HomeMy WebLinkAboutAPA2049d pt2PART 2
Population Dynamic.of Arctic Grayling
in the Upper Susitua Basin
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POPULATION DYNAMICS OF ARCTIC GRAYLING
IN'THE UPPER SUSITNA BASIN
1984 Report No.4.Part 2
by Dana Scnmidt and Mike Stratton
Alaska Deparcment of risn and Gaae
Susiena Hydro Aquatic Studies
2207 Spenard Road
Ancnorage.Alaska 99503
AJlSTRAC7
'rne effects of an anticipated s~ort fisnery fot'Arctic 1ra;tling on tne
tributary st:'l!at:l.S of tne upper Susiena basi:'!1s ~"at:l.ined ~?:!!0~:!llin1
:~e e:=ects of n:'7ot~etical na~lest.~ne inC:'e~sed :e~el~0::cr:ali:7
craaced ~y a spar::i~ne~l cau~e a rapic sni=t in tne age ~t~Jc:~re dOC
consequently t:l.e s1=e of tne fisn cau!nt.:0 caintain a "r;r:l::m~l"
fi~nery on a susta1ned yield basis.a caten a~ri release iisnerJ appea~s
to be ..,arranted.ender tne assw:rl'~tions of tne :!lodel.tne :..,ta':.I'a~=-ber
of all fisn cau3nt:13 :lot substantially =ecuced 'Hi:~~~t:par;lt;~:,el:':'li;';!'l
level,]of tisning.?ossib.i.e explanations "f ene d!1ierences :'r.
population structure,of tne ~eadman Creek draina~e and tne icpoundment
tributaries are discussed.
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TABLE OF CONTENTS
Page
ABSTRACT •••••••••••••••••••••••••••••••••••••••••••••••••••••••••
LIST OF FIGURES ••••••••••••••••••••••••••••••••••••••••••••••••••
l.0 L-mlODUCTION ••••••••••••••••••••••••••••••••••••••••••••••••
2.0 METHODS •••••••••••••••••••••••••••••••••••••••••••••••••••••
2.1 Study Locations ..••••.••••...•.••••..•..•..•••..•.••.••
2.2.Flsn Data Collection ..•••••••••••.••••••.••••••••••••••
Z.3 Data Analysis .••.••.•.•••••••••..•••••..••••••••..•..••
3.0 RESULTS .
3.1 Population D:tnam1cs of .~ctic Grayling .....••.••..•.•••
3.=Sport Fisnir.g HarJ'8S:'XOdel..
!.,I)!:'!SCUSStON •••••••••••••••••••••••••.••••••••••••••••••••••"
5.0 CC~;!RI3lrTORS ..•.•.....•..•••..•..••.•••...•..•.••••••..•••••
Ii.t).\..C:;Ql'O~.:r.:::tGi:2~rrs•••••••••••••••••••••••••.••••••••.•••••••••
i.O L::L7E?.A!UR..E C!:~.
3.0 AP?::1!D!C!S ••••••.••.••.•....•...••.••••.•••••.•..•.•.••.••.•
A9?er.di~1.E~uations used to ~del ?opulation cnar.ges .....
••Contents••••••••••••II......
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3 Compari~on of che ei:ecc~ot inc=e~entall:
increasing tr.e ?ercentage of spar:caught :is:\chat
are released unhar=ed on the scstai~ed annual tot31
catch •••••.•............•..••.•....•..•....•••.••.•.•.
9 !he effact 0:sport harvest on the Deadman Creek
grayling population for a ten year period ai:er che
onset of a fi~hery ~ith 90~•50:,and no return
catch and release •...••...•..•••.•••.•••••••••...•.••.
Title---
Study reaches used for modelling the population and
harvest of Arctic grayling in the upper Sustena
Basin ••••...•...••...••••••••..••••..••...•••••••..••.
Comparison of age estimates obtained from the same
fish using otoliths and scales.Numbers of fish are
indicated next to the dots in the lower figure.The
upper figure illustrates :he effect of correction
for age by otolith analysis on growth
de cllIrminations •••.•.••.•.••.••••••.••...••..•.•..•.•••
Population @stimates of each age class of
1~poundment :15h and the 93~confidence inte~'al.
Estimates of 2 and 3 year olds reflect only the
portion of t:t@ ?09ulation that -.las subject to
cJ.?ture QY ;,ook and Ii::':!..••.•............•........._.
