ICHTHYOPLANKTON
Kenneth W. Able
Marine Field Station, Department of Marine and Coastal
Sciences, Rutgers University, Tuckerton, NJ, USA
Synonyms
Fish eggs; Fish larvae
Definition
Ichthyoplankton refers to planktonic portion of the life
history of fishes (fish eggs and fish larvae).
Description
The planktonic portion of the life history of fishes typically
begins at hatching from pelagic or benthic eggs. The duration of development of eggs and larvae is largely influenced
by temperature and can last from days to months. The
planktonic larval stages (preflexion, flexion, postflexion of
notochord) of fishes that occur in estuaries are typically
small (<20 mm but ranging up to 100 mm for the leptocephali and glass eels of anguilliform fishes). In addition,
they are incompletely developed and have adaptations for
living in the water column (transparent or nearly so, with
developing swim bladders) at the varying salinities typical
of estuaries. Many of the major transitions in the morphology, physiology, and ecology in the life history of fishes
begin while they are in the plankton with such events as formation and pigmentation of the eyes, first feeding on external food, development of the gastrointestinal system, gill
formation, development of ability to osmoregulate, fin ray
and scale formation, and pigmentation. Less is known about
the behavior of fishes in the plankton, especially in situ,
because of their relative rarity. Most of the emphasis that
has occurred has been on the study of feeding and schooling
(both transitory and permanent) with less emphasis on predator–prey interactions and at settlement. Pelagic species
remain in the water column after metamorphosis. Benthic
species leave the plankton late or at the end of metamorphosis followed by settlement to juvenile habitats. The numerous transitions that occur while in the plankton may
account for the variability in larval growth and survival
and thus the variability in annual year class strength that is
so common in fishes (Able and Fahay, 2010).
Distinct seasonal patterns in the occurrence of
ichthyoplankton are well defined in boreal and temperate
estuaries but are often less defined in tropical estuaries.
The species composition can be derived from numerous
sources including spawning in estuaries (residents),
in freshwater (anadromous), in saltwater on their way
to freshwater (catadromous) or estuarine nurseries, or
combinations of the above. Resident species typically hatch
at small sizes early in development while transients coming
from the ocean are larger and later in development,
often with behaviors, such as vertical swimming,
that provide for tidal stream transport into estuaries.
Many of these categories of ichthyoplankton include species
of economic importance in recreational and commercial
fisheries. Some dominant families in terms of species diversity and abundance include sciaenids, engraulids, gobiids,
pleuronectids, and clupeids.
Bibliography
Able, K. W., and Fahay, M. P., 2010. Ecology of Estuarine Fishes:
Temperate Waters of the Western North Atlantic. Baltimore:
The Johns Hopkins University Press.
Cross-references
Ichthyofauna
Zooplankton
INFAUNA
Francisco Barros
Laboratório de Ecologia Bentônica, Instituto de Biologia,
Universidade Federal da Bahia, Salvador, Bahia, Brazil
Synonyms
Endofauna
Definition
The infauna refers to benthic animals that live in soft
sediments.
Description
While the infauna lives in bottom sediments, those fauna living on the sediments are termed the epifauna. Benthic organisms can be categorized in different ways (see Gray and
Elliott, 2009). For example, they can be separated according
to (1) size, from microfauna to megafauna and from microflora to macroflora; (2) level on the shore, that is, whether they
occupy the supratidal zone, intertidal zone, or sublittoral
(or subtidal) zone; (3) movement, that is, whether they are
mobile, or sessile; and (4) their position in relation to the sediment. Some investigators separate organisms based on
whether they are moving over the sediment (mobile
hyperbenthic fauna), are on the sediment (epibenthos –
including the attached epiflora and epifauna and the mobile
and sessile epifauna (some workers use the term exofauna)),
or are in the sediment (infauna or, less commonly, endofauna).
Bibliography
Gray, J. S., and Elliott, M., 2009. Ecology of Marine Sediments:
From Science to Management, 2nd edn. Oxford: Oxford
University Press.
