Trophic ecology of fishes,polyculture, food analysis and fish deformities

1. Trophic Ecology Of Fishes
SubmittedBy;
SYEDAASIMHAQ
ROLLNo.
A.M.U
M.Sc.ZOOLOGY

2. Trophic Ecology Of Fishes
 The study of the feeding relationships of organisms in
communities and ecosystems is known as trophic
ecology.
 Focus on the interplay between feeding relationships
and ecosystem attributes such as nutrient cycling,
physical disturbance, or the rate of tissue
production by plants and the accrual of detritus.
 Trophic relationships can be represented
as a Food web or as a Food chain.

3.  Food webs depict trophic links between
all species sampled in a habitat, whereas food
chains simplify this complexity into linear
arrays of interactions among trophic levels.
 These trophic levels are not always simple integers, as
organisms often feed at more than one trophic level.

4. Three fundamental questions in the field of
trophic ecology are important:
(1) What is the relationship between the
length of food chains and plant biomass
(2) How do resource supply to producer and
resource demand by predators determine the relative
abundance of organisms at each trophic level in
a food chain
(3) How long are real food chains, and what
factors limit food chain length

5. Trophic Level And Food Chain
The trophic level of an organism is the position it
occupies in a food chain.These are
 Primary producers; are principally green plants and
certain bacteria. They convert solar energy into
organic energy.
 Consumers; Above producers who ingest live plants
or the prey of others.
 Decomposers; such as, bacteria, molds, and fungi
make use of energy stored in already dead plant and
animal tissues.

6. Further trophic levels are numbered
subsequently according to how far the organism
is along the food chain.
 Level 1: Plants and algae make their own food and are
called primary producers.
 Level 2: Herbivores eat plants and are called primary
consumers.
 Level 3: Carnivores which eat herbivores are called
secondary consumers.
 Level 4: Carnivores which eat other carnivores are
called tertiary consumers.
 Level 5: Top Carnivore which have no predators and
are at the top of the food chain

8. Feeding In Fishes
Food eaten by various species of fishes has been
divided into four categories;
 Main Food; natural and preferred by the fish.
 Secondary Food; consumed by the fish when
available.
 Incidental Food; enters the gut by chance with
others.
 Emergency Food; Taken only under unfavorable
conditions when basic food is not available.

9. Generally fishes are described as;
 Herbivorous (Labeo rohita , Labeo calbasu ,
Ctenopharyngodon idella etc )
 Carnivorous( Wallago attu , Mystus seenghala ,
channa marulius etc )
 Omnivorous( Cirrhinus mirgala , Clarius batracus
, Heteropneusts fossilis etc )

10. Ctenopharyngodon idella
(Herbivorous )
Wallago attu
(Carnivorous)
Heteropneusts fossilis
(Omnivorous)

11.  Other specific categories are ;
 Plankton feeders
 Insectivorous
 Crustacean Feeders
 Mollusk Feeders
 Larvivorous
 Piscivorous etc

12. Fresh water fishes can also be divided into three groups
on the basis of their ecological zone of feeding
 Surface Feeders ( Catla catla , Hypophthalmichthys
molitrix, Hilsa hilsa etc)
 Column Feeders ( Labeo rohita , Wallago attu , tor
tor etc )
 Bottom Feeders ( Labeo calbasu , Labeo bata
Cirrhinus mirgala etc )

13. Catla catla
Cirrhinus mirgala
Labeo rohita
(Surface Feeder)
(Column Feeder )
(Bottom Feeder )

14. Polyculture

15. Polyculture
 It is the practice of culturing more than one species of
aquatic organism in the same pond.
 The motivating principle is that fish production in
ponds may be maximized by raising a combination of
species having different food habits.
 Polyculture of fish is based on the concept of total
utilization of different trophic and spatial niches of a
pond in order to obtain maximum fish production per
unit area.

16. Fig; Fishes utilizing different niches in polyculture system

17.  In India polyculture with carps (IMC) is widely being
carried out.
 These include Catla catla , Labeo rohita and Cirrhinus
mirgala.
 These are stocked at the ratio of 3:3:4 respectively.
 Besides these , polyculture with Chinese carps (silver
carp , grass crap and common carp) is also being
carried out.