Comparison of the age specific populations when
length data were used to estimate age from the
length/age relationships developed f~om scale data
and from otolith data.Total population estimates of
age 4 and and older fish are included •...•...•...••..•
7':!rceatages of se:rually 1:'.atur':!Arc::'c 3ra::linl§:cf
each age class.All ag':!s ~ere dete~inec by otolith
examination ...•...•....•..••.•••_.••.•••......••...•..
rercentage change in total egg production of Arc:ic
grayling ?opulations of the icpoundment tri~utar1es
and the Deacman Creek draina~e ·.lith and -.li:hout
simulated catch and re~~ase fisheries.The catc~and
release fi.;r..:~rJ assw;led lC~c.ortalitj'0:;::"e
captured fish •..•...••.......•..•...•..•••.••••••••.•.
~ffects of increasing sport£ish ha~lests (lOO~
nor:.alit:'~on ::-:e sustained :..~eld .:.a:ch 0:"ar~"us
~;':!:c::or:;;of ::-:e :p..J.C:::lan C::,=e(,-~=a:,:.:.~;:
P.:l;lul....;:ion .............••..•..........................
3
1
7
LIST OF FIGURES
Figure
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II
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1.0 LvrRODUCTION
During tne 1983 studle~on tne upper Susitna basin Arctic.grayling
populations.data were obtained tnat are u3eful in revision of toe
population dynamics model ",oien ",as constructed from 1982 data (ADF&G
1983a).we obtained refined data on age estimates by examination of
atoHeus in acidit.ion to a broader sac.ple of spawners during toe spring
of 1983.In addition.a study was conducted on Deadman Creek outside of
toe proposed :!.l:lpoun<bent boundaries (see Part 1 of tnis volw:e.).In
t~ls report,~e exaaine toe effects of reclassification of coe a~es of
fisn collected during 1982 on toe conclusions of toe earlier co~el.~e
als;)e:t?lore ef:ec:s of various levels 0:e:Qlo:!.:3tlon on t:!e ::'~?=o
cuc:lon or tnese populations.orne effects or eaten and release ma-
:1av,etlent strateg1~s on narlest of tni!:se :i3n and conpari30ns of i:~H!
~e3d~n Creek P09ulation ·..lien tne ocner tri~l.:t3ries are included.Tne
infornation presented snould be useful 1n developini a mic1gaeion plan
!t)r dealing ...,1tn toe ei:ects of increased eX?loitation of tne ::'sn s-
tacks associated ...,ito ~roved acce~s.
..
••••••••••••
•
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2.0 MEn!OOS
2.1 StudY Locations
The approximate location of the sampling sites are depicted in Figule 1.
The data collected for the tributaries within the impoundment zone were
primarily obtained during the summer of 1982,with spawning data and
otoliths obtained trom these tributaries during late May and early June
of 1983.Detailed deseriptions of ehe sampling sites and study loca-
cions were described in ADF&G (l983b)and in Appendix I of ADF&G
(1983a),The remainder of the data were obtained from the Deadman C::eek
d:-ainage du::ina::he suc:er of 1983.~ese data a:'e :-eported in ?a:::1
of this report.
2.2 :ish Data Collec:~on
A~~data collection methods are described in ADF&G (l~a3a.1983b)anc in
?art 1 of this report.The only data not ?re',1ousl;r descr1\)ed a=e ':~e
otolith collections :rom tributaries within the impouncicent zone.These
otoliths were collec':ed alor.g ..n.th scales.in sn iden'::!.cal :l.e,;~od '''i,:h
2.3 ~ata Acal'ls1s
Data sumcaries from the collection afforts of the open ....·ater =ie':'d
season of 1982 and 1983 '..ere used to estimate dl.::e·.ent parameters ~£
" f-~ ) I \{,..J (/ \ • ·-...:;.--~-~ c: LJ [VII CANY O N \. __ _
· "v c UAIA S ITE ' .... .,.. . ~ •. ' ~~ s' :17
PRJN C I P~.b. .§US ITNA RIVER
AND IRH!!.J TARY GRAY LING
PO P ULAT!O ~ S TUDY RECORDS
(Dev i l Co nyott lo Oshetna River)
J.
0
AD F b a FIELD CAMP
Af<(;TIC GltAYLINO POP·
ULAfiO U STUDY REACIIES
I IA III:.S
10 __,
\
L ()
--------------~----_.·----~------~
f i9ure 1. Sludy r 1:111lt l :S u st:d f ot· uto<.l c lliu!J the po pul cJ li o u a nd hd r vc s t
o f Ar c l k ~·..,y llug in th(; u~p er Su ~il111.1 Bd s in.
