population Surveys
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Throughout the history of the Oregon red sea urchin fishery, surveys have been conducted at a network of sites important to the sea urchin populations. These surveys are used to understand sea urchin populations over area and time, revealing the oceanographic and fishery effects that guide fishery management.
In addition to data on the fishery target (red sea urchins), these surveys have provided a wide variety of other useful data regarding nearshore invertebrate populations (e.g. other sea urchins, abalones, sea stars, etc), vegetation and habitats.
Sea urchin population surveys are based on an index sampling design where sites are visited over time. Sites are chosen within fished areas and reserves in key harvest areas throughout the coast. Index sites include: Depoe Bay (Fished areas, Otter Rock Marine Reserve, Pirates Cove Research Reserve, and Whale Cove Habitat Reserve), Charleston (Fished areas and Gregory Point Research Reserve), and Port Orford (Fished areas and Redfish Rocks Marine Reserve)
Surveys are subtidal belt transects of 30-40 meters. A team of two SCUBA divers count and measure each sea urchin within a meter on each side of the transect. Other species such as abalones and large sea stars are also counted to monitor key changes in those species. Surveys are generally performed in good summer weather, located at depths from 10-70’ of water and each take about 30 minutes of down time.
example:
Figure 2. Illustration of sea urchin subtidal belt survey
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Figure 1. Key population areas of red sea urchins in Oregon. |
