Ocean Science on the neighbourhood beach
Author: Jeannette Bedard ~
Opportunities to view the marine world can come from cutting-edge ocean networks like Venus and NEPTUNE equipped with video cameras and other sensors to provide a window into the sea; or they can be as simple as a jaunt to the beach with a seine net.
Recently, I joined the local Natural History Society for a beach seine at Willow's Beach in Oak Bay. An early winter Friday evening turned out to have the best low tide. It was not too windy and I only noticed the chilly air when standing still. On the dark beach, waterproof clothing, toques and headlamps made it difficult to recognize individuals, but we found each other easily as we were the only folks on the beach. Excitement and curiosity dominated everyone's mood as many of us had never witnessed a beach seine before. A beach seine is long wall of mesh, like a fence; ours was about 15 metres by 1.5 metres. A lead line holds down the bottom, while the top rope is held up with floats.
The seine was hauled out into the surf and over an eelgrass bed. Once the net was in position offshore, those of us on the shore pulled it in using long ropes attached to each side of the net. Everything, that couldn't fit through the mesh got pulled ashore, including seaweed, animals and garbage. All sorts of interesting intertidal life was pulled up.
Eelgrass beds, like the one at Willow's Beach, are a common temperate water ecosystem found both on sandy beaches and in muddy estuaries. At low tide the grass floats on the surface and at high tide it is often completely submerged. In addition to being edible, eelgrass has been put to all sorts of uses: from creating the smoke for smoking fish to insulating a house. The most important role eelgrass plays is at the base of an ecosystem supporting a range of invertebrates, fish and waterfowl. Kept healthy, eelgrass improves water quality. Unfortunately, these ecosystems often inhabit areas people use, which puts them at risk to pollution and dredging.
After sorting the critters from the seaweed, we put them into buckets to keep them healthy. The fish catch included: walleye pollock, English sole, starry flounder, sharpnose sculpin, sailfin sculpin, sandlance, roselip sculpin, tubesnout, high cockscomb, surf perch, Pacific spiny lumpsucker (the cutest fish ever) and penpoint gunnel. A fish of each type was put into a clear ziplock bag along with plenty of water and passed around. By holding the bags up to my headlamp, I got a good look at each critter.
The penpoint gunnel intrigued me because it was neon green – a tropical water colour in our temperate zone. This fish looks like an eel, but isn't, and it gets it's colour through eating the local seaweed – a nifty technique that ensures it blends in with its surroundings. The bright green colour of the one we found would allow this fish to blend in almost perfectly with the eelgrass. Can you think of other creatures whose colouration comes from what they eat? Flamingos pop to my mind, but I'm sure there are lots of other examples.
A cool damp evening spent on the beach turned into a great opportunity to learn more about the ocean ecosystem just beneath the waters off Willow's Beach.
(Pacific spiny lumpsucker courtesy of Royal BC Museum..photo by G.Hanke)
