2 results
Evaluating fish scale preservation in sediment records from the oxygen minimum zone off Peru
- Renato Salvatteci, David B. Field, Timothy Baumgartner, Vicente Ferreira, Dimitri Gutierrez
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- Journal:
- Paleobiology / Volume 38 / Issue 1 / Winter 2012
- Published online by Cambridge University Press:
- 08 April 2016, pp. 52-78
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- Article
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Fish scales accumulating in marine laminated sediments can provide a record of population variability of small pelagic fishes. Although some studies have noted signs of scale degradation that could affect estimates of population variability, there are presently no well-developed means to evaluate degradation. We developed several indices as indicators of fish scale preservation in two box-cores that we collected off Pisco (14°S), one at 301 m near the center of the oxygen minimum zone (OMZ), and the other at 201 m near the upper limit of the OMZ. These indices include (1) an index of fish scale integrity (estimate of scale wholeness relative to fragmentation), (2) the fungi-free area of fish scales and vertebrae, (3) the ratio of fish scales to vertebrae (as well as fish scales to vertebrae and bones), and (4) the ratio of whole scales to fragments. We address whether lower numbers of anchovy scales occurring in association with reduced total organic carbon fluxes and higher bottom-water oxygen concentrations are due entirely to lower abundances of anchovy or whether differential preservation of the fish scales in the sediments plays an important role in reduced scale abundances. Comparison of temporal sequences between the two cores provides the means to assess whether there are differences in the preservation of fish scales. The combined indices indicate that the lower numbers of fish scales in the earliest period have been affected by degradation, and to a greater degree in the box-core from 201 meters, which can be subject to higher oxygen concentrations. On the other hand, decadal-scale variations in fish scale abundance within the period of better preservation are unlikely to be caused by degradation. We discuss the utility and drawbacks of different indices of preservation for reconstructing past changes in fish population sizes with fluxes of fish debris and also briefly discuss the utility of these indices to other paleobiological systems.
4 - Variability from scales in marine sediments and other historical records
- Edited by Dave Checkley, Scripps Institution of Oceanography, University of California, San Diego, Jürgen Alheit, Yoshioki Oozeki, Claude Roy
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- Book:
- Climate Change and Small Pelagic Fish
- Published online:
- 08 January 2010
- Print publication:
- 20 August 2009, pp 45-63
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- Chapter
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Summary
Summary
Records of variability in populations of small pelagic fishes exist from a variety of historical sources that precede industrial fishing catch records. We review the historical records of artisanal fisheries, archeological remains, and fish remains from marine sediments. Fish scale deposition rates from ocean sediments offer the most quantitative records with little bias from anthropogenic factors. As quantitative estimates from fish scale deposition rates and their comparison with other records depend on chronostratigraphies, we discuss chronological development in detail, as well as the preservation and significance of fish scale flux. The different historical records indicate considerable variability in small pelagics prior to industrial fishing. However, the historical records provide little support for paradigms of ecosystem variability based on industrial catch records, such as synchronous worldwide fluctuations in abundance of small pelagic from different boundary currents or alternations of sardines and anchovies within a given boundary current. Rather, a variety of different modes of variability in small pelagics is consistent with paleoceanographic evidence for many different climate states and modes of variability.
Introduction
Some of the best evidence of long-term variability in marine populations comes from different records of pelagic fishes. There is evidence from industrial catch records of many decades in length, artisanal catch records, historical observations, archeological remains, and fossil remains in marine sediments. Small pelagics reflect many aspects of climate change effects on fisheries, since their recruitment and population size are sensitive to environment conditions. However, understanding variability in population size of small pelagics is intertwined with understanding their migrations (presumably in search of ideal environmental conditions).