Shannon, C. E., and Weaver, W., 1949. The Mathematical Theory
of Communication. Urbana: University of Illinois Press.
Spellerberg, I. F., and Fedor, P. J., 2003. A tribute to Claude
Shannon (1916–2001) and a plea for more rigorous use of
species richness, species diversity and the ‘Shannon – Wiener’
Index. Global Ecology and Biogeography, 12, 177–179.
Cross-references
Species Richness
SHELL BEDS
Luca Ragaini
Department of Earth Sciences, University of Pisa, Pisa,
Italy
Synonyms
Coquinas; Lumachelles; Shell gravels
Definition
Dense deposits of biologic hard parts more than 2 mm in
size in estuarine and other environments are generally
defined as shell concentrations (Kidwell, 1991). They
are also known as coquinas, lumachelles, or shell gravels,
as well as the more familiar term “shell beds.”
Description
Although the term “shell beds” refers to a particular geometric arrangement of biogenic remains, the great variety
of shell beds reflects the diverse descriptive approaches
used to classify them. The scheme proposed by Kidwell
et al. (1986) is based on different field observations
of the shell deposits, such as their biofabric, geometry,
taxonomic composition and internal structure, which can
be measured in the field by nonspecialists. This procedure
allows investigators to obtain a range of ecological, hydrodynamic, and topographic data on the mode of the shell
bed formation (Fursich, 1995).
There are different classification schemes for shell beds.
In the basic approach proposed by Kidwell et al. (1986),
shell beds may be plotted in six areas of a schematic ternary
diagram: biologic, sedimentologic, and diagenetic processes are the end-members, whereas three mixed areas
reflect combinations of these factors. Comparative analysis
may yield data on environmental indicators to characterize,
according to prevailing shell bed types, the ideal transect
from marginal marine to fully marine depositional settings,
even if the same type of shell bed may appear in different
environments. In general terms, marginal marine environments (e.g., estuaries) exhibit a diverse assortment of biogenic and sedimentologic concentrations. In the intertidal
and supratidal settings, for example, biogenic concentrations include channel-margin oyster bars, mussel clumps,
levels of deep-burrowing infaunal bivalves in life position,
ray pits, bird’s nests, and hermit crab-generated beds,
whereas sedimentologic concentrations may be produced
by lateral migration of channels and by storm surges
(shell pavements and spits). The more refined genetic
scheme proposed by Kidwell (1991) on the basis of their
depositional histories and stratigraphies organizes shell
beds into four broad categories: event, composite, hiatal,
and lag concentrations. In this manner, the interpretation
yields a stratigraphic signature of the shell-rich sedimentary
body to identify the final concentration process and
a “taphonomic characterization” of the fossil remains to
reconstruct their history before and during the concentration event(s). These four types of shell beds are not
discrete categories because they intergrade, and each one
may be present in the supra-, inter-, and subtidal environments characterizing the estuarine systems.
Bibliography
Fursich, F. T., 1995. Shell concentrations. Eclogae Geologicae
Helvetiae, 88(3), 643–655.
Kidwell, S. M., 1991. The stratigraphy of shell concentrations. In
Allison, P. A., and Briggs, D. E. G. (eds.), Taphonomy. London:
Plenum Press, pp. 211–290.
Kidwell, S. M., Fursich, T. T., and Aigner, T., 1986. Conceptual
framework for the analysis and classification of fossil concentrations. Palaios, 1(3), 228–238.
Cross-references
Biogenic Sedimentary Structures
Biogenous Sediment
Sedimentary Structures
Stratigraphy of Estuaries
SHELLFISH PRODUCTION
Islay D. Marsden
School of Biological Sciences, University of Canterbury,
Christchurch, New Zealand
Definition
Shellfish production involves evaluation of shellfish
resources, often collated from annual surveys, listing the
wet weight and monetary value of capture fisheries and
aquaculture. In ecological terms, production quantifies
biological productivity, the amount of organic matter, or
its equivalent in dry matter, carbon, or energy which is
accumulated over time.
Introduction
World fisheries and aquaculture production have
increased over the past five decades at a rate of 3.2 %
per year to 148 million tons, worth $217.5 billion USA
dollars, with most used for human consumption (FAO,
2012). Highest consumption has been in Asia, where
annual consumption reached 20.7 kg/capita. In China,
with an expanding economy and increased domestic
SHELLFISH PRODUCTION
573
of Communication. Urbana: University of Illinois Press.
