Icelandic Rivers Research Articles

Climatic and Oceanic Variations Affecting Yield of Icelandic Stocks of Atlantic Salmon (Salmo salar)

Regression analysis was used to investigate the effects of variations in climate, weather, and ocean conditions on yields of Atlantic salmon (Salmo salar) to anglers from 15 Icelandic rivers. Catches of grilse from the northern and northeastern group of rivers fluctuated together, as did catches from the southwestern and western group of rivers, but seldom did catches from the two groups of rivers fluctuate together. The dividing point for grouping rivers with similarly fluctuating catches was the northwest peninsula, which separated warm Atlantic water from colder north Icelandic waters of the Iceland Sea. Changes in atmospheric circulation (mid-1950's to mid-1960's) resulted in marked changes in hydrography off north Iceland from 1965 to 1970, which coincided with declines in primary production and standing crops of zooplankton, in reduced abundance and altered distribution of pelagic forage fishes, and in declines in salmon yields from north coast rivers. Few grilse were also caught from most rivers in 1980 after low sea and air temperatures in spring of 1979. Highly significant relationships were found between mean June–July sea temperatures at Hraun on the north coast and yield of grilse the following year from the northern rivers Vatnsdalsá, Vídidalsá, Hrútafjardará, and Midfjardará and its three tributaries. Sea temperatures in April–May and May–June were also closely correlated (P < 0.01 and P < 0.05) with grilse catches from these rivers. Correlations were similar but less close for two-sea-winter salmon. Fewer statistically significant relations were found between sea temperatures and yields for south coast rivers; sea temperatures were higher there and varied less between years. Inasmuch as low sea temperatures and low river temperatures often occur in the same years, salmon yields may be regulated by several adverse climatic and hydrographic factors acting in combination, resulting in delayed smoltification and reduced growth and survival at sea.

The Pleistocene History of Some Rivers in Western Iceland

Little detailed work has been carried out so far on the profiles of Icelandic rivers, mainly because of lack of survey information. During the course of a geomorphological investigation in Western Iceland in the summer of 1961 an area which included parts of two rivers was surveyed in detail (Ashwell, 1964) and the results of this survey have interesting implications both for Icelandic Pleistocene history and for the study of worldwide marine levels. The surveyed area (Fig. 1) covers the boundary between the highland plateau of Central Iceland, which in this district forms a Pliocene erosion surface at 3-400 m above sea-level (Einarsson, 1958, pp. 19-20) and the coastal lowland of Western Iceland. Structurally it forms part of the Tertiary basalt province of Western Iceland, in which the beds of lava dip at about 5? to the SSE. Although the amount of dip is small, horizontal erosion surfaces show up well against it. The structure exerts an important control on the relief (Fig. 2) in that outstanding rock features can often be traced to the same hard beds of basalt, while the rivers have in some cases cut along the strike of the basalt beds where intercalations of tholeeite basalt or soft sandstone occur. Faulting may have been widespread since many landscape features run parallel to the strike of the basalts. One of these is important to this study, since it forms a cliff, about 40 m in height, between the highland valley of Flokadalur, running between the ridges of Kroppsmuli in the north and Varmalaekjarmuli in the south, and the coastal lowland. This cliff is referred to as the Brekkurl cliff. This type of threshold occurs in two of the other valleys running parallel to Flokadalur. It does not appear, however, that the valley of Fl6kadalur or most of the landscape features in

The Pleistocene History of Some Rivers in Western Iceland

The Pleistocene History of Some Rivers in Western Iceland

Geomorphological Studies of Sandur Plains and Their Braided Rivers in Iceland

(1962). Geomorphological Studies of Sandur Plains and Their Braided Rivers in Iceland. Geografiska Annaler: Vol. 44, No. 3-4, pp. 328-346.

Geomorphological Studies of Sandur Plains and Their Braided Rivers in Iceland

Geomorphological Studies of Sandur Plains and Their Braided Rivers in Iceland