Perspectives and dilemmas for small-scale fisheries management in African freshwater fisheries - PowerPoint PPT Presentation


PPT – Perspectives and dilemmas for small-scale fisheries management in African freshwater fisheries PowerPoint presentation | free to download - id: 5d3970-YjAyY


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation

Perspectives and dilemmas for small-scale fisheries management in African freshwater fisheries


Title: 3 major dilemmas on small-scale fisheries management: Author: Kolding Last modified by: Kolding Created Date: 9/25/2007 9:06:25 AM Document presentation format – PowerPoint PPT presentation

Number of Views:121
Avg rating:3.0/5.0
Slides: 66
Provided by: Kold5


Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Perspectives and dilemmas for small-scale fisheries management in African freshwater fisheries

Perspectives and dilemmas for small-scale
fisheries management in African freshwater
  • Jeppe Kolding (University of Bergen)
  • Small-scale fisheries - A challenge for fisheries
    management - Experiences and lessons from
    developing countries and Norway.
  • Fisheries Forum (Fiskerifaglig Forum)
  • 4 5 October 2007

  • Inland fisheries (and small-scale fisheries in
    general) are the social security system in
    Africa A common good!
  • Serves as the last resort when everything else
  • How should they be managed?
  • How can they be managed?

3 major dilemmas on small-scale fisheries
  • Why does the common property theory (CPT) only
    apply to man, and not to other predators? they
    are also harvesting a common.
  • Why are we controlling effort increase (f), while
    we at the same time refine and develop the
    catchability (q)?
  • Why is man the only predator that has a
    harvesting pattern completely opposite all other

Small-scale fisheries comprise
  • gt 30 of total world captures
  • gt 50 of total landings for human consumption
  • gt 90 of all fishermen
  • 80 live in Asia
  • Many ecosystems only exploitable on a small-scale
  • Coastal lagoons
  • Tidal flats, shallow shores
  • Estuaries
  • Coral reefs
  • Most freshwaters (contribute 25 of global

Marine and inland capture fisheries top 10
producers 2002
China, India and Indonesia have populations of
nearly 1 billion people living below the UNDP
poverty line of US 1 per day (Staples et al.
(SOFIA 2004)
Importance of fish for people
The richer the less dependent on fish
Relationship between the proportion of fish
protein in human diets and the relative wealth
(measured as GPD) of the nations they live in.
From Kent (1998)
Small-scale fisheries
  • Research generally very, very small (mostly
  • Most fisheries biologist are dealing with large
    scale industrialized fisheries
  • Quantitative SSF data limited or nil
  • Problems and management?
  • copied from industrial fisheries
  • (the ruling paradigm)

Small-scale fisheries
  • Mostly associated with developing countries
  • traditional - antiquated - primitive
  • poor - needs development
  • unmanaged - resource depleting - challenge
  • overfished
  • Tragedy of the commons
  • Having a negative image
  • Illegal and destructive gears
  • Ignore regulations and legislation
  • Unruly members of society
  • Subject to Maltusian overfishing
  • Poverty trap
  • Unselective, indiscriminate fishing methods

Small-scale fisheries
  • Thus, plenty of arguments for
  • They need to be managed!
  • 90 of projects use one or several of the above
    reasons for justifications
  • But how to manage them? when
  • Little research little knowledge
  • Multi-species and multi-gear situations
  • Negligible monitoring
  • Unwillingness to abide
  • Costly to enforce
  • The present answer (panacea) seems to be
  • Co-management and MPAs
  • They must learn to understand their own good

But do we understand their best ?
Traditional fisheries management
Management paradigm
  • The present mainstream research is focused on
  • Industrial (valuable) fisheries
  • Single-species considerations
  • F, TAC, Quotas, size-limits
  • Enhanced selective harvesting strategies
  • Purpose A selective kill on targeted species and
  • Result Dominate our thinking (paradigm) and
    forms our perception on small-scale fisheries
  • EAF (ecosystem approach to fisheries) is only
    recent on the agenda (Johannesburg 1992) and
    only conceptually debated we dont know how!

