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.

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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.

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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 k^th 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
Year of release	Number released	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
Year of release	Number released	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

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

²No 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

⁴Because 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.

^{^}R₁is 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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Halibut -> Estimating survival and exploitation rates from a tagging study on juvenile Atlantic halibut

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