Characters most useful in identification of fish eggs are the following: (1) egg shape-spherical, ellipsoidal, irregular, or oth- erwise; (2) egg size-fish eggs range in size from 0.5 to 26.0 mm; (3) oil globules-presence or-absence. Identification of Fish Eggs - SWFSCswfsc.noaa.gov › publications Search for: How can you tell a fish egg?

1. CHARACTERS USED IN THE IDENTIFICATION
OF FISH EGGS AND LARVAE
Ashish sahu

2. IDENTIFICATION OF FISH EGGS
The important characters generally used in identifying
fish eggs are:
1).Shape of the egg 2).Size (diameter)
3).Nature of egg membrane-
smooth, sculptured etc.
4).Extent of perivitelline space
5).Presence or absence of oil
globules
6).Size of oil globules
7).Homogenous or segmented
yolk
8).Embryonic characters

3. Examples of characters of pelagic fish egg

4. In the later stage of development of the embryo the
following characters are used.
1) Presence or absence of pigmentation on yolk sac or
oil globule.
2) Pigmentation pattern on the embryo.
3) Degree of pigmentation of the eyes.

5. 1) Shape of the egg:
 Spherical-Most fish eggs are spherical in shape.
Mugil cephalus –striped mullet
 Oval or Pear shaped- Stolephorus (anchovies),
Gobies, Blennies, some pomacentrids.
Eggs laid in masses or nests are usually not round
because they are deformed by adjacent eggs.
Non spherical eggs are more common in demersal eggs
than in pelagic eggs. Demersal eggs- Clupea harengus,
Capelin

6. 2).Size
Most fish eggs are about 1 mm in diameter, with the
size range of about 0.5 mm to about 8 mm.
Range of diameter of egg Some examples
0.5-1.0mm Caranx spp.
Cynoglossus, Kowala,
Anodontostoma, Mackerel
1.0-1.5mm Saurida spp.
S.longiceps, S.fimbriata, Coilia
1.5-2mm Chirocentrus
Fistularia
Above 2mm Eel, Trichiurus

7. Pelagic eggs are generally smaller (0.5 mm to 5.5 mm)
than demersal eggs (up to 8 mm), and since pelagic eggs
are rare in freshwater fishes, eggs of marine fishes are
smaller than those of freshwater fishes.
Mouth-brooding marine catfishes (ariids) have the largest
eggs of any teleost- 14 to 26mm.

8. 3).Chorion texture
The chorion of most fish eggs is smooth.
The eggs of some species are ornamented with
filaments that are characteristic of particular
species.( Atheriniforms, which includes the
halfbeaks(hemiramphidae) and flying fishes
(exocoetidae), have filaments on their eggs)
Other fishes have sculpturing of their egg chorions.
Similar hexagonal sculpturing seems to have developed
independently in several groups the right-eyed
flounders, the rattails, pearlsides, and the lizardfishes
(synodontidae)..

9. 4). Perivitelline Space.
 Immediately following spawning during a process called water
hardening, a space (perivitelline space) develops between the
inner edge of the chorion and the membrane around the
cytoplasm of the egg itself.
 The relative width of the perivitelline space changes little
during the rest of embryonic development. In most species it is
fairly narrow < 0.1 mm), But quite wide in (e.g., in flathead sole
[Hippoglossoides elassodon], Sardinella spp.
Filaments are more common in demersal eggs
than in pelagic eggs
Chorion of pelagic eggs is thinner than that of
demersal eggs

10. 5). Oil globules (size and number)
• Oil globules are characteristic features of most pelagic
fish eggs.
• Their absence is an important character in certain groups
(e.g., most right-eyed flounders [pleuronectids]),
Sardinella sirm, Chanos chanos, Opisthopterus tardoore,
Muraenid eels.
• Most eggs possess one oil globule of a specific
size(Trichiurus-0.65mm), but some eggs have more than
100 oil globules of irregular size(Setipina, kowala,
Anodontostoma spp. )
• The placement of oil globules within the egg relative to
the developing embryo varies, and in some fishes may
change during development

11. 6). Yolk characters
 The yolk of most fish eggs is homogeneous .
 But it is segmented in some, notably in lower teleosts such as
herring-like fishes (clupeiforms), eels (anguilliforms), and
salmon and their relatives (salmoniforms), and in some higher
teleosts such as jack mackerel (Trachurus symmetricus).
The color of the oil globules themselves, as well as any
pigmentation on them, is also an important character –
Pigment on oil globule seen in Caranx spp. and Trichiurus
Oil globule in yolk at anterior part- Caranx spp. and Mullidae
family.
The yolk of most pelagic eggs is transparent, but in many
demersal eggs it is opaque and colored.