Patterns of exploitation
  • Selectivity rooted in all fisheries theory
  • Mesh size regulations
  • Gear restrictions
  • By-catch
  • Destructive methods
  • seining
  • beat fishing
  • barriers, weirs
  • small mesh sizes
  • In industrial fisheries non-selectivity BAD
  • Result Universally applied - also in

Almost universally banned in Africa
The selectivity paradigm
  • FAO 2003 (Ecosystem Approach to Fisheries)
  • "Selectivity, or lack of it, is central to many
    biological issues affecting fisheries. Bycatch or
    incidental capture is responsible for endangering
    and contributing to extinction of a number of
    non-target species. In addition, the discarding
    of unwanted catch, which is particularly
    important in unselective fisheries, is being
    considered by society not only as wasteful but as
  • The Code of Conduct dedicates a whole section to
    the issue (8.5). It promotes the use of more
    selective gear (7.6.9 8.4.5) and calls for more
    international collaboration in better gear
    development (8.5.1 8.5.4), as well as for the
    agreement on gear research standards.

SSF management Copypaste
  • Industrial fisheries are single species fisheries
    with single species management
  • They are so large and valuable that research and
    CMS is invested for management decisions
  • Small-scale fisheries are multi-species,
    multi-gear, too small to warrant research.
  • Our understanding and assumptions on which we
    base our management is directly inherited from
    large-scale fisheries.

Q1 Why does the common property theory (CPT)
only apply to man, and not to other predators?
  • In the balance of nature it is generally
    assumed that
  • predation is the most important factor in natural
    mortality of fish (Sissenwine 1984 Vetter 1988
    ICES 1988),
  • adaptations tend to maximize fitness through
    optimal utilization of resources (Slobodkin 1974
    Stearns 1976 Maynard-Smith 1978),
  • predators and prey are co-evolved (Slobodkin
    1974 Krebs 1985) and,
  • there is an uni-modal response of prey
    productivity to predator densities
  • (sigmoid curve theory logistic Gordon Schaefer

Logistic growth Surplus production
The rate of change in biomass production as a
function of the biomass is uni-modal
Logistic growth - predator-prey
  • From above principles it is reasonable to assume
    that predation would 'maintain' prey populations
    close to their highest average production rate
    (Slobodkin 1961, 1968 Mertz Wade 1976 Pauly
    1979 Caddy Csirke 1983 Carpenter et al.
  • The argument follows simply from the sigmoid
    curve where the highest surplus production of the
    prey population (dN/dt max) is the 'carrying
    capacity' (K) of the predator population.

Thus predators can in theory grow to reach K (
MSYprey), but if they overshoot they will reduce
prey production and consequently decline
themselves. This is the background for density
dependent cascade theory, and the coupled
time-lagged oscillations observed between
predator and prey
Predator-prey Cascading effects
  • Inverse biomass trends illustrating trophic
    cascades in the Black Sea (from Daskalov 2002)

What has this to do with CPT?
  • The big question is if effort is controlling the
    productivity or if the productivity is
    controlling the effort? Are small-scale fishermen
    different from other predators?
  • The answer to this dilemma is fundamental for
    applying CPT and co-management!
  • If we close for open access it will have severe
    consequences for the last resort option
  • By closing open access we are in fact, closing
    the social security system of Africa!

Productivity in African lakes
  • Morphology
  • of a lake, particularly area, volume, depth, and
    shoreline development or gradient, is of major
    importance to the productivity (Ryder 1978).
  • The mean depth encapsulates several of these
    attributes and is considered as the most
    important (Rawson 1952, Ryder et al. 1974, Mehner
    et al. 2005).
  • Nutrients
  • Lakes do not maintain fertility unless continual
    external loading of nutrients is applied
    (Schindler 1978, Moss 1988, Karenge and Kolding
    1995). Water inflow is a major contributor and
    serves as a proxy for nutrient load.
  • Hydrology
  • The flood pulse advantage is the amount by
    which fish yield per unit mean water area is
    increased by a natural, predictable flood pulse
    (Bayley 1991). The flood pulse keeps the
    environment in a stage of early succession, which
    means that it is dominated by biota with
    r-selected traits (Junk et al. 1989).

