International Coiiricil for the Exploration
C.M. 1992/G:3
of ihe Sea
Sess. P
GRomiI IS A MANY SPLENDiD rinNä: ANALYSES IN WITCH FiOiJNriER
(GLYPTOCEPHALUS CYNOGLOSSUS), PATTERNS /\ND IMPLICATIONS.
'
O.K~ Gutvik, C.C.E~ Hopkins, E. M. NiiSseo; R.
Nilsen; &
..
A~ Hermannsen
The Norwegian College of Ashery Sclence, UniverSity of TromS0. N-9037 Troms0. N~rway.
Abstract
AIthough growth is commonly arid corivenientlyexainm~ iIi fish as chinges in length Per unit time,
the growth phenoinenon represeniS numerous array of processes arid Parameters 'which a priPri ruive
their origin in a bioenergetic model. Conscious of. the comPösite natUre of gfowth, the present study
quaniines and. conceptualises the mwtipUcitf. of growth in the witeh' flounder . (Glyptoeephalus
cynoglossus) and itS.rel3rlonship tOthe Wonnation conteilt resid~nt in the otolith, mchiding the question
of age validation. Exaßiinition of sever.l1 otOlith Parameters Oengthand wet-; dry- and ash weights of left
arid righi otoliths) iridiciuCd that sexual dimorphism oCcWTed
about Six years in the right otoUth but
waS aboui ä year older iri the left otolith. Sexual. dirriorphisl'l1. in to..allength arid. staßdard lengm waS
apparent from abOut severi yearS of age whereas he3d lengm dimorphisin was manifeSt from about foür
yearS. Tbus, the irifonnation resident in the fight otolith is &reater thari lhii in the left otOlith, and the
infonnation resident in the head .length is grCater thari that. in eitherthe totällengm standMd length.
When sextiaI dimol-phism occwTed, it waS always the female which was the laIger.
a
•
arter
cr
DisCriminant function aruuysis <oFA) provideS ~ növei. and objectlve tOOl ~. age vaÜdation. In the
otolith-baSed DFA it was the weight measlires iather th3n length, m .both lert arid right otoUths, which
provided the greätest contrlbutions to age discrimination.Tbe body-b3Sed DFA indicated thatthe grCatest
discrimination waS provided (in descending order of irnP<)rtance) by the"skeletoll", heoo length, and the
ventral and dOCsal fillets; the golWi 2nd liver, although also prÖvidillg significant contrlbutionS, were
muchless inlPOrtalii. Both the DFA apprOOches provided conSi>icuoos segregation in the age-gi-oups from
two tÖ five years while overlap was greater thereacter. PieSentirig the resUIts using "pi'edicied" age (i.C:.
provid~ on the basis of re-classification ofage from DFA) iithei thiii otolith "read" age substantially
reduc~ datä-Scalter. In both the otolith-basedand the body-basCd DFA's the HrSt discriminant
. primarilyexplainCd age related variability. In the body-b3$Cd DFA,in coritcisttO the otolith based DFA,
the seCond discriminant axiS clearly explain~ sex re13ted variability. Tbtis, although both DFA's
. distinguishCd age equ3IIy weil, lhe body-ba5ed DFA. was suPerior in diStinguishing bQU1 age. arid sex.
Although otolith length and weights
evidently gOOd age discrlmmatOrs. their Use in sex discrimination
is equivoc3I. TbC apparent overall misCI2SSification of age was about 20% in bOth DFA approaches. Tbe
otolith-basCci DFA indicated a peak misCiassificätionat .about 6 to 8 years; thus occUrring just after
recuiTent "inf1ection POint" at 4-5 years, noted in the plotof.the fuSt diScriminaDt uis agiinst age iri bÖth
the DFA /iPProaches.Tbe DFA"inßection" age coneun 'Nith that al .which sexiial "siZe" dimorPhism
clearly manifests itsCIf in he3d length, 2nd sÜghtly ~ mat at which divergence becomes appan:nt
in otolith lengih and weighL Although sexual diritorphism in tOtal~ or standärd lenglhs was imperceptible,
signs of gfOwth inflections were seen at about foUr years old; these coincidc with a reduction in speeiHc
growth rate and matkCd rise inthe goriadoScim~ltic index_ This probably reflectS the advent of the age at
matunty. (AFM), in the present study,
4-6 years in bOth
chailgei iJithe appearance and
cOllsistency of otolith zones in wite:h >S years old are common and probably. indicative of AFM having
been reached. Ai. AFM intcgriites both grÖwth änd moitaIity effects, understaßding itS vanatiori in the
coi1tex~. of bioenergetic and ecological coercion is of Parucular impoltance for prudent fisherieS
managemenL
axis
are
a
a
ai
sexes;
GutVik et al.: Growth anti age discrirnination in "-witchfloulu:Jer
2
INTRODUCrION
Characteristic markS appearing at intervaisduring the, giOWili of fish otolitbs are frequently
, , used aS indicators of age (Bllicker, 1974; Williarns & Bedfoid;, 1974; Jearld, 1983;
CasSelriiail, 1987). 'Tbe aceurate detennination of age frOm tish otoliths is essentiai as
subsequent age-relaied errors, pamcUlarly whcn the degree of error is not constant
,throughout ,the life span, may iIripak the reliability of the, estiiriates for, a multitude of
popUlation dyna.riUcs' parameteci (Gulland, 1969; Bevenon & Holt, 1957; Ricker, 1975).
