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Otoliths Reveal a Diverse Age Structure for Humper Lake Trout in Lake Superior

 

作者: MaryK. Burnham-Curtis,   CharlesR. Bronte,  

 

期刊: Transactions of the American Fisheries Society  (Taylor Available online 1996)
卷期: Volume 125, issue 6  

页码: 844-851

 

ISSN:0002-8487

 

年代: 1996

 

DOI:10.1577/1548-8659(1996)125<0844:ORADAS>2.3.CO;2

 

出版商: Taylor & Francis Group

 

数据来源: Taylor

 

摘要:

Humpers are one of at least three morphological variants of wild lake troutSalvelinus namaycushthat maintain self-sustaining populations in Lake Superior. In an early study, bumpers from Isle Royale were shown to have a sharply truncated age distribution that was attributed to high mortality after age 11, but we suspected that these fish were underaged. In August of 1989 and 1992 we collected spawning humper lake trout from the same area and estimated their ages using both scales and sagittal otoliths. Humpers in our sample ranged from 5 to 13 years, based on scale annuli, but counts of sagitta annuli revealed ages of 8 to 28 years. Individual discrepancies between ages from scales and sagittae varied from –2 to 20 years, but differences between scale and otolith ages did not increase with individual age. We applied the von Bertalanffy growth model to the humper length-at-age data to indirectly assess the accuracy of aging estimates. The model significantly overestimated mean asymptotic length when scale ages were used, but the mean asymptotic length estimate was more similar to observed lengths when sagitta ages were used. Our results corroborate evidence that bumpers in Lake Superior grow more slowly and mature at a smaller size than lean lake trout; however, the age composition of bumpers is more diverse than previously thought. This particular population experiences little or no exploitation; the presence of older fish provides one standard by which the success of lake trout rehabilitation programs can be evaluated and emphasizes the need for accurate aging techniques.

 

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