SK Curriculum HC4.2 d; DL6.1; DL6.2
One fish, two fish, trout fish, whitefish!
Fish are an important part of the traditional and contemporary diet of many Saskatchewan residents. In the Northern lakes pickeral, trout and
whitefish are a dietary staple – delicious fresh, smoked, fried or dried. Fish is a healthy source of protein, and fishoil provides many nutrients
essential to human health. Fish oil contains DHA , an omega-3 fatty acid that plays an essential role in brain and eye development in children,
and long-term memory in adults.
Fish are also very intelligent, themselves – yes they are!
By tagging and releasing fish, Western scientists have found that being caught once makes it less likely for a fish to be caught again. This
indicates that fish learn to avoid the negative experience of getting caught. Studies focused on lake carp also show that these fish use ‘mental
maps’ to remember the geography of lakebeds, and seem to give directions to other fish using complicated movements called ‘body language’.
If this is true, why, after thousands of years, can we still catch fish? The reason may be that there are so many fish in our lakes that most of
them have never been caught. Or maybe, it is because fish that are caught on a hook or net rarely escape to share their teachings!
How do people know where to fish? Traditionally, people observed lakes and the numbers of fish that they caught. When the catch was low
they went down they would move to another lake, or location on the lake to make sure that there would be enough fish left to survive. The
Dene people and Woodlands Cree people have lived in Northern Saskatchewan for thousands of years and have a deep understanding of the
lakes that they fish – this understanding is connected with culture, language, and traditional values and stories. Are there traditional fishermen
or women in your community who you can invite to speak with your class?
Nowadays, many people enjoy fishing in Saskatchewan’s lakes who come without deep understanding of land and tradition. Sometimes they
hire local guides to help them find the best fishing spots. Other times they may go by trial and error, or by past experience at other lakes,
fishing in areas they expect fish to be found in - like reed beds where there are lots of bugs for fish to eat.
Environmental scientists are also interested to know how many fish are in a lake, and how many are caught each year. They keep track so that
they can understand the impact of changes that may happen in a lake through time. Changes may happen naturally, or as a result of human
activities like mining, road construction, and disposal of waste near lakes. How do you think they might estimate how many fish were in a
lake? One approach is called ‘Bag and Tag’
MATERIALS: per small student group: yogurt pail and marbles or pom-poms, small stickers (red dots), bowl, graphing paper
RELATED MEDIA: Fish scale art gallery (in development); Fish Scale Art Activity; Making Fish Scale Glue
Activity part 1: ‘Bag and Tag’ 15 min












On the graph paper make a table with the columns ‘bagged’ and ‘tagged’, with rows ‘1st sample’, ‘2nd sample’ etc.
Fill the pail with marbles
Have one student reach in and grab a handful of ‘fish’ - record
Tag your fish with the stickers and record the number in the column ‘bagged 1st sample’, ‘tagged 1st sample’ will be N/A
Release the ‘fish’ back into the lake, put on the lid, and shake it up so that the tagged marbles are mixed back into the ‘fish
community’
Have another student ‘go fishing’ – record the numbers bagged, and how many are tagged, in your column for 2nd sample
Set up a proportion to determine the total number of fish in the lake
(bagged 1st sample/total population) = (tagged 2nd sample/bagged 2nd sample)
rd
Try a 3 and 4th sample – do you get the same value for ‘total population’? What is the precision of the ‘bag and tag’ method?
Count all of the marbles in your pail and check the accuracy
What could you do to get a more accurate or more precise number of fish?
CHALLENGE: Based on what you know about fish intelligence, would this mathematical model produce a high or a low estimate of
the number of fish in the lake?
Would the traditional observational method of fish ecological management or the WS math-based model be more accurate for a
large lake? How about for a small, stocked catch-and-release trout pon?
This hands-on activity was contributed by Stavros Stavrou, Department of Mathematics Summer Outreach Coordinator, with the support of the
Pacific Institute of Mathematical Science (summer 2013)