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this as an interesting example of how an organism could adapt itself to conditions. This observation led to further work, which was summarized in 1908 in an important paper by H. P. Jacobsen and A. C. Johansen, entitled “ Remarks on the Changes in Specific Gravity of Pelagic Fish Eggs ” (Medd. Komm. Havunders. Fiskerei, III, No. 2). These authors write : “ During the development of the ovary of fishes with pelagic eggs a series of processes are in progress which, among others, produce the result that the specific gravity of the eggs approximates to the specific gravity of the sea-water, so that generally just after spawning they keep just at the surface or suspended in intermediate layers, etc. In the same locality and at the same niveau the specific gravity of the eggs is not very variable, but if we regard the whole area in which the eggs of a certain species occur the range of variation in many cases becomes very considerable. The specific gravity of cod eggs varies at least as sea-water between 8 and 35 per cent. salinity.”
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MOLLUSCA OF RANDERS FIORD.
It is a fair statement of the known facts to say that in water with a salinity higher than 5 the fish-fauna is predominantly marine. That this is true of groups other than fishes is exemplified by A. C. Johansen's researches on the mollusca of Randers Fiord (Blöddyrene i Randers Fiord, Copenhagen, 1918). The salinity of the water ranges from 0 to 24. The predominance of the marine species, immigrants from the Kattegat, in water with salinity higher than 5, and the inability of the majority of the fresh-water species to live in water with a salinity higher than 3, is well shown in the accompanying diagram. Of 71 species, 36 are fresh-water, 34 are marine, and one only (not included in the diagram) is a brackish-water form, found in water with salinity of 1 to 20.
THE NORWEGIAN FIORDS.
Hjort (The Depths of the Ocean, pp. 477-8) has given a short general account of the invertebrate fauna of the Norwegian fiords, showing how the difference in physical conditions (temperature, salinity, etc.) and in the nature of the bottom, between the island belt and the inner parts of the fiords, determines the biological differences. There is a diminution in the number of species, some penetrating a greater, some a less distance ; but the fauna of the fiords is marine.
The first half of Dr. Hjort's description is sufficient to illustrate the general character of the littoral fauna of the inner parts of the fiords :—
“ The Fjords.—We have seen that the fauna of the littoral zone among the skerries, especially in the tidal area and laminaria belt, is abundant both in species and individuals. There is a diminution, however, as we penetrate farther into the fjords. In the tidal area of the inner fjords, and at greater depths also, we miss the limpet and the purple snail, while the hydroids to be found on the fucus in the skerries become less and less abundant, until even Dynamena pumila disappears.* This change in the fauna is mainly due to the decrease in salinity, since the surface of the inner fjords, for a greater part of the year at any rate, is occupied by a layer of less saline water in which these forms cannot thrive. Far up the fjords, however, in the tidal area, we get the barnacle, the mussel Mytilus, and the black periwinkle, which seem to be less affected by a difference in salinity, though even they require a certain percentage of salt, since they disappear, for instance, from the tidal area in the more enclosed parts of the fjords, where, owing to the great accession of fresh water, the salinity is particularly low. The mussel and black periwinkle, it is true, may sometimes occur even here also, but only in fairly deep water. We also find the horse mussel in the fjords. The great thickets of Laminaria hyperborea, which are so characteristic of the skerries, are absent from the inner fjords, and so are most of the forms associated with them. In their place, however, we get Laminaria digitata and L. saccharina, but in comparatively small quantities.
* It is interesting to note that Dynamena pumila is also found in the estuary of the Elbe as far up as Cuxhaven.
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“ The difference between the inner fjords and the skerries is not so marked when we descend to greater depths, since a good many forms are equally at home in both. Some of the littoral fauna, like the lancelet, appear to avoid the fjords altogether.* Two forms, which rarely ascend far up the fjords of West Norway, are the lobster and the common edible crab ; but the common shore crab (Carcinus moenas) penetrates to their inmost recesses. The big black sea-slug (Cucumaria frondosa) is another form which abounds among the skerries and in the outer parts of the fjords, but very exceptionally penetrates far in. No doubt their presence is due to the feeble currents, or the greater or less accessions of fresh water prevailing in the fjords—local conditions that are bound to affect the distribution of the fauna.”
FISHES OF HAMILTON INLET.
From the distribution of cod in the Baltic it is perfectly clear that if they do not penetrate into Hamilton Inlet beyond the Narrows they are not deterred by the decreased salinity of the water ; also that as they breed in the Baltic in regions where the salinity is 7 to 10 at the surface and 10 to 20 at the bottom, they will not be prevented by the salinity of the water from breeding in parts of Hamilton Inlet in which the salinity is 10 to 15 at the surface and reaches 26 at a depth of about 20 fathoms.
Cod live at depths down to 100 fathoms, but the majority of them do not go beyond 50 fathoms ; thus it may readily be admitted that the region immediately west of Henrietta Island, with shores descending steeply to depths of 150 fathoms or more, is quite unsuitable for cod. But beyond this, commencing with the Valley Bay—Neveisik Island district, are considerable areas of the right depth for cod, and it is not unlikely that cod may be found there, especially where the bottom is rocky, pebbly, or weedy. In forming this opinion I bear in mind the fact that the deep area west of Henrietta Island would be a check to the normal immigration of cod along the bottom ; but it would not, I think, act as an effective barrier cutting them off from the more favourable regions further west. Cod do not always swim at the bottom and in certain circumstances, e.g., when in pursuit of prey swimming near the surface or in mid-water, might occasionally cross this area. Moreover, larval fish might swim over, or be carried across by strong tides.
Dr. Hjort states that in Norway no immigration of cod takes place into fiords where barriers exist and shallow entrances lead into deeper and wider basins farther inland.