Although growth is comnioniy aIld coriveniently exPfessed in fisheries ,biology aS
changes in length Per unit time (Ricker, 1975;,Weatherley & Gill, 1987), the growth
phenomenon represenci an array of processes and parameters which have thdr origiIi iri a
bioeri~getic niodel(BI'ody. 1945; Brafleld & UlewellYn.1982). Growth is thus a complex
coricept. encompassing not only energy supplied (e.g. food consumption) but alSo energy
required for different, and lit ~es competing. processes and purposes (Calow. 1985;
Hopkiris et aL, 1986; Reiss, 1989). "Trade-offs" frCquently occur when energy is limited;
orie of the most nouble heing that the advent of first liiaturitY. with increased energetic
investnlent in goriads, often.occursat the exi>eDSC of somatic growth,or bödy reServes
(Gadgil & Bossen, 1970; Calow~ 1985; Clärke. 1987; Woöiton; 1990). Unfominaidy
iricreased errors in age determiriatiori commonly arise artei tbe age ai flrSt matini& (AFM)
oWing to the tendency, for otolith iOne increments aitd theiTcllmij .to" decreaSe with
rei>eated. often annual, repI'OOuctive investment. (Blacker. i974;, RoHefsen. , 1933).
Furthennore•.' AFM is prohably the single most, iIiflueritial life hislory chaiaderisnc
(Cole. 1954; peters.1983;Reiss. 1989; Krebs. 1985). WitbincreäSed mOitality &equently
oemg associated with a reducrlon in AFM. better empirical deteiniinatiori of AFM frOin
imProved comprehension of bcidy
otolith growth should öffer benetits fOf prudent
fisheries Iriäriageme'nt ,
,'.
•
as
aoo
Consdous'of the .compOsite minlfe of gmwth, regrenably. few stucÜes, have applied
inultivarhite starlstic3.1 analyses in exariiliiliigeither otolith, growth. or the contnbutions and
demarids of different' bOdy cömix>nentS and processes to growth of the tish aIld that of the
otolith (see thougb Boehlen, 1985; H6pkins et 31.1986; RijnSdorP et al. t 1990). With
reference to witeh floi.lI1der, (GlyptoceplUzlus cynoglossUs)., the preserit. studyqUantifies
arid concepnialisesthe, multiplicitY . of, growth " (as registefed. iil vanous, key, bcidy
componeots) arid itS relationship, to the. irifonnanon content, resident in the otolith,
inclucfuig the question of age validation., DiSCrlminant ,ftincrlon äriatysis (DFA) appliCd to
detemiine the varymg ability of a niimbei' öf parnmeters fOf otoUths (length and wet-, dry,and aSh woghts of left and right otöliths). bodY lengm (tota11erigm. standard lenith~ head
, lengtIt) äiidbody weightS .(weightS of: dorsal lind ventral fiUets, "skeleton". liver, gonad,
and stomach with contentS) tödiSciiniinate fish age and
The outeome of the DFA is
lised tc. provide empiric31 critCria fordistingÜishing AFM iri.Ii1ales aS well'as feiruiIes. Tbe
, findiiigs arediscuSsed in the coniext of cuiTerii arid future perspectives iil fisheries .reSearch
and management, wnere ißcreasmg emphasis iS plaeCd upori dCciphenng bioenergetic arid
ecologic31 IDreipläY.
is
sex.
•
Gutvik et a1.: Growih aTuJ age discriminarion in witchfloulider
3
~tATERIALS & METHOnS
;
'.
TraWlin~ Md' saIDPÜn~
WitCh floUnder, werc sampled frOm 220-290' in November i 986, With a cteffierSal
prawn trawl towed by RV "0tiät", at AghipSvik (690 30'N 180 13'E) in Malangen, a north
NOrWegian fjord. Deciils ofthe trawl and its deployment are given in Nilssen et 31. (1986),
Nilsen et al. (1991) an~ Gutvik(1991).
. "
m
On deck the witch flounder weresoned fröm the rest of the catch, ind groups of fl"e
, to 10,tish were packed carefully in sealed Polytherie bags tiefore being frozen onbciärd and
stored (-200C) until fuIther treatirient in th~ labOrniory ashore.
'
weiebt and lenm cleteiminaUOOS
•
.'
Iri the iabOTatöry ashbre the .froz~n'Witch flounder were thawed ovemlght at SOC.
Iridividual fish were placect on a SatiferSM 1600 topwdght, and the "rotirid" total weight
(1W) deteimined to an accliracy of 0.01 g. Tow length (TI..; measured to the nearest nm
aS the distance from the tiP. of tbe .lower jaw to' the tip of the Iongest niedian caudal fin:
ciy), standaid lengm (SL~ measured to the nearest ~ as the distance fro rn the tip of the
, lower jaw to the postenor end ofthe uliiIriate caudal vertebia), a.l'1(1 head lengm (HL.
measured tiy vemier Callij)ers to the neäiest 0.01
the disiance. frcirri ,the tip ofthe
lower jaw to the hindriiOst Point where the operewum meetS the body) of mdividUal fish,
" were then detenDined.. Gerieräl detailS regarwng tish leögm measu.rementS and aSSociatecI
teriIiinology are given iIi Lagler (1978), Ricker (1979) and AndersOo & Gutreuter (1983).
After thaWing, the abdommal cavity. was cut open, aod the stomach arid intestirie
removed (cut ariteriorly at the oesophagus and 'posteriorly in frönt of, the anus) before the
stornach itself waS 'separatCd (cut posreriorly m frOnt of the pylorie caeca). Thc total
weig~t of the stomach (SW) waS deteririineci .,efore the contents were removed and the
'stomach itself weighed alone. The liver arid gonad (the lauer havmg fuStbeen used to
deternune the sex of the fish) were' 3.!so removect arid weighCd separately,(liver weight =
LW; goriad weighi ~ GW; Mettler HKI60 electrotialanee, accuracy ± 0.001 g).
mm as
,
•
""'"'',
. " '.
.
'.'
." After thls
. '
'.'
, "
. . ' ,
'".
,,'
1
I, .
. ' .
.'
:..
