Partitioning survival during early marine migration of wild and hatchery-reared Atlantic salmon (Salmo salar L.) smolts using acoustic telemetry

Table 1 Summary information and estimated survival for Atlantic salmon (Salmo salar) smolts tagged in 2017 and 2018

Release dates	Fish type	Mean length (cm)	Mean weight (g)	Tag type	Tag weight in air (g)	Tag frequency (kHz)	Mean tag:body mass %	Tagged (N)	Released (N)	Survival brackish lake (%)	Survival estuary (%)	Survival early marine (%)	Overall survival (%)	Detection period (days)	Mean daily mortality (%)
2017
04/05 & 16/05	Hatchery	19.2	76.2	V7	1.6	69	2.2	45	41	100	95	62	59	8.8	5.8
16/05	Wild	16.6	40.7	V7	1.6	69	4	15	12	100	92	73	67	5.1	7.6
12/05	Hatchery	19.5	80.3	V5	0.65	180	0.8	10	9	100	100	–
04/05 & 12/05	Wild	16.7	40.8	V5	0.65	180	1.6	10	9	100	100	–
2018
11/05	Hatchery	19.2	83.7	V7P	1.7	69	2.2	6	6	100	67	75	50	8	9.6
10/05–17/05	Wild	16.8	46.7	V7P	1.7	69	3.7	4	3	67	100	50	33	3.9	67.4
11/05 & 12/05	Hatchery	19.6	85.3	V7	1.6	69	1.9	20	20	100	95	63	60	6.3	4.2
10/05–12/05	Wild	15.4	34	V7	1.6	69	4.8	20	20	100	100	65	65	10.2	3.3
2017 & 2018 combined
	Hatchery			V5/V7/ V7P		69/180		81	76	100	89	66	58*
	Wild			V5/V7/ V7P		69/180		49	44	98	98	67	63*

Survival is partitioned through three key sites: the brackish lake (Lough Furnace), estuary (Rosmore) and early marine (to Clare Island arrays). Number released is the number of fish included in survival estimates after potential tag mortalities were removed (i.e. continuous tag detections at the receivers located at the release location). The detection period is the maximum number of days between the release and the last detection at the marine array. V5 tags were only tracked to the exit from the estuary therefore values marked with ‘*’ include V7 and V7P tags only

ISSN: 2050-3385