L AK E CA MP
••
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the Arctic grayling populations under study_These parameters include
We independently
!he sportiishinginstantaneousIllortalityratesfromsportfishing_
'..nere:
recapture studies.instantaneous rates of Illortality from fishing pres-
t~e ~ead2an Creek :1sc populations.
Creek and the impoundment tributaries.
used to describe projected fishing pressure mortality for both Dead1:an
length-age relationships using scales or otoliths,instantaneous rates
Fecunciity estimates were derived rrca Tack(197u)~h:!.ch reilec:ed fec~nrl-
and frolll the iapoundment tributary studi~s,with t~e ~:ccept~on of the
calculated these estimates from the Deadman Creek drainage study sites
sure.and percentage spawners of each age class.
morcality rates measured from the impoundment tributaries in 1982 were
of natural ~rtality from catch curves,densit7 est~tes froQ mark and
r
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A population mod.l which included incremental sport fishing exploitation
as a component was developed using the approach de~crlbed by Clark
(198J)and also used by Allen (1955a.1955b),aeverton and Holt (1957).
and Jensen (1981).The methods duplicated Clark's study except that
differential oortality rates were assigned to each of the age classes of
the populations.Equations used in the model are listed in AppendL~1.
:"he equations ;Jere entered 101:0 a com:tl.ercial spreadsheet prog=am ..,hieh
features interactive graphics (1-2-3 by Lotas Inc.).~!ost IJ!the
illustrations of output of the model 1n this report are produced di-
rectly from this prog::-am.
~is ::lodel does not adcress de!:.sit7 de?endent ::or:al::'t::c:t~t!etit;:0
recruit portion or the li:~cycle.Constant recruit~e~t ~AS ass~ed.
n
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3.0 RESULTS
'.
3.t Population Dvnacics of Arctic Gravling•
7ne :le'"populac:.cn
.-~..---::0-'
Tnese values were obtained iterat.ivel~HO cnat tttet.nis population.
a survival rate of O.is ..,as used for tne age III.IV,8:ld .,conorts of
:1t to tne catcn curve data.For purposes or oodelling tne po?ulatlon,
1'?S3 re;:or,:::(~4.:i4 "~=sas 13.~5C).::te ::,H;;ral 3c.:-::":a1.rat~:0=:::e
age V!anc older fisn ~as es:ioated to ~e 0.36 by using a leas:s~~ares
fisn :l0·...tne :,o\.:.n@;esc concrt of t.ne populacion.
:.\U?!:G 1983aL
is cepic::ed in ?i%ure 4.Tnis adjustment '';85 :lade to consider sp:"i:1%-
to maturity of tne Arct.lc grayling populations w1enin tne t.ributary
f:'gure illustrates tne consistent pattern of underestimating i'~e by
0:~ne ~ai:~naole populaci~n nave sni:ted one year ~ien tOle :our year old
~st.imates of tne !,opulations previously recorded irom toe 19~2 st.:1dy
,):ene ;lopulat1on a::::er accounting tor en:',;.:nan~e ii i:';,iiar co i:ne
of Arctic ~ray11ng and were compared to scale anal~s1s (Figure 2).tots
:':1e ?opula:ion esc~ces :or i::le ::oungesi:aget:::'3n consid'H'ed as ?ari:
Devil Canyon impounamencs.vcolitns were OOtained irom a range of sizes
During toe spring of 1983.ye obtained additional inforcation on t~e age
scal~analysis ai:er a~e V.~ne oe01ieD readings are assuced to be :ne
streacs adjacent to tne reatn of river to be ~~undated by tne ~at3na and
:lOSt accurate of cne t"'.JC.T::is soift in age:st.:-uc:':Jra nas al:i!:,ed ::1e
I
5 6 7 a 9 10 II 12 13
OTOLITH AGE (YRS)
..••400
~••380 ..••360 ..••~
E 340
~•320
i •E 300-290 .1J:260 oftollg~~Z 200
UJ 180 .3.
•-Otoliths
-I r 60
140
~-Scoles120.1100
I234567a910II1213
AGE (YRS)
I
~
1Cl
III 91c::-:~-
UJ
(!)0
~
5III
UJ 4
-I
~3 /
13;,;
.:"j t~'
I II
2 3 4
Figure 2.Comparison of age estimates obtained from the same fish us~ng
otoliths and scales.Numbers of fish are indicated next tJ
the dots in the lower figure.The upper figure illustrates
the effect of :orrection for age by otolith an,lysis ongrowthdeterminations.
•
10,000
Comparison of the age specific pcpulacions ~hen length d~ta
were used to estirr.ate age from the length/dge re1ationship~
developed from scale data and from otJlith data.ota]
oopulation estimates of age 4 and older fish are incluoed.