,~
were
the tish
tllietCd, by carefully dissectingthe light and left (as. wiich
flounder. eyes are pl:iCed on tJ1eright.'uppermost side ofthe body,the tWo fillets are
henceforth refenid 10 cis "dorsal" lind "velural" fillerS, DF and VF, respeetively) swimmiiig
muScles away trom the skeleton. The .sWimming muScles,' with ana.chC<i Skiti were
individually woghCd. Frnally the relnainder ,of the fish (comprising the head, skeleton and
caudal fin) was weighCd and
the c"skCIeton" (SkW). All wCights .were deterri1ined
With accuracy of ± 0.01 g by -a Saurer SM 1600 balance.
an
tcrmCd
Inv~srlganoris ~f accUräcy arid pr~isiori durlng length and wCight deteimiIiarlons wecc
conduct~
aS descnbed iri GuMk (1991).
Qyanes. testeS arid SeX deierirljnatioQ
Tbc sex arid degree of gonad maturity of individuaJ. tish weife deterrilinCdaS describe4,
by,Gutvik: (1991) incorporating irifonriation in Fulton (1891), Otterstr~m (1914), Powles
(1965), Pitt (1966), änd J likupsstovu &
(1988).
Haug
Gutvik et al.: Growth and age discrimiriarion in witchflounder
4
sac-like
InuDature ovaries are seen as right. thin;,waIled, transparent, and'
and lie
postenor to the vent in aß. extended body caviiY, one on each side of the ventraI caudalvertebrae (otterstrom 1914). The ovaries are shiny and vary frOm a pale celom in
jUverilles to more whiti: cr creaniy-yellow in eolour iri older fenla1es. Mature ovaries are
reddish, the eggs are visible. and they fill the exti:iidecI bOdy cavity as far häck as the
caudal fin., The OYaries 011" ihe right side are larger, ihlinthose on, the left, side. ,The sex of
wii~h flounder with matüre ovanes rnay also be diSceniCd by holcfuig the tish agamst a
stiorig light (Bowers 1960)., '
da
Tbe testes
'not have the same elorigatedshape nor do they, fill the extended bOdy
cavity to the same exteilt a;' the ovanes. The testes are flatter and more 10001 man the
ovarles. Iri juveriilesihe testes eire reIativeIy transparent while iri older tish they are more
white oropaque. ,Iri older. marilrC rriaIes the testes are full or distellded arid the right one is
Iarger than the left one. In the case of rlght rDaIes (TL<20 cm). the testes were tiriy and
particularly ham to discem with the miked eYe. aIthougIt fenla1es of similar siÜ: coilld also
be problematicaJ.. Iri the
of diffic~t 'specimenSsex deterinirianon requrred ,the
morphoIögical inspeCtion of gonluis iliider, a 'WIld M3 stereririliciöscöpe at 6.4 x
rnagnification.
'
'
caSe
OtOliths arid ai' 'deteItn1narion.
, One ofthe commoriest methods determining age in fish is by cotinting gfowth iones
'in hard body paris.espeeially those,in the otoliths (Bagenäl & Tesch 1978; Blacker 1974.
Härkönen 1986). In the present shidy the sa~ttae were extraeted
the
ofwiteh
flounaer usmg Sca1PelaridtWeezers (WilliaIIlS & BecIfofd ,1974, Jearld 1983), and then
stored iri nUinberect ViaIS eontaining 30% ethanol iri fi1tered seawater (Härkönen 1986).
Prior to age reading the otoliths were reinoved frOiii their vials ahd i'ubbed betWeen the
.thumb lind iridex finger to remove mucus aiid aeDris (Boweis 1960; BageIlat &. Tesch
1978). Age was reaci with the saginae iinriieiSed inglycerol. iJSing reflectCd lighiöri a dafk
background such that opaque zanes appearwhite arid hyiilirie zanes apPear d:irk (Jearid
1983). Ethanol preserves the otolithsdtiring storage. while it lind the glycerolenhance the
visibility and countingof ,the ririg-striicnires which fonn the OOSis for age interpretation
(Willhims & BedfoIu 1974).
' .
oe
froni
sacculi
The use" of reflected light agamst a dafk bäckgfutiiid haS previousiy beeil> uSed for
witch floUixier bY Bowers(1960) andPowles & KeMedy (1967). A1~ough Molarideir
. (1925) lind Bowering (1976) iliO, ü5eci
öf ilhimination, they applied itto
ground arid not whOle otoliths. Grindirig of the oioliths waS not üsed in the preserit study
as iing-sttuctUrCs wen: generälly consideIed' to bC eäSily diScenuble. In the case of
"yoWig" fiSh « 5~7 years eId) age
pnIIiaIiI{iUd
the
side Of the right
otolith. while, in older tish (>, 5-7
öld) the
of the left otolith was mostly
used (Molander 1925). IIi older tish. the ring-sttUctures iri the lcft otolith were genecilly
spacCd more everily and were more distinct (Molarider 1925, Bowerißg 1976), but the
right otolith was easier to re3d in some cases.
.
thc'same imnner
was
yem
from
inner side
inner
in thiS paper rings and zones are used syßonymously arid describC bands of concentric
material (thc former tieing a Zone composCd pmriarily oftransiucent
material that passes ligh~ the latter bCing ci zone comPosed pnIIiaIiIy of white, optically
demsematerial) seen in the otolith and cOlintecI for age detCrmination.
anl1Ulu.r referS to
a ring or zone (hyaline or opaque) depositCd with annual perlodicit}r. Reviews of
hyaJi~ or opaque
An
GutVik et 3.1.: Growlh afZd age discrimination in wilchjlouiuier
5
•
teriirlnology arid definitions used in fish ageing are provided by JenSen (965). CaSsdzTIan
(983) arid Jearld (1983).
.