12. 7).Embryo Characters.
 As the embryo develops, it acquires characters that help
identify the egg. Pigment often forms and is seen in
characteristic patterns on the embryo, the yolk sac, and oil
globules.
Myomeres form and reach nearly the number of vertebrae
found in the adults during embryonic development.
The basic body shape of the larva can be seen in later
embryos: whether it will be elongated or deep-bodied,
and the relative length of the gut.
 Some species develop rays in some fins, and some of
these can be elongated, pigmented, and ornate.
The state of development at hatching is another character
that varies among species.
In general, larvae from demersal eggs are further along in
development than those from pelagic eggs.

13. A. striped mullet (Mugil cephalus):
small egg, no oil globules, sculptured
chorion, well-developed embryo.
B. Pacific saury (Cololabis saira):
ovoid egg; chorion with filaments;
well-developed, heavily pigmented
embryo.
C. boxfishes (Ostraciidae): slightly
ovoid egg, heavily sculptured
chorion.
D. Pacific sardine (Sardinops sagax):
wide perivitelline space, embryo
coils more than one revolution.
E. Pacific viperfish (Chauliodus
macouni): large egg, wide
perivitelline space
F. Pacific hake (Merluccius productus): oil globule, pigment bands on embryo, eye of embryo
well developed. G. Pacific spiny lump sucker (Eumicrotremus orbis): embryo well developed
before hatching. H. king-of-the-salmon (Trachipterus altivelus): large egg, ornamented
elongate dorsal fin rays of embryo develop in egg. I. black-belly dragonfish (Stomias
atriventer): small egg, double egg membrane, wide perivitelline space.

14. IDENTIFICATION OF FISH LARVAE
• M11.11.Morphology 2.Pigments
3.Meristic Characters
8.Specialized Larval Characters
Myomeres Fin Rays
Head
spines
6.Gass bladder
4.Gut
5.Eyes
7.Shape and Size of the body

16. 1.Morphology
 Larval shape can vary from stout and robust to quite
slender and elongated
 The ratio of body depth at the pectoral fin to standard
length is usually sufficient to characterize the overall body
shape.
 The head and eye size and shape may also be important.
The length of the gut, measured as the ratio of the pre anal
length to standard length is quite useful.
 As larval shape characters vary with development, so the
size and stage of development should be noted when
comparing the shape of an unknown larva to illustrations
and descriptions of known specimens.

17. MORPHOMETRICS
Landmarks for measurements of post flexion larvae

18. 2.Pigments
• Pigmentation available as taxonomic characters on
larvae is limited to melanophores, since other pigment
cells (e.g., xanthophores) do not retain their color in
currently used fixatives and preservatives.
• In some cases, pigmentation consists of a group of
melanophores in a specific area. In others, the
pigmentation consists of an individual melanophore.
• Preflexion larvae are less pigmented than later larvae.
• In most fishes, between the preflexion and
transformation stages, there is a definite larval pigment
pattern, which is relatively stable and unique to species
in many cases.

19. 1. Heavily pigmented
Holocentridae, Belonidae, Balistidae,
Coryphaenidae, Pegasidae, Istiophoridae and
Cephalacanthidae
2.Only some parts of the body are pigmented -
Exocoetidae, Atherinidae, Theraponidae, mullidae,
Stromateidae, Lobotidae and Platycephalidae
3.Few pigments - prolarvae of Engraulidae,
Apogonidae, Serranidae, Leiognathidae,
Scomberomoridae, Thunnidae, Pleuronectidae and
Cynoglossidae

20. 3.Meristic Characters
Myomeres:
• Myomeres are the first meristic character to stabilize,
and the number usually reflects the number of adult
vertebrae.
• The number of vertebrae varies from, 20 ocean
sunfishes to 200 (e.g., most eels and relative
[elopiformes]).
• Use of polarized light often facilitates counting
myomeres.
• Myosepta are frequently more clear than the
myomeres, and if they are counted, two should be
added to the count to account for the myomeres
anterior and posterior to the first and last myosepta.

