Béarez et al. confuse individual migration with species range and provide no data supporting migration. Between 91 and 94% of Peruvian G. peruvianus are caught in coastal water less than 15 m deep (and all in water <35 m deep)--thus, their habitat is ideally suited to reflect regional SST (7). All age/size classes were captured throughout the El Niño/Southern Oscillation (ENSO) SST cycle in north-central Peru (2), suggesting no ontogenetic or seasonal migration. Strong correlation between modern ¹⁸O_otolith profiles and SST at Puerto Chicama demonstrates that these fish remained in nearby waters throughout their lives (1, 2).

Béarez et al. fail to explain how their hypothetical migration scenarios could cause the ¹⁸O_otolith profiles. The seasonal ¹⁸O range of the Ostra otoliths is similar to that caused by the 1997-1998 El Niño in modern otoliths, with negative summer ¹⁸O values similar to modern otoliths during El Niño (1, 2). Therefore, neither southerly nor vertical migration, both of which would result in more positive ¹⁸O values, can account for the data. For migration to cause seasonally negative ¹⁸O values, the fish would have had to transit between tropical Ecuador and central Peru twice annually. This scenario is highly unlikely for many reasons, including the tendency for fish to narrow, not expand, their ambient temperature range. ¹⁸O values at the Ostra otoliths' margin, indicating the season of death, show both winter and summer capture, further undermining the migration hypothesis.

The suggestion that local estuaries caused the ¹⁸O_otolith profiles is misleading to those unfamiliar with the Peruvian coast. Compared to other regions, the Peruvian shore face is steep, the tidal range is narrow, and the volume of water in the braided rivers is low. The Peruvian "estuaries" are only small river mouths. The ¹⁸O_water in the mouth of the Santa ranges from -12.8 to -14.1 (8). No otoliths record any value similar to this.

Regarding the proper identification of otoliths, archaeological remains were originally identified to family level for sea catfish (Ariidae) at Ostra and Siches (5, 9). The otoliths were later identified as G. peruvianus because they are morphologically most similar to otoliths from that species, which is the only common ariid in the area today. All archaeological G. peruvianus are identified this way, including those of Béarez (10). As Béarez et al. note, the only alternative species to G. peruvianus are tropical, contradicting their assertion of temperate SST. The otoliths in (1, 8) were bisected at perpendicular angles; thus curvature variation is an artifact of sample preparation and meaningless for identification.

Although Béarez et al. are correct that Siches is 4°30'S, their argument regarding its significance is unfounded. The difference in mean SST between the Paita and Talara datasets is less than 0.4°C, not 2° to 4°C (11, 12). This small variation is within the ~3° to 4°C range we stated in (1) and does not change our conclusions. Furthermore, the Siches samples contain the smallest ¹⁸O range of all the otoliths. This suggests that these fish did not pass through a large temperature gradient, supporting our arguments for the non-migratory nature of the fish and the significance of our paleotemperature estimates.

The comments by Béarez et al. focusing on diversity, equitability, and trophic level are based on a misinterpretation of our text. We do not attribute causality to presence/absence of anchovies alone, but to changes in the overall food web in response to upwelling variation (1). Thus, the comments related to anchovy range have no bearing on our conclusions about multispecies ecosystem changes.

In their discussion of Ostra, Béarez et al. suggest that the former embayment near this site could have provided habitat for some fish species. Geochemical records from embayment mollusks suggest this environment was evaporative (13, 14). As stated in (1), fish entering the embayment would record more positive, not more negative, ¹⁸O_otolith values. Thus, the embayment cannot account for the ¹⁸O_otolith profiles.

Béarez et al. suggest that a sessile proxy may be better suited for SST reconstructions. To that end, we present ¹⁸O data from the cockle Trachycardium procerum (Figs. 1 and 2) that corroborate our enhanced seasonality interpretation of otolith data from Ostra. Modern T. procerum were collected near Casma in 1984 after the strong 1982-1983 El Niño (15). The ¹⁸O_shell range measured during El Niño is 1.5 (Fig. 1). Including published data from contemporaneous T. procerum, the mean El Niño range is ~1.3 (13, 15). The ¹⁸O range from an Ostra shell (5830 ± 90 ¹⁴C yrs B.P.) is 1.6 (Fig. 2). The mean ¹⁸O range in four T. procerum from fossil deposits near Ostra is ~1.5 (13). All but one ancient shell have ¹⁸O ranges greater than that measured in carbonate precipitated before the 1982-1983 El Niño depicted in Fig. 1 (13). It is unlikely that each of these five shells, dating to four different periods (5500 ± 150 to 6100 ± 150 ¹⁴C yrs B.P.), grew during an El Niño event of equal or greater magnitude than the 1982-1983 event. A more likely explanation is enhanced seasonality similar to that measured in the contemporaneous otoliths (1). This conclusion is supported by the Ostra specimen (Fig. 2) that contains two consecutive ¹⁸O oscillations indicative of seasonal, not inter-annual, variation. Unfortunately no absolute paleotemperatures can be calculated because the Santa embayment was evaporative, thus the molluscan ¹⁸O values are elevated relative to nearby marine values (13, 14).

Béarez et al. argue that warm-tropical, transitional (wide temperature-tolerant species), and warm-temperate mollusks co-existed in the Santa embayment. We addressed this previously (16), demonstrating DeVries and Wells' data (17, 18) do not support contemporaneity of these faunas. We have now analyzed the data (13) cited by Béarez et al. and find the radiocarbon dates on mollusks in the Santa and adjacent Salinas de Chao embayments unequivocally support our contention of warmer SSTs before 5800 cal B.P. and cooler SSTs thereafter (Fig. 3) (1, 6, 19).

Close examination of the comments and citations of Béarez et al. strengthen our original interpretations. Our data represent the most direct measurement of mid-Holocene paleotemperature on the coast of Peru, and are part of a larger body of research supporting the hypothesis of significant changes in mid-Holocene Pacific SST and ENSO history (6, 20-25).

C. Fred T. Andrus
Savannah River Ecology Laboratory
University of Georgia
Drawer E
Aiken, SC 29802, USA
E-mail: andrus{at}srel.edu
Douglas E. Crowe
Department of Geology
University of Georgia
Athens, GA 30602, USA
Daniel H. Sandweiss
Department of Anthropology and
Institute for Quaternary and
Climate Studies
S. Stevens Hall
University of Maine
Orono, ME 04469, USA
Elizabeth J. Reitz
Department of Anthropology and
Georgia Museum of Natural History
Natural History Building
University of Georgia
Athens, GA 30602, USA
Christopher S. Romanek
Department of Geology
University of Georgia
Athens, GA 30602, USA and
Savannah River Ecology Laboratory
Drawer E,
Aiken, SC 29802, USA
Kirk A. Maasch
Department of Earth Sciences and
Institute for Quaternary and
Climate Studies
University of Maine
Bryand Global Sciences Center
Orono, ME 04469 USA

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28.	Funded in part by Department of Energy grant DE-FC09-96SR18546 (C.F.T.A., C.S.R.), Geological Society of America (C.F.T.A.), Explorer's Club International (C.F.T.A.), NSF Grant ATM-0082213 (D.E.C), the Heinz Charitable Trust (D.H.S.), and the University of Maine Faculty Research Fund (D.H.S.).