Some of the best known aquatic ecosystems are the so-called kelp forests along the West Coast of our province.
Kelp are large, brown algae that live in cool, relatively shallow waters close to the shore and grow in dense groupings much like a forest on land. They provide important three-dimensional, underwater habitat that is home to hundreds or thousands of species of invertebrates, fish and other algae.
Some species including fish aggregate spawn in kelp forests or utilize these areas as juvenile nurseries. Sharks and marine mammals are known to hunt in the long corridors that form in kelp forests between rows of individual plants. While these plants have established naturally they are not unlike some of our terrestrial forest plantations. Some recent studies have focused on the causes of sea star die-offs which can impact the kelp forests due to increases in sea urchins which are usually controlled by the sea stars and sea otters.
Some of our local lakes also have important aquatic ecosystems that act as nurseries for native juvenile fish. So far I have not been able to find much information on these ecosystems but the 1980 publication “Aquatic plants of B.C” has some line drawings of two plants that look similar to some that I have seen in our lakes. They look to be in the class of submergent rooted plants that are mostly under water as opposed to the water lilies that have the beautiful yellow flowers that float on the surface. The best examples are the Potamogeton and Polygenum which look similar to the plants that I have seen. My assumption was these weedy areas are important to small fish since I could always find large schools of juvenile fish in or close to these underwater plants which were providing some protection from predators.
On my last trip to the lake I witnessed an interesting migration of hundreds of these small fish (two-to-three inches and less) feeding along the weed-free shore at sunset and I presume they kept feeding during the night. Around 6 a.m. the next morning (for about half an hour) there was a steady movement of these fish back to the weedy environment. I am not sure how long this daily migration had been taking place since I only noticed it on my second night at the cabin.
While the migration did not occur the next day, there was a large concentration of similar-sized fish in the protected side of a small island. I have visited this weed-free area many times and have never seen this many small fish in one large group. Since I am only a summer resident I can’t presume these are not common occurrences and would be interested in hearing from fish biologists or persons that spend more time on the Interior lakes if these migrations are regular events. If this is a relatively new phenomenon we could attribute it to climate change which has also been implicated in the star fish dying.
Not all aquatic plants are considered important fish habitat with Eurasian water milfoil causing the most problems on many of our lakes requiring expensive methods of control.