THE BIOLOGY OF HAMILTON INLET, THE NARROWS AND LAKE MELVILLE.
BY DR. A. G. HUNTSMAN,
Director, Marine Biological Station and Fisheries
Experimental Station, Atlantic Coast.
In the second paragraph of his article Mr. Regan takes exception to the use by Mr. Jones (Canadian Case, pp. 1927-1928) of a certain definition for percentage of the density of sea-water or percentage of sea salinity. It is a matter of common practice to express density or specific gravity (meaning density relative to water) by subtracting 1 and multiplying by 1,000. The density 1,024 becomes 24, as is the case throughout in Hydrographical Tables by Martin Knudsen, Copenhagen, 1901, which tables were prepared under the direction of an international committee. When Mr. Jones uses this practice as a basis for calculating his percentages, and at the same time gives the actual extended figures of relative density for the water samples, his meaning is, or should be, perfectly clear.
We may ask what Mr. Regan's definition of percentage of salinity is. On page 6 of his article he quotes in support of his contentions and emphasizes by putting it in italics, “ sea-water between 8 and 35 per cent. salinity.” The salinity, as ordinarily defined, of the open Atlantic is only in the neighbourhood of 3½ per cent. The authors, from whom he quotes, did not make this error, but used the sign ‰ (meaning “ per mille ”), which in his article becomes “ per cent.”
The coast placed “ under the care and inspection of our Governor of Newfoundland ” by the proclamation of the 7th October, 1763, was “ to the end that the open and free Fishery of our Subjects may be extended to and carried on upon the coast of Labrador and the adjacent Islands.” What is then the extent of the coast selected for a fishery purpose ? There can be no question as to the nature of this fishery. Cod has been the lure that has brought European fishermen to the coast of North America for centuries, and to this day in Newfoundland and Labrador fish and cod are synonymous terms.
The cod is distinctly a deep-sea fish, and a characteristic fish neither of the estuaries nor of the fresh waters. Typically it is to be found on the offshore banks, but it not infrequently occurs during part of the year close to the shore. This is true particularly on the coast of Labrador owing to the
peculiar hydrographic conditions. On that coast the cod is at the northern limit of its range. It approaches that coast only during a short summer season, that shortens as one proceeds north, being only about a fortnight in duration at the entrance to Hudson strait, where lies the terminus of the cod's migration.
The main mass of the Labrador current is of very low temperature (below -1°C.) and consequently unsuitable for the cod. The shallow coastal portion warms during summer sufficiently to be suitable, and in it the cod are to be found. The Labrador fishery is, therefore, distinctly a coastal fishery.
The largest river system of the Labrador coast discharges through Lake Melville into Hamilton inlet. The geological evidence shows that Labrador has a drowned coast, the result of subsidence. This subsidence has brought the mouth of Lake Melville to sea-level. Does that fact make Lake Melville a part of the coast, in particular a coast for cod fishing ? Where does river end and sea begin ? The river brings a steady stream of fresh water driven by gravity. The sea, through the pumping action of the tide, sends its salt water into the river mouth. Hamilton inlet connects with Lake Melville through the Narrows. The chief struggle between river and sea has been, and still is, taking place at that point. The evidence shows clearly that the river still prevails in Lake Melville (though with a definite sea-water influence shown), and that the sea prevails in Hamilton inlet (though with a pronounced fresh-water influence shown). What is the evidence ?
The mean level of Lake Melville is higher than that of Hamilton inlet by more than five inches (Stewart, p. 1914). The tide entering from the ocean scarcely increases in amplitude when approaching the head of the inlet, and, in passing through the narrow passage from Ticoralak island to Caravalla cove into Lake Melville, decreases in amplitude by more than 75 per cent. (Jones, p. 1929). This gives on a much reduced scale an effect similar to that seen in the reversing falls at the mouth of the St. John river, New Brunswick, the outside water being on the average about a foot higher at high tide and about two feet lower at low tide than the inside water. The river influence through the Rigolet narrows is shown in several ways. The outflow is 80 per cent. stronger (Jones, p. 1926) than the inflow, and continues for about 15 per cent. longer time (Jones, p. 1926). The outflowing water from surface to bottom in 18 fathoms is about 15 per cent. (outside ocean water as standard) less salt (Jones, p. 1928) and about 4° warmer (Jones, p. 1919) in summer than the inflowing water.
