In its inaugural year of monitoring, the rock reef complex at Westridge Marine Terminal is coming alive with promising signs of successful inhabitation. Installed in spring 2023, this dynamic environmental offset initiative spans the intertidal and subtidal zones of the Westridge Marine Terminal water lot lease and offers a diverse habitat for finfish and invertebrate species.

Photo caption: The rock reef complex boundaries are superimposed in this bird's eye photograph of the western foreshore of Westridge Marine Terminal.

What is the rock reef complex?

The rock reef complex consists of nursery, integrated, and adult reefs that support the various life stages of finfish and invertebrate species, including rockfish, lingcod, salmon, herring, crabs and sea stars, along with encrusting algae, anemones and kelp. Its integrated design offers rocky habitats for both juvenile and adult organisms. For example, nursery reefs provide structural complexity and shelter for young fish maturing in the foreshore area. These reefs feature small cracks to discourage large predators. Meanwhile, the adult reefs are made of thick layers of medium to large boulders, creating crevices that serve the habitat needs of mature fish in deeper waters.

Signs of Life

After the rock reef was installed in spring 2023, initial assessments showed the emergence of algae, crabs and sea stars, with juvenile fishes also spotted near the new reefs. Clear signs of life appeared within the first two months after installation in the intertidal and shallow subtidal reefs. These areas saw an increase in invertebrates, including more crabs and sea stars, as well as algal growth.

Photo caption: At low tide on May 31, 2023, the intertidal sections of Nursery Reef 1 and Nursery Reef 2 were revealed, showing early signs of colonization.
Photo caption: During a moderate tide on July 6, 2023, the intertidal and shallow subtidal sections of Nursery Reef 1 and Nursery Reef 2 were visible. Algae and invertebrates were observed.

Rock Reef Complex Installation

The rock reef complex is made up of 10 reefs covering more than 10,400 m2 – about the area of a city block. It consists of three layers, including a bedding layer, a rock mattress layer and then depending on the reef type, various sizes of quarry rock and rip rap to protect the foreshore from erosion.

The rock mattresses were created specifically to ensure stability of the rock reef complex. First, clam-shell buckets and bomb-bay boxes positioned the rocks in a high-strength geotextile. Derrick barges fitted with a specialized lifting device then strategically placed the mattresses onto the seafloor. Other equipment, including aggregate supply barges and an unloading conveyor, added more rock layers. 

During installation, turbidity curtains were installed, where appropriate, to prevent sediment suspended in the water column from disturbing surrounding areas.

Photo caption: Before rock layers were installed during construction of the rock reef complex, the rock mattresses were visible on the sea floor on January 27, 2023.

The reef complex rocks were sourced from local quarries in Abbotsford and Saanich Inlet, BC. Ranging from 0.2 m to 1 m, all rock sediment, dust and potential contaminants were removed before installation. Altogether, more than 39,760 metric tonnes of rock were used to create the new fish habitat – or the equivalent of 3,000 loads from an average dump truck!

Future of the Rock Reef Complex

A new 10-year rock reef complex monitoring program, managed by a qualified team of biologists and divers, is tracking its colonization success. Information such as fish size, population and species in subtidal and intertidal reefs is recorded, alongside observation of marine birds and mammals. This data is compared against equivalent information from nearby control sites. Effectiveness monitoring reports will go to Fisheries and Oceans Canada in years 1, 2, 4, 6, 8 and 10 after the rock reef complex installation.

Approved by Fisheries and Oceans Canada in 2017, the rock reef complex is part of the Fisheries Act Authorization (FAA) for the Westridge Marine Terminal Expansion.

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