Protecting Sponge Gardens
The main skeleton of Cloud Sponges is formed of fused strands of glass. For this reason they are
extremely fragile and are at risk of being shattered from human activities such as fishing and diving. There are a
number of ways in which the human impacts on these Sponge Gardens can be greatly reduced.
Are You A Prawn Fisher? In Saanich Inlet sponges occur only shallower than 230 ft. Here prawn fishers can avoid damaging sponges by keeping their traps below 250 ft. as long as the water has oxygen. However, in other inlets sponges may be destroyed at depths down to 400 feet. On an Easter weekend, biologists mapped the locations of 64 prawn traps (red dots) in the recreational fishery in Saanich Inlet, B.C.. Commercial fishermen can each deploy 150 to 300 traps at a time.
Are you a Crab Fisher? Please keep traps shallower than 100 ft. and on soft bottoms.
Are You A Line Fisher? Please lift up cannonballs and lines to shallower than 100 ft. when near known sponge gardens such as in Saanich Inlet.
Are you a scuba diver? Practice outside the sponge beds, avoid flailing kicks, adjust your buoyancy to stay off bottom and photograph but don’t touch.
Not all impacts are physical. Suspended sediment in the water like smog in air can affect organisms in a variety of ways.
The map shows sedimentation rates in blue, in grams per square meter per year in Saanich Inlet (after Drinnen 1995). Note that rates increase toward the mouth of the Saanich Inlet. This is opposite to the condition in most fjords. (e.g., Farrow et al 1983). The distribution of the Cloud Sponge is shown in red. It does not occur where sedimentation rates exceed roughly 1000 grams per square meter per year
Back in 1982 divers in the PISCES submersible saw sponge skeletons some 30 meters (100 ft) below any living sponges. This means that some time in the past the oxygenated water extended 30 meters deeper into the basin. A likely explanation is that there was less pollution by nutrients from, for example, farming, clear cutting, landscaping, sewage, and maybe global warming. It we could date the sponges; we might be able to identify events which caused lowered oxygen. These dead sponges might also tell us that low or no oxygen water may extend into shallower water in the future.
At Christmas Pt., in Saanich Inlet only 8% of the sponges had dead bases while at Senanus Reef in Saanich Inlet 80% of the sponges had dead bases
The rate of sedimentation is twice as high at Senanus Reef compared to Christmas Pt.
While amount of sedimentation or associated high suspended particulates may be correlated with % of dead bases, we cannot exclude some other factor(s).
How glass sponges respond to artificial addition of sediment is discussed under “keeping clean” in the Natural History Section.
DFO ANNOUNCEMENT REGARDING SPONGE REEF CONSERVATION
Fisheries and Oceans Canada has implemented fishing closures to protect nine glass sponge reefs in the Strait of Georgia and Howe Sound. Commercial and recreational bottom-contact fishing is prohibited within 150 metres of all nine glass sponge reefs. FN0415
Effective June 12, 2015 all commercial and recreational bottom contact fishing activities for prawn, shrimp, crab and groundfish (including halibut) were prohibited within the areas listed below in order to protect the Strait of Georgia and Howe Sound Glass Sponge Reefs. These closures will be in effect until further notice.
On April 1, 2016 these closures also went into effect for all First Nation Food, Social and Ceremonial (FSC) fisheries that participate in bottom contact fishing activities for prawn, shrimp, crab and groundfish.
British Columbia’s ancient glass sponge reefs are a globally unique ecosystem that provides important habitat for many marine animals including spot prawns, rockfish, herring, halibut, and sharks.
The protection of coral and sponge reefs is a key component to a number of international commitments made by Canada through the United Nations Convention on Biological Diversity and the United Nations Food and Agriculture Organization (FAO) Code of Conduct for Responsible Fisheries.