The physical basis for lake productivity
Not considered here
Generalised effects of climatic, morphological,
edaphic and hydrological factors (X-axis) on
productivity (Y-axis)
Relative Lake Level Fluctuation Index (RLLF)
  • encapsulates the morphological, edaphic and
    hydrological driving forces for productivity into
    a single quantity.
  • is a dynamic extension of the MEI index that
    only incorporated morphological and edaphic
  • builds on the flood pulse concept (Junk et
    al. 1989) and the flood pulse advantage
    (Bayley 1991)

Hydrology and fish yields
  • Variability around the trend of total inland
    catches of the SADC countries show decadal
    fluctuations possibly influenced by long term
    climate variations (water levels)

Lake levels as drivers of fish productivity
Lake Kariba 1982-1992 Karenge and Kolding (1995)
Lake Turkana 1972-1989 Kolding (1992)
  • Mean annual catch rates varies with water levels
    in most African fisheries. This has long been
    known by local fishermen, but not much

Data on catch, effort and water levels
  • 17 major lakes and reservoirs in Africa.
  • Monthly time series (Min years 9) of lake
    levels from gauge readings (N 13) or satellites
    (N 4)
  • ESA http//
  • Yield and effort estimates from 1990s (Updated
    from Jul-Larsen et al. (2003) and various
    projects we have been involved with).

Kolding and van Zwieten (2007)
Highly fluctuating
Africa Yield (production) is highly correlated
with RLLF
  1. Data too old for comparison (1970s)
  2. Oligotrophic large areas inaccessible
  3. Unreliable records Kapenta not incl.

Similar results from Asian reservoirs..
From Kolding and van Zwieten (2006)
  • Relationship between mean annual yield (t/km2)
    and relative seasonal lake level fluctuations
    (RLLF-s (annual draw downs/mean depth)) in 15
    reservoirs of the lower Mekong countries. Data
    from Bernascek (1995)

Africa Fishing effort is highly correlated with
  1. Data too old for comparison (1970s)
  2. Unreliable records

but catch rates are not correlated with RLLF
  • Indicating.

effort seems self-regulating (from CPUE)
Average yield per fisher is 3 ton per year
irrespective of system
Is yield driven by effort or is effort driven by
Adapted from Jul-Larsen et al. 2003
  • No management Natures management

Does CPT apply?
  • Effort in African lake fisheries seems
    self-regulated by system productivity
  • Effort grows until the average catch rate per
    fisher reaches around 3 ton per year
  • Highest effort in most productive and resilient
    systems. Less effort in low productive vulnerable
  • is there need for co-management?

Q2 Why are we afraid of effort increase (f),
while we at the same time refine and develop the
catchability (q)?
  • What are the options of management regulations?
    They can all be traced back to the simplest
    version of the so-called catch equation
  • We can regulate directly or indirectly on Yield
    (Y), Fishing mortality (F) or Biomass (B).
  • That is all. Any available or conceivable
    regulation can be reduced to one of the three

Management regulations what are the options?
BMSY, Minimum SSB, MBAL, Bpa
Size of capture tc Mortality index
ZFM Exploitation rate E F/Z Effort control
f F/q F control F0.1, Fmed etc. Closed
area Closed season
Management regulations
  • The choice of management regulations depends on
  • Knowledge of the stock (research, monitoring)
  • Control of the fishery (compliance, statistics)
  • Management level (distribution, quotas)
  • In terms of required knowledge (
    management costs) then
  • B gt Y gt F, where for the latter f gt q

SSF q - management
  • For fisheries where little or nothing is known,
    management regulations are always based on
    regulating catchability q (in particular
  • Mesh size
  • Size of capture
  • Gear regulations (e.g beach seines)
  • Closed area or season (e.g. MPAs)
  • When nothing is known these regulations are based
    on assumptions (often based on model results).
  • Next step is effort (f) control, then TAC etc.
  • Each new step requires exponential increase in
    research and monitoring.

