The Dulnain was surveyed by electrofishing intensively in 2012 with some sites revisited in 2013 to monitor whether the better salmon fry densities noted in 2012 had resulted in improved parr densities this year. Four sites were revisited in 2013, the sites geographically spread in varying habitat along the Dulnain mainstem.
The River Dulnain is one of the larger tributaries of the Spey and it contains about 6% of the juvenile habitat available in the Spey catchment. The habitat is generally of good quality, although downstream of Carrbridge the gradient is lower and the channel has been subject to quite a lot of management with flood banks etc. Conductivity in the upper reaches is lowish; it is therefore not the most naturally productive but it appears to be capable of support a good juvenile population.
Photos of the sites are shown below for reference.
The salmon size distribution graphs from the four sites are shown below, earliest survey for each site first. The graphs show the abundance in 1mm size intervals. The colours indicate the ages of the fish based on scale readings collected during each survey. The actual breakpoint may not be as clear cut as indicated as a large 1+ parr could be bigger than a small 2+ parr but based on many years scale reading experience within the Spey catchment we have reasonable confidence in the breakpoints. Note that the vertical scales on each graph varies!
The actual area surveyed each year varied slightly due to water levels etc but the sites were effectively the same.
Site D15 has a long survey history and usually supports a lot of fry. The parr density in 2013 was the best recorded at this site.
Site D21 has only been surveyed twice, both fry and parr were more numerous in 2013. There were more larger parr, fish that are more likely to smolt the following year.
The Dalnahaitnach site was also only been surveyed twice but again there were many more fry and parr recorded in 2012 than in the previous year.
The Suspension Bridge site has a long survey history. The results from here have been highly variable. The 2013 fry density was below average but the parr density was the best recorded at the site.
These sites were resurveyed in 2013 for a specific reason: to try and understand the juvenile salmon population dynamics in the Dulnain. So what can we deduce? Well as anticpiated the population of 1+ parr increased dramatically following the good 2012 fry yearclass. But the 2013 1+ parr population were able to develop with little competition from older yearclasses. It will be interesting to see how the current, even better, crop of fry matures with what will be strong competition from the 2+ parr year class in 2014? To that end we will endeavour to resurvey these sites again next year.
The presence of a strong yearclass can have a significant influence on smolt age. Competition could result in more parr having to remain in the river for another year, i.e. smolting as three year olds rather than two. Conversely a weak yearclass could be partly compensated for by earlier smoltification; the net effect being to smooth out smolt production between years. Salmon population dynamics are quite interesting!