Types of fisheries

Dr. Anukriti Nigam
Fergusson College (Auto)
Pune

Prepared By: Dr Anukriti Nigam

Area:-

Thermal Stratification of a Lake
 Lakes in temperate latitudes exhibit marked seasonal temperature
changes which may be described as follows:
 Winter:During winter the coldest water forms ice at 0°C (32°F) and floats at
the surface.
 The water at increasing depth below the ice is progressively warmer and
denser. The heaviest water, at the bottom of the lake, has a winter temperature
of 4°C and throughout winter the water remains relatively stable.
 Spring: Following the ice melt, the surface water gradually warms to 4°C. At
this point the water column is nearly isothermal, i.e., all the water is of
uniform temperature and density. Hence, the strong spring winds cause
considerable stirring, which results in a complete mixing of water, dissolved
oxygen, and nutrients from the lake surface to the lake bottom, a phenomenon
known as the spring overturn or spring turnover As the spring progresses,
however, the surface waters naturally become warmer and lighter than the
water at lower levels, as a result, the lake becomes thermally stratified into the
following three zones

 (a) Epilimnion:
 The upper stratum, which usually has the
highest dissolved oxygen concentration and
is characterized by a temperature gradient
of less that 1°C per metre of depth, is the
epilimnion (literally the “upon-lake” or the
“upper lake”). This stratum contains more
or less uniformly warm, circulating, and
fairly turbulent water.
 (b) Hypolimnion:
 The lower stratum of water characterized
by a temperature gradient of less than 1°C
per metre of depth is the hypolimnion
(literally the “lake below” or “Bottom
Lake”). This part contains more dense,
cooler, and relatively quiet water.
 (c) Metalimnion:
 It is the transitional stratum of marked
thermal change between the epilimnion and
hypolimnion. The middle layer of the lake,
characterized by a temperature gradient of
more than 1°C per metre of depth is the
thermocline. The term thermocline refers to
the plane or surface of maximum rate of
decrease of temperature in the metalimnion

The depth at which the thermocline forms is not fixed, being determined by
the degree of solar heating, the transparency of the water, and the
morphometry of the lake, but wherever it forms it effectively divides the lake
into two layers, the upper epilimnion, and the lower hypolimnion. This
division is not merely an interesting physical phenomenon but it has
consequential effects on the ecology of the lake.
The epilimnion is well lit and oxygenated with sufficiently high temperatures
to promote algal productivity and hence to support zooplankton and fish.
When nutrients are in ample supply, algal growth is accelerated and blooms
may occur. By contrast the hypolimnion is cold, dark and becomes
progressively deoxygenated as the decaying remains of organisms sink down
from the epilimnion.
Conditions in the hypolimnion may become so extreme that anoxia follows
after which the biological productivity becomes least. Under less extreme
conditions the epilimnetic material provides an energy source for benthic
invertebrates. The sinking of dead algae and zooplankton from the epilimnion
not only contributes to the potential deoxygenation of the hypolimnion but
also prevents immediate recycling of nutrients. Nutrient depletion may
become so high that algal growth is limited.

Summer:
Unless the lake is very clear and permits
photosynthesis, the hypolimnion frequently becomes
depleted of oxygen in summer because of the
biological oxygen demand of bacterial decomposers,
the reduced photosynthetic activity, and the minimal
mixing with upper waters as a result of density
differences .
 Winter:
As the winter approaches, the lake gets colder until
the water attains a uniform temperature of 4°C at
which it has maximal density. As the surface
cools below it becomes lighter. Eventually the
surface water may freeze at 0°C. During the
winter season, the ice cover forms on the surface
and in such ice-bound lakes there exists an
inverse stratification of water temperature, with
the coldest water (ice) at the surface and the
warmest water (4°C) on the bottom.
 Lakes undergoing complete circulation in spring
and autumn separated by thermal summer
stratification and winter inverse stratification are
called dimictic lakes (Wetzel, 1983). Such lakes
are quite common among temperate lakes of moderate
size.

 There are several type, kinds and categories of lakes in
the world.
 Lakes are classified on the basis of
 a) Origin
 b) Trophic levels
 c) Mixing of water.
 d) Nature of Inflow-outflow.