Find one example where one or several of these do
not apply
  • Introduced because of the failures of enforcing
    existing management regulations
  • Based on the same assumptions as conventional
    management (CPT, i.e. avoiding the tragedy)
  • Tragedy can be avoided if the common (read
    open access) is removed ? fishers become
    responsible for the resources
  • Regulations are the same (always q-based) but
  • Who are the fishers?
  • Who will control access? Who will benefit?

Fishing mortality (F)
Better methods Increasing these is development
Fishing mortality (F)
So while we manage and develop the fishing
mortality stays the same. Who are we helping?
More of the same Decreasing these is management
Catchability vs. effort
  • Increased efficiency (q) requires increased
  • Decreased effort (f) requires increased control
  • But the exploitation pressure on the fish stocks
    will often be the same
  • - or even higher with investment (q) driven
    development (exit is no longer easy)
  • Only difference is a few rich vs. many poor
    fishermen but that is not a biological issue!!

  • The conclusion of Jul-Larsen et al. (2003) was
    that investment driven growth (q), was much more
    dangerous than population driven growth (f)
  • But this is exactly what we promote!!

Q3 Why is man the only predator that has a
harvesting pattern completely opposite all other
  • Related to previous question
  • Per definition then
  • F q s when effort 1
  • ? Fishing mortality catchability selectivity
    for one effort unit
  • Harvesting pattern is how the fishing mortality,
    catchability, or selectivity is aimed at the
    target species (prey) over its lifetime

Predation vs fishing mortality..
.. is almost exactly opposite
Fishing mortality
From ICES (1997).
..and this is what happens
Median age-at-maturation (sexes combined) of
Northeast Arctic cod based on spawning zones in
otoliths (from Jørgensen, 1990).
But we know that we even use it as a sign of
Age and size structure changes under selective
fishing to younger and smaller individuals.
Age and size structure
  • As age and size structure changes
  • under selective fishing to younger and smaller
    individuals, there will be a decrease in
  • size (age) of maturity
  • fecundity,
  • egg quality
  • egg volume,
  • larval size at hatch,
  • larval viability,
  • food consumption rate,
  • conversion efficiency,
  • growth rate.

So, is this inevitable?
Life history and natural selection
  • Dying is more certain than giving birth!
  • Most ecological processes and life history traits
    can be related to the prevailing mortality
  • The unstable environment characterised by
    discrete, density independent, non-predictive,
    non-selective mortality induced by physical
  • The stable environment characterised by
    continuous, density-dependent, predictive, and
    size-selective mortality induced by the biotic

Copes rule
Mean size of organisms
Stable period
Stable period
Stable period
Stable period
Geological time
Cope's rule states that evolution tends to
increase body size over geological time in a
lineage of populations. But the precondition is
geological stability. During unstable periods
with mass extinctions the large lineages are more
susceptible. Investment in age (size) is
investment in future.
Life history r-K selection
  • r-selected species
  • Small
  • Rapid growth
  • Early maturation
  • No parental care
  • Opportunistic
  • Colonisers
  • Unstable environment
  • Resilient
  • K-selected species
  • Large
  • Slow growth
  • Late maturation
  • Parental care
  • Specialised
  • Competitors
  • Stable environment
  • Vulnerable

