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Fish EcologyLab 1

October 16 th 2002Heather Varaleau

230005521

Using a sample of 25 northern pike minnows we in!estigate" the si#e

relationships between !arious ph$sical fish features an" o!erall fish si#e %"escribe" as

stan"ar" length of the fish&' ( comparison of northern pike minnow mass an" stan"ar"

length re!eale" a strongl$ correlate" allometric relationship between these two features

making stan"ar" length an accurate measurement of o!erall fish si#e' )e foun" that

numerous measurable fish features ha" a "irect relationship to the o!erall si#e of the fish

with some hol"ing a stronger relationship than others' *n a""ition we e+amine" a group

of , "ifferent fish species to i"entif$ relationships between fish bo"$ form %as a

relationship between fin area an" con"ition factor& swimming mo"e an" li!ing

en!ironment'

RESULTS

Northern Pike Minnow %-able 1&

( log.log plot of northern pike minnow stan"ar" length !ersus mass %figure 1&

re!eale" that these two features are "irectl$ relate" %/ 2 0', 52&' *n a""ition anal$ses

of this plot re!eale" that stan"ar" length an" mass share an allometric relationship

%$ 0'5+ 3'0,12 &'

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( comparison of stan"ar" length an" total fin area using a log.log plot %figure 2&

re!eale" that these two features are also strongl$ correlate" %/ 2 0' ,5& although not as

strongl$ as stan"ar" length an" mass' urthermore these two features also share an

allometric relationship %$ 0'1066+ 1',044 &'

)e also looke" at the girth of the fish at three "ifferent areas an" plotte" these

against stan"ar" length %figure 3&' )e plotte" the girth at the operculum the girth at the

anterior e"ge of the "orsal fin an" the girth at the narrowest portion of the cau"al

pe"uncle' ach of these plots showe" a strong relationship between girth an" stan"ar"

length %/ 2

0',53, / 2

0',42, / 2

0' respecti!el$&'urthermore we looke" at aw features in relation to stan"ar" length %figure 4&' (

plot of stan"ar" length !ersus aw length re!eale" that these two features are strongl$

correlate" %/ 2 0' 55 & whereas a plot of stan"ar" length !ersus aw wi"th show a

relationship that is less strongl$ correlate" %/ 2 0'2504&'

)e also looke" at a two features relate" to the e$e %figure 5&' ( plot of stan"ar"

length !ersus the "istance from the snout to the anterior margin of the e$e re!eale" that

these two features are strongl$ correlate" %/ 2 0',42,& whereas stan"ar" length an" e$e

orbit "iameter are less strongl$ correlate" %/ 2 0'5 65&'

Different Species %-able 2&

-o make "ata from the nine separate species applicable to each other as a group

we stan"ar"i#e" the measurements an" plotte" con"ition factor !ersus total fin area

"i!i"e" b$ length s7uare" %figure 6&' -his plot re!eale" a strong relationship between

con"ition factor an" fin area %/ 2 0' 226&' 8oints along this line fell into three general

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regions along the line' -he first group of fish ha" con"ition factors ranging from 0'0, ,

to 0'4 3,,2 the secon" group ha" factors ranging from 1'230 , to 1',6,1, an" the last

group consiste" of one fish whose con"ition factor was 4'1 ,345' -he first group of fish

ha" a similar anguilliform bo"$ shape the secon" group ha" a wi"er range of bo"$ forms

containing in"i!i"uals with both streamline forms an" forms a"apte" to li!ing along the

substrate an" the thir" group consisting of a single in"i!i"ual %the buffalo sculpin& who

has a substantiall$ flattene" bo"$ form'