I I I j
10 II 12 13
@506
26Z~
@ -1983 Otolith Data
n =14,174
•-1982 Scale Data
n=13,750
I ,j Ia7ai
AGE (YRSl
@Z4tl
@1917
,
5
i..
2.904.
2.454 •
1••5@
i
2
Figur£.3.
lI)
lU
I-1,000
<t
:E
l-
ll)
lU
Z
0
:-
<t
-I
:=>a.looi0a.
~
--•••••••..
•
•••
•••10,000
•;;;POpulatio n E sfimote •I :;95 %Confidence Intgrval •I1 t •
r
1 I •:J:
(/)1,000
!.L •T!.L
•0
1 T
r
:I)
I ~c:::•Iu.J I •CO
1
1 I !~
;:)•Z 100
I.,
j I .I.
I 1•I
I
.I.
'",-1 1
2 3 ..j 5 "7 3 9 0 12 13';
A G l:.(YRS)
:-ig ure
J ?opulatlon ~stimates of eacn age cjass or 1moounamenr:fisll
and the 951 confidence interv~l.~s:imates of 2 and 3 year
olds reflect only toe portion of the ~opuJation :~at ~dS
subject to capture by hook and line.
.,d.l approx1uted the ag.class specific populations observed in the
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approximatdy 13 generations.This method of estimadon of natural
The .,d.l reached Cl steady state aftet',simulation offield.
survival rates replaced the estimates used in the previous report which
relied on population diiferent1als between each age class for survival••estimates.Th.revised population est1Jo\ates suggested the constant
recruitment assumptions were suificiently violated tha~ac~ual ':lopula-,-
tion estimates of the younger cohorts could not be used to estimate 3ge
specific survival rates.
The eontributio~of each age cohort co the spatlning population is
depicted in F1gur~5.This analysis suggests seQe four year ole fg~3:2S
becace sexually :3ature and a higher percentage of :enales recai:;,ed
-1:eos_es.
::'e l.1:;2r Arc.:ic
?opulation est1J::tates by age class -"ere not
3ecause otolith a~in8 requi:ec:!k.!.lli:::.~~he :13h.·..e cic ~c:
iopoundee.nt boundor~es.
carked and recaptured in the ?opulation estiClates conducted on speci=ie
::~e Arctic 31'oy11ng populacion of the I:=~:,uta=ies ·.n:~1n che ?r-:?ose~
possible because of che cCClparacl',ely small cU1llbers at fish that ~ere
sample lar;e :lumcers 0:t~e older age classes.
:i1~pO~lUlaclon ~a=aJ:l.eters of c=e represen:ati',e reac::es 0:Je:lc:=.:l~C:''!2::
Creek were usually males.which suggests higher oor:al!.::,:oates :::)r
:-:a~1Jre unti:age V::.7:-:.g thr~e :i3n collected o.,~=A~e :~I:';er'!!:a::••••••••~..
100-
90 ·
>-80 -
0 "10· z w 60 -::>
0 50· w
0:: 4 0 lL
~ 30 -
0
20 -
10 ·
L__] M ALE S
l~Wffl FE MALE S
11-~7
u::t2
2 3 4 5 6 7 8 9 10 II !2 13
AGE (YRS)
1 t~lll'l! !>. l 'erce uld!J e~ of sex u..a l ly maturE: 1\t-c t ic gray I i ug of eac h age
c l a~s. All il\Jl!S were J de nuiuc d by oto l ith ex untin a tion .
Coaparison of t;,e
::1 all ..::asc!s.;:he
The mocel has been operatec incependen:::17T t'or
=ecruito.er.t assu:lption of t;,e :l:!odels.3us:ai:1ed 7ial::?r=~ac:ions ",;ere
:~e i::pounc.::en::=i;'u;:...r'ies and tor Deadman C.eek.
that would provide a population estimate of age IV and older fish
:'he ~gg produccion aed ?ercent spatolUer da:a developed iroo fiel~cata
ob;:a1:ted after tan ~enerat10ns of ~onstact :1a:::~ral :or:ali:y ac:cepanied
effects on egg production of sustained harvest (assuming 100%oo!'t~li:y
numbers of fish ha~Tested refer :::0 populations ~tthin :::he reaches 0:a~l
as inpu:::to the 0.0ce1.
"b:::ained during 1;:3 and fro!!!:::he ~i:::c!ral:ure sources descrioed c!arl:!.c!r
aga III,IV.and V c:ohoru for simulation of the population by the
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SER4C!Pan 2
reaches.Survival rates calculated.frotl the least squares fit of the
eateb curve.data ver«,).76.This value vas applied t.9 the age n and
older cohorts of this population.This value vas also applied to the
·..r!.:h :::he t:lpe of fishing ;aortality being aumined.