Logistic growth r-K selection
Carrying capacity B8 K
  • r-selected species
  • Small
  • Rapid growth
  • Early maturation
  • No parental care
  • Opportunistic
  • Colonisers
  • Unstable environment
  • Resilient
  • K-selected species
  • Large
  • Slow growth
  • Late maturation
  • Parental care
  • Specialised
  • Competitors
  • Stable environment
  • Vulnerable

r-K selection as a function of mortality pattern
Slope total mortality rate Z rmax
Abundance (Log N)
Age (size)
Kolding (1993)
K-selection Stable environment, biotic mortality
(predation) predictive r-selection Unstable
environment, abiotic mortality non-predictive
Evidence Size selection genetic changes
Increased mortality on
Mean individual weight at age for six harvested
populations after 4 generations. Circles,
squares, and triangles represent the small-,
random-, and large-harvested populations,
After Conover and Munch 2002
Effect of size-selective fishing
Mortality on
Trends in average total weight harvested (A) and
mean weight of harvested individuals (B) across
multiple generations of size-selective
exploitation. Circles represent small harvested
lines, squares are the random-harvested lines,
and triangles are the large-harvested lines.
Conover and Munch 2002
Size selective fishing with large mesh sizes on
adults Copes rule in reverse. We are
deliberately inducing r-selection on the stocks.
Man has a harvesting pattern that is opposite to
what most fish stock are naturally adapted to
Predation mortality
Instantaneous rate of mortality
Age (years)
When yields are declining our prescription is
even larger mesh sizes, which will only make
matters worse, and which we already know is wrong
North Sea multispecies system Effect of mesh
change from 85 to 120 mm
  • Percent changes in the long term fishery yields
    for North Sea stocks resulting from an increase
    in trawl mesh size from 85 to 120 mm for the
    directed fishery for cod.
  • Results are presented for
  • MSVPA including interspecies predation and
  • single species (but multi-fleet) assessment.
  • Lower yields in the MSVPA results are due to
    greater predation rates from large predatory fish
    (cod, whiting, haddock, saithe) released by the
    larger mesh sizes.
  • Source Anonymous 1989. Report of the
    multispecies assessment working group. Int.
    Counc. Explor. Sea., C.M. 1989/Asess 20,

Is non-selective fishing bad?
  • There is no empirical evidence
  • The notion comes from a theoretical model (Y/R)
    which is 100 synthetic and biologically wrong
    (constant parameters no density dependence)
  • On the contrary we know that selective fishing is
    bad, but we still advocate it!
  • But how do we impose gear-, mesh-, and size
    restrictions in a multi-species fishery?

Multi-species community
How should it be harvested? What should be
minimum mesh-size?
Biomass-size distributions
Selective fishing will change the slope
Size spectra
  • The distribution of biomass by body mass follows
    regular patterns

slope steepens when large fish removed
Jennings Blanchard, 2004
Fishing effects on community size-structure
Trends in size-spectrum slopes of the North Sea
Rice Gislason (1996)
Rotate the size spectra and..
Quaternary consumers
Tertiary consumers
Secondary consumers
Primary consumers
Primary producers
  • we get a Lindeman trophic pyramid

EAF What is the right fishing pattern?
How do we manage a multi-species fishery? What
is the right gears and mesh sizes?
How ?
How much ?
Small-scale fisheries are often non-selective !
Can we fish everything proportionally?
Example from lake Kariba, Zambia where fishers
are using illegal small-meshed nets
Parallel slopes, only intercept lower
Kolding et al. 2003
  • The system remains unchanged, except everything
    is less

  • The Tragedy of the commons is the tragedy of
    our current management thinking.
  • Can we universally apply notions that are
  • Developed for single species fisheries
  • Mostly theoretical
  • Often dubious
  • On SSF - of which we know so little?
  • We are mammals and we apply all our models and
    concepts based on mammal biology.
  • But fish in their breeding strategy are
    closer to insects or trees!!

Final questions
  • We try our best but are we doing it right?
  • Is our theory and paradigms appropriate?
  • How much do we know?
  • Why are we in the management mode when we have
    hardly started our research mode?
  • Most SSF in Africa are still largely unmanaged,
    but that is not a challenge - it is an
  • For studying the impact of fishing and learn!

Thank you for your attention
  • For SSF the real challenge for management is
  • How can we evolve our theories?

Slightly modified from Non Sequitur Herald
Tribune 11-12/8- 2007