Smolts

Smolts

Arguably the best measure of a rivers salmon population is gained from monitoring the smolt output. To achieve this for the whole Spey is an ambitious task but during 2005 to 2008 attempts to do this were implemented. Two 6ft rotary screw traps were installed in the lower Spey during Spring 2005 to 2008. These were operated from early March through to June each year and all the fish captured were identified, measured and a scale sample obtained from the salmon and trout before returning the fish to the river.

Salmon smolts were the most abundant fish captured followed by trout smolts. An adult salmon and some sea trout were also captured. Other species captured included minnows, eel, three-spined stickleback, pike and rainbow trout. An adult river lamprey was also captured which is thought to be the first definite record in the Spey.

Each year a proportion of the salmon and trout smolts were marked using a simple dye tattoo and then released upstream of the smolt traps. The numbers of these marked smolts recaptured was then used to develop population estimates for the Spey smolt output. Using the 2006 to 2008 data and the Petersen Recapture model, salmon smolt output was estimated to range from 600,000 to 1.6 million. However, the numbers of marked smolts recaptured was very low indicating poor trap efficiency and so this approach turned up as many questions as it did answers. For further information on the study see Laughton, Burns and Reid 2008: Laughton, Burns, Reid and Miele, 2008.

A great deal was achieved through the installation of the smolt traps in the mainstem and some better data on the total smolt output for the Spey salmon population has been gained. However, the Spey Research Committee reviewed the data in the summer of 2008 and considered that the next step in collecting smolt data would be to station the traps on some of the Spey’s tributaries. This approach was implemented from 2009.

Tromie and Truim Smolt Traps

Several locations were tested for suitability and the best sites were found on the Tromie and Truim. Both these tributaries offer good study locations since they are known to produce spring salmon and extensive electro-fishing datasets are also available. Scottish and Southern Energy (SSE) also utilize the tributaries for water abstraction and power generation so better data is needed regarding the effects of this scheme on the fish populations. A trap was installed in the Tromie in 2009 and again in 2010 while one was installed in the Truim in 2010. Both locations proved to be a good ones with salmon smolts, trout and other fish species captured. A proportion of the salmon and trout were marked using a simple dye tattoo and then released upstream of the traps. The numbers of these marked smolts recaptured was recorded and used to develop population estimates for each tributary.

The initial years of operation indicate that valuble salmon smolt data can be collected from these tributaries. So thanks to generous support from Scottish and Southern Energy and Phones Estate the project will continue into 2011.

Download reports for each tributary: Tromie 2009-2010   Truim 2010

Spey Dam Smolt Trap

In collaboration with Rio Tinto Alcan, a smolt trap has been installed at Spey Dam on the upper mainstem of the Spey since 1973. Juvenile stocks above Spey Dam have been patchy and the area above the Dam has been targeted for enhancement using hatchery reared stock on several occasions. In the 1990s the salmon stocks declined further and a more ambitious program of enhancement was planned.

The area of suitable habitat available above the Dam and the number of salmon fry that could be released into it were calculated and, as part of the CASS LIFE project, suitable salmon stock from the upper river were raised in Tulchan hatchery and stocked as fed fry above Spey Dam from 2004 onwards. The amount of salmon fry required was initially estimated at approx 250,000 and the hatchery has reared between 150,000 and 270,000 between 2004 and 2008. The salmon fry are fed at the hatchery, typically for a period of 2-3 months, before being stocked above the Dam.

This approach continued in 2010 with a further 160,000 fed fry being released. To monitor the stocking input the original smolt trap was replaced in 2005 by a more modern, light-weight version also supported by funding from the CASS LIFE Project. Smolt output has shown an encouraging increase in the last few years and work is underway to examine fry to smolt survival rates. Summaries of the Spey Dam stocking and smolt trap project can be found in Annual Reports.