Ecology of Greenland halibut (Reinhardtius hippoglossoides) during the early life stages in the Eastern Bering Sea and Aleutian Islands
Greenland halibut (Reinhardtius hippoglossoides) have decreased in the eastern Bering Sea and Aleutian Islands since the 1970s. The reasons behind the poor recruitment are unknown, and important knowledge gaps of the ecology of the early life stages have been identified. The objectives of thesis res...
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| Other Authors: | , , , , , |
| Format: | Master Thesis |
| Language: | English unknown |
| Published: |
Oregon State University
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| Subjects: | |
| Online Access: | https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/s4655k011 |
| Summary: | Greenland halibut (Reinhardtius hippoglossoides) have decreased in the eastern Bering Sea and Aleutian Islands since the 1970s. The reasons behind the poor recruitment are unknown, and important knowledge gaps of the ecology of the early life stages have been identified. The objectives of thesis research were (1) to examine geographic distributions and drift pathways from egg to settled juveniles (age-1) by a retrospective analysis in order to understand connectivity and different habitat utilization through ontogeny, (2) to describe vertical egg distribution using a one-dimensional model in order to understand patterns of vertical egg distribution and their association with water column hydrography and currents through the egg developmental stages, (3) to investigate diet of Greenland halibut larvae and pelagic juveniles diet using stomach content in order to understand foraging behavior, and (4) to examine otolith microstructure of Greenland halibut larvae and pelagic juveniles using otolith analysis in order to establish aging guidelines and other features related to bio-ecological changes (e.g. hatching, mouth opening etc.). The results of the thesis indicate that Greenland halibut early life stages from eggs to newly settled juveniles have a long duration in the plankton and are subject to extended drift pathways. In the eastern Bering Sea and Aleutian Islands, Greenland halibut spawn along the continental slope between Akun Island and the Pribilof Islands, and between Umnak Island and Akun Island in the Aleutian Islands. Spawning most likely occurs in winter from December to January. At-sea observations of egg density ranged from 1023.5 kg/m³ to 1027.8 kg/m³. Based on modeling results, variability of egg density would affect vertical egg distributions. Eggs were found between 50 m and 400 m, in particular, most eggs were concentrated between 200 m and 300 m. Hatching probably occurs in deep water, below 500 m, and larvae rapidly rise in the water column to depths above 45 m. The mechanisms of slope-shelf ... |
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