As Lake Melville is in places more than 150 fathoms deep, the densest water reaching it through the Narrows is permitted to accumulate at the bottom and remain practically undisturbed for long periods. Yet in both 1921 and 1923 the deep water even at a depth of 172 fathoms was far from being as salt (under 2.8 per cent.) and was little colder (over 0°C.) than the water passing toward the lake at the bottom opposite Rigolet during July and August. Let us contrast with this the conditions, which we found in Mistanoque bay on the north shore
of the Gulf of St. Lawrence inside Belle Isle strait, in Temple bay, Labrador, at the outer end of that strait, and in Notre Dame bay on the east coast of Newfoundland in 1923. Each of these is shallow at the entrance (for the two former indeed less than ten fathoms) in comparison with the water inside. In each of these the bottom water was salter and colder (salinity over 33 per cent. and temperature below -1°C.) than any water at the entrance, and than any water for a considerable distance outside the entrance. These facts prove that the winter water of the Labrador and Newfoundland coasts is, as would be expected, both colder and salter than that of summer and enters and remains at the bottom of the deep fjords throughout the summer. Lake Melville differs from these in that, as shown by its deep water, the dense, salt water is never able, even when winter conditions stop both rain and the melting of ice, to dominate the Rigolet Narrows and enter Lake Melville. The river outflow must, therefore, control the strategic situation in the Narrows throughout the year.
Animals and plants are distinctly limited by the physical conditions of their environment. On land the contrast between the coast and the interior of Labrador is largely one of temperature, the coast being dominated by the sea, which carries a burden of ice coming from the north. On the coast the snow persists in places at sea-level and with a south exposure at least as late as September and as far south as the strait of Belle Isle, as we found in 1923. Hamilton inlet shows this condition, its waters bearing fragments of icebergs and its shores with snow patches as late as August. Lake Melville, on the contrary, has the warmer temperature of the interior. The flora reflect this climatic contrast, the sub-arctic treeless vegetation of the coast steadily giving place to the north temperate forest vegetation of the interior as one passes towards the head of Hamilton inlet, the most abrupt change taking place finally at Rigolet Narrows. As this difference is the result of sea influence, it should not be surprising that the life of the water should show as great or even greater contrast. Temperature as well as salinity here distinguish ocean from river and lake. Hamilton inlet shows a decrease in salinity and an increase iii temperature from its mouth to its head, as is the case with estuaries generally. Into the Rigolet Narrows water with the low salinity of that at the surface of the ocean off the coast (density at 60° F., 1.0240) enters as a bottom layer and is thoroughly mixed with the brackish water from Lake Melville. This mixed water (density about 1.020) flows out in large volume and occupies the upper levels of the inlet. The same mixed water enters Lake Melville (probably only during the winter, when it is coldest and therefore heaviest) and occupies the depths below about twenty fathoms from the surface (data in Jones, p. 1945). From twenty fathoms depth up in Lake Melville there is at first a slow and later a rapid decrease in salinity till at the surface, particularly near the head of the lake, the water is nearly or altogether fresh. There are accordingly the following water : sea-water toward the bottom in Hamilton inlet, estuarial Water above in the inlet, produced in the Narrows, and below in Lake Melville ; and brackish to fresh water near the surface in the lake. The
temperatures of these waters were : sea-water, 31° to 35° F. ; estuarial water, 35° to 45° F. ; and brackish to fresh water, 45° to 57° F.
The above described variable conditions set limits to the distribution of the marine and fresh-water life of the region. Dr. E. M. Kindle (pp. 1989 and 1990) has traced the distribution of two estuarial animals, the detection of whose presence or absence can be readily made as they live in the intertidal zones. These animals are the periwinkle, Littorina rudis, var. groenlandica, and the barnacle, Balanus balanoides. The former was found on the shores of Hamilton inlet and of the Narrows as far up as Henrietta island. It did not occur on the shores of Lake Melville. It was found along the channel on the north and west of Henrietta island, but not along the other channel (Pike Run) on the east side of that island. This is in harmony with the expectation that the rotation of the earth would deflect the inflowing (and therefore estuarial) water to the western channel, and the outflowing (and therefore brackish) water to the eastern channel. The barnacle occurred with the periwinkle, but did not extend as far through the Narrows on either shore. Dr. Kindle states that the other species of animals commonly associated with these did not extend west of the Narrows. These facts clearly show that these estuarial animals are limited by the extent of the estuarial water and have failed to invade Lake Melville, with its brackish water.