22. • Prolarvae of Balistidae, Aluteridae,
Monacanthidae and Tetradontidae - 24
myomeres
• Mugilidae, Sphyraenidae, Carangidae- 23 to 24
myomeres
• Clupeidae,Engraulidae,Thunnidae,Belonidae-
35 to 40 myomeres
• Dussumeiridae, Bermacerotidae->50 nos
• Muraenoid leptocephalus -120 to 140 nos

23. Fin Rays:
 The developing median fins contain several bits of
taxonomic information.
 The principal caudal fin count is often an ordinal character
and since it generally reaches its adult state shortly after
flexion, it is very useful and relatively easy to determine in
larvae.
 The number, position, and order of development of the
dorsal and anal fins, and their composition in terms of
spines and soft-rays, are important characters.
 The length and number of rays of the pectoral fin are useful
characters. The number of pectoral rays may vary within
species and among species in a genus.
 The pelvic fin position and formula is generally stable at a
high level of classification (order)

24. Head spines:
Some fishes have head and operculum spines which
are important as armour against predators.
Spination is useful diagnostically for most marine fishes
that have pelagic larvae.
Spines are present in the pre-larvae of all perciformes.
Spines are important diagnostically for Lobotidae (head
spines) and cobitidae (spines below the eye)
Larval head spines are prevalent in sculpins and
scorpion fishes (scorpaenids) and occur in some
members of groups such as squirrelfishes and their
relatives (beryciforms), perch-like fishes, and flatfishes
(pleuronectiforms).

25. 4.Gut
• All fish have a rudimentary straight gut (alimentary
canal) as pre-larvae
• The gut folds or coils as the digestive tract develops
and as the diet changes, with the timing and shape
differing between species
• The anus tends to move closer to the head as a fish
develops
 Vent is generally situated behind the midpoint of the body - Prolarvae of
Clupeidae, Dussumieriidae, Engraulidae and Synodontidae.
 Vent is far forward - Prolarvae of Brogmacerotidae, Atherinidae,
Trypauchenidae and Blenniidae

26. 5.Eyes
Most fish larvae have round eyes except in
Clupeoid larvae which have oval eyes.
Most early pre-larvae - no pigment in their
eyes ( pigment appears after one day)
Belonidae and Adrianichthyidae - eyes are
already developed and densely pigmented
during hatching .

27. 6.Gass bladder
By the Pre-larval stage- most species develop a
visible gas bladder- shape, size and position.
The larvae of Clupeiformes and Gobiidae -visible
swim bladders .
Juvenile or adult - gas bladder is usually not
visible.
Larvae of Ambassis spp. are transparent as adult,
but once fixed in formaldehyde their internal
features are not visible.

28. 7.Shape and Size of the body
 Prolarva of Leiognathus - 1.2 to 1.4 mm
• Engraulis - 2.2 to 3.0 mm
• Epinephelus spp. - 1.4 to 1.6 mm
• Sillago spp. - 1.6 to 2.0 mm
• Pleuronichthys -3.6 to 3.7mm
Elongate- Clupeidae, Belonidae, Hemirhamphidae, Syngnathidae,
Synodontidae, and Blenniidae
Slender - Sillaginidae, Sphyraenidae, Bregmacerotidae, Cepolidae, Gobiidae-
Elongate ribbon like- Muraenidae and Ophichthyidae
Short fusiform body-Mugilidae, Pomadasyidae, Thunnidae, Scombridae,
Scomberomoridae, Stromateidae, Scorpaenidae
Globular- Ostraciontidae and Tetraodontidae
Deeply compressed body- Flatfishes

29. 8..Specialized Larval Characters
Specialized characters of larvae are those that
are overgrown or otherwise lost by the end of
the juvenile stage.
Such as elongated fin rays, trailing gut,
serrated fi spines, stalked eyes….

30. 8.Higher-Level Characters
 As larvae of more and more fishes started to be recognized, it
became apparent that closely related species looked more
similar to each other than to more distantly related species.
 For example, tarpons (elopiforms), bonefishes (albuliforms),
and eels all have a leptocephalus (leaf-like) larval morphology.
 The larvae are shaped like willow leaves, they are laterally
flattened and taper anteriorly and posteriorly. They are lightly
pigmented and possess large, sometimes fang-like teeth.
 Among the orders with leptocephali, the tarpons and
bonefishes have forked tails, whereas the eels have pointed
tails.

31. REFERENCE
• Miller, B.S. and Kendall, A.W., 2009. Early life history
of marine fishes (Vol. 36, No. 4). Berkeley: University
of California Press.
• Termvidchakorn, A. and Hortle, K.G., 2013. A guide to
larvae and juveniles of some common fish species
from the Mekong River Basin. Mekong River
Commission.
• James, P.S.B.R., 1989. Proceedings of the summer
institute in recent advances on the study of marine
fish eggs and larvae.

32. THANK YOU