;;:odiEc:at1ons to :'nc0r'?0ra::.e cat=~and re~ease ::!..sh1:v~.
~del.The population estimates for the baseline year of each age class
were approx1lDated by choosing an initial recruitm.ent of age III fish
of Deadman Creek thac 1s under consideration in this study.
reported in Part 1.This value is approximately 8000 fish for the reach
sicilar to the number estioated by che mark and recapture methods
II
r
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SER4c.:/Part 2 •
impoundment tributaries.The simulations of harvests of Deadman Creek
!>eadcan Creek simulation plots for numbers caught:under alte~atio.l'e
:'he optimal
C:d.SS
?ressure prior to the present)and continuing for the nCl(t ten :rears.
10:30rtality (90%survival)of the fish that were cap~ured 1s depicted
of all caught fish)with a catch and release fishery that produces only
on Figure 6.Because of the average larger size and older age of the
illust=ated in the sioulation OUC?ut plot on F1~ure 8.
the catch over this period.
ling assucing 100%:'!o~tality of aE caught fish i.n t~e Dead::::an C=e':!k
assuming 100 hours of f:'shing per mile of st::eam.Hgure 9 .':so
~~bers actua:ly caught (assuming re~~ases of =ish wi:hout mortality)~s
Deadman Creek fish.a more rapid decrease in the spawning cohort (and
?~~ure i illust=ates :he ef:eet or increased ha:vest pressure on 5=3::-
a:'l.d ~elease of spar:caught fish 0:90.80.iO,60.SO,and 0::of the
cat.:.h rata is cla.lrly a function of tha pe::centage 0:the caught f:'sh
successfully returned.
catch and release strategies are ?rovlded.
a~ou~~O hours ?e~~:~annually whereas :he =uL~~um yield of age !~anc
anc the impoundment tributaries demonstrated similar ;rends so only ;~e
older fish oc:~~s at less than 10 hours per ci1e.~.e effects of catc~
consequently,egg production)occurs than under stcilar harvests in the
:'::cstraces the effects of assuming 90:,50:and no success:ul return ~n
study area.Note that the maximum sustained yield of all fish occurs at
•
3C
, 0 )
60
C!!3dman Cr~e!<
40
o o
0 0 o 0 0 0 00
Relative rishing £~fol"t (Hrs/~.Iile)
20
o
o
o
:~ooundment Tributaries
o
o
?ercentage chan~e in total ~~g ~roduc:~cn )f Ar::~c ~r3yl:n~
~opu'ations of the impoundment tributar~es and :he Ceacman
Creek drainage with and without s;muiated catch and release
fisheries.The catch and release fisher'l assumed la',
mortality of the captured fish,.
Grayling Egg Production Analysis
Catcn and Releose versus 1 OO~Harvest
=~~ure o.
100 *,
90
0
80
0
0-70u,
'll
0 60 1~
lL
'"1'"50..,
0 I•40 ~~
J
~,
()30-I0..20
10 -,
II
0 I
0
•••••••--'•
•
••
•••••
'0'0'0
lola"HOI""INf'10111.1)1 Str.om
Analysis of Deadman Cr.Grayling
"'""Uel'Su.taln.d TI.ld Mo,..••,
700 -/
'00 ~~..,
0 '000<
;;.
<00,,
u
<·"0,••0
J
7';ure 7.=:f.:'ects of ~nCr~:tSing socr~fis:h ;'ar'les.s "'('C"-Cl"'''-'~'''_.•
~~e Sustained yieid catch of various ag~e ~~~o~~s"o;~;~~!
""'''.-1m3"C""•-'_"...~~_.,~e~gray 1ng popujat~on.
•
100
::~d.gsCd
-O~-
'"50!lS
0 60!lS,70!lS
x 8095
0 :'O~
6060
Number ot Hrs.Fished/Mile of Stream
20
Sustained Annual Catch of Grayling
Effects of Cotch and Release
0.9
-0.8
.t:..,
0.70u
.t:~0.5••
j;;"c
·0o.0.5c'00
.Q'=
Et:.0.4,
Iz
0.3
0 1
0 I>-0.2 ,,
I
0.1 J,
I
0 I
0
,
;
;•
~-;
"=~·.~.-o,
..••••••••
"..........Q~••,,"r;.......
~.-:I !.,,;..'/,,,,,,'./"
'/'.:-,",/"
,.,
f,;..,/.,•'..
