Aadil Hussain Magloo SKUAST-K Faculty Of Fisheries

1. CREDIT SEMINAR
TOPIC : STOCK ENHANCEMENT STRATEGIES
PG STUDENT :
AADIL HUSSAIN MAGLOO
Reg. no: 2017-F-72-M
DIVISION : FISHERIES RESOURCE MANAGEMENT

2. • Major Advisor: Dr. Farooz Ahmad Bhat.
• Major Subject: Dr. Tasaduq Hussain Shah.
• Minor Subject: Dr. Adnan Abubakr.
• Major Supporting: Dr. Bilal Ahmad Bhat.
• Additional Member Dr. Feroz Ahmad Shah.
• Dean’s PG Nominee: Prof.(Dr.) M.H. Balkhi.
Advisory Committee

3. INTRODUCTION
 The aim of Stocking, transfer or introduction of fish is to improve the
quantity or quality of catches.
 Over the past 50 years 237 species have been introduced into 140 countries.
 Stocking is commonly used to mitigate loss of stocks and enhance catches
 Enhancements are separated into two types:
– Stock enhancement of wild fisheries - The enhancement of stocks in wild,
large water bodies with species that may or may not be self-recruiting.
– Culture-based fisheries - The stocking of small water bodies. stocking activity
is the only means of sustaining the fishery.

4. OBJECTIVES OF STOCKING
 The reasons for stocking are many and varied but generally
fall into four main categories
Stocking for
mitigation
Stocking for
enhancement
Stocking for
restoration
Creation of new
fisheries
i.
ii.
iii.
iv.

5. STOCKING FOR MITIGATION
 Stocking carried out to mitigate a disturbance to the environment
from human activities such as reservoir dam construction, land
drainage works or similar habitat perturbation.
 Stocked fish may be released into unaffected parts of the river
catchment or lake, and the impact on the wild stocks in these areas
must be considered.

6. BAGLIHAR DAM
STOCKING FOR MITIGATION

7. STOCKING FOR ENHANCEMENT
 Stocking carried out where production is less than the potential of
water body.
 This type of stocking is used where fishermen express
dissatisfaction with the quality of fishing.
 To enhance stocks in sections of river where access is restricted by
natural barriers.
 The majority of stocking activities falls into this category.

8. GANGBAL LAKE
(JAMMU AND KASHMIR)
STOCKING FOR ENHANCEMENT

9. STOCKING FOR RESTORATION
 Stocking carried out after a limiting factor has been removed, e.g.
water quality improvement, habitat restoration or the easing of
passage for migratory fish.

10. CREATION OF NEW FISHERIES
 This category includes attempts to establish a new
stock of fish in a water body, which has not
previously held that stock because of natural barriers,
evolutionary isolation.
 AIM:- increase species diversity, improve fish yield
or fill an apparent vacant niche.

11. Potential risks from stocking
Genetic interaction Ecological interaction

12. Genetic interaction
– Salmon from different catchments, and to a lesser extent
from within the same catchment, exhibit genetic variation.
These genetic differences may manifest themselves in
growth potential, age at maturity, fecundity and adaptation
in a particular environment.
– Stock from non-indigenous sources may be less adapted to
the environment into which they are released, and stocking
may be less successful than expected.
– Where possible, stocking should be restricted to those using
fish derived from local populations or fish that have not
been held in captivity for more than one generation.

13. Ecological interaction
 Carrying capacity of the target habitat
 It is the capacity of the recipient system to support the enhanced
stocks.
 If too many fish are present, it will result in increased mortality
rates and increased dispersion.
 While stocking may increases the fish numbers but no more fish
will survive than the habitat will allow.
 Overstocking can lead to a reduction in the performance of the
fishery, below that prior to the introduction.
– example, when the spawning stock of salmon exceeds an
optimal level, the number of smolts may decrease.

14. Disease control
 With the transfer of stocks between water bodies, there is an
obvious risk of disease transmission. So all fish should be
certified disease-free before stocking.
 If any possibility of disease transfer exists, the fish should be
held it quarantine until the risk has been assessed.
 It is also possible that fish introduced from one system to
another may not be resistant to an endemic disease and the
stocking exercise may be unsuccessful.

15. Stocking strategies
When undertaking a stocking programme there are many procedures which
should be considered, like :-
Source of fish Stocking density
Size or age of stock Timing of stocking
Mechanism of
release
1
3 4
2
5

16. Source of fish
FOR SYSTEMS WHERE SPECIES IS
EXTINCT
For depleted or relict stocks
For rivers where new species to be
introduced1
2
3

17. Options for rivers where new species
to be introduced
• Farm-reared fish, certified disease-free.
• Stock from a lake or part of a river with a similar environment
should be quarantined.
• Stocked fish should not have been reared in captivity for more
than one generation.

18. Options for depleted or relict stocks
 Build-up of stock by hatchery production based entirely on
local stock and return brood stock to home system.
HATCHERY DAL LAKE
Schizothorax spp. (seed)
BROOD STOCK

19. OPTIONS FOR SYSTEMS WHERE
SPECIES IS EXTINCT
• Donor stock should have the same biological characteristics as
the recipient system.
• Stock chosen from a lake or part of a river with a similar
environment (e.g. size of stream, gradient, water temperature,
flow regime, altitude).
• Obtain stock from anywhere they are cheaply available, ideally
from a number of sources, to maximize range of genetic
material

20. Preconditioning and acclimatization
• Fish should be preconditioned to survive the
prevailing conditions in the receiving water body.
• Fish which are to be transferred from still water to
a river should be exposed to running water
conditions for an extended period before their
release. This exercising builds up the red muscle
tissue in the stocked fish, thus increasing their
ability for sustained swimming.
• Acclimatization to temperature is also thought to
be important.

21. Handling and transportation of stock
• Handling and transportation cause stress and possibly damage
to fish.
• The techniques employed to capture the fish should cause
minimum damage; seine netting and ‘controlled’ electric
fishing are the preferred techniques.
• All fish should be starved for at least 24h prior to
transportation to reduce oxygen demand, and minimize
ammonia production.
• If the fish are to be transported long distances consideration
should be given to reducing the effective toxicity of un-ionized
ammonia by lowering the temperature.

22. Stocking density
• In lakes a relationship exists between shore line development,
depth and predicted fish biomass.
Stocking rate (S) = { q p/w} e –z(te-to)
• S = no. of fish to be stocked q = yield that can come from spp. In question
• W = mean wt. at capture to = age at stocking
• te = age at capture -z = total mortality rate

23. Stocking density
No definitive relationship is available for calculating
stocking density of different species in rivers.
It is generally based on the experience of the
managers.
The most important issue is that overstocking should
be avoided.

24. Size and Timing of stocking
 Size :-
• Fry is the most effective life history stage to stock as the return rates are
greatest.
 Timing of stocking :-
• stocking in spring is more efficient (4—12 times) than winter.
• Fish should be stocked when the flow rates and water temperature are
generally low, to minimize displacement of fish and stress respectively.
• The stocking should preferably take place when the productivity of the
receiving water is high.

25. Mechanism of release
• Three mechanisms for releasing fish are used
I. Spot planting - introducing all the fish into the
receiving waters at the same site.

26. II. Trickle planting
Introducing fish into the same region over a period of
time.
STOCKING OF 2017 SPRING COHORT
STOCKING OF 2018 SPRING COHORT

27. III. Scatter planting
Introducing fish into several sites in the same
region.