Hofsa: Expanding the stock by moving the salmon
Local Hofsa-expert Haukur Geir Garðarsson places a twenty pounder into a holding box prior to the fish's "transfer" to the upper regions. Photo by Ólafur Johnson.
In 2007, an article was released by fisheries biologist Thorolfur Antonsson reflecting on the work done on Hofsa by placing wild salmon above the unaccesable fosspool in order for them to spawn in the prolific moorland part of the river. This has been done on other rivers as well but here we have the account of an expert and how things went and what to expect.
Here is a translation of the article, done by the owners of the website www.hofsa.is who are the outfitters of Hofsa. Hofsa is one of our listed rivers. Read from here:
„From the time that rod fishing commenced on Icelandic rivers, an interest in increasing the stock in the rivers has existed. Moreover, there has always been an interest in utilizing the inaccessible areas above waterfalls that salmon cannot climb.
From 1940 onwards fish ladders were installed so salmon could penetrate otherwise inaccessible areas. As a result, about 900 km. of, previously unexploited, river has been opened to salmon fishing in various parts of Iceland, but not all areas have been successful. For example, river bottom conditions must meet the requirements for favorable making of redds, and nutrition must be adequate. The height of the river is crucial, not too high, not too much snow in winter, etc., etc.
There are significant river areas above inaccessible waterfalls, which have benign areas for the bringing up of parr and smolts. In some cases the height of the waterfall is excessive, in others the accessibility of the location of the waterfall would be progressively expensive in terms of construction. In others, construction of a ladder might negatively affect the appearance of the waterfall, spoil the environment, etc. Whilst on other rivers, a combination of all these factors determines the feasibility. Some Fishing Associations resort to releasing so-called summer parr, in the upper regions of rivers. This, however, is often difficult because of accessibility and high costs.
Another feasible way to utilize these regions is to move mature salmon and have them spawn there in a natural environment. The salmon and its offspring will distribute itself over the spawning area. This was done in 1987 and 1988 when such salmon were moved to inaccessible areas above the This article deals with the results of parr found above the Foss, as well as the outcome of the transport and release of live whole salmon, to areas above the Foss.
Hofsa is known as one of Iceland's main "big fish"-rivers. Photo from Hofsa.is
The methodology: Since 1998 live fish have annually been transported above the Foss and released there.These fish have been caught by fishermen and put in boxes located in the main pools on the Hofsá river. The transport takes place in special boxes, with input of the necessary oxygen during the transport. At the release points above the Foss the fish are put in so-called adjustment boxes at two such release sites, at Brunahvammur and Mel. After a couple of days in these adjustment boxes, the boxes are opened and the salmon swim freely out of them.
The reason for putting these transported salmon into the adjustment boxes is to make sure they get adjusted to the “new water” conditions at the release point. If not done, the risk is that the fish will just swim down the river to their previous environment. To test the results of the release of fish above the Foss, electro-fishing has taken place in late August at two points in 2002 and 2006. Late in 2006 the electro-fishing was expanded to 8 points above the Foss. Sites above the Foss were subsequently compared with site below the Foss.
In electro-fishing the parr get adjusted after the electric shock, at which point they are stunned. During the sleep they are measured, weighed, etc., and then put back in the river, when they soon get adjusted again to normal conditions. Scales are taken from some of the parr. The size of each site was measured and an index computed for density per 100m2 of bottom space for each age group. This report will also show the returns for tagged small parr (so-called summerparr), which were released above the Foss during the years 1991-1997. The total of such releases were 18,500 below the Foss and 33,500 above the Foss. The large area available and the distribution of the parr explain the low density.
It came as somewhat of a surprise that the length and weight of these parr was higher than in the regular areas on the Hofsá below the Foss. Every year since then parr have been found representing 2 to 3 age groups. Density has been low, but in 2004 a strong year came along, representing the high number of fish taken above the Foss in 2003 - a record total of 101. This caused higher density, which has been the case since then. The length and weight of parr above the Foss has been higher than below the Foss. The density, however, has been lower. There is more space for the parr, which explains their comparative well-being. At the eight points that were electro-fished in 2006, parr were found at all of the locations. The widest distribution was of the 2 year old parr. Even at points 8,9 and 10, located at 400 metres above sea level, such parr were found.
Local angler Jakob Bjarnason with a huge Hofsa cock fish. Photo by Marinó Guðmundsson.
Discussion: In the year 2000 an assessment was made of the suitability of the Hofsá river bottom to provide suitable conditions for spawning. This assessment provided information to the effect that 30% of the bottom area most suitable for spawning, was above the Foss. This provided an opportunity to expand the stock of salmon in Hofsá.The results of this project show positively that utilization of the areas above the Foss provides an opportunity to expand the stock of salmon in Hofsá The fact that parr show a more rapid growth, in terms of length and weight, in areas above the Foss, compared to below the Foss, is proof of the possibilities inherent in utilizing these areas. So as to fully utilize the potential of these areas, it is recommended that the number of salmon taken above the Foss be expanded and it is recommended that fish released above the Foss should be in the order of the 2003 figures.“