A Wlld-Heerorugg M3 stereonucroscope (6.4 - 40 x rruigmflcadon) was uSed for
VieWing aiid cowitirig the
of hyllllne iories (anmili) present. The outermosi. edgezone of the otolith waS also noted aS either opaque or hyaline. The ololiths in Witeh
floul1rler ean .vary rrorii ä more circuI8.r shape ~ juveooes' to the aSsumption of a more
rounded-Square shape iri older fish (Molander 1925. Härkönen 1986). Inrierinost. the
otoUths have'a darker nucleus followed bya broader whire Zone. OutSide theSe followed
the fiist opaque zone. followro by the first hyaline zone. arid alternate zones there3.fter
dei>eiidirig on the age of the fish. It was generally rellitively simple to distinguish between
opaque, and hYa.lirie wnes iri fish up to five to seven years of age. I.ri younger fish « 5-7
yem old) the, opaque zOneswere Wider than the hyaline mies.
in oider fish the
opaque rones became riairowei andage determination waSnlore laooIious. Otoliths which
were espeeially demanding regammg, reamng arid interpretatiori were exari:liried sevenu
umes <>ver longer interVals.
.
.
number
while"
.
•
o
,;
.',
Witeh flowider are notCd for havirig a relatively lerigmy spawni.r1g periOd spanrung
from March to September. with apresumed peak from May to July (Bigelow & Sehfoeder
01953). Egg development (spaWni.rig to hatching) takes 7-8 days at 7.8 to 9.4 oe
(EhrCnbaum 1905. BigC10w & Schföeder 1953. RusseIl 1976).,The yolk sac of the IarVa is
absoi-Ded aft.Cr about 10 days (Emenbaum 1905. Nybeliri 1935). Onthe b3.Sis of this lind
our own observations.the hatChirig tißie (birthdate) of Malangen Witch flounder was set
as 01 June. arid the age of tiSh froin otolith Ieadi.rigs estiriiated to the nearest month. Thus
fish(öoth maIes and feiriaIe:s),eaught in November with a sirigle hyaline arid tVlO opaque
iones
considered to bC 17 months old. Some of these fish exmbited
iliitiation of
an outermost hyalii'le zone.
were
the
saginae
The lengfus of the ieft and right
were ineasUiro to the nearest 0.06 mm. and
theii wet weights and dry wdghis (after diyirig for 48 hI' in a desiccator, With Selfindicäting silica gel) were determi.ried to the nearest 0.001 mg. Both·saginaewere
analyzed rcr ash (weighed to the nearest 0.001 mg. after.iricmeiation at 5400e in amUfflefurnace).
•
Tbc age-group system (Cushing 1981) is tised to des.cribC the y~ai of life ,of lhe fish; 0group refers to those iri their flfst year
12 months old), I-group are those in their
second year (13-24 months öld) arid so fonh.
.
«
Data-baSe and StitiStieal and empi~iciii treatment
Dili ror 20 variableS [sex,
age,total lenith~ caudaI ICl1gm. head iel1gtlt; total bödy
weight; arid weights of "skeleton". dociaI and ventral fillets, gonad. liver, stomach with
contenci; lerigthsand wet-. dry-.
ash-weighis of.leftand right sa~ttaI';OlolithS] for
iridiVidual witch flounder were registefed iri the SYSTAT dara editor (Wilki.ri~Ori •..1988a).
and
oeScriptive Statistics for the exainined age-groups were" c3.Icu1:ltecI using the: STATS
mooule of SYSTAT (Wilkirison. 1988a).
'
Gutvik et al.: Growth alu1 age discruninanon in witchjlou1Ukr
6
oiscrlrriitÜmt Euricrlon Analysis CDFAt in the SYSTAT MGLH mOdule (Wilkinsori,
1988a) was employed to analyse arid test for diffex-enees in otolith size (leng!h arid various
weight parameters) and body eOnlix>nents aniong the examm&!, age-gi-eups, arid to identify
the eontribution of these features ,in disciiminatiItg arnong the apriOri eategorized agegroups (Le. observed ages, read ficim otolith annuli). DPA generates a set of orthogonal
diScrimimint funetions, or canonica.l "ariales, thai maxirilize the ratio of ainong-groups
residUal varianee to the withiri-grOups residual variance (Fisber, 1936; Cooley and Lohnes,
1971; Aic~ey and BryaJlt, 1975). The WIlk's himbda srarlStic. and its approximate
triuisformation to the F-stattstic were u5ed to test for differences between popUlation (agegroup) ceritioidS (see Porebski, .1966). The suceess of ihe. diScriIriinant tUrictioris ean be
assessed by eonsttucting a contißgency table of "correct"aß<i ':meorrect" Withrespeet to a
priori allocations of indiViduaIS to. age-groups aIid sexes, arid testmg,with the likelihOOd
ratio chi-square test in the TABLES mOdule of SySTAT (Willdnson, 1988a). Two DPA's
were perfomied on the witeh flounder däta:the firSi üsiIig otolith lerigih and weightS (wet,
dry, and ash), the second usmg b6dy lengms (totallength! suiridärd length, bead lengm)
arid body eomj)onent (dorsal and ventral fillets, "skeleton"; goriäd, livei', stomach ,with
eontents) .' wdghts. LOgarithmic (lne) transformations were applied to all otolith, bOOy
length arid bOdy eomponent daci.
.
Treridfinin i
Where it has been ctesirable to fit a eurve illuStriitirig a bäsic trend iri the data, this has
been achieved by avoidirig semi-subjecrlve regression ieChriiques ,lind ratherusmg. ~'IOcally
weighted Scätterplot smooth" ("Lowess") methOOs (Cleveland 1979) unplemerited in the
SERIES module in SYSTAT and in SYGRAPH (Wilkinsori 1988a, b).
.
.
.