.:.--.,.,,,...
,-~,:-.:.i ",.':.:'\""'i~,'----'."',,.
,,
,
;•··J:-:-
:2:;·.~.-o
Flgur@ g.Th@ @ff@ct of soort narv@st on the Oe~aman Creek grayling
'ooulation for a :en year oeriod after the onset of J f!sner~
~ith 90:,50:,and no r~turn c~tcn and release.
. I
:r:::'s
1I:1poundmene Arctic gray1iog
5i::e
tn.spavning and maturity oftn.
::;e ;c;ulat::'ons 0:::le :..::;ounci.::e:::t=:.ou:a=:'es ar.c.:ea,;:=3:l ;;=;e:<.
c=ee!c.cuc,:,encly prOVides a c'ropny qual::'t:r fi.snery !:!1at :!.3 ur.usual :0:'
est:!.:1ate ene =esu1.:s of ·rar:'ous :tana~eme!1:al:e:-:tat:":es on ::l.e ':'..:n;::O!:~
?ro~o!cc scenario.l:':J.e Jea<i:tan C:,eek d:'ai=ai~is a :i~:ely candiea:e co
?opulac::'ons ·"il':'':Ie subjec!:ed co :'::c:,e...seri tla:--:escs :me.:!:-a ?os;:
-:';le analysis ?,:,esenc!!:d and tne :ollowi::.g d::'sc-..:.ss'L:n -.ri.:.l 3.t:a:?'.:to
::aries cnat :.Ie:,:!st:.:died ".J1:1 ;)e irundaceri,t:le areas aoove :::.e
DRAET/PAGE ,9
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SER4C!Part:2
previous studies,in addition to new information on Deadman Creek and on
:ne Sus1tna R1-,er because of easy boac access i:lto ar~as ·...nere nm"
::::ea~C:eek.!~e ~evelopmCl;n:0:tne project ~7 provide addi:iona~
si::l.ulaced sport f1sn1ng narvests an toe impoundment tr1butar:'es and .:In
populations,nas prOVided a :Dore precise look at toe effeces of
'Ine refinement:of cne population and age structure data presenced in
~eans ~y ~n:!.cn na~Jest of toese Eisn 13 ?osstble.A!:~ougn ~~e ~:.":!.~u-
!.i!ngtn oel:".Ieen ene lower por':ion of !:ne c=eek nea:-ene falls <.'!.l'.c Deac::tan
:'ake.
:1elicopcers or,:!.~a sinall numbe.r of a:.":!as,fbat planes are ::le onl.::
access and narlest pressure 00 tne clear water tributaries draining into
4.0 DISCUSSION
•
ocher impoundm.ent tributaries and hov the re:Doval of passage barriers
=ay affect chis population.
possible reasons vhy Deadman Creek produces larger Arctic grayling chan
r
sport fisbery vitbi-':l cbeu stuUlS.
DRAFT/PAGE I 10
5/24/84
SER4C/Part 2
In addition,we w111 explon the
n
•••
The ef~ects of sport fishing harvests on the population structure of
ii'/er.Adciic1onaily.computer coae.i;il nave been used co descrioe sc::'eac.
:i"heries for a variu7 of species in the lower fony-eight (Clar~(u
•••
•••
••
CU::'data i=otl :'cok a~r.1.:.::.e
_.._~-'-_:-_~_.oa_
comparing t:te cutcoces 0::ou:~odel .it:"actual =esults of e~?loitat~on.
daCa on t:"e st:-'.Jc::ure at
:011 ~c:icn .iU 66 eS :3 •di'::eran:::ial ;:==b ..bili:'j'oJ::~?:::'J,=e c:::-.e
di::erent sizes of fish ·",h~c::",.!Ii~':::I.1:~canc anou;:"'0 a.i::ac:::-.e
~se :~e le~;t~st=uc:ure of an ag~conort as a coeponent i~:~e :ociel.
