Atlantic Halibut fishing mortality estimated from tagging on the Scotian Shelf and the southern Grand Banks



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Cowen, L., Walsh, S. J., Schwarz, C. J., Cadigan, N. and Morgan, J. 2009. Estimating exploitation rates of migrating yellowtail flounder (Limanda ferruginea) using multi-state mark-recapture methods incorporating tag loss and variable reporting rates. Canadian Journal of Fisheries and Aquatic Sciences 66, 1245-1255.

Hoenig, J. M., Barrowman, N.J., Hearn, W. S. and Pollock, K. H. 1998a. Multiyear tagging studies incorporating fishing effort data. Canadian Journal of Fisheries and Aquatic Sciences 55, 1466-1476.

Hoenig, J. M., Barrowman, N.J., Pollock, K. H., Brooks, E.N., Hearn, W. S. and Polacheck, T. 1998b. Models for tagging data that allow for incomplete mixing of newly tagged animals. Canadian Journal of Fisheries and Aquatic Sciences 55, 1477-1483.

McCracken, F.D., 1958. On the biology and fishery of the Canadian Atlantic halibut, Hippoglossus hippoglossus L. J. Fish Res. Board Can. 15: 1269-1311.

Neilson, J.D., Waiwood, K.G., and Smith, S.J. 1989. Survival of Atlantic Halibut (Hippoglossus hippoglossus) caught by longline and otter trawl gear. Can. J. Fish. Aquat. Sci. 46, 887-897.

Pollock, K. H., and Raveling, D. G. 1982. Assumptions of modern band-recovery models with emphasis on heterogeneous survival rates. Journal of Wildlife Management 46, 88-98.

Seber, G. A. F., and Felton, R. 1981. Tag loss and the Petersen mark-recapture experiment. Biometrika 68, 211-219.

Stobo, W., Neilson, J.D., and Simpson, P. 1988. Movements of Atlantic halibut (Hippoglossus hippoglossus) in the Canadian North Atlantic: inference regarding life history. Can. J. Fish. Aquat. Sci. 45, 484-491.

Trzcinski, M.K., Armsworthy, S.L., and Wilson, S. 2010. Atlantic Halibut on the Scotian Shelf and Southern Grand Banks (Divs. 3NOPs4VWX5Zc) – Industry/DFO Longline Survey and Tagging Results to 2008. Research Document.



Trzcinski, M.K., Armsworthy, S.L., Wilson, S., Mohn, R.K., and Campana, S.E. 2010. A Framework for the assessment of the Scotian Shelf and southern Grand Banks Atlantic halibut stock. Working paper.

Table 1. Expected number of recoveries given fish tagged and released in year i and recovered in year j assuming a constant instantaneous natural mortality M, year-specific instantaneous fishing mortality under complete mixing and under incomplete mixing, constant immediate tagging survival , constant tag reporting rate and a probability that a fish released with 2 tags will have t tags retained (t=1, 2) in the kth year after release (k=1, …) . The extension to recovery years 4 and 5 follows the same pattern. Fishing is assumed to occur uniformly over the calendar year. Incomplete mixing of tags in the second half of the calendar year of release is allowed.




Expected recoveries in year




1

2

3

1







2








3












Table 2. The number of halibut tagged and released as part of the all-sizes tagging program by NAFO between 2006 and 2008 (n=2061).

NAFO

Proportion

Allocated



2006

2007

2008

Total

Proportion

of Total


3N

0.22

93

54

54

201

0.10

3O

0.13

32

57

58

147

0.07

3Ps

0.19

30

237

143

410

0.20

4V

0.19

103

264

185

552

0.27

4W

0.16

165

132

166

463

0.22

4X

0.12

103

84

101

288

0.14



Table 3a. Summary of recovery data. Each cell has two entries. The first entry is the number of fish with a single tag recovered; the second entry is the number of fish with both tags recovered. All fish released had two tags. Pooled over all lengths at release, all areas released, areas recovered, etc. Year classes are calendar years.

Year of release

Number released

Year of recovery

2006

2007

2008

2009

2010

2006

526

1 / 15

13 / 25

9 / 17

7 / 12

4 / 4

2007

828




5 / 13

34 / 75

23 / 35

12 / 12

2008

707







3 / 18

12 / 43

11 / 6



Table 3b. Summary of recovery data. Each cell has two entries. The first entry is the number of fish with a single tag recovered; the second entry is the number of fish with both tags recovered. All fish released had two tags. Only fish released that are 71+ cm but pooled over all areas released, areas recovered, etc. Year classes are calendar years.

Year of release

Number released

Year of recovery

2006

2007

2008

2009

2010

2006

478

1 / 14

12 / 25

8 / 16

6 / 11

3 / 2

2007

732




5 / 12

33 / 71

20 / 33

9 / 9

2008

659







2 / 15

12 / 42

11 / 6



Table 5. Estimated cumulative tag-loss.

Time at large (days)

Recovered fish with double tags

Recovered fish with a single tag

Estimated cumulative tag-loss.