He had before him the memoranda prepared by Dr. Kindle and Mr. Prince, but not the fuller information as to the topography and hydrography of the Inlet which is contained in the Canadian atlas and hydrographical reports ; thus it may be doubted whether the Hamilton Inlet fully corre-
* The reason for this may perhaps be that the lancelet requires pure sand or shell-sand to live in, while the bottom of the fjords generally consists of mud.
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sponds to the fiords he had in mind and whether in any of these “ the deep basin behind the entrance ” is succeeded after a few miles by a region with large areas of comparatively shallow water. His reference to the “ possibility of an accidental and very rare inflow of water from outside ” is further evidence that his memorandum was prepared without knowledge of the tides and currents in the Narrows.
The only information available with regard to other fishes is that capelin “ were not seen ” west of Henrietta Island, that there are salmon fisheries, and that “ salmon-trout ” are caught west of Henrietta Island.
The capelin is a member of the smelt family (Osmeridæ). According to Smitt (Scandinavian Fishes) it “ never enters quite fresh water.” Collett has recorded that “ in Varanger Fiord there is a good and sure spawning place off the mouth of the Jacob Elf. At the flood the capelins ascend high up the river, as far as the water is brackish enough.” Jordan and Evermann (Fishes of North America) term the capelin a marine species that sometimes ascends streams. The eggs of the capelin are deposited in sand at the edge of the water, and if there are any sandy beaches in Hamilton Inlet the shoals would probably resort to them in the spring or early summer for breeding purposes ; from what is known of their habits elsewhere it seems unlikely that they would be deterred by the salinity of the water from visiting any part of the Inlet, except perhaps the extreme western end.
The salmon of Labrador is the same species (Salmo salar) as that of Britain. Its life-history has been very fully worked out. The adults make their way into rivers from the sea in order to spawn on the gravelly shallows ; when they have finished breeding they go back to the sea, or make the attempt, for many are so enfeebled that they die. The young fish live in the rivers until they are about 6 inches long, a length generally attained in two years, although the period may be longer ; they then make their way straight to the open sea, where they feed on other fishes and grow rapidly, attaining a weight of several pounds in a year ; after one or more years in the sea they return to the rivers to breed. For such fishes the Hamilton Inlet may be presumed to be mainly a passage leading to and from the rivers in which they breed ; it is improbable that more than a small proportion of either young or adult fish do more than travel through it. The migratory habits of the salmon are of great importance for the fishery, the object of which is to intercept the fish on their inward migration, either in the rivers or as they approach the river mouths.
The “ salmon trout ” mentioned by Dr. Kindle is presumably a char, Salvelinus fontinalis, for Jordan and Evermann state that “salmon trout ” is the Canadian name for sea-run individuals of this species. This is a smaller fish than the salmon and does not go so far out to sea ; it is probably resident throughout the Hamilton Inlet. It runs up rivers to breed and forms permanent fresh-water colonies in the rivers it enters ; in the breeding season the residents in the rivers would be joined by those ascending from the Inlet.
It is probable that in the rivers of the east coast of Labrador there are no true fresh-water fishes, as these would have become extinct owing to the
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conditions that prevailed in the Glacial Period. The Hamilton River may possibly have established connections since which have enabled it to acquire a few species (e.g., Catostomus catostomus, C. commersonii, Perca flavescens), but these, if present, would not venture into the Inlet except in the immediate vicinity of the mouth of the river.
It may be noted that of the marine fishes common to Labrador and Scandinavia some have a wide range in the Baltic, e.g. Lumpsucker (Cyclopterus lumpus), sea-snail (Liparis liparis), and sea-scorpion (Cottus scorpius), and would not be deterred by the salinity from entering the inner part of Hamilton Inlet ; these, and other species also, may be expected to occur beyond the Narrows, especially in the bays, where the depth and salinity of the water would seem well suited to them. No investigation of the fauna of these bays seems to have been made, and until this has been done the statement that marine fishes do not penetrate beyond the Narrows cannot be accepted.
INVERTEBRATES OF HAMILTON INLET.
Dr. Kindle's report on the intertidal fauna and flora shows that in this respect Double Mer and the Narrows are typically marine. On nearly every boulder or rock outcrop in the vicinity of Rigolet are numerous barnacles (Balanus balanus) and periwinkles (Littorina rudis), but, according to Dr. Kindle, neither is found west of Henrietta Island. From the map it appears that for a distance of about 8 miles westwards from Henrietta Island the inlet is about 4 miles wide and is very deep ; the 50-fathom line is close inshore and the shores appear to rise abruptly from the water ; without having seen the place I cannot be certain, but I think it probable that in this area there is no intertidal zone with rocks, and that the apparent absence of barnacles and of periwinkles may be due to this. Dr. Kindle's statement does not appear to be founded on an examination of the fauna of Valley Bay and Etagaulet Bay ; if he has made such an investigation he has not given the results of it.
The barnacle, Balanus balanus, extends from the Arctic Ocean southwards to Cape Cod and the English Channel. It occurs at all depths from the surface, i.e., the intertidal zone, down to 90 fathoms. It is found in the south-western part of the Baltic, in a region where the average salinity of the surface-water is 8 to 10 ; this salinity appears to be too low for it, and in the littoral zone it is replaced by another species, B. improvisus, but it has been found in the Fehmarn Belt at depths of from 3 to 17 fathoms, where the average salinity at the lesser depth would probably not exceed 12, and has also been recorded from 15 fathoms well to the east of this (55° 16´ N. 13·12´ E.), where the average salinity of the water at this depth appears to be less than 12.
From this it seems clear that the salinity of the water would not prevent this species from inhabiting the greater part of the Hamilton Inlet west of the Narrows ; in such areas as Valley Bay and Etagaulet Bay, if there are
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