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The Identification
of Pike by Means of Characteristic Marks ABSTRACT INTRODUCTION METHODS The criteria of similarity was noted as when three key areas showed similarity, between pike being compared. In practice when three key areas were found to be similar, all other key areas were also similar. Comparison of the two sides of a pike showed that the markings, though similar in size and shape, were not necessarily similar in position. It was therefore concluded that comparisons of markings were only valid for pike photographed from the same side. A standard method of photography was therefore employed. All pike which were either hand held or laid on the ground were photographed with the head of the pike facing the right of the picture. This was in effect, with the pike's head facing left from the holder's point of view. RESULTS
Oval spots tend to vary in size, from 10 to 25 mm depending on the locality and size of the pike. Round or stellate spots vary similarly. The longitudinal bar pattern is very typical of pike of Irish Loughs. It is uncommon for pike to display more than one pattern type in one particular environment. However, examples of all three patterns have been noted by the present author in one of the Fenland Drains. In order to establish the unique nature of the markings of all the pike examined, each were compared with each other. In no case was more than one key areas similar between individual pike. Often the difference in spot pattern was enough to signify `no similarity'. A small number of pike were dye marked and photographed. Recaptures of four different fish were made 2 years later. Each fish was found to be similar on the basis of at least three key areas being comparable. This indicated that the markings remain similar for at least two years. A large number of other fish, (860-1120 min) which have been at liberty for up to one year were also found to retain the same markings. Figs 3 and 4 shows one such fish captured from Loch Lomond (A.), on four occasions in 1978 and 1979. Figure 3 shows the fish as captured in 1978 and Fig. 4 as captured in 1979. The caudal area of this fish has particularly characteristic marks. Growth increments of dye marked pike were up to a maximum length increment of 50 mm and weight increase of 2.75 kg. Table 1 presents the weights, age & fork lengths of the four pike noted above. TABLE 1. Weights, lengths and ages of four pike recaptured after 2 years
DISCUSSION ACKNOWLEDGMENTS REFERENCES Christensen, J.M. (1961) Survey of the Danish sole tagging experiments with notes on the growth rate. Conseil permanent internationale pour I'Exploration de la Mer, 1961 Meeting Northern Seas Committee Paper, No 126 14pp.. De Roche, S.E (1963) Slowed growth of lake trout following tagging. Transactions of the American Fisheries Society, 92, 185-186. Eschmeyer, P.H. (1959) Survival and retention of tags, and growth of tagged trout in rearing ponds. Progressive Fish Culturist, 21, 17-21. Shetter, D.S. (1967) Effects of jaw tags and fin exision upon growth, survival and exploitation of hatchery rainbow trout fingerlings in Michigan. Transactions of the American Fisheries Society, 394-399. This article first appeared in Fish Management (1982) 13, No. 2
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