Feasibility of Tagging Walleye Pollock Captured with Hook and Line using External Tags

Figures & data

Figure 1. Study location in Southeast Alaska, where the feasibility of applying external tags to Walleye Pollock was evaluated.

Figure 2. Length frequency distribution of Walleye Pollock that were used in the tagging feasibility study.

Table 1. Survival of Walleye Pollock that received lock-on tags or T-bar anchor tags and that were transferred between tanks via dipnetting or by use of wet, bare hands (non-dipnetting).

Handling method or tag type	Live	Dead	Total
Dipnetting
Lock-on tag	42	63	105
Non-dipnetting
Lock-on tag	66	9	75
Anchor tag	55	8	63
Total	163	80	243

Table 2. Observed mortality (N_mort) of tagged Walleye Pollock in the holding tank according to handling technique (transfer between tanks via dipnetting or by use of wet, bare hands [non-dipnetting]) and tag type (lock-on tag or T-bar anchor tag). All of the anchor-tagged fish were transferred by non-dipnetting. The total number of fish in each group is given in Table 1.

	Lock-on tag
	Dipnetting			Non-dipnetting			Anchor tag
Day	Nmort	Cumulative Nmort	Cumulative %	Nmort	Cumulative Nmort	Cumulative %	Nmort	Cumulative Nmort	Cumulative %
<1							1	1	12
1				3	3	33	2	3	38
3	2	2	3
4	9	11	17
5	3	14	22	1	4	44	1	4	50
6	11	25	40
7	7	32	51
8	19	51	81	2	6	67
9				1	7	78
10	5	56	89	1	8	89
12	2	58	92
13	1	59	94
15	1	60	95
19	1	61	97				1	5	62
32							1	6	75
33							1	7	88
45							1	8	100
50
69	1	62	98
82
105	1	63	100	1	9	100
Total	63			9			8

Table 3. Days in captivity until death and number of dead Walleye Pollock for each category of mortality. Fish were transferred between tanks via dipnetting or by use of wet, bare hands (non-dipnetting).

	Dipnetting		Non-dipnetting
Category	Number dead	Days alive	Number dead	Days alive
Dermal infection due to scale loss	43	3–19	5	5–9
Fin loss	15	4–15	2	10–32
Torn jaws	0–3		3	45–82
Internal	5	4–105	0
Unknown	0–7	<1–50
Total	63		17

Table 4. Number (percentage in parentheses) of surviving Walleye Pollock that were assigned to each tag infection category at the time of release (1 = no infection; 2 = the flesh was off-color, but there was no open wound; 3 = the flesh was infected, and the wound around the tag site was less than 5 mm in diameter; 4 = the flesh was infected, and the wound around the tag site was greater than 5 mm in diameter). Fish received lock-on tags or T-bar anchor tags and were transferred between tanks via dipnetting or by use of wet, bare hands (non-dipnetting). All of the anchor-tagged fish were transferred by non-dipnetting.

	Lock-on tag
Category	Dipnetting	Non-dipnetting	Combined	Anchor tag
1	0 (0)	0 (0)	0 (0)	4 (7)
2	8 (19)	20 (30)	28 (26)	21 (38)
3	29 (69)	28 (42)	57 (53)	27 (49)
4	5 (12)	18 (28)	23 (21)	3 (6)
Total	42	66	108	55