the humboldt current system of northern and central chile - figema

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MARTIN THIEL ET AL.Sea surfacetemperatureanomaly °C3210−1−2−3Numbers10000100010010Nesting pairsn.d.JanuaryFebruaryNumbers20001000Boobies at sean.d. n.d.1999 2000 2001 2002 2003 2004Numbers40002000Total birdsPercent of all seabirds at sea0302010302010n.d.n.d.Percent in feeding flocksn.d.n.d.Percent attendingfishing vesselsn.d. n.d. 0 01999 2000 2001 2002 2003 20040Figure 8 Abundance of breeding and foraging seabirds in the vicinity of Coquimbo, Chile (30°S), and therelationship with sea-surface temperature (SST) anomalies in the southeast Pacific. Upper panel shows SSTanomalies during the study period; middle panel shows nesting pairs of Peruvian boobies in a breeding colonyon Pájaros Island (29°35′S), and boobies counted during censuses at sea in the Upwelling system of Coquimbo,between 29°08′ and 30°11′ (see Weichler et al. 2004 for more details); lower panel shows total number of allseabirds counted in the study area in January of each year, and the percentage of birds foraging in feedingflocks or attending fishing vessels in search of food.useful quantitative assessment of the impact of marine vertebrates on fish stocks and may serve topredict changes in fishery practices or effects of fish stock sizes on seabird and seal numbers.Simple predictions would be that species with specialised feeding methods and a high dependenceon specific diets, which have been reduced in availability (due to fisheries or oceanographic226
THE HUMBOLDT CURRENT SYSTEM OF NORTHERN AND CENTRAL CHILEconditions), would be most likely to decline in numbers. In order to develop the models to testthese predictions, a long-term research programme is necessary to assess (1) breeding populations,(2) feeding ecology, (3) reproductive biology and (4) energy budgets, under different environmentalconditions. In particular, it appears to be important to examine the breeding biology of seabirds.There is an indication that populations of seabirds in northern and central Chile may be limited bythe availability of undisturbed breeding islands (see Schlatter 1984, 1987, Schlatter & Simeone1999). While additional research is necessary, present knowledge already identifies the protectionof undisturbed breeding sites as one of the highest priorities for seabird conservation in the HCSof northern and central Chile.Sandy beachesSandy beaches are a common feature of the Chilean coast between 18°S and 41°S (Figure 9), wherethey offer breeding habitats and important food resources for migrating shorebirds. The extent anddistribution of sandy beaches offers unique opportunities for studying the factors driving thepopulation dynamics of invertebrate consumers along the coast of northern and central Chile.Beaches are found along exposed shorelines, sheltered bays and coastal islands and their total extentand average length show a clear latitudinal trend, increasing toward southern-central Chile(Figure 9). Sandy beaches of the coast of Chile show a general zonation pattern of three zones thatdiffer both in their physical characteristics and biological communities (Figure 10) (Jaramillo 1987,Average distancebetween beaches (km)Average lengthof beaches (km)Total extentof beaches (km)6 4 2 0 6 4 2 0 300 200 100 0−18°−20°−22°−24°−26°−28°−30°−32°−34°−36°−38°−40°−42°Southern latitudeA B CFigure 9 (A) Average distance (mean ± standard error) between beaches, (B) average length of individualbeaches, and (C) total extent of sandy beaches within each sector; individual sectors correspond to the coastlinebetween two subsequent degrees of latitude (information extracted from GOOGLE-EARTH, a total of 810sandy beaches were measured between 18°S and 42°S).227
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the humboldt current system of northern and central chile - figema

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