Based on origin, lakes are classified into:
 a) Tectonic lakes
 b) Lakes formed due to landslides
 c) Salt lakes
 d) Oxbow lakes
 e) Crater lakes
 f) Sinkhole lakes
 g) Lakes formed due to erosion
 h) Kettle lake
 i) Artificial lake
 j) Fjord lake

Classification based trophic levels:
 This classification is based on the productivity of the lakes or some might say on the
relative nutrient richness of the lake. Trophic level states a Water body’s Ability To
Support Plants, Fish, and Wildlife. The richness in nutrient level is called as
Productivity. It is the basis for the trophic concept of classification. The lake
water is also reflected in this parameter as nutrient poor means super clear w
 Lakes are classified into 8 categories as:
 a) Oligotrophic lakes
 b) Mesotrophic.
 c) Eutrophic and
 d) Dystrophic lakes
 e) Acidotrophic lakes
 f) Alkalitrophic lakes
 g) Argillotrophic lakes
 h) Siderotrophic lakes.


 Classification based on mixing cycles of water:
 The next system of classification is based on the extent
to which the water is mixed and the number of times
during the year. It is also based on water circulation
pattern in a year. This is commonly refered to as
"Turn-over cycle of the lake”.
 The types of lakes which belong to this category are:
 a) Amixis,
 b) Holomixis and
 c) Meromixis.

 The holomictic lakes, those lakes that mix entirely at
least during one period a year.
 We have four types of holomictic lakes :
 a) Oligomictic lakes.
 b) Polymictic lakes
 c) Monomictic lakes
 d) Dimictic lakes

Introduction to Cold Water Fisheries
 Cold water Fisheries occupy an important place amongst
the freshwater fishes of India. The cold water fisheries
deal with fisheries activity in water where temperature of
water ranges from 5 to 25 degrees centigrade. The water
temperature under cold water fisheries should not be more
than 25°C even in summer.
 Such conditions in India occur in Himalayan and
peninsular regions. India has significant resources in terms
of upland rivers/streams, high and low altitudes of natural
lakes in addition to man-made reservoirs existing both in
Himalayan regions and Western Ghats

 Government of India established National Research
Centre on Cold Water Fisheries (NRCCWF).
 Species of Cold Water Fisheries:
 Mahaseer, Garra
 Exotic Fishes:
 Trouts, Cyprinus Carpio

Field Incubators:
 On account of difficulty in handling culture practices
at the breeding grounds in hilly tracts, field incubators
are designed which are easy to handle.
 A feeble current is maintained inside so that eggs are
not damaged and agitated. The fertilized eggs of
Schizothorax spp. a cold water fish endemic to
Kashmir are gently placed in hatching troughs inside
the incubators with top covered. The hatching period
of the eggs is about 8-15 days, later newly hatchlings
can be transferred in the nursery tanks.

What Is an Estuary?
Derivation-The term estuary is derived from the Latin word “Aestus”
meaning heat, boiling or tide
 According to Pritchard in 1967 -“An estuary is semi-enclosed coastal
body of water which has a free connection with the open sea and
within which sea-water measurably diluted with fresh water derived
from land drainage.”
By Perillo, 1995, “An estuary is a semi-enclosed coastal body of water
that extends to the effective limit of tidal influence, within which sea
water entering from one or more free connections with the open sea, or
any other saline coastal body of water, is significantly diluted with
fresh water derived from land drainage, and can sustain euryhaline
biological species from either part or the whole of their life cycle.”
 Estuaries come in all shapes and sizes and can be called bays, lagoons,
harbours, inlets, sounds, wetlands and swamps.

Introduction
 Estuaries are unique environments to which plants and
animals have specially adapted.
 Transition from land to sea and fresh water to salt water
 Estuaries are protected from ocean forces by reefs, barrier
islands, headlands and deltas.
 Estuaries transport and trap nutrients and sediment
through the combined action of freshwater flow, wind,
waves and tidal action.

Ecological Value
 Estuaries are one of the most productive
ecosystems on earth.
 They maintain water quality through natural
filtration as microbes break down organic matter
and sediments bind pollutants.
 They help maintain biodiversity by providing a
diverse range of unique habitats that are critical
for the survival of many species.

Economic Value
 They are tourist attractions.
 Used for transport and industry.
 They have ecological importance to commercial fisheries.
 Maintain water quality ,benefits both people and marine life.
 Natural buffer between the land and ocean, absorbing
floodwaters and storm surges.
 They help maintain biodiversity by providing a diverse range of
unique habitats that are critical for the survival of many species.
 Many species of commercially important fish and shellfish use
estuaries as nurseries to spawn and allow juveniles to grow.

