sustainalbe fishery management / fishery resource and stock
DESCRIPTION
Fishery Resource is Aquatic Animals and Plants which is good for fishery Fishery resource is a renewable resource. Stock is an unit of fishery management. Various method of stock identification A stock has its sex, length and age composition. Chi-square test is used for test the difference of sex ratio. Age determination is conducted from various age character (scale, otolith, shell etc) Length composition will be converted to age composition by using ALKTRANSCRIPT
Fishery Resource and Stock
Takashi Matsuishi At SERD, AIT, Thailand 24Feb-14Mar, 2014
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Resource
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Resource
Things that human do NOT use : things, garbage
Things that human use: resource
Fish: good for use / not good for use
Fishery Resource
Aquatic Animals and Plants
which is good for fishery
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Categories of Resource
Environmental Resource
Non Renewable Resource
Renewable Resource
Environmental Resource
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Water, Air, etc
It circulate as it is.
Usage: Use it without pollution or contamination
Stock
Non-Renewable Resource
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Finite Resource
Resource that does not renew itself at a sufficient rate for
sustainable economic extraction
Oil, Gas , metal ores
Usage: Use it as small as possible to use it longer
Stock
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Renewable Resource
Resource which can fill up again with the passage of time,
either through biological reproduction or other naturally
recurring processes.
Fish, Forest, Crops, Animal husbandry
Usage: Use as much as its reproduction
Stock
Reproduction
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Fishery Resource is a Renewable Resource
Reproducible
Unlimited sustainable Use
May deplete if the usage is wrong
Stock
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Resource and Stock
Resource
a stock or supply of materials or assets
Stock
a supply of goods or materials available for sale or use
(Concise Oxford Dictionary)
CONFUSING
If resource is gathered for use,
it is called Stock.
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The unit of stock
Stock : the population that made same population
dynamics
Species / population / sub-population etc.
Genetic definition: Mendelian population with a same
gene pool(Numachi1974)
Stock
= the object of stock assessment
= the object of fishery management
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Stocks of Walleye Pollock around Japan
Sea of Japan
Catch (2009)
15,000t
Nemuro
Catch (2009)
9,500t
Pacific
Catch (2009)
169,000t
Okhotsuku
Catch (2009)
26,000t
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Walleye Pollock
J-stock P-stock
Cat
ch (
1000t)
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Stock Identification
Morphological Method
Proportion, number of bones
Morphometric / Meristic
Character
Ecological Method
Difference of Spawning
season, Spawning area,
Length composition
Mark-Recapture Method
Confirm the existence of
mixture
Fishery Condition
Consistency of the catch
trends
Genetic Method
Test the samples are from
same Mendelian Population
Genetic difference made by
mutation
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Example of Herring around Hokkaido
Hotta, Matsuishi, Sakano, Kanno, 1999, Nissuishi
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Japanese Sand Smelt
Suzuki, Kobayashi, Matsuishi, Numachi (2000) Nissuishi
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Property of stock
The stock will described in the item
Habitat Area / Fishing Ground
Morphological Features (Body Length, Pictures, Colour)
Ecological Features (Prey, Predator)
Life History (Age at Maturity, Longevity)
Composition
Sex composition
Length composition
Age composition
Sex ratio
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Sex ratio
Ratio of male to female.
Basically it is near One for fish.
If the behaviour of the fish is different in sex, the sex ratio
in a certain fishing ground would not be one
If the growth of the fish is different in sex, the sex ratio in
a certain fishery with length dependent selectivity would
not be one.
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Statistical test of that the sex ratio
Number of male : n1(≥5)
Number of female: n2 (≥5)
If
then the sex ratio is significantly different from one.
(p<0.05, chi-square test)
It is difficult to test that the sex ratio is EQUAL to
one. You may find some difference from one if you
collect more samples.
