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Classifying sea lamprey marks on Great Lakes lake trout: observer agreement, evidence on healing times between classes and recommendations for reporting of marking statistics

Journal of Great Lakes Research

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Abstract

In 1997 and 1998 two workshops were held to evaluate how consistent observers were at classifying sea lamprey (Petromyzon marinus) marks on Great Lakes lake trout (Salvelinus namaycush) as described in the King classification system. Two trials were held at each workshop, with group discussion between trials. Variation in counting and classifying marks was considerable, such that reporting rates for A1-A3 marks varied two to three-fold among observers of the same lake trout. Observer variation was greater for classification of healing or healed marks than for fresh marks. The workshops highlighted, as causes for inconsistent mark classification, both departures from the accepted protocol for classifying marks by some agencies, and differences in how sliding and multiple marks were interpreted. Group discussions led to greater agreement in classifying marks. We recommend ways to improve the reliability of marking statistics, including the use of a dichotomous key to classify marks. Laboratory data show that healing times of marks on lake trout were much longer at 4A?C and 1A?C than at 10A?C and varied greatly among individuals. Reported A1-A3 and B1-B3 marks observed in late summer and fall collections likely result from a mixture of attacks by two year classes of sea lamprey. It is likely that a substantial but highly uncertain proportion of attacks that occur in late summer and fall lead to marks that are classified as A1-A3 the next spring. We recommend additional research on mark stage duration.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Classifying sea lamprey marks on Great Lakes lake trout: observer agreement, evidence on healing times between classes and recommendations for reporting of marking statistics
Series title:
Journal of Great Lakes Research
Volume
29
Year Published:
2003
Language:
English
Contributing office(s):
Great Lakes Science Center
Description:
p. 283-296
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Great Lakes Research
First page:
283
Last page:
296
Number of Pages:
13