Cultural Value
 People value estuaries for recreation, scientific knowledge,
education, aesthetic and traditional practices.
 Unique estuarine habitats makes them valuable laboratories for
scientists and students.
 Estuaries also provide a great deal of aesthetic enjoyment for
the people who live, work, or use them for recreation.
 Estuaries were a resource sought after by Maori. Timber for
building materials, rongoa (medicine), harakeke (flax) for
weaving, kai (food) which included birds, fish, rats, eels,
shellfish, humans.
 Eel FISHERY an important part of the Maori diet.

Features of estuary-Several unique features are seen most estuaries with
regards to the physics, chemistry, geology and biological features.
 Still except for the changes brought about by tides.
 The depth and width generally increases.
 Waters tend to become clear.
 The bottom gets built up due to deposition of materials brought by the
floodwaters.
 Physical environmental characteristics like penetration of light and
temperature change compared to shallow upland river stretches.
 Salinity, dissolved gasses and chemical nutrients again show variations.
 . The estuary can show marine, freshwater and intermediary characters
nearly freshwater during monsoon season and flooding periods, marine
characteristics in pre-monsoon or summer and between monsoons an
admixture feature of seawater and freshwaters.
 Tidal regimes also influence the estuarine characters with high tide bringing
more seawater into the region and on withdrawal of same during low tide
with more freshwater entering the area.

•Biologically an estuary is more unique and euryhaline organisms
capable of tolerating some degree of variation in salinity of the waters
develop and thrive here.
•Estuaries thus support freshwater life forms, marine forms and finally
the brackish water forms, capable of inhabiting waters with changing
salinity features
•During flooding and monsoon conditions, only freshwater forms are
present and during dry period euryhaline brackish water forms exist
during rest of the period.
•The estuaries are considered as the highly productive .
• They are ideal and favorable nursery areas for a wide variety of
commercially important marine fin fishes and shellfishes, as the waters
are more sheltered with favourable conditions for breeding and feeding.
•Many estuaries support a thriving commercial fishery of brackish water
finfishes and shellfishes.
•Owing to their sheltered nature, estuaries offer safe navigation and
anchoring of boats and ships.

Estuaries Classified by Geologic Features
 Estuaries can be described by how they were formed
or by the characteristics of their circulation. This
classification of estuaries is based on geologic
features (geomorphology of an estuary, the geological
history of the area, and the prevailing climatic
conditions). Classifications include
 coastal plain estuaries,
 tectonic estuaries,
 bar-built estuaries,
 fjord

Coastal plain estuaries
 Coastal plain estuaries were
formed at the end of the last ice
age. As the ice melted and the
waters warmed, sea level rose.
The rising seas invaded low-lying
coastal river valleys. These valleys
are usually shallow with gentle
sloping bottoms. Their depth
increases toward the river’s
mouth.
 This type of estuary is common
throughout the world. Examples
include Thames River (England),
Ems River (Germany), Seine
River (France),
Coastal Plain Estuaries are formed by the sea
level rising and filling an existing river valley

Tectonic estuaries
 The earth’s crust is
constantly in motion. This
motion causes large cracks
or faults and folds to form
in the crust. Often due to
folding and faulting, the
land sinks or subsides.
Tectonic estuaries are
created when the sea fills in
the “hole” or basin that was
formed by the sinking land.
 San Francisco Bay is a
good example .
Tectonic Estuaries are caused by the folding
or faulting of land surfaces.

Bar-built estuaries
 Formed when sandbars
build up along the
coastline. These sand bars
partially cut off the waters
behind them from the sea.
 Bar-built estuaries are
usually shallow, with
reduced tidal action.
 Wind is frequently the
most important mixing
tool for the fresh and salt
water.
 This type of estuary is
common along the Texas
and Florida Gulf coasts
(East Matagorda Bay),
Bar-built Estuaries form when a shallow
lagoon or bay is protected from the ocean by
a sand bar, sand delta or barrier island.

Fjords
 Fjords are valleys that have
been cut deeper by moving
glaciers and then invaded by
the sea. They have a shallow
barrier at their mouth that
limits water exchange
between the deeper waters of
the fjord and the sea.
 They are narrow with steep
sides and usually straight and
long.
 Fjords are found in areas that
have been covered by
glaciers. Examples coasts of
Chile etc
Fjords and Rias are U-shaped valleys formed
by glacial action.

Estuaries Classified by Water Circulation(Salinity
gradient)
 Most estuaries have a range of salinity from salty sea
water to nearly fresh water.
 Estuary classifications based on water circulation
include
 salt wedge estuaries,
 partially mixed estuaries,
 well-mixed estuaries, and
 fjord type estuaries.

salt wedge estuaries
 The high flow rate of the
river holds back the lesser
flow of salt water.
 The salt water is drawn
upward into the fast-
moving river flow.
 Salinity is given in parts
per thousand.

