Is fisher knowledge reliable ?
Murray crayfish (Euastacus armatus) in Australia
Sylvia Zukowski
Robyn Watts, Allan Curtis
Local ecological knowledge (LEK)

A group of individuals hold a body of
knowledge, often site-specific, about their
ecological systems

Generated through experiences and can
be passed down through time
Fisher LEK
Often broad and detailed
 Stems from

– ongoing and often extensive interactions with
the environment in which they fish
– interactions, knowledge transfer and
observations of other fishers
Fisher LEK
BUT ongoing arguments
between fishers,
scientists and managers
about reliability of
knowledge.

Thus, often
underutilised
Questions
1.
Is fisher LEK comparable to scientific
studies?
2.
Can recreational fishers provide a reliable
source of knowledge for fisheries
management?
Case study
Compare fisher ecological knowledge and
scientific investigations
 Murray crayfish (Euastacus armatus)
 Size and sex ratios

Murray crayfish (Euastacus armatus)

Iconic and highly prized recreational
fishing species
Current status unclear
 Reported population disturbances i.e.
changes in abundance, distribution and
size and sex ratios.

Current NSW MC Fishing Regulations
MIN SIZE: 90 mm orbital carapace length (OCL)
BERRIED FEMALES: Protected
BAG LIMIT: 5 per day per person
NET LIMIT: 5 per person
CLOSED WATERS
OPEN SEASON: May to Aug inclusive
Data Collection
1.
2.
3.
Qualitative fisher interviews
Quantitative fisher catch cards
Quantitative crayfish field
surveys
Field sites
Results
1.
Qualitative fisher interviews
2.
Quantitative fisher catch cards
3.
Quantitative crayfish field surveys
1. Fisher interviews
Observations
1. Skew in sex ratio of larger crayfish 2. Catch dominated by crayfish < 90
towards females
mm
All been fished out, now nothing but small males We’re only pulling up small crays now.
and large females.
Taking just the males could lead to problems. The Last year we got a whole heap of small crays but
number of large males has decreased and the you never get the big males anymore.
large females increased.
25 years ago, there were a lot more large males Used to catch heaps around here, big ones too. Now
and not so many large females, now there’s many there’s only the small ones left and not much of them
more large females than large males.
around either.
There are now a lot more bigger females than It’s not sustainable, the big guys are getting wiped
males. That can’t last in the long term.
out and there are too many little guys.
Don’t even get any larger males anymore, all I have been catching Murray crayfish for over thirty
that’s left is the large females that you can’t take years and the big hauls of legal sized crayfish are a
anyway.
thing of the past.
2. Fisher catch cards:
Length frequencies
30
Frequency
25
Females
Males
20
15
10
5
0
30 40 50 60 70 80 90 100 110 120 130 140 150
Occipital carapace length (mm)
3. Crayfish surveys:
Length frequencies
Females
Males
60
Frequency
50
40
30
20
10
0
40
50
60
70
80
90
100 110 120 130
Occipital carapace length (mm)
Female gonopores
3. Sex ratios
Sex ratio
(OCL)
Fisher
Scientific
Fisher vs.
catch cards
surveys
scientific
Ratio
(M:F)
Ratio
(M:F)
P Value
All size
classes
0.72
1
0.70 1
0.6781
≥ 90 mm
0.36
1
0.46 1
0.3905
Male
Great success!
1.
Fisher LEK and catch data was
comparable to scientific studies.
1. The sex ratio of larger crayfish (≥ 90 mm OCL)
was skewed towards females.
2. Catch dominated by crayfish <90 mm OCL.
2.
If fisher LEK = scientific data, previous
papers have deemed it reliable.
Integration into management

Pro-active management

Engagement of fishers
Scientist
Manager
Fisher
THANK YOU