Habitat Usage of Cutthroat Trout
The data come from a graduate student, Rich Brown, working in the biotelemetric unit in the Department of Biology at the University of Waterloo. He is interested in examining habitat usage versus habitat availability of a particular species of fish, cutthroat trout.
Rich implanted radio transmitters in 27 trout in Dutch Creek, Alberta. The fish were initially caught (by angling) from upper, middle and lower parts of the creek. (You might assume that these captured fish represent a random sample from the population of cutthroat trout in those particular sections of the creek.) Each fish was radio-tagged and then returned to the creek at the location of capture. Twenty-three trout were tagged at the end of August or the beginning of September and then each trout was relocated every third day starting September 1, 1995 until disappearance or January 12, 1996. Four additional fish were tagged in mid-November, 1995 and then relocated every three days until January 12, 1996.
The particular kilometer along the stream that the fish was in when relocated and the depth (cm.) at which it was then swimming were recorded. As well, the distance (m.) moved from the previous location, either upstream (positive distance) or downstream (negative distance), was recorded.
Below is a table indicating the particular kilometers of the creek that each fish was found to be swimming in when relocated over the period of the study.
Kilometers used by each fish in the fall and winter
|Fish #||KM tagged in||KM used:||KM used:|
|Fall (Sept. 1- Oct. 31)||Winter (Nov. 1-Jan. 12)|
|141||7||not yet tagged||7|
|1522||12||not yet tagged||12|
|2112||7||not yet tagged||7|
|2312||15||not yet tagged||15|
* no data on availability recorded
Since habitat conditions changed with the presence of ice, the depths available to the fish were measured in the fall (not at all or once) and in the winter (not at all, once or twice). The available depths were measured in each kilometer along the creek using 20 equi-spaced transects (straight lines) per kilometer. (The particular kilometers surveyed for availability are labelled 4, 6, 7, 9, 12, 14, 15, 18, 19, 20, 21 and 22. The other kilometers were not surveyed.) The transects were run perpendicular to the stream starting from the wetted edge. The depth (cm.) was measured at meter intervals along the transect, although individual transects are not identified in the data set.
The primary objective of your analysis should be on the testing of whether the fish show a preference to certain depths from those available. Rich is interested in comparing preferences to availability for both the fall (Sept. 1 - Oct. 31) and the winter (Nov. 1 - Jan. 12).
The data are contained in an ASCII file called use.txt and the variables are, in order:
- fish ID (FISH),
- calendar day of the month (DAY),
- month (MTH$),
- distance moved from last location (DIST), and
- depth (DEPTH).
Note that a few depths are missing (denoted by ".") and the initial distance moved by Sept. 1 was not (or could not be) measured and is denoted by ".". The first row of the data file contains the variable labels in brackets above.
The data are contained in an ASCII file called avail.txt and the variables, in order, are
- kilometer (KM),
- day (DAY),
- month (MTH$), and
- depth (DEPTH).
The first row of the data file contains the variable labelled as in brackets above. Note that more detailed data records, either for usage or availability, are not obtainable.
For your information, he grouped the depths into seven depth categories (0-19, 20-39, 40-59, 50-79, 80-99, 100-119 and > 119). The summarized usage and availability data that he analyzed are contained in the ASCII file rich.txt. (This file is a combination and condensation of the two files use.txt and avail.txt.) The variables in rich.txt are, in order:
- fish ID (FISH),
- the number of times the fish was found in each of the seven depth categories (U1-U7),
- the total number of times the fish was relocated (TOTU),
- the particular kilometer(s) the fish was found in for the particular season being recorded (KM$),
- the number of meter intervals measured for availability in each of the seven depth categories (A1-A7),
- the total number of meter intervals measured for availability (TOTA), and
- the season 1=fall, 2=winter (SEASON).
The first row of the data file contains the variable labels in brackets above. You, however, may prefer to re-examine and analyze the original data (in use.txt and avail.txt). If you have any questions about the data, you may get in touch with me (Jeanette O'Hara Hines) via e-mail at email@example.com.