumed, but the modal size for all of them throughout the season was around 9 to 11 cm in total length. The range of sizes available in the environment is greater than the range chosen by the European shag, which suggests that this bird selects a narrow range of prey sizes.