Cross-references
Epibiont
Macrofauna
Meiofauna
Soft Sediment Communities
360
ICHTHYOPLANKTON
Kenneth W. Able
Marine Field Station, Department of Marine and Coastal
Sciences, Rutgers University, Tuckerton, NJ, USA
Synonyms
Fish eggs; Fish larvae
Definition
Ichthyoplankton refers to planktonic portion of the life
history of fishes (fish eggs and fish larvae).
Description
The planktonic portion of the life history of fishes typically
begins at hatching from pelagic or benthic eggs. The duration of development of eggs and larvae is largely influenced
by temperature and can last from days to months. The
planktonic larval stages (preflexion, flexion, postflexion of
notochord) of fishes that occur in estuaries are typically
small (<20 mm but ranging up to 100 mm for the leptocephali and glass eels of anguilliform fishes). In addition,
they are incompletely developed and have adaptations for
living in the water column (transparent or nearly so, with
developing swim bladders) at the varying salinities typical
of estuaries. Many of the major transitions in the morphology, physiology, and ecology in the life history of fishes
begin while they are in the plankton with such events as formation and pigmentation of the eyes, first feeding on external food, development of the gastrointestinal system, gill
formation, development of ability to osmoregulate, fin ray
and scale formation, and pigmentation. Less is known about
the behavior of fishes in the plankton, especially in situ,
because of their relative rarity. Most of the emphasis that
has occurred has been on the study of feeding and schooling
(both transitory and permanent) with less emphasis on predator–prey interactions and at settlement. Pelagic species
remain in the water column after metamorphosis. Benthic
species leave the plankton late or at the end of metamorphosis followed by settlement to juvenile habitats. The numerous transitions that occur while in the plankton may
account for the variability in larval growth and survival
and thus the variability in annual year class strength that is
so common in fishes (Able and Fahay, 2010).
Distinct seasonal patterns in the occurrence of
ichthyoplankton are well defined in boreal and temperate
estuaries but are often less defined in tropical estuaries.
The species composition can be derived from numerous
sources including spawning in estuaries (residents),
in freshwater (anadromous), in saltwater on their way
to freshwater (catadromous) or estuarine nurseries, or
combinations of the above. Resident species typically hatch
at small sizes early in development while transients coming
from the ocean are larger and later in development,
often with behaviors, such as vertical swimming,
that provide for tidal stream transport into estuaries.
Many of these categories of ichthyoplankton include species
of economic importance in recreational and commercial
fisheries. Some dominant families in terms of species diversity and abundance include sciaenids, engraulids, gobiids,
pleuronectids, and clupeids.
Bibliography
Able, K. W., and Fahay, M. P., 2010. Ecology of Estuarine Fishes:
Temperate Waters of the Western North Atlantic. Baltimore:
The Johns Hopkins University Press.
Cross-references
Ichthyofauna
Zooplankton
INFAUNA
Francisco Barros
Laboratório de Ecologia Bentônica, Instituto de Biologia,
Universidade Federal da Bahia, Salvador, Bahia, Brazil
Synonyms
Endofauna
Definition
The infauna refers to benthic animals that live in soft
sediments.
Description
While the infauna lives in bottom sediments, those fauna living on the sediments are termed the epifauna. Benthic organisms can be categorized in different ways (see Gray and
Elliott, 2009). For example, they can be separated according
to (1) size, from microfauna to megafauna and from microflora to macroflora; (2) level on the shore, that is, whether they
occupy the supratidal zone, intertidal zone, or sublittoral
(or subtidal) zone; (3) movement, that is, whether they are
mobile, or sessile; and (4) their position in relation to the sediment. Some investigators separate organisms based on
whether they are moving over the sediment (mobile
hyperbenthic fauna), are on the sediment (epibenthos –
including the attached epiflora and epifauna and the mobile
and sessile epifauna (some workers use the term exofauna)),
or are in the sediment (infauna or, less commonly, endofauna).
Bibliography
Gray, J. S., and Elliott, M., 2009. Ecology of Marine Sediments:
From Science to Management, 2nd edn. Oxford: Oxford
University Press.
Cross-references
Epibiont
Macrofauna
Meiofauna
Soft Sediment Communities
360
ICHTHYOPLANKTON