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Salmon in the Burrishoole system
The Burrishoole system has a run of both 1 sea-winter (1SW) salmon, known as grilse, and 2 sea-winter (2SW), or spring, salmon. The spring fish component normally accounts for less than 10% of the total run.
Reading a salmon’s life history
Salmon scale viewed under magnification. Growth patterns on scales can be used to estimate the age and life history of individual fish.
Changes in the recorded salmon run
The spring fish component has not exceeded 100 fish since the early 1960s. Reasons for the decline were early-season drift netting of L. Furnace, which ceased in 1965, the Greenland Fishery from 1962 to date, and UDN from 1967 to the mid-1970s.
The annual grilse run declined from more than 1,100 fish in the 1970s to an average of 450 per year in the 2020s. This is below the current Conservation Limit of 581 grilse.
Grilse first appear in the Burrishoole system in late May, and the run peaks in July. Escapement is primarily influenced by the drift net fishery, which has exploited from 60% to more than 80% of the stock.
Recent data indicate that fish are returning from the sea about one month earlier. More than half are back in freshwater up to two months earlier.
What the census measures
- spawning escapement
- survival between generations
- survival from ova to smolt
- survival from smolt to adult
- survival to kelt, or spawner fish
- survival from kelt to second spawner
- exploitation rates by rod fishing