Implementation of a gross anatomical maturity key for the study of spawning phenology and geography of Pacific cod (Gadus macrocephalus)
Pacific cod (Gadus macrocephalus) is an important species, both economically and ecologically in the Bering Sea and Aleutian Islands (BSAI). However, little is known about its spawning dynamics. To address this knowledge gap, I developed a gross anatomical maturity key for Pacific cod to assess temp...
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| Other Authors: | , , , , |
| Format: | Master Thesis |
| Language: | English unknown |
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Oregon State University
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| Subjects: | |
| Online Access: | https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/ww72bf94c |
| Summary: | Pacific cod (Gadus macrocephalus) is an important species, both economically and ecologically in the Bering Sea and Aleutian Islands (BSAI). However, little is known about its spawning dynamics. To address this knowledge gap, I developed a gross anatomical maturity key for Pacific cod to assess temporal and spatial patterns of reproductive maturity. Gross anatomical maturity keys estimate reproductive maturity by categorizing changes that occur in appearance of ovaries during maturation. Because maturity keys are based on characteristics that change on a continuum, stage assignment can be subjective particularly for ovaries in transition (displaying characteristics of more than one stage). Histological processing is often used to verify maturity key staging by estimating the maturity of individual oocytes from within assessed ovaries. I compared individual oocyte development through histological processing with gross anatomical stage assignments to evaluate the accuracy of Pacific cod maturity key using two approaches. First, assumptions made in delineating advancing characteristics between stages during the development of the key were analyzed by comparing oocyte development from ovaries assigned to key maturity stages by the researchers who designed the key. Secondly, the consistency in the use of the maturity key was addressed by comparing stage assignments to oocyte development for multiple data collectors employing the maturity key in the field. Misclassification rates for the key designers were 22% and field samplers using the key resulted in misclassification rates of 43%. While the misclassification rates are high, the mismatch between histological assessments and gross maturity was very narrow and most often assigned correctly to an adjacent stage. Misclassifications occur most often in the vitellogenin stages where criteria for delineating between stages both histologically and through the use maturity key are based on relative changes in size and color of the ovaries. By using morphological changes to ... |
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