18. Advantages
 Maximum fish production is possible in polyculture.
 More profitable and easy to maintain.
 More Economic.
 Different fish species cultivating in a single pond.
 More fish can be cultivated and produced from short
place.
 Almost all the available niche is being utilized in a
single pond. More efficient use of natural resources.

19. Factors Affecting Species
selection
 Water Temperature
 Market value of fish.
 Feeding habits of fish.
 Pond fertilization practice.
 Tolerance to pond conditions.
 Potential of uncontrolled swamping in grow out pond.

20. Food Habit Analysis

21. Food Habit Analysis
 Description of fish diets and feeding habits provides
basis for understanding trophic interactions in aquatic
food webs.
 Diets of fishes represent an integration of many
important ecological components that include the
behavior, condition, habitat use and inter/intra
specific interactions.

22. Gut Analysis
 Gut content analysis provides important insight into
fish feeding patterns and quantitative assessment of
food habits is an important aspect of fisheries
management.
 All items in gut should be sampled.
 If live fish is sacrificed the stomach contents to be
preserved immediately to prevent digestion (5%
neutralized formalin).

23.  Make a longitudinal cut along the stomach and
transferred to a petri dish.
 Remove excess formalin and keep under binocular
microscope and identify.
 Only the immediate foregut to be sampled.
 For a better understanding of diet data and for
accurate interpretation of fish feeding patterns, time
of day, sampling location, prey availability and even
the type of collecting gear used need to be considered
before initiating a diet study or analyzing existing diet
data.

24. Gut Analysis

25. Methods
 Qualitative ; It involves complete identification of
gut contents. It needs extensive experience and good
support of references.
 Quantitative ; It includes Numerical ,Volumetric
and Gravimetric methods.

26. 1) Numerical Methods
(Only counts of prey items are considered)
 Frequency of Occurrence
 Number method
 Dominance method
 Points method

27. i) Frequency of Occurrence
 The number of stomachs in which each item occurs is
recorded and expressed as a percentage of the total
number of stomachs examined.
a) It provide information on how often (or not) a
particular prey item was eaten
b) But no indication of the relative importance of
prey to overall diet

28. ii) Number method
 The number of individual of each food type in each
stomach is counted and expressed as a percentage of
the total number of food items in the sample studied,
or as a percentage of the gut contents of each specimen
examined, from which the total percentage
composition is estimated.
a)Common method for the analysis of planktivores
b)Drawback: Small prey can represent dominant
component of the diet

29. iii) Dominance Method
 The stomach contents comprising the main bulk of the
food materials present, is determined and the number
of fish in which each such dominant food material is
present is expressed as a percentage of the total
number of fishes examined.
a)Drawback: It yield only a rough picture of dietary of
a fish.

30. iv) Points method
 Food items are allotted a certain no. of points based on
rough counts and judgments by the eye. In a more
modified form, the food items are classified as ‘very
common’, ‘common’, ‘frequent’, ‘rare’, etc.,
a)Food items are classified as common, very common,
frequent, rare etc
b) Personal bias.

31. 2) Volumetric Method
(Best method for herbivores and omnivores where
other methods are meaningless)
1)Point method; Prey items are allotted certain points based
on its volume. Very useful for Omnivores and herbivores
2) Eye estimation
3)Displacement method; Displaced volume of each prey
items is measured in a graduated cylinder. Most accurate
among the three and is suitable for carnivore.

32. 3) Gravimetric methods
 The gravimetric method consists of the estimation of
the weight of each of the food items, which is usually
expressed as percentages of the weight of the total gut
contents as in other quantitative methods.
a)Dry weight – More time consuming
b)Wet weight- Common method for
Carnivores

33. Fish Deformities

34.  A deformity is a major abnormality in the shape of a
body part or organ compared to the normal shape of
that part.
 Deformities in various parts of a fish’s anatomy can
occur in just about any part of the body, but they are
mostly associated with the calcified skeletal structures.
Thus, those structures which commonly exhibit
defects include the vertebral column (backbone), the
skull and various fins.
 To a lesser degree, defects are evident in the internal
organs.

35. Cause of Deformities
 Genetic (congenitally )
 Environmental factors ;
like pollution , radiations, temperature, altitude ,
chemical factors , pathogens , stress , nutrient deficiency
etc

36. Skeletal Abnormalities
 Skeletal anomalies. particularly those of the spinal
column are commonly observed in fish
 Generally caused by effects of environmental factors
such as temperature. salinity. dissolved oxygen.
radiation, dietary deficiencies. and toxic chemicals.
 For example, increased percentages of abnormal
embryos and larvae of Atlantic herring, Clupea
harengus, resulted from experimental exposures to
sulfuric acid waste water (Kinne and Rosenthal 19671
and to the algicides 2,4- and 2.5 dinitrophenol
(Rosenthal and Stelzer 1970).

37.  Exposure of fry to very low concentrations of DDT
«1 ppb) produced anomalies in fin rays (Valentine and
Soule 1973).
 It is seen that high chlorinated hydrocarbon and
heavy metal levels are seemed to be reasons for the
higher prevalence's of anomalies particularly gill raker
deformities in fish from the southern California coast.
 Vertebral deformities in herring fish taken in waters
around the British Isles showed the predominant
abnormality was a cluster of two or three incomplete
vertebrae located near the pelvic fins or anus (van de
Kamp).

38. Several types of abnormalities are reported from various
regions of the world by various authors. Some of the
evidences of abnormalities reported are sites as;
 Skeletal abnormalities in mullet and eight other species
from the Inland Sea of Japan were reported by Matsusato
(1973).
 Komada (1974) and Ueki and Sugiyama (1976) observed
increasing numbers of malformed sweetfish or ayu,
Plecoglossus altivelis , in rivers and culture farms of
japan.
 Gabriel (1944) noted abnormities in vertebrae of Fundulus
heteroclitus due to temperature changes

39.  Mottley (1937) found anomalies in vertebral numbers
of trout due to temperature (and possible oxygen).
 Hubbs (1959) found high prevalence's of vertebral
abnormalities in Gambusia affinis from Texas warm
springs due to high temperature.
 Long-term (10 wk) exposure of minnows (Phoxinus
phoxinus) to sub lethal concentrations of zinc and
cadmium resulted in hemorrhaging, spinal curvatures,
and vertebral fractures, particularly in the caudal
region, in up to 70% of individuals (Bengtsson 1975).
 Spinal curvatures and muscle atrophy were produced
in rainbow trout by chronic exposure to lead
(Bengtsoon).

40.  In earlier studies, summarized by Bengtsson, exposure
to sub lethal concentrations of Malathion, parathion,
and certain other organophosphorus pesticides
produced vertebral damage or spinal flexures in
several fish species.
 Couch et al have also found that trifluralin (Treflan)
induced extensive osseous hyperplasia in vertebrae of
sheepshead minnows when life history stages from
zygote to 28-day juveniles were exposed to 25-50 ppb
trifluralin.

41. Brevoortia tyrannus
(Skeletal Deformity)
Sparus aurata
(Skeletal Deformity)
(Mouth Deformity)

42. (Gill deformity)
(Opercular deformity)
(Fish fin erosion)

43. Certain Chemicals and their effects
 DDT: Necrosis of hepatic cells; lymphocytic infiltration of
intestinal lamina propria; possible degeneration of kidney
tubules.
 Carbaryl (Sevin): Intramuscular hemorrhages adjacent to
vertebral column: atrophy of the lateral line musculature;
myxomatous degeneration of fat; vacuoles within the optic
tectum of the brain.
 Malathion: Subcutaneous hemorrhages at the bases of pectoral
fins.
 Endosulfan (Thiodan): Hyperemia of intestine and brain;
adrenal cortical hyperplasia. 2,4-D: Striking degree of brain
hyperemia; hyperemia of intestine.
 Atrazine: Marked edema of all tissues; changes in skin
pigmentation.

44. Reference
 Pollution-Associated Diseases And Abnormalities of Fish and
Shellfish: A Review CARL J. SINDERMANN
 Textbook of Fish Biology and Fisheries, Khanna, S S & H R Singh.
 Economic zoology by R.C.SOBTI.
 www.ncbi.nlm.nih.gov
 www.eprints.cmfri.org.in
 Wikipedia
 Comparative Physiology , Developmental Biology and Ecology by
ASHOK SABHARWAl.
 www.fao.org