The estuarial Greenland or rock cod (Gadus ogac) shows a similar distribution. According to Grenfell (pp. 2109 and 2112) this fish is taken by ; the natives as far up as Caravalla cove, that is the limit in distribution of the periwinkle. The rock cod is definitely limited by lowered salinity. The capelin is a sea-fish that comes to the coast and into the estuaries to spawn. Dr. Kindle (p. 1991) states that they were common (1921) at Rigolet in the Narrows, but were not seen west of Henrietta island, that is they were restricted to the estuarial water.
The true cod (Gadus callarias) is an ocean or bank fish, but at certain seasons it comes to the coast. Certain varieties range far and wide, accomplishing extensive migrations, but even of these, and, when abundant, very few, and these the immature, penetrate even to the heads of estuaries. This is also true of a huge inlet like the Bay of Fundy. Passamaquoddy bay, which opens into the Bay of Fundy, is about twelve miles along and five broad, and it contains water with a salinity of over 30 per cent. Nevertheless, its cod fishery is confined to the passages at its mouth. In correspondence with this, Dr. Kindle, from his investigations of Hamilton Inlet in 1921, states (p. 1982) : “ The cod is unknown in the Narrows and the waters west of them. Cod-fishing is confined to the waters adjacent to the islands in the eastern part of Hamilton inlet.” Mr. Jones, from investigations made in 1923. states (p. 1930) that “ it was learned that occasionally, and late in the fall only, they were caught in the vicinity of Double Mer Point.” Also he states (p. 1931) : “ A fisherman who had spent the last eleven seasons on the Labrador coast, said the farthest up the Inlet that ha had known cod-traps to be set was at Black Island on the north side and at
Turners Bight on the opposite shore. These places are twenty-five and thirteen miles respectively below Rigolet.” Professor Coleman, as reported by Professor Prince (p. 199i), on his visit to Hamilton inlet, saw no cod being taken there, though the waters outside were swarming with fishing craft. Dr. Grenfell states (p. 2113) : “ I have seen schooners from the south fishing in this inlet as far as Turners Bight, Ticoralak and Double Mare,” and “ I have never seen or heard of any genuine summer cod, or any other fishing carried on in Hamilton inlet . . . above the Narrows.” All these accounts agree as to the cod occurring in abundance only in the outer part of Hamilton inlet and as to its inner limit being the outer part of the Narrows, that is only so far as the sea water extends along the bottom where the cod live. The cod accordingly is shown to be limited to the extent of this sea water, which is unable to penetrate through the Narrows into Lake Melville.
The investigations extended from Indian Harbour (well out in Hamilton inlet) inwards through the Narrows well into Lake Melville. They give the most definite evidence that marine fishes and invertebrates are co-extensive with the sea water and the superficial estuarial water, which do not penetrate beyond the Narrows.
MR. C. TATE REGAN'S “ HAMILTON INLET—
OBSERVATIONS ON THE FAUNA AND FLORA.”
Mr. Regan claims to have disproved a contention “ that the marine fauna and flora do not extend beyond the Narrows owing to the reduced salinity of the water . . . by showing that the species specially selected to illustrate it are found elsewhere in water of salinity as low as, or lower than, that of the Hamilton inlet west of the Narrows.” He makes the mistake of considering that, since under certain conditions lowered salinity fails to exclude certain marine species, it must necessarily always fail to do so, although the conditions other than those of salinity may be very different and the species themselves may be of different varieties or races in the two cases. His argument is the more surprising as it is made in the face of actual observations of the distribution of certain intertidal animals, the determination of whose presence or absence does not present any particular difficulty. His assumption that Dr. Kindle “ did not think it worth while to find out whether they (certain species found in the Narrows) reappeared in the more shallow areas further west, in which the salinity is considerably higher than in the Baltic, where some of these species occur ” is not justified in view of Dr. Kindle's statement on page 1960 (which Mr. Regan should have noticed) “ during the field work the writer traversed the north and south shores of Lake Melville.”
The following is an example of reasoning that is false through failure to take account of variable material and variable conditions. A person with a knowledge of fresh water only might argue that water cannot remain liquid below 32° F., but a seaman knows that salt water will not freeze until