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Report: ASSESSMENT OF KOKANEE MOVEMENT AND ABUNDANCE IN COQUITLAM RESERVOIR, SPRING 2015 16.COQ.02
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The 2015 study was carried out between 24-Mar and 14-May by comparing the distribution of fish in the Kokanee smolt (60-90 mm) and the smolt predator (greater than 270 mm) length classes during six hydroacoustic surveys at night. Every hydroacoustic survey was supported by gillnet sets to verify species composition of hydroacoustic targets.
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Author: D.J. Degan
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Old Reference Number: 16.COQ.02
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Old Reference System: FWCP Fish Wildlife Compensation Program Coastal
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Date Published: Mar 2016
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Report ID: 50807
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Audience: Government and Public
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Coquitlam Reservoir does not have a spill way that would allow salmon smolts to leave the reservoir at the surface, migrate to the ocean and return as adult and anadromous Sockeye Salmon. The only way to leave Coquitlam Reservoir by passing the dam is by way of small diameter water release pipes with a deepwater intake that has had limited success to date (Plate et al. 2014). While it was hypothesized that the water intake to these pipes would be hard to find by smolts and thus outmigration would always be limited to very few fish (Plate et al. 2014), an alternate hypothesis was that smolts had lost their genetic drive to migrate towards the dam and leave the reservoir. In this context, the construction of a surface spillway would only lead to more smolts leaving the reservoir, if it could first be proven that smolts were migrating towards the dam. Therefore migratory behaviour of Kokanee smolts was investigated in the spring of 2015.
The 2015 study was carried out between 24-Mar and 14-May by comparing the distribution of fish in the Kokanee smolt (60-90 mm) and the smolt predator (greater than 270 mm) length classes during six hydroacoustic surveys at night. Every hydroacoustic survey was supported by gillnet sets to verify species composition of hydroacoustic targets. During the first survey on 24-Mar, the majority of fish in the smolt and predator lengths classes, were observed in the north and central basins of the reservoir while very few fish (greater than 2%) were observed in the south basin closest to the dam. This picture changed in the beginning of April when greater than 20% of the smolt and predator sized fish were found in the south basin closest to the dam. A second increase of smolt sized fish at the beginning of May in the south basin again coincided with an increase in predator sized fish. Net catches of the typical Coquitlam predators, Northern Pikeminnow and Cutthroat Trout, also increased at the log boom close to the dam in the middle of April.
In general, the average abundance of all fish targets in 2015 was slightly lower than in 2011, 2010 and 2005 (Bussanich et al. 2006; Plate et al. 2011; Plate et al. 2012). Kokanee depth distribution changed considerably over the six surveys between 24-March and 14-May. While the majority of fish targets detected in the pelagic zone of Coquitlam Reservoir was observed in the top 2 m of the water column on 24-March and 1-Apr this pattern changed for the last four surveys until 14-May when the majority of the fish targets were detected between depths of 5-25 m.
The 2015 gillnet catch was mainly composed of Peamouth Chub (33%), Largescale Sucker (30%), Northern Pikeminnow (24%) and few (7%) Kokanee and therefore different from previous years when the majority of the catch represented Kokanee (Bussanich et al. 2006; Plate et al. 2011; Plate et al. 2012). This difference is likely based on the differences in net set locations. For all previous hydroacoustic studies in Coquitlam Reservoir the nets were set in the pelagic zone targeting Kokanee. In 2015, the majority of nets was set in the shallower and littoral zone of Coquitlam Reservoir close to the log boom that is blocking access to the dam forebay.
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Report Type
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Fish and Aquatic Habitat Information |
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Subject
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Fish Species - Kokanee - Oncorhynchus nerka |
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Region - Lower Mainland |
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Fish and Fish Habitat - Fish Inventory |
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Fish and Fish Habitat - Research |
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