RESULTS
Otolith len~h
and weight tharacteristics arid age determinaiioDs
Plots of ~et weigh~ diyweight,and ash weightofright·aiid left otolithsaS ä fwietiori
of otolith lerigth all show a weak positive exponeritial relatioriship, With the oteUths of
feinaIc fiSh being Slightly heavier th3D rDales for otoliths targer than abOüt 5.5 Inni (Fig.
Fig. lA-F).PlotSof otolith length andweights (wet, dry, andash) as afuriction of fish
age (reäd fIllm the otoliths) shows iii approxiinäteIy linear reIatioriship, With the otoliths
of fmales beCciining IMger thäri those of riiales frOrii 6 yem of age in the nght otolith
while the bifurCation point for the left otölith wäs aoout a
older (Fig. 2 A-H).
,
yeu
Age relatfd body lenjth measures
Iri tot& lengm arid siandaid lerigili a ~lear sextially related divergence, With feInaies
DecoriUng larger tluUt rDaIes, is only appareilt from about 7 years of age, while in the case
of head lengm divergence is riotable froin äbout four years of age (Fig. 3 A-C).
•
Guivik et aI.: Growrh aluJ age discrimina/ion in wi/chflouluier
7
Age related variation in total body weight arid body cOmprinentS
In Novembci, the dorSal fluet is heavier than the ventral one in ooth rriaies arid females,
arid the weight of the two' filletS combinCd is approxiIIi:itCly equivalerit to thai of the
"skeleton". At this time of the year, the gomids are srDall in both sexes and they tögether
with the liver and stomach with its cOluents accourit for < 2% of the total body weight
(Fig. 4 A-D.).
The weights of. dofSaJ. and ventral rillet$, arid th.lt of the skeIeton,. show a ,.i.,e:1k
. eXponential increase with age but no clear Sexual differences are appareiii (Figs. .5 A, B &
F). The weight dfthe. stomach With.its contenci exrubitSa large degree of scatter With
relation to both age and sex (Fig. 5 E). Liver weights of öoth Iilales and feiriales increase
relatively slowlY. up .to an WIection point at six yearSof age after which cl sieeper rate of
incre3se is notable (Fig. 5 C). The ovanes increase in weighi reIatively slowlyup 10 about
fiveyears of age :irter which an acceleration is clearly seen, whereas the testes eXhibit ci
weale rate of increase over the whole age range (Fig. 5D).
.
An3IysLs of age ami Sex disci-imination
bisCrirrijriaot fuöCtioll aIläJySjs usini otolith lerietb arid otolith wei~ht parameters
.The diScriminani function analysis using otolith lengm and weights (wet, dry, ash)
indicates thllt although. an the variables provide high1y significäiit (P <:0.00 t) coritributioris
to age discriminadon, diy weight.and wet weight provide the greatest contributions (Table
1). Nearly all the vanaricc in the agc data is explainCd along thc first discrimiriarit aXis
(OFt) cind a large degree of segregation in the age-gioups is seen frOm tWo to five years
while iherC: is a larger degree of overlap therearter (Figs. 6 A & B). Comparisons of the
centroidS With 95% ccinfiderice liriiiiS for "read" age arid "predicioo" age clearly show that
less overhip of age groups is seen afterfive yem of age in the latter caSe (Figs. 6 A &B).
A plot of DFI agamst "re:ld" and "pre&cted" age indicates in irlfleciion point iri both
cases, With regaro to the inclination in the relatioriship, ai aböut 4. years (Figs. 6 C & D); a
greater degree of separation is anairied
the sexes
five
onwards using
"premctCd" age rather than "re:ld" age.
hetWeen
fi()m
years
-'
•
DiscDmwapt fuöctioo analysis tlSini' bOdy le'n~ Md body wei2hi parameters
The discrüDinarii nmcrlon anaiysis using bOdy lerigtb. (tOtal lengili, .ställdai"d length, head
-length)aix1 body wdght (weights of: dorsal and ventral fille~ "skeleton", liver, gönad,
and sieimach With contents) parameters indicates thai .althoUgh all the. vanäbles provide
highly signmcant (P <O.(XH) contributioris to age discrlinination, the greätest contrlbutions
aie provided (in desccndirig eiider ofiri1Pönance)by the "skeleton", he3d leiiith. arid the
venträI and doisaJ. filletS (Table 2). As opposed to the DFA using the citolith parameters, a
signmcant proportion of thc variancc in the data is also aCcouritCd for by the secorid
disCrinunalu ws (OF2)(Table 2). The fIrst discririiiJicint
(DF1), asm the caSe of the
otolith bcised DFA; pruDariIy explains the age related väIiability (Figs. 7 A-D). However,
in contiast to the otolithbased DFA~the seconddiscrimin3.nt ws(OF2) clc~arly explains
the sex related variabilii}i (Figs. 7 E &. F). A plot.of DFI against ."read" arid "pfedicted"
age reiterates the disUnct inflection Poiili in the inclination of the relanonship, ai. abOut 4;.5
years (Figs. 7 C & D). Altbough a large degree of segregation is seen ~ the rlata fröin 3-6
ws
Gutvik et aL: Growth anti age discrimination in witchjlou1uJer
8
years-old, inieriDingllflg With regard 10 sex is more eVident Cor the 2 year-olds (they are
though distinct from the other groups with regard tri age)., Infish > 6 years old distinetion
with regard to agelsex is less, apparent, refleciirig a combinatiori of i'educed age-related
incrernents as weil as fewer daia (Figs. 7 A & B).
"
Classificati6n pr a~e Md sex uSjn~ the tWo diSci;ririnant agproaches
A cibulatiori of "correct':" arid "irico~~t" age arid sex claSsification Ca wiari ';correct"
age arid,
denoted by the, age react
the otolith and me sex detennined frOm
anatoriiic31 examiriation of the gon3ds respectively) as indicated by discririünani fuliction
analysis higJilightS a number .cf interesting features in the otolith arid hody, tiased
, approaches (Table 4, Fig. 8 A-D). In the case of sex~ the otolith bäSed DFA suggests :in
overall incorrect deteimination, of abOut 20% with inisclaSsifications heing apparent
tllfoughout most (2 to 8 year-olds) of the ages exammed (Fig. 8 A), while me bcidy baSed
DFA suggests overall iricorrect detimnination of abciut 7% Wim misclassifications Only
.
