As you hike along the Brooklin Lions Wilderness Trail, you may notice wooden posts with numbers - This initiative began in the year 2000, highlighting various parts of nature along the trail.
You can spot "Post 4" from the trail - and the cache is hiding a few metres closer to the creek. Post 4 represents "Life in the Creek". The Lions Trail website has a wonderful write-up for each of the posts along the trail - here's some insight into creek wildlife:
As anyone who has gone fishing knows, there is life in a healthy creek. This section of the East Lynde Creek is classified as a warm water fishery by the Central Lake Ontario Conservation Authority (CLOCA). Their 1983 study of the entire Lynde Creek watershed recorded 10 species of fish in the East Lynde including the Red-side Dace, a nationally vulnerable species listed by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).
The creek also serves as a migration corridor for spawning fish. In 1983, CLOCA recorded Rainbow Trout north and south of the trail. In 1999 White Suckers were observed moving upstream to spawn. The presence, or lack thereof, of certain species serves as indicators of water quality.
http://www.lionstrail.org/trailguide/4.html