Science Response 2022/007
Glass Sponge Reef Adaptive Management Zones for the Hecate Strait and Queen Charlotte Sound Marine Protected Area, British Columbia
Context
Marine Protected Areas (MPAs) play important roles in conserving marine ecosystems worldwide. Under Canada’s Ocean’s Act, Fisheries and Oceans Canada (DFO) established nine Glass Sponge Reef Marine Refuges in the Strait of Georgia and eight in Howe Sound, British Columbia. Further to that, DFO established the Hecate Strait and Queen Charlotte Sound (HSQCS) MPA (Figure 1) to protect glass sponge habitats within three spatially-distinct reef complexes—the Northern Reef, the Central Reefs, and the Southern Reef (Government of Canada 2017). Each reef complex is made up of three management zone types: the core protection zone (CPZ), adaptive management zone (AMZ) and vertical adaptive management zone (VMZ). While all harmful human activities are prohibited in the CPZs, the MPA Regulations allow for some limited fishing activities in the AMZs and VMZs—including recreational fisheries and Indigenous fishing for Food, Social and Ceremonial purposes. Currently, all commercial bottom-contact fishing and midwater trawling in the MPA is prohibited by Fisheries Act Variation Orders. While the HSQCS MPA is designed to protect unique marine ecosystems formed by glass sponge reefs, the effectiveness of the MPA depends on how well the AMZ boundaries function as a protective measure. The existing AMZ boundaries within the HSQCS MPA range from 0.6 to 4.5 km from the CPZ boundaries. The glass sponge reefs off British Columbia are the habitat for many commercially important fish and are subject to fishing pressure such as bottom-contact trawl fishing. Bottom-contact trawl fishing can result in physical damage to habitat directly, and also negatively impact on glass sponge reefs indirectly by suspending a large amount of sediment, which can then be transported into the CPZ.
Glass sponges are highly efficient water filterers that constantly filter and pump in organic and inorganic particles. However, they can quickly arrest their pumping activities in response to the exposure to sediments. Multiple arrests may reduce energy uptake of glass sponges, which could negatively affect their health; while the long-term effects of repeated sediment exposure and arrests on their health and population remain to be a knowledge gap (Grant et al. 2019). Grant et al. (2018) found that in the Strait of Georgia, glass sponges cease pumping (arrested) at suspended sediment concentration far lower than concentrations that can be triggered by bottom-contact trawling. Furthermore, Grant et al. (2019) found that different species of glass sponges in the HSQCS MPA respond differently to the exposure of suspended sediments. They showed that the distance required from the AMZs to the CPZs depends on ocean environmental conditions and suggested that the existing AMZs in the HSQCS MPA may not be adequate to achieve effective conservation.
DFO Oceans has requested DFO Science to: 1) assess whether the existing AMZ boundaries are sufficient to protect the glass sponge reefs from suspended sedimentation impacts of mobile, bottom contact fishing gear, and 2) estimate new AMZ boundaries if the current boundaries do not provide sufficient protection for the sponge reefs.
Figure 1. The HSQCS MPA located in British Columbia, Canada, consists of four glass sponge reefs (grey lines) enclosed by the core protection zones (black polygons) and adaptive management zones (red polygons). N, Cn, Cs, and S represent the northern, central northern, central southern and southern reefs respectively. The red triangle depicts a vertex of the core protection zone for the northern reef, where the model current is compared with observed currents at the two nearby sites (black open circle and black solid circle). The observed currents are from Grant et al. 2019 (black solid circle), and the Institute of Ocean Sciences (black open circle).
This Science Response Report results from the Regional Science Response Process of November 20, 2020 on Adaptive Management Zones for Hecate Strait/Queen Charlotte Sound Glass Sponge Reefs Marine Protected Areas.
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