,.
.."',
sex
=:
'....
.
'.
:
',_
I . ' . '"
,. .
";"
_,',
'
from
an
~~e~~~min~~~tU:So~~~i~c~:~/~e=ti~~ a;;'a~~ ~~o/~,t~~ ~~
_
most widespread misClassification Occurring aboui 6to 8 years in the case of the otolith
baSed DFA (Fig. 8 C) while the body based DFA inisclaSsifieation
rel3.tivdy
widespread frOm about 4 years arid older (Fig. 8 D).
was
Plots and lin~ regressions of the relationship between DFA premcted age (involving
otolith parameters, and body parameters) arid read age (Fig. 9 A & B) show highly
significant relationships (P<o.<XH) With'me regression consUntS (ci) not bCing siinificantly
different frOm 0 arid the regression 'aiefficient (P) not being Signiflcaritly different frOm 1
in both eases., it is evident that discrepanciesbeiween predicted arid ,re3d age recome more
commen
6 yeais of age iri the otolith baSed DFA (Fig. 9 A),wbile discrepancies are
beCome apparent frOm abOut 4 years of age in the OOdy based DFA (Fig. 9 B).
trom
• <
•
DISCUSSION
The lengm and weightS (expresSed äs wet-, dry-, ai1d ash weights) öf the right arid left
otoliths of the witeh floWlder eXlrlbitCd clear-cüt, Positive reiationships with thc "react" age
of the fish.ThiS was wo true for the relationship betWeen ihe vanous hody leri~ (total
lengrn, staitdard lellgth, arid, heäd length) ,measuleS arid "iead" age. Sexual,dimorphism
flrst beCaine apparerit at different ages dependirig on thc'pamcular ':size" standard applied:
divergence occurfCd after abOut six years of age in, the right otolith while it was about a
year older in the left otolith, iJi, the casC of iotal length aßd, scindaid lerigm sexual
divergence was apparent rrom aoout seVen years of agc but in head leri~ divergence ~as
notable'frOmabout four years of age. When sexüal diIIlorphism occurred, it waSaIways
the feniaIe which ~as the larger. These fmdirigs are in gerieralaccoriiaiice \\tith WidesPre~
knowledge of witch flounder which indicate tha~ where size-at-age differences ,have, been
apparent, it is ,the feIDale as ,a rille which is t1le tärjCi seX (Beacham. 1982, 1983;
Bowering, 1987, 1989; Molander, 1935; Bowers, 1960; Nusenet al.;l99l), aIthough aS a
sPecles the size at age differe,nces Mve rarely
shown to be subStantiaL lIowever, the
present study clearly illustrates that the pwcular meaSUI'CS usCd to exprc:ss growth are of
considerable imi>ortance: the information resident inthe right otolith is greater.than that iJl
the left otolith~ arid the infOmiation resident in the head length is greater than that in either
been
•
Gutvik et al.: Growth aiuJ age disCrimiMdon in witchflou!Ukr
9
the total iengm or swu1ard length. This is clearly seen with regard tO the ability to discem
dimciphism <".divergence") at an earlier age aS weil as the degree of divergence.
. Discriminant furiction analysis (DFA) is tisecl relatively &equently in stock claSSification
and biomemcs (PimenteI, 1979; MiSia, & Ni. 1983; Taylor & McPhail. 1985) but appears
to have reen weil-nigh neglected for the piUpose of, age discriIDiriation (see though
Hopkißs et al.~ 1989).The present study indieates.that DFA offers a novel arid objective
. investig,uive-tool in fish age validation. Being a· rilUltivaiiate technique it allows the
vanous measuresinvolved to beranked with regard to their abilitY. to disCrimiiiate, and
funhennore appliesthe 'measlires jointl~ in the cisk of diScrimiriation· (Pimentei, 1979;
Legeridie & Legeridre. 1983). Inthe case of the otolith-baSed DFA~ it was apparent that
although all the employed vanables provide, highly" Sigiillicant coniributions to, age
diScrimiriatiori. it was. the weight measiIres (wet-.dry-. and aSh weights) in boththe
otoliths which proVided the greatest coritribtitions. The suPerioritY of wdght. remg a rDasS '
measure•. over lengm in. otolith b3.sed age determinations iS to ,00 ,äntidpaied. Recerii
studies (pawson. 1990;Fletcher. 1991) haveemphasised the applicability ofotolith weight
in ageing tish. Th6 body-baSed DFA indicated that the greatest contributions were
provided (m deseendirigorder of importance) by the "skeleton". head, lerigth, and the
veiüral. arid" dorsal fillets;' the gon3.d and live-. although, also ProViding significant
contributioris," wen: much less impoi-täni - these characteristically eXhibit substiritial short- '.
'sc3.le temJionlJ. variabilitY (e.g.. gonads iIi near-aclult and adult fish eXhibit seasonal
maniiation cycles supenmPosed on age. and livers undergo transient chariges iri siZe
according, to digestive or feediiig conditionsarid iri feIDa1es commonly. exhibit seasorial
size-variabiliiy associatCcl Wirb ovanan nianrration cyCles; Krivobok. 1964; Love. 1970;
Hopkins et al.~ 1986).
.