al.1980;Clark 1981.1983).The model developec by Clark is s~=ilar co
7nis
Increased
Tne departmenc nas
L~ss cO;::~II:,ti:lon for cer:-itories :.?t:le
?egardless of -.lOic~n::?oC:lesis is co::-::,!!ct.tne :!.noo?:::,e::,t ;:Jroc!ucti\·il:::c:
Or..AFT!PAGE iJ 13
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SER4C!Part 2
of :isn snould not cnange,assuming ~ecuced populations caused oy
iisnin.g :::Iortalit::could ':!!:lulate any densit;'dependent oorcality e'::ect;;
tne streao snould :lot :'e af:ec:ed.and conseqcently :ne sust3i~ed 7ia1d
~i:n tne older fiso ~ay result in an iQproved ~ro\ltn rate,
is created by ni~n censity dependent mortality of tne younger a~e class
tne fisn passage barrier,suggests tnat toe current populacion str.ucture
pressure tnan Deadman Creek because of Coe publicity cqis lake received
portion of Kosina Creek may be subjected co significantly more fisning
an are:l to act as a resecfe,:1ort,]lity rates of t:le :,oun~o!r a%e cl.asses
,;;;a.i..':'.H nu;::oer of t",e :,ounger conort of toe Jeaclr.an Cr'!ei-.po~ulation
otner small fisn occur in haeitats associated ~itn tne cains~em Sus!t~a
reduced tne bag l1ut to cwo fisn ~er day on cnis lake.
mortality wiCR toe data base ~e nave available.
fisning mortal1:::y on cne syscem could aoc be separaced from nacural
Tne second nypo~neses,and one tnat may nave i~plicatlons ior recoval of
curing tne presidential cour of Jimmy Carter.
:1sn to tne system by ret!loval of cne barrier falls.tne ?opul3.~ion
:!.sn.T:lis may occur because tne f911s prevents tne ilZl.tllgration of fisn
•
a crapny sport fisnery .
system after inundation of tne fall.::f,coupled witn a.n1gn1y regulated
DRAFT/PAGE g 14
5/24/84,5/31/84
SER4C/Part 2
Careful monitoring of tneonpopulationsurvivalandgro~n rates.
sport fisnery,may prOVide some 1ns1gnts onto noW'to manage and maintain
••
DRAFT/PAGE iJ 15
5/24/84
SER4C/Part 2
5.0 CONTRIBUTORS
Graphics support was provided by Sally Donovan and the typing ~Ias done
by Skeers Word Processing Services.
•
DRAFT/PAGE 9 16
5/24/84
SER4C/Part 2
6.0 ACKNOWLEDGEMENTS
Funding for this study was provided by the Alaska Po~er Authority.
Thanks to Richard Clark.Jr.of the Michigan Department of Natural
Resources for providing the programs used in his published studies and
:or his suggestions on this stacy,
Appendix I eo
A model of tne1983a.
.Uaska Depar:!:1eDt of 7i30 arod
Arctic ~rayiins scudi=!5 ~r.A':.u:<a.
7ac::ors ai:ecr.i:1~tne ef:'ic!.enc:;c:resr::=ict!.·..!!
Susiena Hydro aquat~c studies pnase II basic caea
~9aZ.
1955h.
1983b.
Journal of Science and Tecnnology 35:~98-329.
cne Alaska Cepartcenc of :15n ar.d Gdoe,)1'::'510n of Sport F:'.:;n.
DRAFT/PACE'17
5/24/84,5/31/84
SER4C/Part 2
regulations In f:sneries m3na~e!:lent.II.3ag Lioits.Ne·..,Zealand
structure of Arctic grayling above Devil Canyon.
Alaska Oepart:::lent ci Fi3n and Gal:!e Susie:1a S:,C.=O "'-Cluatlc Se:.:dii!s.
report.'lolume 3.Upper Susiena aiver !.;:?ounc.cent se:.ldies.i982.
effect of incremental increases in sport fisning on population
August,1982.
ra~ulat~ons in ::"i.;;ner~es :anageoent.1.Si=e li:::llts.~:cw Zealand
Ga=e Susitna Hydro Aquatic Studies..\ncnorage.Alaska.
;cu~a:of 5ci-:!nc~and :'ec:loolo~y 36:3(1~-nlr..
:labit:at relaticnsnips .(2 parts).
Synposis of tne 198:aquatic studies and 41nalysis of fisn and
Ancnorage,Alaska .
7.0 LIT~TURE CITED
Allen.:<.a.
Ar:::3trong.i.
Alaska Departoent of Fisn and C4Ime (ADF&G).
.H:en.:C i.
30ard of Canada.Ottawa.Canada.
••••••..
DRAFT/PAGE •18
5/24/84
SER4C!Part 2
1957.On the dynamics of ex-
Potentia.!.ef:ects of.voluncar:'catch and
Analysis of "Quality ..shing"regulac.ions
2f:ects of ex?lui:a:ion on the ?opu!.a:ion
Computation and interpretation of biological
1983.
1981.
198 t.
19:5.
