File:Marine biological report for the year ended and the half year ending (1918) (14774172502).jpg

Identifier: marinebiological41918cape (find matches)
Title: Marine biological report for the year ended ... and the half year ending ..
Year: 1913 (1910s)
Authors:
Subjects: Marine biology
Publisher: Cape Town : Cape Times Ltd., Govt. printers
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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s made of the locality, condition of thefish, size and sex. In all 1,902 of these labels were attached.The factories and fishermen were notified of the experiment,and were requested to give information of the recaptureof these marked fish. A reward of 6d. for each fish returnedwas offered the fishermen. Of the 1902 liberated only 21 were again found. Thismay point to the great quantity of crawfish present in theneighbourhood, and this is rendered probable by the factstated below where 115 crawfish were labelled in one day,and, of 1,500 caught by a fisherman the following day in thesame place, with a view to capturing the labelled crawfishand obtaining the reward oflered, none were labelled. Itmay, however, be due to overlooking of marked fish, thoughthe label is conspicuous, and in the repeated handling ofthe fish in the boat and factory could hardly be overlooked.There is reason to believe also that the reward offered wasnot sufficient to induce the fishermen to trouble about retain-
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9 ing the marked fish and returning it. The results attained,however, sufficiently justify the method employed and in-dicate that it should be followed up on a larger scale. Theyshow that there is in some cases migration to some distance,in others the fish remain apparently at or near the same spotfor some considerable time. Thus of the 21 recaptured fish 8 were found near thesarne spot. Of these six were recaptured within i to 9 daysafter being released. Two, however, were recaptured in39 and 31 days respectively near the same spot. Of the cases where a considerable movement is shown thishas usually taken place at no great rate apparently as a con-siderable period has elapsed between release and capture.The method employed, however, does no more ^:han indicatethe minimum rate at which the fish may have travelled. One case indicates that there may be a very considerablemigratory movement apart from the slow wandering aboutin searchof food. This was when a fish (No. 50) set free offMil

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