The Migrating Fish of Metchosin
By Moralea Milne for publication in the February 2003 issue of Metchosin Muse
Sherwood Creek, located within Devonian Capital Regional District Park and Gooch Creek, off William Head Road are at least two creeks in Metchosin that are home to the migrating fish species, sea run cutthroat trout (Oncorhynchus clarki ckarki) and threespine stickleback (Gasterosteus aculcatus).
We all know the fascinating life cycle of salmon, whereby the fish spawn or breed in freshwater, spend their adult years in saltwater and return to spawn in their original home stream. The scientific word used to describe fish migrating between freshwater and saltwater is anadromous and only one percent of all fish species in the world have this ability.
Metchosin has been fortunate to retain some of it’s native cutthroat trout habitat when many small streams on Southern Vancouver Island have been lost to urban development. There are a few residents who remember some fine fishing off Taylor Beach.
“Cuts”, an affectionate term used by many who appreciate our cutthroat trout, can be either entirely freshwater dwelling (often called residents) or spend part of their adult life cycle in saltwater. In the case of the fish in Devonian Park, they originally would have been able to access the Juan de Fuca Strait through Taylor Beach, but now have very limited access. Only when there are exceptionally high tides and high water tables can Sherwood Creek forge a path through the gravel and cobble beach. The trout are opportunists though and will seize the occasion to migrate. Changes to the original lagoon are inevitable over time as the lagoon slowly closes in, becoming only intermittently open to the saltwater, then closing completely. Upland development, with it’s diversion of water for wells, irrigation, ponds, etc. and a climate change to drier conditions has probably accelerated the process. However, the fish are capable of adjusting their lifecycles to adapt to these changing conditions.
Fish in the Gooch Creek watershed are still able to access the Strait every winter and spring, when a small stream can be seen emptying through the north end of Taylor Beach.
Sea run cutthroat trout are considered a blue-listed or “vulnerable” species and at maturity are usually about 12-18 inches long and 1 to 4 pounds in weight, with a characteristic red streak under their lower jaw. They are very adaptable fish and can spawn any time from fall through May, depending on location and conditions. Around Metchosin they spawn from January to March in shallow, relatively slow moving water in small coastal streams. The female prepares a scooped out gravel bed or redd where she lays from 200 to 4400 eggs. The male fertilizes the eggs and they then mound the gravel over the eggs and leave them to incubate. Clean water is vitally important as muddy, silty water will smother the eggs and prevent oxygen from reaching the embryos.
The eggs incubate for six or seven weeks before they hatch and after hatching the young “fry” remain in the nest another week before they are free swimming. They remain in their home streams for one to three or more years before migrating to the ocean, the young dining on aquatic insects and the older trout feeding on insects, fish eggs, shrimp, and small fish such as sticklebacks. While some “cuts” may never leave their stream, most venture out to saltwater for additional feeding opportunities. While in the ocean they generally hunt close to shore, not too far from their home streams, preferring to feed in shallow (to 10 feet), cobble and barnacle shorelines. Although some cuts do overwinter in saltwater, most return to their home streams to feed and spawn.
Cuts are unlike their salmon cousins and do not die after spawning. If conditions are favourable they can live to 12 years of age and return to reproduce many times. As the female trout ages, she produces larger eggs in larger quantities. Aren’t we glad that doesn’t hold true for us! Imagine your first pregnancy produces a single small baby, the next larger twins, then triplets……However, most trout do not have life expectancies much beyond 4 years as they suffer from high rates of predation.
The threespine stickleback is our other migrating fish, which, like the cutthroat trout can be either freshwater dwelling or spend part of their lives in saltwater. They are a much smaller (5-10 cm.), bony fish with a row of three sharp spines on their back. They feed mainly on the larvae of aquatic insects, fish eggs and small snails, and are considered satisfactory eating by water birds, including kingfishers and herons, some diving beetles and our cutthroat trout.
The male sticklebacks are the new age dads of the fish world. When the water reaches 12-15ºC he prepares a small (approximately 2 cm.) nest in a sandy, weedy spot, using plant material and a sticky substance he excretes from his kidneys. He then burrows into the mound, creating a tunnel shaped nest. By this time he has also developed a bright red colouration on his underside and his back has turned white. This, coupled with a zig-zag courtship dance seduces a female into the nest where she lays her eggs. The dad then takes over all egg and juvenile fish rearing responsibilities. He fans the water, allowing the all important oxygen to move through the nest and chases away predators. He continues this responsible behavior once the eggs have hatched and will even capture a straying baby in his mouth and spit it back into the nest! Well, we’ve probably all had some experience with “straying” children that make us want to spit too!
Most adults then die within the next several months and the young, depending on circumstances and species, will either stay in their local stream or pond or migrate to saltwater.
There has been some success with using them for mosquito control, something to note with the potential for our newest invasive pathogen, West Nile disease.
Clean, oxygenated water is important to the success of spawning fish and to help preserve our natural resources we need to be stewards of our land. Protect your water by preventing erosion and it’s twin evil, siltation. Allow streamside vegetation to grow which will reduce erosion, filter out contaminants and keep the water cool (by shading). Enjoy your land, relax by your water and try to leave some space for our native plants and animals.
Walk carefully by the snake fence along Sherwood Creek in Devonian Park and you may still be able to see some cutthroat trout spawning. Throughout the summer you should be able to catch a glimpse of the young trout darting stealthily, searching for food and cover. Unfortunately last summer something happened upstream which stopped the flow of water for several days. This was just enough time to dry many of the pools and most of the young trout perished. With the series of droughts we have experienced lately and the reduction in water flow to creeks, it doesn’t take long for serious consequences to occur. It is a lesson in the drastic effects of our tampering with the flow of water. Any work in a stream must be approved by the provincial and/or federal government.
If you have information on other fish bearing waters in Metchosin, please contact Moralea Milne at 478-3838 or through e-mail at: firstname.lastname@example.org
Monday, October 13, 2008
Migrating Fish of Metchosin
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