Food.Volume 19.tondon.England.
dynamics of Arctic grayling in the Chena River.Alaska.~!aster's
ploited Ush populations.Fishery Investigations t ••Series 2.f!arine
statistics of fish populations.3ulletin.191.Fisheries Research
release of rish en recr~aticnal fisheries.~orth Acerican Juurnal
~epar:tlent of ~atural 3.esources.P'isheries Research Re;:ort 1395.
through matheaatical siltu:acion of a 'Jrown t=ouc i!sher::.~!ic:-'~g3n
Journal of :ish~ries and AquatiC Sciences 38:6S7-66~.
Fisheries.Great Britain.}liniscry of Agriculture.Fisheries.and
of Fisheries ;!anagement 3:306-314.
can Fisheries 50ciecy l09:38i-60~.
description of trout-stream fisheries.Transactions of t~e ADeri-
Ann Arbor.~1chtgan.USA.
Bevertan,R.J.B••and S.J.Ho ...t.
:ticker.lJ.E.
~ensen.A.L.1981.Op:i~um size limits for :rout fisheries.Canadian
Clark.R.D••Jr .•G.R.Alexander.and H.Gow1ng.1980.Mathematical
Clark.R.D••Jr.
Gr~backi.S.T.
Clad,-,~.D.•Jr.
DIAPT/PAGE ,19
5/24/84
SD4C/'art 2
Tack.S.L.1974.D1atr1bution.abundance and natural hi.tory of the
Arctic Irayliq 1D tb.taaaaa I1ver dr.ina,a.¥aDual laporte of
Pro.r....1973-74.r.daral Aid in Fllb "storatioD Project 1-9-6.
Job R-I-A.1.-1-3,a-I-e.
APPENDIX 1
Equations Used to ~ode'Population Changes
•
•~•••..
••..I....
.......
The following equations were used to project population changes:
••••II
II
•1
.1
11--
where:
Nt and Nt +1 are known
for each age class and
aive estimates for St
for each age class.n
In an e)(oloited fishery then,
ThE'annua 1 tota 1 morta 11 ty
rHe.A,is related to S,U:
-z
(4)Stn+F ~e t and,~here:
Nt~l ,.Population number ot age
class t plus o~e y~3r.
Population number of age
class t fish
,.Natural survival rate of
oge t f1sh
Survival rate of age t
fish after combined
natural and fishing
mortalities.
Z 2 Instantaneous rate of totJ)
t mortal ities of age :-:.fhoh .
( 6 ) Mt· = -1 n S tn
wh e re:
where:
Ft = Insta ntaneous r ate of
fishing mortality of age
class t ~ish .
Mt = Instantaneous rate of
na tural mortalit ies of
age class t fish.
Since Mt is available from Nt and Nt+l data, it is poss ibl e t o
subs t itute (model) values of Ft fo r a hypoth e tica l fi shery an d ;Jreaict
the resulti ng ag e structure of the copulation with time . To do this,
the fol lowing assumptions are made. (1 ~ The rata of catch fo r ea ch og~
class of fish pP.r unit of fishing effort exp er i enced by ADF~G wi . hcid
true for th e general public. (2) Only grayling of age III and olcer
are sub j ect to in creased mort a iity by (hook and line ) fi sh in<;. (3 )
Rec ruitment of age rr class fish i s constant.
!n an exp l oited sy stem then , Ft is viewed as:
·.yhere:
r.rd qt is est1mated f rom :
t 3' q = -1 n ( 1-u ) using, t t
qt = ca tchJbility of a~e
cla s s t; prooor:ion~a
fi~n u~r· unit t!me · hllt'-J .
= ·•srino ef.cor':, t '?a.~s
nrs or 6.05 hr s , mi 'e
~::ri'Jrr'.
I
I
I
I
I
1
where:•nuntler of grayl ing marked in
July 1982 that were recapturl:!(1
in August 1982 by age
class t.
M'•t nume,.of grayling markp.d in
July 1982.by a90 class •.
The term u t is called the rate of exploitation and was calculated from
the mark-recapture fishing data found 1n AOF&G (198J).
Calculation of the anr.ual total mortality rate (A tn+F) n equation (3)
thus a~lows calculation of predicted catch at different levels of
exploitation.
where:A.c ~annual fishing mortality
"
..3.nnual naturai
mortali ty
t ::X!!t·
~L AtF X Nt
t ..LV
::to,ta 1 c.a ten
simulat~d by r~duction of toe ;~'uJ ~r.e oe!',:::n':.:l':!of iiS"r2i~:1se1
•
'llithout mor~Jlity.The catch then included the 'fatue frem eQuation li
in addition to the numbers of fish rele:sed.tr.e difference :,e>;',<le20 F!
lS5umi "9 lOO~mortality ar.d F';assuming,the aporopriate lEvel
successful catch and rele3se.