(0,100]

36

3

0.04

(100,200]

16

11

0.26

(200,400]

99

46

0.19

(400,600]

46

30

0.25

(600,800]

42

29

0.26

(800,1200]

30

21

0.26

(1200,2000]

5

4

0.29




Table 4a. The number of halibut tagged and released as part of the all-sizes tagging program by month between 2006 and 2008 (n=2061).

Month

Years

Total




2006

2007

2008




4

0

0

99

99

5

11

164

71

246

6

254

0

441

695

7

218

653

96

967

8

43

11

0

54



Table 4b. The number of halibut recaptured as part of the all-sizes tagging program by month between 2006 and 2008 (n=409).

Month

Year

Total




2006

2007

2008

2009

2010




1

0

5

13

17

6

41

2

0

4

14

11

17

46

3

0

6

6

15

7

34

4

0

1

5

4

7

17

5

0

2

6

16

0

24

6

1

5

35

25

8

74

7

1

10

35

21

3

70

8

3

9

16

11

1

40

9

5

4

11

5




25

10

3

5

2

2




12

11

2

3

8

2




15

12

1

2

5

3




11



Table 6. Summary of parameter estimates using the incomplete-mixing model under several scenarios for the initial tagging survival (ITS) and tag reporting rate (RR) and two subsets of fish released. First entry in estimates of F represents F* (instantaneous fishing mortality during the first 6 months after release) and the second entry represents F for complete mixing.







Parameter Estimates1




Model

M











R1^

R2

AICc4




M(dot), F(t), F*(t), R(2), ITS=0.8, RR=0.9 ALL fish

0.184

0.092

NA2



0.061

0.149


0.092

0.218


NA3

0.174


NA3

0.092


0.83

0.91

-1739.4




M(dot), F(t), F*(t), R(2), ITS=0.8, RR=1.0 ALL fish

0.203

0.086

NA


0.055

0.134


0.083

0.198


NA

0.157


NA

0.084


0.83

0.91

-1739.5




M(dot), F(t), F*(t), R(2), ITS=0.9, RR=0.9 ALL fish

0.205

0.085

NA


0.055

0.132


0.082

0.196


NA

0.156


NA

0.083


0.83

0.91

-1739.6




M(dot), F(t), F*(t), R(2), ITS=0.9, RR=1.0 ALL fish

0.222

0.076

NA


0.050

0.119


0.073

0.178


NA

0.141


NA

0.076


0.83

0.91

-1739.6




M(dot), F(t), F*(t), R(2), ITS=1.0, RR=0.9 ALL fish

0.222

0.076

NA


0.050

0.119


0.073

0.178


NA

0.141


NA

0.076


0.83

0.91

-1739.6




M(dot), F(t), F*(t), R(2), ITS=1.0, RR=1.0 ALL fish

0.237

0.069

NA


0.045

0.107


0.066

0.161


NA

0.127


NA

0.069


0.83

0.91

-1739.6




M(dot), F(t), F*(t), R(2), ITS=0.8, RR=0.9 71+ cm

0.226

0.101

NA2



0.066

0.169


0.080

0.249


NA3

0.197


NA3

0.096


0.83

0.91

-1571.7




M(dot), F(t), F*(t), R(2), ITS=0.8, RR=1.0 71+ cm

0.248

0.090

NA


0.060

0.152


0.072

0.227


NA

0.179


NA

0.088


0.83

0.91

-1571.9




M(dot), F(t), F*(t), R(2), ITS=0.9, RR=0.9 71+ cm

0.250

0.089

NA


0.059

0.150


0.070

0.224


NA

0.177


NA

0.087


0.83

0.91

-1571.9




M(dot), F(t), F*(t), R(2), ITS=0.9, RR=1.0 71+ cm

0.270

0.080

NA


0.054

0.135


0.064

0.204


NA

0.161


NA

0.080


0.83

0.91

-1572.0




M(dot), F(t), F*(t), R(2), ITS=1.0, RR=0.9 71+ cm

0.270

0.080

NA


0.054

0.135


0.064

0.204


NA

0.161


NA

0.080


0.83

0.91

-1572.0




M(dot), F(t), F*(t), R(2), ITS=1.0, RR=1.0 71+ cm

0.288

0.072

NA


0.049

0.122


0.058

0.185


NA

0.146


NA

0.073


0.83

0.91

-1572.2




1 Standard errors were computed, but are not reported here and are approximately (after adjusting for ) 0.10 for M; 0.04 for Fi; 0.06 for Ri.

2 No estimate is available for the instantaneous fishing mortality in year 1 for complete mixing (see text)

3 No estimates are available for the initial instantaneous fishing mortality for incomplete mixing for these years because releases terminated in 2006

4 Because subset of data was used for the analysis of fish in the 71+ cm size category, AICc should not be compared between these two analyses.

# F2010 is based on tags recovered up to the end of August and so does not represent a full fishing year.

^ R1 is the annual tag retention rate in the first year of release on an annual basis. It is prorated for the first ½ year after release in the model.


Figure 1. Estimated cumulative tag-loss by time-at-large.




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