Comparison of Three Nonlinear Models to Describe Long-Term Tag Shedding by Lake Trout
作者:
MaryC. Fabrizio,
BruceL. Swanson,
StephenT. Schram,
MichaelH. Hoff,
期刊:
Transactions of the American Fisheries Society
(Taylor Available online 1996)
卷期:
Volume 125,
issue 2
页码: 261-273
ISSN:0002-8487
年代: 1996
DOI:10.1577/1548-8659(1996)125<0261:COTNMT>2.3.CO;2
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
We estimated long-term tag-shedding rates for lake troutSalvelinus namaycushusing two existing models and a model we developed to account for the observed permanence of some tags. Because tag design changed over the course of the study, we examined tag-shedding rates for three types of numbered anchor tags (Floy tags FD-67, FD-67C, and FD-68BC) and an unprinted anchor tag (FD-67F). Lake trout from the Gull Island Shoal region, Lake Superior, were double-tagged, and subsequent recaptures were monitored in annual surveys conducted from 1974 to 1992. We modeled tag-shedding rates, using time at liberty and probabilities of tag shedding estimated from fish released in 1974 and 1978–1983 and later recaptured. Long-term shedding of numbered anchor tags in lake trout was best described by a nonlinear model with two parameters: an instantaneous tag-shedding rate and a constant representing the proportion of tags that were never shed. Although our estimates of annual shedding rates varied with tag type (0.300 for FD-67, 0.441 for FD-67C, and 0.656 for FD-68BC), differences were not significant. About 36% of tags remained permanently affixed to the fish. Of the numbered tags that were shed (about 64%), two mechanisms contributed to tag loss: disintegration and dislodgment. Tags from about 11% of recaptured fish had disintegrated, but most tags were dislodged. Unprinted tags were shed at a significant but low rate immediately after release, but the long-term, annual shedding rate of these tags was only 0.013. Compared with unprinted tags, numbered tags dislodged at higher annual rates; we hypothesized that this was due to the greater frictional drag associated with the larger cross-sectional area of numbered tags.
点击下载:
PDF (1265KB)
返 回