Introduction Marine oil spills can affect the ecosystem both through their physical influence on the organisms and through the effect of the various chemicals in the oil. On the physical side, organisms can get caught in the viscous oil. Oil can also form a barrier to the surface, which can be damaging for some species of fish when they come to the surface to fill the swim bladder (Sundby et al., 2013). There are also several chemicals in the oil that can increase the mortality for eggs and larvae (Neff et al., 2000; Barron et al., 2004). Oil can stimulate the formation of marine snow (Passow et al., 2012) that may subsequently sinks to the ocean floor where it can impact the benthic fauna. If conditions become anoxic, oil in the sediment would decay more slowly since the biological remineralization of the oil is retarded in anoxic conditions. The use of dispersants to increase the rate of remineralization has also received attention in terms of its potential negative effect on the ecosystem (Kleindienst et al., 2015; Vikebø et al., 2015). This study focuses on the seas around southern Norway (Figure 1), where the currents are dominated by the Norwegian Coastal Current (NCC) that flows along the coast all the way from the Skagerrak to northern Norway. This current would primarily transport oil spills, eggs, and larvae along the coast. In the northern part of the area, the NCC flows side by side with the Norwegian Atlantic Current (NAC), which is a more saline current also directed northwards. Strong winds of variable directions and high waves occur frequently, particularly during winter, and contribute to the upper layer drift. The area has strong mesoscale activity, particularly in the frontal region between the fresher NCC and the eastern branch of the NAC, and thus it is difficult to predict the local currents on short time scales. The tidal amplitudes, and consequently the tidal currents, are small (<1.0 m) in the southern parts of Norway, but become larger in northern Norway.

1. Ashish sAhu

2. 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.

3.  Factors that have been proposed to alter fish egg mortality
rates can be broadly divided into two categories; ( Health,
1992)
ENVIROMENTAL FACTORS
1. EXOGENOUS
2. ENDOGENOUS
 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 .
 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.
Cyclops

7. American bald eagle

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

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

10. Temperature
Oxygen concentration
Salinity
Solar and ultra violet radiation
Mechanical stress

11.  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.

12. • Length of egg incubation varies b/w species at same temp. and is related to
egg size.
• Larger embryos developing at a slower rate than eggs of smaller diameter.
• Embryos of fish are most sensitive to temperature change early in
development particularly during cleavage and gastrulation.
• Mortality rates at high temp. are reduced when egg are exposed at later
stages of development.
• Temperature effects on larval fish physiology and biochemistry through
ontogenesis.

13. Incubation tine plotted in relation to
temperature
“Incubation period decrease
with increasing temperature
vice versa.”

16. Source: Rombough, 1996

17.  Inverse relationship exists between salinity and mortality in pelagic fish eggs.
 The ability to tolerate is the internal fluids in range of conditions, exact mechanism is
controlling osmotic and ionic regulation in 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.
 Lower salinity will make prolong incubation periods in white flounders and pacific cods.
 Salinity represents an osmotic cost

19. • Oxygen uptake in fish eggs increase with development and is dependent on temperature.
• In the sea, fish eggs mortality may be influenced by the complex intraction of factors other than
temperature and salinity, including DO.
• 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.

20.  An accumulation of lactic acid occurs lack of heart beat or movement of the embryo.
 Pelagic fish eggs drift in the upper water column where oxygen saturation is sufficient to meet the
demands of development.
 Oxygen is essential for larval metabolism and growth.

21. In teleost eggs, elevated 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.
 Destructive effects of radiations on teleost eggs in the sea will depend on the wave length, and
exposure dosage received.
 Mainly depend on the weather condition and vertical distribution, especially in calm periods.
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.

22. Salmon alevin larva with yolk sac.
(courtesy Uwe Kils).
“Fish eggs and larvae are
specifically prone to UV-B
radiation.”

23.  UV radiation, specially UV- B, is the most biologically injurious component of sunlight.
 In transparent embryos, Radiation passes without absorption.
 In pigmented eggs, radiation is blocked, due to impigment on sensitive organs or systems.

24.  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,

25.  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.

27. “ Tides are caused by the
interaction of the forces of the sun
and moon; in most places, tides
occur twice daily.
Tides have the biggest impact on eggs &
larvae of marine organisms that live on
coastlines.

28. “Juvenile of oil sardine comes to
shore area due to tidal action in
California beaches.”
“A lot of juveniles of oil
sardine comes to shore area
due to tidal action in
California beaches.”

29. “Larvae of different fishes
collected during tide and
wave action.”

30. Giant Gastropod (Adelomelon brasiliana) egg capsules on the beach of a
lagoon due to tidal action

31. Fertilized eggs of Common cuttlefish (Sepia officinalis) on beach

32. Egg cases (‘a sea wash ball’) of the Common edible whelk Buccinum undatum
Affected by tidal action

33. “ Cod eggs comes to the beach
area”

34.  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 : Malformation in yolk sac, spine curvature & darkening in eyes as well as
skin.


35.  Microbial diseases induced by opportunistic pathogens (e.g. Vibrio spp., Francisella sp., IPN,
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
 The water is heated, filtered, disinfected and aerated; both the live feed and the fish are fed and kept at
relatively high densities, which may increase the bacterial load.

36.  It’s a common fungus that affects the eggs.
 This affects the dead eggs first & later it cause heavy mortality of the developing eggs.
Trout eggs infected by Saprolegnia fungus

37. Saprolegnia infection on
fish eggs in the lab
Larvae infected by
saprolegnia

38. water mould disease which affects wild and cultured
freshwater fish and fish eggs worldwide.