Indian Oil Sardine
Encyclopedia
Indian Oil Sardine is a species of ray-finned fish in the genus Sardinella
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Sardinella longiceps is one of the two most important commercial fishes in India (with the mackerel). The Indian Oil Sardine is one of the more regionally limited species of Sardinella and can be found in the northern regions of the Indian Ocean. These fish feed on phytoplankton (diatoma), zooplankton (copepods)
Diagnostic Features
The body of these Sardinella are particularly elongate even to the point of being subcylindrical, They have a slightly rounded belly and have 8 rays on their pelvic fin. They have a very large number of gill rakers and a faint golden spot behind the gill opening. They also have a faint golden midlateral line as well as a black spot on the hind border of the gill cover.
Growth and Development
Sardinella longiceps attains sexual maturity around 15cm at around one year of age. The life span of this fish is a highly debated issue because researchers struggle to establish the significance of growth rings. The overall consensus is that the lifespan is limited to about 2.5 years. The difficulty in determining the age of these fish is that the annual rings in their scales may be formed for several reasons. Scientists argue that after the first year the rings are reliable because they may be formed due to the reduced feeding activity associated with planktonic scarcity during the rise in temperature of the environment in summer. An experiment was done by measuring scales from a selected body area, and then determining the relationship between the fish-length and scale-length.
According to these tests the average lengths for each ring were 14.3, 16.4 and 18.4 cm. at the age of one, two and three years respectively.
Reproduction
The movement of the fish was determined to be less seasonal than hydrologically dependent according to water conditions, (directly before and after monsoon season). This affects the spawning season and means that it may vary from any period between June-December. These fish only spawn once during the spawning season. The distribution of the fish throughout the spawning season is determined by the size and age of the fish. Early in the spawning season many of the oldest most mature adults between 17-19cm while the juvenile Sardinella arrive to spawn later in the season. The peak period for commercial catch is June and July when the juvenile fish have fattened themselves to prepare for their first spawning season. Rarely do Sardinella survive a second spawn but this is much more common in females.
Ovary development is classified in stages I-VI. Stages IV, V and VI are able to spawn. Fish at stage IV have ovaries that fill two thirds of their available body cavity. By stage VI these ovaries fill the body cavity and are made up of large transparent ripe eggs. These fish only spawn once in a spawning season and produce around 75,000 eggs. The development of the egg requires only 24 hours. These eggs are spherical and range from 1-4mm in diameter. These fish are called oil sardines because there is an oil globule which makes up a major part of the egg yolk. These fish have 53 myotomes in the larval stage but adults have only 46-48 vertebrae.
First day of development includes minimal movement but it travels by serpentine swimming. By the end of this first day the oil globule in the yolk disappears or is used up.
On the second day of development the pigmentation of the larva is stable and the eye coloration stabilizes to a silvery white sheen.
During the Third day the yolk is completely used up.
Sardinella
SardinellaSardinella is a genus of fishes in the family Clupeidae. This genus currently contains 21 recognized species. These fish are generally coastal, schooling fish, and abundant in warmer waters. They can be found nearly anywhere in the tropic and subtropic oceans of the World...
.
Sardinella longiceps is one of the two most important commercial fishes in India (with the mackerel). The Indian Oil Sardine is one of the more regionally limited species of Sardinella and can be found in the northern regions of the Indian Ocean. These fish feed on phytoplankton (diatoma), zooplankton (copepods)
Diagnostic Features
The body of these Sardinella are particularly elongate even to the point of being subcylindrical, They have a slightly rounded belly and have 8 rays on their pelvic fin. They have a very large number of gill rakers and a faint golden spot behind the gill opening. They also have a faint golden midlateral line as well as a black spot on the hind border of the gill cover.
Growth and Development
Sardinella longiceps attains sexual maturity around 15cm at around one year of age. The life span of this fish is a highly debated issue because researchers struggle to establish the significance of growth rings. The overall consensus is that the lifespan is limited to about 2.5 years. The difficulty in determining the age of these fish is that the annual rings in their scales may be formed for several reasons. Scientists argue that after the first year the rings are reliable because they may be formed due to the reduced feeding activity associated with planktonic scarcity during the rise in temperature of the environment in summer. An experiment was done by measuring scales from a selected body area, and then determining the relationship between the fish-length and scale-length.
According to these tests the average lengths for each ring were 14.3, 16.4 and 18.4 cm. at the age of one, two and three years respectively.
Reproduction
The movement of the fish was determined to be less seasonal than hydrologically dependent according to water conditions, (directly before and after monsoon season). This affects the spawning season and means that it may vary from any period between June-December. These fish only spawn once during the spawning season. The distribution of the fish throughout the spawning season is determined by the size and age of the fish. Early in the spawning season many of the oldest most mature adults between 17-19cm while the juvenile Sardinella arrive to spawn later in the season. The peak period for commercial catch is June and July when the juvenile fish have fattened themselves to prepare for their first spawning season. Rarely do Sardinella survive a second spawn but this is much more common in females.
Ovary development is classified in stages I-VI. Stages IV, V and VI are able to spawn. Fish at stage IV have ovaries that fill two thirds of their available body cavity. By stage VI these ovaries fill the body cavity and are made up of large transparent ripe eggs. These fish only spawn once in a spawning season and produce around 75,000 eggs. The development of the egg requires only 24 hours. These eggs are spherical and range from 1-4mm in diameter. These fish are called oil sardines because there is an oil globule which makes up a major part of the egg yolk. These fish have 53 myotomes in the larval stage but adults have only 46-48 vertebrae.
First day of development includes minimal movement but it travels by serpentine swimming. By the end of this first day the oil globule in the yolk disappears or is used up.
On the second day of development the pigmentation of the larva is stable and the eye coloration stabilizes to a silvery white sheen.
During the Third day the yolk is completely used up.