Salmon and recreational fisheries monitoring: traps

Juvenile Emigrants

Dataset available for download here: http://dx.doi.org/10.7489/1017-1

Juvenile Atlantic salmon emigrate from the Girnock and Baddoch Burns at two distinct times of the year; spring and autumn. Juvenile salmon caught in the descending traps are measured and a sample of scales is taken from one in five fish to determine the age structure of the migrant population.

A plot of total emigrant numbers from the Girnock and Baddoch Burns is shown in Figure 1. Counts are shown by year of sea entry, with autumn parr numbers included in the following spring total. Juvenile salmon emigrating in the autumn typically over-winter downstream before entering the sea the following summer (Youngson and Simpson, 1984). Migrant numbers were generally higher in the 1970s at the Girnock but there is also substantial inter-annual variability in recruitment.

Numbers of spring and autumn migrants and returning adult salmon can be used to determine adult return rates.

Figure 1. Count of total juvenile salmon (spring smolts and autumn parr) emigrating from the Girnock and Baddoch Burns by year of sea entry. The green line shows corrected counts of emigrants in years where trap effort at the Girnock was considered low (See Bacon et al. [2015] for further information).