Both the otolith- and body-baSed DFA approaches eXhlbitci1 conspicuous segregation
in.the age-groups from two to five years while there ,wlls a greater degree of,overlap
thereafter. However. presenting th,e reswts usirig "predicted" age. (that provided, on the
.baSis ofre-classification of age on the basis <>fthe DFA) rather thän "read" age iiiiproved
coherence byreducing the Scatter in the dati Iri hath the otolith-baSed arid the body-ba5ed
DFA's the flrSt discriminant
PriniarilY explairis the agerelated vanability. Inthe bodybased DFA~ iri contraSt to the otolith based DFA.the second disciiminant ws clearly
exphiiried the sex reIated vanability. Thus. although hath DFA-approaches diStinguish weil
with regard toage. ,the body-b3sed DFA proVides suPerior distinction for hQili age and
sex.. Rather tinexpected1y•. the body-baSed DFA was equ:illy profieient, at age
diScriniination as the otolith.;b3.sed DFA: hath indicatro that there had been an ovefall
miscIaSSificanori of about 20%. The degree of mischissificatioo in tbe case of the oiolithbasect DFA peakedabout 6 to 8 years; thus occUning just after the "innection Point" ai 45 years. noted inthe plot of the fiist discriiniriarit axis against age in hath otolith-b3.Sed aS
weIl aS the bOdY-OOsedDFA's.
DFA"iI1fIection" age coocurs With that atwhich sexual
"siZe" dimoi'pruSm cle3riy inaitifests itselfiIi he3d lengm•. aßd sllgJitly precedes thai at
which divergence becomes apparent iri otolith lerigm änd weight. Although 00 sexual
diniorphism iri total,; or standard lengths is perceptible. they both exhibit indicanons of an
inflection at about. four yem of age; theSe ci>incide with a levelling. off in, the specmc
growth rille (Gutvik. 1991) arid rises irithe gonadosomirlc iridex (GutVik unpiibl.).These
pomts are all indicative of age at maiUrity (AFM) bemg reached ät siiiiilai ages (4.;6) years
iri riiäIes and femates. Chäiiges in the appearimce arid consistencY.of otolith zones in wiich
>5 years old
coimDon (GutVik & Hermarinsen. unpubl.); SinillaI sudcteö chariges have
heen noted in the otoliths, of plaice arid mdieative of AFM haviJig reen reached (e.g.
RijnSclorp et äl.; 1990; RijnSdoi-p & Stortreek. 1991). .
ws
•
The
are
GutVik et al.: Growrh and age discriminarion ili wirchflounder
10
Although the .use cjf otolith lengtb, arid weightS aie of, greai Potenclal in, age
diSciimißation., theii 'use in sex, di~ation appeals to be Poor. ExäiDimition of
"incorrect" sex viä otolith-based DFA suggested an overiill miSclaSsificarlon of 21.2 %.
TIus value, ho~ever .. has to be treated with some Scepticism aS sex det6miinätion was
carrled out -yery carefully in the preSent study,With reeolirse to mieroscopic analysis when
scißdaid Visual obServations ofthe goriads were of little bendit 1t is pi-acrlcally
impossible, for exarnple, to rriiside:ntify the sex of :i large Witeh- such thai suggestions of .
mistalcen sex detemunations in about 50% of 8 yearolds is unreascinable. nie body-based
DFÄ suggests a se~iial miscl3.SSification cf abOut 7% ovel-an; the majorit}' of corUusion
, is due to younger (3-6 years) Illalt~s mistäken sex is ac6ntingency, albeit slnall.
as
, The advent of matul"ation in
flsh is dependCrii on reachlng ä definite size or .age (Ahri,
1959; Weatherley& Gill, 1987). Agc appe3I's to
bC the mostiriiPoriani inspeeies which
matiIrc eafly, while siZC is the more imponant factor in those. which mature latC (Roff,
1982). nie inherent plasticitY of tish in respcinding to enVirOOmC:ntal peIturbadons dm
resU!t in changes iri the age lind/or siiC of first maturation (AFM)aS growth rate changes
(Stearns & Crand3.ll, 1984). The AFM has agreat mnuence on Population growth' rates
(Cole, 1954; ,Steams, 1976; Roff, 1984, 1991). Iri ,Witeh flounder, studies frOIri the
Canadian nonhwestem Atlaotic indieate thai AFM arid/or sizc at fmi inatuiit}' (SFM)can
vary front area to area (Bowenng. 1976)~ Beach3.ID (1983) relatedtmsto differerices iri
ambient temperaniiC affectirig growth rates. In tliemajoritY.of tish sPeCies rilales often
exhibit a lower AFM arid SFM thäri femaIes (Nlkolskii, 1969), arid ihiS oftert appliesto
witch flounder (BowCrlng, 1976). In Witch flounder, AFM has beCome lowered in areas
where stocks have t:leen rehitively heavUy flShed arid older age;.groups have disapPeared
(Beacham, 1983; Bowering, 1976); SFM, (expresSCd as length)
roughly similarin
males and feniales, probably refleCt:i.Og dissimilar growth rates in the tWo sexes. As AFM
integrates bOth growth, and rriorialityeffects, which
classiCally highly correlated
(Beverton & Holt, 1959; Alni, 1959; AdamS, 1980; Hoenig~ 1983; Roff, 1991),
mcinitoring AFM imd ici variation has an excellent pOtential for ex3miniIig envirorimental '
charige, particUlarly in the context, öf fishenes. management. Dati .on Witch floUnder
indicates that the lower liriiit of AFM is about 4 yeärs (Molaßder•. 1935; Bageriäl, 1963):
tishing iritel1sitY that haS forced thc Population AFM closC to thiS level has generiilly
foUowed. by stock. collapses. arid overfishirig' charactenstics (Bowermg, 1987, 1989;
GutVik, 199 ~; Nilsen, Gutvik & Hopkins. in prep.).
was
are
'I
been
AckßöwledgementS '
, "We thank sidpper KAre Bendllcseii of RV ';OttM'; for his.help and erithusiasm at sea.
