Effect Of Various environmental factor On Fish Eggs And Larvae 

1. RAGHUNATH
FSM-2021-20-
07
Kufos
Effect Of Various environmental factor
On Fish Eggs And Larvae

2. INTRODUCTION
 Early larvae stages are the most crucial &
vulnerable stages in the life cycle of a fishes.
 Also affect the development, survival,
distribution, or migration behavior of larvae.
 There are also several chemicals in the oil that
can increase the mortality for eggs and larvae.
 Factors that have been proposed to alter fish egg
mortality rates can be broadly divided into two
categories; ( Health, 1992)

3.  ENVIROMENTAL FACTORS
 1. EXOGENOUS
 Predation
 Abiotic effects from changes in Temperature and
salinity, Oxygen concentration, Wave action, UV
Radiation and Pollutants, Wind speed, Turbulent
sea conditions ,Upwelling intensity, SST
 2. ENDOGENOUS
 Inherited genetic normalities, or poor parental
condition prior to spawning.

4.  Plankton like Cyclops hurt the egg shell.
 Chironomids larvae bite the eggs with mandibles &
damage the eggs.
 Saprophytes cause mortality of developing eggs.

5.  Predation of Scolopsis affinis during daytime by the
Bobbit worm
 Bobbit is covered with
sand and lures its prey with
the protruding antennae
The Bobbit grasps
the fishes

6.  Predation of salmon egg by
American dipper birds

7. Important food source for many predators like larger fish
(salmon), sharks, marine mammals (seals), sea birds
(cormorants), and also humans.
Predation and threat of
squid eggs
Masses of squid eggs
comes to the shore area

8. PHYSICAL FACTOR
 Temperature
 Oxygen concentration
 Salinity
 Solar and ultra violet radiation
 Mechanical stress

9. Temperature
 Eggs are one of the most thermally sensitive life
stages in fishes.
 Tolerance limits: + 6 degree C of the spawning
temperature for many species (Rombough 1997).
 In the open ocean, direct lethality caused by rapid
changes in water temperature such as high fish
egg mortality.
 Most of eggs can tolerate is roughly the same, i. e.
Plus or minus about 6 degree Celsius.
 The rate of egg development increase to maxi. at
high temp. after which development will be
adversely affect & death of the larvae occurs.

10.  Larger embryos developing at a slower rate than
eggs of smaller diameter.
 Mortality rates at high temp. are reduced when egg
are exposed at later stages of development.
 Length of egg incubation varies b/w species at same
temp. and is related to egg size

11. Incubation time plotted in relation to temperature
Incubation period decrease with increasing
temperature vice versa .

12. Salinity
 Inverse relationship exists between salinity and
mortality in pelagic fish eggs
 Less than about 15 ppt embryos will die prior to
hatching.
 Fluctuation in salinity is low during blastula and
gastrula stages.
 Even in population that migrate to brackish water
to spawn , the eggs can survive in a constantly
varying salinity environment due to their euryhaline
properties
 In demersal eggs mortality increased at higher
salinity levels.

13. Oxygen concentration
 Oxygen uptake in fish eggs increase with development
and is dependent on temperature.
 Demand of oxygen during the early embryonic stages is
partly provided by oxygen stores in the yolk and
perivitelline fluid.
 Deeper eggs or thicker mass eggs may affect due to an
inadequate oxygen supply or poor water circulation.
 Egg survival declined with decreasing oxygen
concentration.
 At low oxygen concentrations, salinity significantly
affected egg survival.

14. Solar and ultra violet radiation
 In teleost eggs, increased levels of UV
significantly increase the rate of mortality.
 In embryos that survive, it retards growth, reduce
buoyancy and alter the physiological process
such as heart rate.
 Mainly depend on the weather condition and
vertical distribution, especially in calm periods.

15.  Some pelagic eggs that float on the sea
surface will be vulnerable to UV radiation.
 So marine teleost eggs are sensitive to light
and elevated UV radiation.
 Due to UV, reduce survival rate, increase
abnormalities and reduce buoyancy of pelagic
eggs.

16. Light
 Light is a strong biological regulator in fish.
 Feeding, digestion, and reproduction, depend on
light.
 Light comprises different components such as
Quantity- (light intensity)
Quality- (spectral composition)
Light distribution- (point source or
evenly)
Cycling- (photoperiod and season).
 Outdoor light conditions (Natural condition)
depending on latitude, season, depth, and algal
blooms.

17. Mechanical stress
 Osmoregulatory capicity is lost and as a result
the embryo sinks rapidly and dies.
 Pelagic eggs distributed near the surface in
open water may be exposed to the physical
effects of mechanical pressure from wave action and
sea spray

21. Chemical factors
 Metabolites may originate from the reared
organism itself and from bacterial activity, mainly
consisting of compounds such as ammonia
(NH3), nitrite (NO2), nitrate (NO3), and CO2.
 Deformation of eggs are increase with increasing
of ammonia concentration(0.06 to 1.5 mg/l).
 Due to high ammonia: weight loss of larvae.
 High unionized ammonia : Deformation in yolk
sac, spine curvature & darkening in eyes as well
as skin.

22. Microbial affect
 Microbial diseases induced by opportunistic
pathogens (e.g. Vibrio spp., Francisella sp.,
Pasteurellosis) may cause high losses.
 Stability of microbes is depend on water quality
and environmental parameter.
 It is highly important to ensure optimal gut
function and digestion of the feed.
 At larval and juvenile stages of the fish has no
developed a specific immune defense due to
this

23. it”s a common fungus that affects
the eggs