Influence of feeding conditions on breeding of African penguins importance of adequate local food supplies

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1 The following supplement accompanies the article Influence of feeding conditions on breeding of African penguins importance of adequate local food supplies Joël M. Durant 1,*, Robert J. M. Crawford 2,3, Anton C. Wolfaardt 3,4,5,6, Kobus Agenbag 2, Johan Visagie 4, Leisha Upfold 2, Nils Chr. Stenseth 1,7 1 Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, PO Box 1066 Blindern, 0316 Oslo, Norway 2 Oceans & Coasts, Department of Environmental Affairs, Private Bag X2, Rogge Bay 8012, South Africa 3 Animal Demography Unit, Department of Zoology, University of Cape Town, Rondebosch 7701, South Africa 4 CapeNature, Private Bag X29, Rondebosch 7701, South Africa 5 Marine Research Institute, University of Cape Town, Rondebosch 7701, South Africa 6 Joint Nature Conservation Committee, PO Box 585, Stanley, FIQQ 1ZZ, Falkland Islands 7 Institute of Marine Research, Flødevigen Marine Research Station, 4817 His, Norway * j.m.durant@bio.uio.no Marine Ecology Progress Series 420: (2010) 1

2 Supplement 1. Additional information on the study and results Fig. S1. Major African penguin colonies (D) in the Western Cape, South Africa. Cape Town is indicated by and the study colony, Dassen Island, indicated with a double mark, is divided into 9 management areas (see insert). Burrow nests in portions of 5 of these areas (areas A, B, D, F, G) were checked regularly (about once every 15 d) between 1995 and 2008 for the presence of breeding birds 2

3 Table S1. Correlation analysis matrix using Pearson s product moment between environmental variables. Df = 12 p r SOI t SOI t 1 ln(anchovy) ln(sardine) Mean SST nursery Mean Max. SST nursery Max. SOI t SOI t ln(anchovy) ln(sardine) Mean SST nursery Mean Max. SST nursery > Max

4 Fig. S2. Schedules of time series used in the study (see Fig. S3) 4

5 Fig. S3. Time series used in the study: (a) Proportion of burrows occupied (Max-O) at Dassen Island, (b) Mean date of burrow occupancy (Date-O) in Julian dates with 1 = 1 October, (c) Per Capita breeding population growth rate, (d) Sardine and anchovy biomass (in 000 tonnes) estimated by hydro-acoustic surveys in November (from information in de Moor et al. 2008), (e) Southern Oscillation Index (SOI; yearly average calculated on 12 mo starting 1 October), (f) Sea Surface Temperature (SST in C) from satellite imagery calculated for the nursery and spawning grounds 5

6 Fig. S4. Influence of the abundance of fish, in log(1000 tonnes), as estimated by hydroacoustic surveys in November, on the purse-seine catch of fish, in log(tonnes), around Dassen Island in the following year (sum for the 12 mo). The dotted blue line shows the linear relationship between biomass and catch for anchovy. Estimates of the yearly fish catch of sardines and anchovies around Dassen Island were obtained from J. van der Westhuizen (Department of Agriculture, Forestry and Fisheries) Fig. S5. Relationship between explanatory variables. Model predicted values are given by 1 covariate effects (Y t = α + s 1 (x 1,t ) + ε with s being a nonparametric smoothing function, specifying the effect of the covariates x on the dependent variable Y; α being an intercept; and ε being a stochastic noise term). (a,b) Anchovy abundance, (c) Sardine abundance, and (d) Max. SST at the spawning ground. In (c) and (d) the slope of the linear relationship is indicated 6

7 For all graphs, s(x,y) is the smoothing term where X represents the explanatory variable and y is the estimated degrees of freedom of the smoothing term. The shaded areas indicate the pointwise 95% confidence intervals. : partial residuals around the significant covariate effects The exploration of the explanatory variables showed a negative effect of SOI on sea temperature at the spawning ground (Fig. S5d). In other words, our results are consistent with previous studies showing that the temperature pattern in the Alghulas region is driven by the SOI (e.g. Schumann et al. 1995). Our results show also a positive effect of SST at the spawning ground on both fish populations (Fig. S5a,b for anchovy and Fig. S5c for sardine). The link between SOI and African penguins breeding as shown by our models (Table 1) can thus be explained by an indirect relationship involving the action of SST on fish production LITERATURE CITED de Moor CL, Butterworth DS, Coetzee JC (2008) Revised estimates of abundance of South African sardine and anchovy from acoustic surveys adjusting for echosounder saturation in earlier surveys and attenuation effects for sardine. Afr J Mar Sci 30: Schumann EH, Cohen AL, Jury MR (1995) Coastal sea surface temperature variability along the south coast of South Africa and the relationship to regional and global climate. J Mar Res 53: