This document summarizes mineral deficiency and toxicity in fish. It discusses that fish require certain minerals for normal life processes and can obtain some from their diet and environment. It then covers the essential minerals for fish and their functions. The document outlines signs of deficiency and toxicity for various important minerals like iodine, iron, copper, zinc, selenium and more. It discusses factors affecting mineral availability and concludes that commercial diets need supplementation to avoid deficiency conditions due to interactions between diet components.

1. Mineral deficiency &
their toxicity in fish
Aditya Kumar Baruah
(AAH-MA7-01)
Non-
infectious
diseases &
disorders
(AAH508)

2. Introduction
• Nutritional diseases: (Snieszko,1972) the deficiency, excess or improper balance of
the components present in a fish’s diet.
• One of such disease is the mineral deficiency or toxicity.
• All forms of aquatic animals require inorganic elements or minerals for normal life
processes.
• Fish have the ability to absorb some inorganic elements not only from their diets but
also from external environment.

3. All the living organisms contain most of the naturally occurring
inorganic elements from periodic tables.
Out of about 90 elements 22 elements are known to be essential for living beings.
Structural elements: C, O, H, N, P and Sh
Macro elements : Ca, Mg, K, Na and Cl
Micro elements (Trace): Chromium, Cobalt, Copper, Fluorine, Iodine, Iron,
Manganese, Molybdenum, Selenium, Zinc,
Nickel, Vanadium, Silicon, Arsenic
Minerals

4. Essential element:
An element is considered essential when a deficient intake produces an impairment of
function when restoration of physiological levels of the element prevents or relieves the
deficiency.
Main function of essential elements in the body:
• Formation of skeletal structure (Ca, P)
• Maintenance of colloidal system (Na, K, Cl, )
• regulation of acid base equilibrium (Phosphates, Carbonates , Bi-Carbonates)
• Important components of hormone, enzyme and activator system(Ca, Mg, Mn)

5. • Trace minerals important for fish:Cobalt, Arsenic, Copper, Molybdenum, Iron, Fluorine,
Manganese, Lead, Selenium, Nickel, Zinc, Silicon, Chromium, Vanadium, Iodine, Lithium.
Mineral Requirement(mg mineral/kg dry diet)
Iron 30-170
Copper 1-5
Manganese 2-20
Zinc 15-40
Cobalt 0.05-1.0
Selenium 0.15-0.5
Iodine 1-4

6. Bioavailabilty of minerals
Factors influencing bioavailability of minerals include
 the intake level of the nutrient,
 its chemical form,
 the digestibility of the diet,
 particle size,
 interactions with other nutrients,
 chelators,
 inhibitors,
 physiological and pathological changes of the animal,
 water chemistry,
 type of feed processing etc.

7. Effects of mineral supplements in
experimental diets
• Although fish have ability to derive certain elements from water, both
practical and purified diets require mineral supplementation.
• Purified diets without mineral supplements result in loss of appetite, growth
depression, hypochromic anaemia, high mortality, cranial deformities(Nose
et.al, 1972).
• An imbalance of dietary minerals in certain diets predisposes the Atlantic
salmon to BKD (Lall et. al, 1985).

8. Iodine
• Fish meals contain iodine, so modern diet do not exhibit iodine deficiency.
• Deficiency causes Goitre (thyroid hyperplasia)- originally described as
Adenocarcinomata.
• The trend towards replacement of fish meal with plant protein sources may bring
goitre back into picture.
• Iodine supplementation at 4.5 mg I/kg was beneficial to Atlantic salmon exposed to
BKD.(Lall,2002)
• Salmonids - Thyroid hyperplasia , goitre

9. Iron
DEFICIENCY:
• Hypochromic normocytic anaemia demonstrated in iron deficent brook trout, yellow
tail, red sea bream, carps, eel and catfish.
• Hypochromic microcytic anaemia (C. carpio).

10. Iron
EXCESS:
• Toxicity at high level is a major problem than deficiency.
• Melanomacrophage system of the haemopoietic tissues plays an avid role in
retention of iron in body following hemorrhage or infection.
• Toxicity of ferric ions in contaminated waters is the most observed effect of iron.
• Causes pathological changes in rainbow trout liver, specifically vacuolated
hepatocytes appearing to contain large amounts of fat and reduced levels of
glycogen.
• Hepatocytes exhibit pleomorhic nuclei, with large intranuclear inclusions and
peripheral clumping of chromatin.

11. Copper(deficiency)
• Copper deficiency is most unlikely because of its ubiquity in water.
• Shrimps unable to meet dietary requirement from sea water.
• Deficiency signs in shrimp: reduced weight gain, feed efficiency and copper level in
body.
• Requirement high because in invertebrates copper is a constituent of oxygen carrying
pigments in blood.
• Satoh et.al(1983) reported that carp fed high ash diets without copper supplementation
developed cataracts.
• C. carpio -Reduced growth, cataracts

12. Copper(toxicity)
• High copper exposure (diet or water): growth reduction, increase in intestinal cell
proliferation and apoptosis.
• Reduced growth (dietary level above 15mg/kg)
The liver and spleen appear pale and
degenerate
The gill epithelium is inflamed, thickened and
degenerate; excessive mucus is secreted, gill
function and resistance against parasite
and bacteria establishment are compromised.

13. Potassium(deficiency)
General deficiency signs:
• Reduced growth and feed efficiency.
• Anorexia
• Convulsions
• Tetany
• Death.

14. Magnesium
• C. carpio: Reduced growth, sluggishness, anorexia, convulsions, high
mortality, reduced bone magnesium content, cataracts
• I. punctatus: Anorexia, reduced growth, sluggishness, muscle flaccidity,
high mortality, depressed Mg content in body and blood serum/bone
• A. japonica: Anorexia, reduced growth
• O. mykiss: Reduced growth, anorexia, cataract, sluggishness, calcinosis of
kidney, increased mortality, vertebral curvature, degeneration of muscle
fibres and epithelial cells of pyloric caeca and gill filaments, reduced bone
ash, Mg and elevated Ca content
• Poecilia reticulata: Reduced growth and feed efficiency, high mortality

15. Manganese
• Mn deficiency reported in fish fed on diets with high calcium or ash content.
• Deficiency: poor growth and feed efficiency, nutritional cataracts
• Skeletal abnormalities noted for rainbow trout, carp and tilapia(Roberts,2012).
• Egg hatchability in rainbow trout is reduced when broodstock fed without Mn
supplementation.(Takeuchi et.al.)
• O. mossambicus : Reduced growth and appetite, loss of equilibrium, mortality.
• C. carpio: Reduced growth , short body dwarfism, cataracts.
• O. mykiss : Cataracts, reduced growth, short body dwarfism, abnormal tail growth.

16. Phosphorus
• Fish can obtain from rearing water but water levels are too low to supply the needs of
fish.
• Phosphorus deficiency not seen when fishes fed with fish meal.
• Deficiency signs: anorexia and dark colouration.
• Specific signs: deformities of head, ribs and vertebrae.(primary role in bone
mineralisation)
• Combined deficiency of P and vit C causes failure of ossification and bones become
rubbery.
• Deformity of stress sites (articulation of the jaw)- may lock open to produce deformed
fish called ‘screamers’. (painting ‘The Scream- Edvard Munch)
• Other signs: Reduced growth, poor feed efficiency, bone demineralization, skeletal
deformity, abnormal calcification of ribs and the soft rays of the pectoral fin, cranial
deformity, increased visceral fat.

17. Atlantic salmon from fast growing stock on
phosphorus/ascorbate deficient diet showing
deformity of the head bones and jaw
articulation.
Spinal vertebrae of salmonids on
phosphorus deficient diets. A = normal
rainbow trout, B = experimental deficiency
in rainbow trout, C = deficiency in farmed
Atlantic salmon. The deformity is principally
in the dorsal spinous processes of the
vertebrae.

18. • C. carpio- Reduced growth, poor feed efficiency, bone demineralization, skeletal
deformity, abnormal calcification of ribs and the soft rays of the pectoral fin, cranial
deformity, increased visceral fat.
• I. punctatus - Reduced growth, poor feed efficiency, bone demineralization.
• Pagrus major- Reduced growth, poor feed efficiency, bone demineralization,
increased muscle, liver and vertebrae lipid content , curved and enlarged spongy
vertebrae, decreased liver glycogen.
• A.japonica- Anorexia, reduced growth.
• O.mykiss- Reduced growth, poor feed efficiency, bone demineralization.
• S. salar -Reduced growth, poor feed efficiency, bone demineralization.

19. • Degeneration and collapse of one or more cervical or lumbar vertebrae, with
resultant kyphosis or scoliosis.
• Twisted or curled shape to the dorsal
vertebral spines, frequently encrusted
with mineralised plaques (Roberts,2012).
Upper: scoliosis
lower: lordosis

20. Selenium
• Se deficiency depresses growth in rainbow trout and channel catfish, but does not
induce pathological changes unless vit E is deficient(Roberts, 2012).
• Se and vit E supplementation prevents bland muscular dystrophy.
• S. salar: Increased mortality, muscular dystrophy, depressed glutathione
peroxidase (enzyme)activity, reduced growth.
• C. carpio: Reduced growth, cataracts, anaemia.
• I. punctatus: Reduced growth

21. Toxicity(Se)
• Excessive intake of Se as sodium selenite causes reduced feed intake and weight
gain.
• Associated with nephrocalcinosis(Hicks et al.)
• Reacts with Cu to increase susceptibility to infection.
• Protein chelates less toxic than inorganic forms.
• Naturally present as mostly selenocysteine or selenomethionine (10-15 ppm easily
tolerated).
• Reduced growth and feed efficiency, high mortality (dietary level above 13mg/kg).

22. Zinc
• Deficiency: bilateral, central or sublenticular cataract development in young
salmonids, poor growth and darkening colour.
• High levels of ash, Ca or phytate in diet inhibits Zn absorption.
• Other signs: erosion of fins and skin, short-body dwarfism and poor egg hatchability.
• I. punctatus: Reduced growth and appetite, depressed bone Ca and Zn content, and
serum Zn.
• C. carpio: Reduced growth, cataracts, loss of appetite, high mortality, erosion of fins
and skin, elevated tissue concentration of Fe and Cu in intestine and
hepatopancreas.
• O. mykiss: Reduced growth, increased mortality, cataracts, short body dwarfism, fin
erosion.

23. Calcium
• High requirement for elaboration of calcified tissues such as bones and scales and
maintenance of electrolyte levels.
• Deficiency unlikely, Ca can be readily absorbed branchially.
• Imbalances with other dietary components leads to metastatic calcification and
impaired absorption of iron, copper and zinc.
• Anorexia, poor growth and poor feed efficiency are the general deficiency signs in
most of the fishes.
• I. punctatus- Reduced growth, low carcass ash, Ca and P content (fed vitamin
deficient diet).
• O. mykiss- Anorexia, poor growth and feed efficiency.
• A.japonica- Anorexia, poor growth and feed efficiency.
• P.major -Anorexia, poor growth and feed efficiency

24. Ca toxicity
• Pisciform granulomata with calcification and nodular granulomata throughout the
body and even in the eye and brain.
• Excess dietary Ca may be associated with nephrocalcinosis and lithiasis.
Obstruction of the ureters with calcified
deposits in the nephrocalcinosis syndrome.
Renal calcification in the rear part of the
kidney in rainbow trout

25. Late stage of nephrocalcinosis. The tubules and
collecting ducts are grossly distended by solid
accumulations of calcified material
Cholelithiasis in a growing salmon. The grey-
white granular ‘stones’ distend the gall-
bladder.

26. Some other toxicity signs
Lead: blackening of the caudal area/black tail and scoliosis, lordosis, anaemia,
degeneration of caudal fin.
Cadmium: very specific syndrome of hypocalcaemia, hyperexcitability and
osteoporosis. Other includes scoliosis, decreased bone calcium content etc.
Chromium: Reduced growth and feed
efficiency.

27. Conclusion
• Where mineral deficiency do arise, they are almost invariably associated with a reduction
in bioavailability rather than straightforward deficiency.
• Availability can be reduced because of interaction between different dietary components,
due to either mineral imbalance or presence of particular levels of dietary ingredients such
as fibre or certain vitamins, which modify uptake.
• Phytic acid, for example, derived from plant proteins, may chelate certain minerals and
reduce their availability.
• Commercial diets, as were formulated in the past, often had high levels of calcium, or ash
supplied to the diet from the fish meal component, especially fish meals produced from
filleting byproduct.
• These can significantly affect the availability of trace elements, which have to be heavily
supplemented if deficiency conditions are to be avoided.

28. References
• Roberts, R.J., 2012, Fish Pathology, Wiley Blackwell Publication, fourth edition,
pp.402-424
• Halver, John E., Hardy, R.W., 2013, Fish Nutrition, Elsevier Publication, third edition.
• FAO corporate document repository,2015, DISORDERS IN MINERAL NUTRITION,
Produced by: Fisheries and Aquaculture Department
• Javed, M., 2013. Chronic effects of nickel and cobalt on fish growth. Int. J.
Agric. Biol., 15: 575‒579
• Watanabe,T., Viswanath Kiron,V., Satoh,S.,1997, Trace minerals in fish
nutrition, Aquaculture 151 : 185-207

29. THANK YOU…