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Title: Development of South African fishes
Author: Gilchrist, John Dow Fisher
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1905
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Abstract:
The following is a first contribution to our knowledge of the development of a few of the commoner Cape fishes. It is more of the nature of a preliminary report than an exhaustive account, and- it would have been well for some reasons to delay publication until time and opportunity were available to go into the matter in more detail. For practical reasons, however, it may be preferable to review the information that has now been procured on some points. These practical reasons are the differences of opinion, involving considerable difficulty in legislative matters, as to the nature of the eggs and spawn of the common fish. Thus it is commonly alleged that the practice of netting, as carried on in the Zwartkops, the Buffalo, and other tidal rivers of South Africa, has proved destructive to the eggs and spawn of fish, those of this opinion asserting with confidence that quantities of fish spawn are brought on shore by the net and left to perish. Another occasion on which the same question arose was on the commencement of trawling in False Bay, and on the Agulhas Bank, near Mossel Bay by the Government Steamer. It was thought that the dragging of the net along the bottom of the sea caused the destruction of great quantities of the eggs and young of food fishes. The Cape fishermen, an observant and intelligent class of men, were of opinion that the fish supply was being seriously endangered by such operations, and the question was felt to be so serious that a Commission of Parliament was appointed to enquire into the matter. The evidence seemed to indicate that many of the common fishes may deposit their eggs on the bottom of the sea. Thus one fisherman, who had had an experience of a life time in fishery matters in False Bay, was of opinion that all fish spawn was on the ground, and that the trawl runs across it, and must destroy it (vide Report of Select Committee, p. 13). Another equally experienced fisherman thought, however, that the spawn floats; on the surface (p. 18). A fisherman of fifteen years experience. at Kalk Bay could not agree with this {p. 21), while another was of opinion that the eggs floated, and could be taken up in the hands out of the water. A practical fisherman of forty-three years' experience considered that the spawn is on the ground, and also floats, adding the additional interesting information : " 1 have seen the spawn- whether of fish or not I cannot say, but it is alive-little round things like eggs, and they smell very nasty, like rotten pumpkins. I have seen it a foot thick on the water" (p. 24). Yet another witness thought that " the fish breed on the ground, but the spawn does not stop at the bottom." Another practical man gave evidence to the effect that the klip-fish deposits its spawn on the seaweed, and it is there destroyed by the trawl (p. 37). On the other hand, in all the instances where the mature eggs had been procured and successfully fertilized on the Government.steamer, the "Pieter Faure," they were found to float, on the surface of the water, and only after the larvae had been hatched out some time did they begin to sink to the bottom. It was also brought to the notice of the Commission that it had already been demonstrated in Northern waters that there was only one fish of practical economic importance depositing its eggs on the bottom (the herring), and only a small species of herring (Clupea ocellata), of little value to the present fishermen, occurs in the Cape seas. On the whole it was felt very necessary that further enquiries should be made into the subject and definite information obtained. Recently facilities have been afforded by Government for more careful examination on shore of the eggs and larvae procured by means of fine nets and from the mature fish, and the following is a review of some of the most important results.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (D.Sc.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.743428  DOI: Not available
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