Salmon Migrations

SOME PRELIMINARY OBSERVATIONS ON THE MIGRATIONS OF SALMON (SALMO SALAR) ON THE COASTS OF SCOTLAND. BY W. J. M. MENZIES, F. R. S. E. Inspector of Salmon Fisheries of Scotland. — 18 — IXED nets for the capture of salmon were from low water mark. This practice of “out- first used on the coast of Scotland just overrigging” the nets is extending and this year it was successfully employed at the experimental marking F one hundred and ten years ago (ca. 1827) station on the west coast where only single nets and from the success which they immediately are still usually employed. obtained, and which has been continued, it is evident that the salmon in the course of their sea When lines of nets are fished in this fashion life come close inshore. At first no doubt it was and two lines of six or more nets each are fished not realised whether the fish were feeding or were with equal success within two hundred yards or so on migration when captured. In later years it has of each other, it is clear that the migration of the become clear that the fish have ceased feeding salmon along the coast cannot be a simple progress before they reach the coast and that they may be in one direction and in a comparatively straight line. considered to be then on their way from the feeding The Figures 1 and 2 are charts of St. Cyrus and to the spawning grounds. For long it was thought Lunan Bays showing the spacing of the nets and the that the fixed nets were only of importance to number used at each position. These illustrate how the rivers near which they were situated and that impossible it would be for salmon to enter the the fish taken by them were to be regarded as part bays only Irom either end and to attempt to swim of the stock of the neigbourhood. It was clear, along the shore or for them to do so from any however, that in certain cases this opinion had to particular point within each bay. For all the nets be interpreted somewhat widely for nets set at con shown in these figures to be successful it is clearly siderable distances from the mouths of rivers of necessary for the salmon to approach the bays from a n y importance were often quite successful. any direction and towards any part of the bay. Little can be learned of the precise movements Similarly were salmon to follow this alleged habit of salmon from commercial fishing beyond the fact then those released from a marking station would that, on a comparatively unindented coast, such as all be captured by a particular set of nets in either the east or north coasts of Scotland, salmon are to one direction or the other and were any consider be found at relatively considerable distances able journey started in the direction of a thickly (twenty or more miles) from the mouths of rivers netted area the attempt would soon be terminated of importance. It has been assumed that the fish by the capture of the fish. swim along the coast close to the shore for con Consideration of all the facts shows that when siderable distances and it has been stated that, at making a definite migration the salmon may do various parts of the coast, the line of migration is the journey in a more or less direct course but at predominantly in one direction. On an open coast some distance, probably greater than half a mile, where bag nets are set singly and at some distance from the coast. On the other hand when near (quarter to half a mile) from each other it is not its destination, or when waiting for water to tempt impossible that the fish should swim more or it to ascend a river, it moves in a straight line less parallel to, and within a few hundred yards along the shore for only a very short distance and of, the shore. But further examination in more these little journeys close to the edge of the water intensively netted areas shows that this suggested are interspersed between quite definite on and off movement cannot occur. In some districts, e.g., St. shore movements that may extend to a distance of Cyrus Bay, Lunan Bay (both near Montrose), and probably several miles from high water mark. Largo Bay in the Firth of Forth bag nets have As justification for the assumption of a move been fished for very many years the one beyond ment predominantly in one direction or the other the other until sometimes six or eight are in a along the coast, fishermen state that they see the fish straight line stretching for roughly half a mile IVeUgretn rus •Œ otel Oondt (Mon JVess J io a d m d e ' * School BU 372 0 C nU m afKirkÿ K x rk ev it C ottage ^ ih^ÿStaivm. WhtUcraigIDuuttäJ Q 1 Mile Pathhead/ ' N ä h e r W arburton • ï ‘f O' >i .11 !• *\1 o ORKNEY Duncansby Head J&arvas HELMSDALE /H elmsdalC føirÆ RSTfc BROftfi HELHSDALE H e lm s d a le /) Naver / ness HELMSDflt-E Ielhsdau DEVEZ?!)* ^Heimsdble iSpey INVERNESS^*? DEDERON DEHERON /Iberdeen HartSDAii Deveron Deveron Montrose 'N.y'SPEY Tw iS1\RUNC Of rom Edinburgh Fig. 3 — 19 — (111, 2) so moving (by watching the progress of a shoal in the inner Moray Firth between the Deveron and which the fish are jumping) or that the fish are Wick, since these fish are within close range of believed to enter the nets from one side more than their own river. It is hard to attach the correct from the other (a bag net has a wall of netting at significance to the other fish which appeared in right angles to the shore which leads the fish into diametrically opposed directions. The two taken a trap and is normally arranged so that fish may on the north coast, where another fish from the enter the trap from either side although very rarely Brora which adjoins the Helmsdale was also caught, it is made so that fish can enter from only one suggest a migration in from the north while the side). two, caught respectively near Peterhead and Salmon certainly do have two quite definite but Aberdeen, to the south equally indicate a move in temporary movements. The first is that they come from the south. As I shall explain later it is to the lee shore in a most marked manner; with possible that these apparently divergent results are a wind blowing on to the shore bag nets will fish the true indication of divided routes of migration. well but with a wind blowing off the shore the In distinction from the Helmsdale results we catches are invariably poor after the first day of have a rather striking uniformity of recaptures to the change of wind. If then the prevailing wind the south of the place of marking in the case of (in Scotland normally south-westerly) blow along salmon marked in Spey and Deveron. These fish any particular piece of coast salmon close inshore have been caught between Peterhead and Aberdeen will normally travel with the wind and can be seen but not at all on the north coast. A similar move so jumping and moving. Salmon when close to is also shown by a single fish from the Naver on the shore also travel temporarily with the tidal the north coast which was recaught near Tarbat stream even if that stream be an eddy and not the Ness in the inner Moray Firth. On the north coast true tidal stream. In certain situations, close to a two fish from the west side of Lewis (Grimersta promontory or in a bay, the true tidal stream may and Barvas respectively) were retaken in or near be succeeded by an eddy stream flowing in the Thurso Bay and another from the West Ross Carron same direction; here salmon will move mainly at Melvich. On the West coast there are only two in the one direction, which is that of the longest recaptures of note but when compared with the flowing stream, combined of true tide and eddy. results of marking in the sea they are of particular Fishermen working in such situations will say that interest. Two salmon marked in the Awe which the fish run in a certain direction. But it is a enters the sea near Oban were captured on the purely local effect and has no relation to the shores of the Minch and were thus returning to main run of fish along a larger section of the coast. their river from a northerly direction. The alleged general movement of salmon in a It became clear that kelt marking was not going certain direction along certain parts of the coast to give any very direct answer when carried out has on several occasions been proved by our on the scale that was then possible and a more marking work to be incorrect. direct attack on the problem of the migrations of The marking of salmon as means of providing the salmon along the coast of Scotland was planned. information regarding the life history of the fish In the normal commercial method of capture in was started in Scotland in 1896 and between then the sea by means of fixed traps (bag nets or fly and 1912 some few indications were obtained of nets) into which the fish swim and in which they the possible movement of salmon along the coasts remain swimming without being caught in the at considerable distances from their river of origin.

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