Abstract

LLERENA, Alizon; MARQUEZ, Cruz; SNELL, Howard L.  and  JARAMILLO, Alberto. Abundance of Amblyrhynchus cristatus in El Niño (97-98) and La Niña (01-02) in Santa Cruz, Galapagos. Ecol. apl. [online]. 2004, vol.3, n.1-2, pp.87-91. ISSN 1726-2216.

The marine iguana (Amblyrhynchus cristatus Bell, 1825) is an endemic species in Galapagos that forages in the sea (Bartholomew & Vleck, 1979). Scientific studies of marine iguanas have shown that El Niño Southern Oscillation events (ENSO) produce negative impacts on the fauna of the isles (Wikelski & Corinna, 2000; Romero & Wikelski, 2001) and in 1997 the Charles Darwin Foundation (CDF) established a permanent sampling site in southern Santa Cruz Island, between Punta Núñez and the CDF dock, to obtain scientific information and extrapolate it to understand the effect of El Niño on other marine iguana populations of the archipelago and their recuperation in succeeding years. Abundance was recorded along a 6.1 km transect divided into sections of 100 m (61 sections) on one day each month. ANOVA and Student’s t-tests were used to compare abundance in El Niño (1997-98) and La Niña years (2001-2002), using only data from the second six months of each year; they differed significantly (t= 4.349, P<0.004). On comparing the abundance of population classes of A. cristatus, adult males were less common during El Niño than during La Niña (t= 2.195; P<0.0039). Among females, abundance means did not differ (t= 0.171; P0.44), while in juveniles the difference is significant, indicating population recuperation in La Niña (t= 7.337; P<0.0004). The results indicate that marine iguanas, after an El Niño event, take about 4 years to recover.

Keywords : Abundante; El Niño-La Niña; Amblyrhynchus cristatus; Santa Cruz; Galapagos.

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