Spellerberg, I. F., and Fedor, P. J., 2003. A tribute to Claude
Shannon (1916–2001) and a plea for more rigorous use of
species richness, species diversity and the ‘Shannon – Wiener’
Index. Global Ecology and Biogeography, 12, 177–179.
Cross-references
Species Richness
SHELL BEDS
Luca Ragaini
Department of Earth Sciences, University of Pisa, Pisa,
Italy
Synonyms
Coquinas; Lumachelles; Shell gravels
Definition
Dense deposits of biologic hard parts more than 2 mm in
size in estuarine and other environments are generally
defined as shell concentrations (Kidwell, 1991). They
are also known as coquinas, lumachelles, or shell gravels,
as well as the more familiar term “shell beds.”
Description
Although the term “shell beds” refers to a particular geometric arrangement of biogenic remains, the great variety
of shell beds reflects the diverse descriptive approaches
used to classify them. The scheme proposed by Kidwell
et al. (1986) is based on different field observations
of the shell deposits, such as their biofabric, geometry,
taxonomic composition and internal structure, which can
be measured in the field by nonspecialists. This procedure
allows investigators to obtain a range of ecological, hydrodynamic, and topographic data on the mode of the shell
bed formation (Fursich, 1995).
There are different classification schemes for shell beds.
In the basic approach proposed by Kidwell et al. (1986),
shell beds may be plotted in six areas of a schematic ternary
diagram: biologic, sedimentologic, and diagenetic processes are the end-members, whereas three mixed areas
reflect combinations of these factors. Comparative analysis
may yield data on environmental indicators to characterize,
according to prevailing shell bed types, the ideal transect
from marginal marine to fully marine depositional settings,
even if the same type of shell bed may appear in different
environments. In general terms, marginal marine environments (e.g., estuaries) exhibit a diverse assortment of biogenic and sedimentologic concentrations. In the intertidal
and supratidal settings, for example, biogenic concentrations include channel-margin oyster bars, mussel clumps,
levels of deep-burrowing infaunal bivalves in life position,
ray pits, bird’s nests, and hermit crab-generated beds,
whereas sedimentologic concentrations may be produced
by lateral migration of channels and by storm surges
(shell pavements and spits). The more refined genetic
scheme proposed by Kidwell (1991) on the basis of their
depositional histories and stratigraphies organizes shell
beds into four broad categories: event, composite, hiatal,
and lag concentrations. In this manner, the interpretation
yields a stratigraphic signature of the shell-rich sedimentary
body to identify the final concentration process and
a “taphonomic characterization” of the fossil remains to
reconstruct their history before and during the concentration event(s). These four types of shell beds are not
discrete categories because they intergrade, and each one
may be present in the supra-, inter-, and subtidal environments characterizing the estuarine systems.
Bibliography
Fursich, F. T., 1995. Shell concentrations. Eclogae Geologicae
Helvetiae, 88(3), 643–655.
Kidwell, S. M., 1991. The stratigraphy of shell concentrations. In
Allison, P. A., and Briggs, D. E. G. (eds.), Taphonomy. London:
Plenum Press, pp. 211–290.
Kidwell, S. M., Fursich, T. T., and Aigner, T., 1986. Conceptual
framework for the analysis and classification of fossil concentrations. Palaios, 1(3), 228–238.
Cross-references
Biogenic Sedimentary Structures
Biogenous Sediment
Sedimentary Structures
Stratigraphy of Estuaries
SHELLFISH PRODUCTION
Islay D. Marsden
School of Biological Sciences, University of Canterbury,
Christchurch, New Zealand
Definition
Shellfish production involves evaluation of shellfish
resources, often collated from annual surveys, listing the
wet weight and monetary value of capture fisheries and
aquaculture. In ecological terms, production quantifies
biological productivity, the amount of organic matter, or
its equivalent in dry matter, carbon, or energy which is
accumulated over time.
Introduction
World fisheries and aquaculture production have
increased over the past five decades at a rate of 3.2 %
per year to 148 million tons, worth $217.5 billion USA
dollars, with most used for human consumption (FAO,
2012). Highest consumption has been in Asia, where
annual consumption reached 20.7 kg/capita. In China,
with an expanding economy and increased domestic
SHELLFISH PRODUCTION
573