84.305.0,12
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2
212
0
nn
nn
Age determination
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Methods of Age determination
In captivity
The growth speed may different to the wild situation
Mark- Recapture Method
Can not estimated absolute age
Length Composition
Difficult to determine the older age
Can not estimated absolute age
Age Character
Labourious but accurate and precise
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Age Characteristics
Scale
Otolith
vertebra
Fin ray
Shell
Scale of
Rosy seabass http://www.pref.niigata.jp/norin/chiiki/suikai/joho/dayori/9gou/akamutu.htm
Otolith of Kichiji Rockfish http://hnf.fra.affrc.go.jp/H-jouhou/seika/hnf98008.html
Shell of Abalone http://www.pref.kyoto.jp/kaiyo/kenkyu-koborebanashi-awabinenrei.html
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Age composition
A stock contains many year class or cohorts
Age composition is the relative abundance of the year
classes at a certain year
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Walleye Pollock Pacific Ocean
Biomass displayed by Year Class
http://abchan.job.affrc.go.jp/digests19/details/1913.pdf
Bio
mas
s (1
000t)
Year
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Dominant Year Class
a year class that predominates in the fishery, often
continuing over several years
It appears frequently in Herring, Walleye Pollock etc
It may be difficult to the appearance of the dominant class
just after the appearance when the young fish are not
targeted for fishery.
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Catch at age
Catch at age is the number of fish caught by year by age.
It is not a age composition of the stock, because the catch
at age is the result of fishery with selectivity
Age based population estimation method (eg. VPA) uses
Catch at Age
Catch at Age is often calculated from Length
Composition and Age length Key
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Length Composition
Length composition / Length frequency distribution
In Stock / In Catch fish
It reflects stock status
If exploitation is too strong, the frequency is moved to small side
If dominant year class is appeared, the length composition has a peak
Peaks sometimes represents year class
In younger age, it is clear
In older age, it is not clear because of the slow growth
In Crastacetean, the peak reflects the molting age
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0
500
1000
1500
2000
2500
8 10 12 14 16 18 20 22 24 26 28 30 32 34 36
Cat
ch in
Num
ber
Body Length
Age Composition of Yellowback seabream Dentex tumifrons
Akamine(2007) P5
How to measure the body length
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Fish Measurement Board
Fish Length
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Age – Length Key (ALK)
Key matrix to convert catch at length to catch at age
Procedure
1. Making ALK
Get sample
Measure length, and aging (e.g. 20 fish for each length class)
Make ALK
2. Length Composition
Get many measurement (e.g. 1000) and get length composition
Estimate total # fish caught (Total Catch / average weight)
Make catch at length table from length comp. and total # catch
3. Calculate Catch at Age by using ALK
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Simple example of ALK
Virtual data
BL (mm)
ALK
1 2 3
[80-100) 100% 0 0
[100-120) 20% 70% 10%
[120-140) 0 20% 80%
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Catch at Length
BL (mm)
Length Composition
Catch at Length
[80-100) 30% 3,000
[100-120) 50% 5,000
[120-140) 20% 2,000
合計 100% 10,000
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Calculation of catch at age
BL(mm) Age
Total 1 2 3
[80-100) ALK 100% 0 0 100%
#fish 3000 0 0 3,000
[100-120) ALK 20% 70% 10% 100%
#fish 1000 3500 500 5,000
[120-140) ALK 0 20% 80% 100%
#fish 0 400 1600 2,000
Total 4000 3900 2100 10,000
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Size Category Composition
Size Category Composition: a kind of size class decided in
market or middleman to classify the fish size for sale
Example: Size Category of Sea Bream in Nagasaki, Japan
You can convert the size category to age composition if
you make the age category key
3S 2S S M L
-15cm 15-20 20-30 30-40 40-
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Summary
Fishery Resource is Aquatic Animals and Plants which is good for fishery
Fishery resource is a renewable resource.
Stock is an unit of fishery management.
Various method of stock identification
A stock has its sex, length and age composition.
Chi-square test is used for test the difference of sex ratio.
Age determination is conducted from various age character (scale, otolith, shell etc)
Length composition will be converted to age composition by using ALK