The well mixed estuary.
 Strong tidal
currents distribute
and mix the
seawater
throughout the
shallow estuary.
The net flow is
weak and seaward
at all depths

The partially mixed estuary.
 Seawater enters
below the mixed
water that is flowing
seaward at the
surface. Seaward
surface net flow is
larger than river
flow alone.

The fjord-type estuary.
 River water flows
seaward over the surface
of the deeper seawater
and gains salt slowly. The
deeper layers may
become stagnant due to
the slow inflow rate of
salt water.

Other categories of esturies:-
 1.Open estuary- found on the mouth of the river.May be
perrenial or seasonal.Chilka lake
 2. Embanked estuary –Confined area exposed to sea
only at the time of low tide. Exampe is Bhasabandh
fisheries of bengal or Bheries

Few more ….
 1. Positive estuary
 It is the one in which the influx of fresh water is sufficient to undergo
mixing and there occurs a pattern of increasing salinity usually
towards the mouth of the estuary. This type of estuary has low
oxygen concentration in the deeper waters and considerable organic
material in the bottom sediments. Vertical distribution of salinity
may range from top to bottom uniformly.
 2. Negative estuary
 In arid regions, where the rate of evaporation in estuaries exceeds the
inflow of fresh water, salinity increases in the upper part of the basin,
especially if the mouth of the estuary is restricted by shoreline
features that check the tidal flow. The salinity distribution in this type
of estuary is the reverse of the positive estuary. Negative estuaries
and lagoons are hypersaline but possess a moderate oxygen
concentration at depths. Bottom mud is generally poor in organic
content.

Biota of estuaries:-
 1. Flora.
 2.Oligohaline organisms (can not tolerate salinity
variation of more than 1%)
 3.True estuarine organisms.( adaptation to wide range)
 4.Euryhaline marine organisms.(salinity upto 15%)
 5. Stenohaline marine organisms.(live on the sea
mouth and need 25% >salinity)
 6.Migrants.(Catadromous and Anadromous)

Fisheries production potential of estuaries of
India
 The National Commission on Agriculture stated that “under the term
estuarine fisheries is included the fishery output from the mouth of
rivers, the large brackish water lakes, the innumerable tidal creeks
and backwaters along the coast and the coastal canal system.
 Fishes of brackish water are usually marine which can tolerate wide
salinity changes and are called euryhaline. These are clupeids,
mullets, catfishes, perches and prawns. Mugil cephalus forms a
large part of the estuarine fishery. In addition, non commercial
species include gar fishes, halfbeaks, eels, flatfishes, sharks, rays and
oysters.
 Some migratory fishes that migrate to freshwater from sea or vice
versa are also included. They include Tenualose (Hilsa) ilisha,
Polynemus spp, Pama pama, Tachysurus spp, Pangasius spp and
the prawn, Macrobrachium spp

Marine fisheries
 The ocean currently covers 71% of the earth’s surface.
 Marine ecosystem is the largest aquatic system of the planet
which includes oceans, coral reefs, and estuaries.
 Since it is a single large and a complex system, it is very
difficult to deal with it as a whole. Therefore the oceanographers
have divided the ocean into many zones according to physical
characteristics, mainly based on depth, light and temperature.
 The two major zones:-
1. Benthic realm bottom region of the sea,
2. Pelagic realm the watery region above the sea
Each of these is further subdivided into many different zones
based on environmental conditions.

Pelagic realm
 Pelagic region subdivided into :
 a. Nerictic zone- Shallow water region,width 240km and
depth of 200 m.
 b . Oceanic Zone- Open sea beyond the continental
shelf.Every thing beyond nerictic is oceanic.
 BENTHIC REALM- Floor of the sea . Div. into
 a. Littoral zone –Sub divided into eulittoral and
sublittoral
 B. Deep sea - Sub divided into Bathyal,Abyssal and
Hadal.

