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An evaluation of fish habitat in Burrard Inlet, British Columbia Haggarty, Dana Rochelle

Abstract

I investigated fish habitat evaluation methods for Burrard Inlet, British Columbia. Burrard Inlet, contains the Port of Vancouver and is surrounded by Greater Vancouver. Nearshore habitat loss and alteration are major threats to the health of the marine environment in the region. Considerable habitat has already been lost or altered in Burrard Inlet. To maintain productive fish habitat, two issues must be resolved: what metrics should be used to assess habitat; and at what scale should they be evaluated? I investigated habitat evaluation in four ways: reviewing habitat classification and evaluation methods used in other aquatic situations; investigating the habitat use of juvenile chum (Oncorhynchus keta) and chinook (O. tshawytscha) salmon; employing community level metrics of habitat; and measuring substrate types along Burrard Inlet's shoreline. Scale is a critical issue in habitat evaluation. Scales range between very broad, regional classifications, to fine, site-level habitat assessments. An intermediate scale, the landscape, is appropriate to classify and evaluate fish habitat. I found a greater abundance of chum and chinook in the western basins of the inlet than the eastern basin. At the site level, juvenile chinook tended to use larger substrates such as bedrock and boulders over sand and mud. More chum were found over cobble substrates than mud. Landscape-level metrics such as habitat connectivity, isolation, rarity, and abundance must, however, be considered as juvenile salmonids use a variety of nearshore habitats as they migrate to the sea. Numerous species of fishes use Burrard Inlet; therefore, community-level metrics such as species diversity and the identification of species assemblages should also be used in habitat evaluation. My data showed separate assemblages of fish are found on gravel-cobble beaches than on sand and mud. Differences in species diversity also existed between some sites. These habitat evaluation metrics are particularly important in urban situations such as Burrard Inlet. My analysis showed that 44.6% of Burrard Inlet's shoreline has already been altered. The Inner Harbour, at 79.7%, is the most altered basin. Landscape-level habitat evaluation metrics such as habitat diversity, rarity, abundance and connectivity should be used to assess nearshore fish habitats.

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