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Document Description

Type: Report (unpublished)

Title: Eelgrass and fish assemblage properties as indicators of biotic integrity in the Clayoquot Sound Biosphere Reserve.

Date: December 2012

Author(s): Cliff Robinson; Jennifer Yakimishyn

Description: The conservation of biological diversity within the Clayoquot Sound Biosphere Reserve (CSBR) is a key element needed to drive the production of ecosystem services for long-term sustainable use by local communities. The main objective of this study was to develop a simple framework for the Clayoquot Biosphere Trust (CBT) to assess fish diversity in eelgrass meadows using a multimetric approach. Eelgrass (Zostera marina) was chosen as a focal habitat because it is globally considered to be one of the most ecologically important coastal habitats providing a variety of commercially, recreational and ecologically important fish species with outstanding feeding and growing potential, and shelter from many piscivorous and avian predators. This study evaluated three eelgrass metrics (water column nitrate concentration, leaf area index, and epiphyte load) and 12 metrics describing fish assemblage species composition, assemblage abundance, proportion of indicator species groups (e.g., fishery species), nursery function, and trophic function. The abundance of one resident iconic species, the Bay pipefish, was also considered. Metric values for eelgrass and fish assemblages were determined for 6 meadows sampled by the CBT in 2008 and 2011, and compared to metric values derived for 22 meadows sampled in Clayoquot Sound (CS) by Pacific Rim National Park Reserve from 2004-2012. The framework allows for evaluation of eelgrass and fish assemblage metrics by comparing CBT meadow values to the distribution of natural variability observed in metric values from 114 observations made elsewhere in Clayouqot Sound. If 3of 12 fish metrics (one quarter) for each CBT meadow fell below the 10th percentile of the 114 CS observations then potential impairment in the fish assemblage was considered. Overall, two major conclusions were made from this analysis and can contribute to CBT vital signs monitoring. First as of 2011, the 6 CBT meadows appear healthy because none of the eelgrass metric values were found near the thresholds for potential impairment. Second, five out of six fish assemblages appeared in good condition in 2011, but CBT Meadow Bawden Bay had 3 out of 12 fish metrics fall below threshold values and it should be re-sampled to confirm for potential impairment. Overall, the limited eelgrass sampling by CBT has demonstrated that meadows are healthy and likely functioning within natural variability. Two major recommendations were made: 1) continue to sample the 6 CBT meadows to build a long term understanding of temporal variability in fish diversity, and 2) map eelgrass distribution and continue to sample fish assemblages in CSBR to better describe and understand the spatial variability in meadow structure and function. Overall, the framework presented will aid the CBT in monitoring the vital signs of fish diversity in ecologically important eelgrass ecosystems.

Web Site: http://www.clayoquotbiosphere.org/web/wp-content/uploads/2012/12/PRNPR_Final%20Eelgrass%20Report.pdf

Document Location: on-line

Geographic-general: Clayoquot Sound

Format: Digital Text File

Language: English