Pelagic realm
 The pelagic realm is further subdivided vertically into five zones
i. Epipelagic zone It covers from the surface of the ocean
and extends up to 200m depth (all light rays are seen here
initially) It is also called as the photic zone or euphotic zone.
ii. Mesopelagic zone -It extends from 200 to1000 meters
depth. It is also called as disphotic zone as; only blue light is
seen here. It is also referred to as the "twilight zone"; its lower
boundary in the tropics is the 10º C isotherm.
iii. Bathypelagic zone - This zone extends from 1000 upto
4000 meters deep (aphotic zone; no light reaches this depth,
there is total darkness); It lies between the boundaries of water
with 10 and 4º C isotherm layers.
iv. Abyssopelagic zone – It lies below 2000 and extends
upto 6000 meters depth (aphotic zone).
v. Hadalpelagic zone - has a depth of 6000-10000 meters
(aphotic zone)

epipelagic, or euphotic zone :
• It is the top layer of the ocean zones. This is the ideal place
for about 90 % of all ocean life to live because of warm
temperature and sunlight that goes down about 660 feet.
• This is the only zone to support plant life because it has
the light needed for photosynthesis.
• As this region is diverse in plant life, there is a variety of
animals including zooplankton, crustaceans, molluscs,
sharks, sting rays, mackerels, tuna, seals, sea lions, sea
turtles, etc.

mesopelagic zone
• Though some sunlight penetrates through this zone, it is
not enough for photosynthesis to occur and plants to grow.
• This zone has some animals including octopus, squid, and
hatchet fish.
• The animals living in this zone must survive cold
temperatures, increased water pressure, and dark water.
• Some fish have extra big eyes to help them see, while
others produce their own light called bioluminescence
using special organs in their bodies called photophors.
• Most fish don’t chase their food but they either wait for it or
stalk it. Some have sharp fangs or big mouths to help them
catch their food

bathypelagic zone
• It can be as deep as 20,000 feet. No sunlight reaches this
zone so it is freezing and completely dark.
• It also has a very intense water pressure which can be as
great as two tons per square inch.
• Just like the mesopelagic zone, there are no plants and even
fewer organisms.
• Some organisms in this zone are vampire squid, giant
squid, amphipod, slime stars, snake dragon fish, anglerfish,
oarfish, gulper eel

Hadal zone
• It is the deepest parts of the ocean, causing it to be totally dark,
and constantly cold, with a very intense pressure.
• The deep-sea creatures have adapted to the darkness by reducing
their use of eyesight.
• The fish do have eyes, though, and they are usually enormous,
which indicates enough flashes of bioluminescent light to keep
their eyes from totally deteriorating.
• The animals that live near the bottom have a reddish or pinkish
coloration, possibly because the red light waves are absorbed in
the topmost layers of the ocean.

Benthic Realm
 Varieties of animals live eg.worms, sea pens, crustaceans, stars, and
protozoa.
 Most are scavengers as they depend on dead flesh as main food source.
 Divided based on depth into five zones as:-
i. Intertidal zone – the area between the lowest low tide and highest
high tide markings, also called the littoral zone.
ii. Sublittoral zone – from the lowest low tide mark to the shelf break,
about 200 m deep. This area essentially coincides with the
continental shelf.
iii.Bathyal zone – from the shelf break to 4000 m. coincides with
continental slope and rise.
iv. Abyssal zone – from 4000 to 6000 m.
v. Hadal zone – sea floor deeper than 6000 m. This includes the
trenches, the deepest part of the sea floor

The organisms of these marine habitats are generally divided
into pelagic and benthic organisms based on their selection of
habitats.
Pelagic organisms- living in the water column .
• The pelagic zone can be divided into photic and aphotic zones.
• The photic zone is the shallow part of the ocean that receives
enough sunlight to support photosynthesis, which is about two
hundred meters deep in the clearest waters, and as shallow as
three meters in turbid coastal waters.
• The aphotic zone is where there is no light to support
photosynthesis, and extends from the bottom of the photic zone
to the ocean floor.
• Pelagic organisms include plankton, which float along with
currents, and nekton, which are active swimmers.

Group of marine Fishery
1. Coastal/Inshore fisheries
2. Deep sea /Offshore fisheries.
 Coastal divided into :-
 EAST COAST
 WEST COAST-More productive
Both divided into 12 zones

Plankton
Plankton are divided into two types
Phytoplankton: which include photosynthesizing
species such as algae.
zooplankton: which are consumer species. Zooplankton
consist largely of copepods (tiny crustaceans).

NEKTON
 Nekton are active swimmers that use diverse means to
propel themselves through the water.
 Some species swim using fins, tails, or flippers.
 Other species, such as cephalopods, move by shooting out
jets of water, known as jet propulsion.
 Nektonic species include fish, octopus, sea turtles, whales,
seals, penguins, and many others.

Coastal fisher
 Elasmobranch fishery
 Teleost fishery-Sardines,hilsa ,Eel,Angula etc.

 Source:
http://ecoursesonline.iasri.res.in/mod/page/view.ph
p?id=41360

Types of fisheries

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