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“FORGOTTEN SIGNALS IN FISHERIES MANAGEMENT”�

By, Deepak George Pazhayamadom

Department of Zoology, Ecology and Plant Science (ZEPS)

University College Cork (UCC), Cork, Ireland

Emer Rogan

(Department of ZEPS, University College Cork)

Ciaran Kelly

(Fisheries Science Services, Marine Institute)

Edward Codling

(Lecturer in Mathematical Biology, University of Essex)

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Fisheries Management

(Traditional approach)

DATA

Fisheries Management

(Alternative approach)

SSB, F

[Estimated Indicators]

(Stock abundance and Exploitation)

MODELS (Assumptions)

Monitor with Reference Limits

(Acceptable, Precautionary, Limit)

Regulate with output controls

HCR (Eg: TAC)

Other measures (Eg: Effort)

Next Year

Limit 1000 1.5

Precautionary 1500 0.8

Acceptable 2000 0.5

F

SSB

Statistical Process Control�[Signal Detection Method]

Statistical Signals

[Stock Indicators]

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Indicator Correlation

Spawning Stock Biomass
80202
76328
79513
81415
75314
59943
50442
51140
54575
57047
57825
64478
62176
68199
70223
62100
60945
63634
59247
59088
54698
58995
74582

Year
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006

Catch Numbers Age 8
7749
8542
6419
4637
6490
8806
5453
3406
3601
2758
1916
2317
3397
3214
3979
4003
3616
4883
2328
2537
1949
3220
1306

Correlation = Degree of relationship

0.7 = Good

0.8 = Better

0.9 = Very good

INDICATORS (Examples)

Catch numbers from age group 1

Catch numbers from age group 2

Catch weights from age group 5

Catch weights from age group 4

Proportion of catch numbers

Proportion of catch weights

CN6 [BAD INDICATOR]

r= 0.09310228

PATTERNS DONT MATCH

CN11 [GOOD INDICATOR]

r= 0.90395651

PATTERNS MATCH

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Y1	Y2	Y3	Y4	Y5	Y6	Y7	Y8	Y9	Y10	Y11	Y12	Y13	Y14

20
17
15
13
10

Acceptable Range (20-10)

Desired Value 15

19

16

18

13

18

15

20

15

12

14

11

10

8

15

5

10

15

20

AVERAGE LENGTH OF FISH FROM CATCH

(Traffic light monitoring)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

GREEN ZONE

PRECAUTION ZONE

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Y1	Y2	Y3	Y4	Y5	Y6	Y7	Y8	Y9	Y10	Y11	Y12	Y13	Y14

Corrective Action

5

10

15

20

1

STATISTICAL PROCESS CONTROL

(SPC)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

This is called a Control Chart

GREEN ZONE

CUMULATIVE SUM CONTROL CHART

(CUSUM)

Limits are statistically defined

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-7

0

(15)

7

POSITIVE DEVIATIONS

NEGATIVE DEVIATIONS

CONSTRUCTION OF

CUSUM CONTROL CHART

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ESTIMATED INDICATOR

Spawning Stock Biomass

STOCK INDICATORS

(Age based catch numbers and weights)

TRADITIONAL APPROACH

ALTERNATIVE APPROACH

COMPARISON

FOR WHICH YEARS ?

1. Cod (IS)

2. Megrim (CS & BB)

Acceptable In Control

Precautionary

Limit Out Control

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68	69	70	71	72	73	74	75	76	77	78	79	80	81	82	83	84	85	86	87	88	89	90	91	92	93	94	95	96	97	98	99	00	01	02	03	04	05	06

GOOD	BAD

Irish Sea Cod (Gadus morhua)

Reference Limits	B_pa B_lim	= 10,000t = 5000t
CN4	= Catch number from age group 4
CW4	= Catch weight from age group 4
CWABOVE	= Catch weight above age group 4
CNABOVE	= Catch numbers above age group 4

I – 1970

II – 1978

III – 1990

OC 1995

Traditional Approach - Spawning Stock Biomass

CN4

CW4

CWABOVE

CNABOVE

MATCH COLOUR CODES

Traditional Approach - Fishing Mortality

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Irish Sea Cod

I – 1970

II – 1978

III – 1990

OC 1995

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84	85	86	87	88	89	90	91	92	93	94	95	96	97	98	99	00	01	02	03	04	05	06

GOOD	BAD

Celtic Sea and Bay of Biscay Megrim

(Lepidorhombus whiffiagonis, L. boscii)

I – 1990

II – 2004