.This work is supported by the Norwegian FishcrieS ReSearch Council aild the University
ofTro~.
,
"
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'
Jäkiipsstow, S.H. i.
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of Ailiintlc haIibu~
HipPoglossüS hippoglossus. in Faeroese waten. Fasb. ReS. 6: 201-215.
."
. .'. '
Jearld, A. jr. (1983). Age deteimiJiation. In: Nietseö, LA.; JohnSon. DL. (edS.) FasberieS teehniques.
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".
. '. .
Jensen. A.C. (1965). A staridard Ternunology arid Notation fer Otolith ReaderS. iCNAF Res. Bull. no. 2.
: p.. S~7. , , '
.
,; ,.•.
" " ' , . " . " """~
.,' . . . .
Krebs. C.J. (1985). Ecology: the uperimental analysis or distribution and abundante. 3rd. edition.
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,'
.
.,.
.' ' ,
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," , .
. "
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Laglet. K.F., (1978). Capture, samplmg'and examination of ftshCs~ In: Bagen8I. T. (Cd.) MethOdS ror
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'"
' '.,
'.. ' .
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. . ' , .. '
"
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: ',"
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. . ' '.. '.
.'.'
.',
."...
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sexually matUre
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season
oe
perm.
oe
rar
Eier und LärVen
d
m~
bOdy'sm.
.'..',
.
....
"
.',....
." " ,
•
•
Gutvik et al.: Growlh aTuJ age discriliiination in wilchjloünder
•
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.0
,.,.
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",
.
',',
'
" ,
: ' , ..,'
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..
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,.
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,
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.
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' . '.'
." ..
".
.
'. .
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.', . . "
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'
o.
0
•
.'
0
0
•
. . '
.'
'
."
'
0'
'0'
•
0
'
,
' "
.,
c'
tbe
•
13
'"'
,
Gutvik et al.: Growth and age discrimination in witchflounder
14
•
Table 1. Discriminant funetion analysis involving 8 age-groups (2-9 years old) of witeh
flounder from Malangen, nonhem Norway, involving length, wet weight, dry weight.
and ash weight of the right and left otoliths (sagittae). F= Fisher-value; d.f. = degrees of
freedom; signifieanee level P<O.OOl (***).
SINGLE DEGREE OF rREEDOM POLYNOMIAL CONTRASTS (d.L =15,d.L =50)
1
2
Right otolith
F
P
Dry weight
Wet weight
Ash weight
Length
72.5
72.4
70.0
51.0
***
***
***
***
Lezt otolitb
F
P
Dry weight
Wet weight
Ash weight
Length
54.7
53.8
49.2
46.3
***
***
***
***
•
MULTIVARIATE TEST STATISTICS
wilks' lambda
= 0.008
F-statistic
DF = 120,
= 2.540
Pillai trace
= 2.307
F-statistic
= 1.351 DF = 120,
Hotelling-Lawley trace =24.508
F-statistic
= 8.425 DF = 120,
Theta = 0.957, S = 8, M = 3.0, N = 20.5,
TESTS OF RESIDUAL ROOTS
Roots 1-8
Chi-square statistic = 253.4,
Roots 2-8
Chi-square statistic = 86.1,
Root. 3-8
Chi-square statistic = 53.8,
318
p
400
P
=
***
*
330 p = ***
P = ***
DF = 120, P = 0.00
DF = 98,
P = 0.79
DF = 78,
p = 0.98
Gutvik et al.: Growrh anti age discrimination in witchflounder
15
Iable 2. Discriminant function analysis of age (involving 8 a priori age-groups, 2-9 years
old) of male and female witch flounder from Malangen, northem Norway, involving
OOdy lengths (total length, standard length, head length) and weights (weights of:
dorsal and ventral fillets, "skeleton", liver, and gonad). F= Fisher-value; d.f. = degrees
cf freedom; significance level P<O.<XH (u*).
SINGLE DEGREE OF FREEDOM POLYNOMIAL CONTRASTS (d.L =15.d.L =88)
1
2
F
p
"Skeleton"
63.7
***
Head length
63.4
***
Ventral fillet
58.7
***
Dorsal fillet
57.4
***
Total length
55.1
***
Standard length
50.0
***
Liver weight
35.8
***
Gonad weight
29.4
***
MULTIVARIATE TEST STATISTICS
Wilks' lambda
= 0.008
F-statistic
= 5.668
DF
Pillai trace
= 2.460
F-statistic
= 2.605
DF
Hotelling-Lawley trace =16.496
F-statistic
=10.894
DF
Theta = 0.929, S = 8, M = 3.0, N
•
TESTS,OF RESIDUAL ROOTS
Root.. 1-8
Chi-square statistic
Roots 2-8
Chi-square statistic
Root.. 3-8
Chi-square statistic
Root.. 4-8
Chi-square statistic
= 120, 588
p
= 120, 704
P = *
=
***
= 120, 634 p = ***
= 39.5, P = ***
= 434.5,
DF = 120,
p = 0.00
= 193.2,
DF = 98,
P = 0.00
=
85.9,
DF = 78,
p
=
53.6,
DF = 60,
p
= 0.25
= 0.70
Gutvik et al.: Growlh and age discrimination in witchflounder
16
Table 3. "Corr6ct'l. and "incorrect" age and sex cia.iisification (a pnorj "correet" ~ge and
sex denoted by age read from. the .otolith arid sex detennined froni anatomiCal
examiIiation of the gonads respecnvely) ,involVing otolith (1engths. and wet,' dlY. arid
ash weights of light and left otoliths) and body (toullength, staridaid length. arid head
length. and weightS of dorsal arid ventral fillets. "skeleton", gonad~ arid liver). bäSed
discriminant function analysis. in witch flounder from Malangeri. noithem NorWay. CS
and CA =no.'s of fish classified as having "correct" sex ai'ld "correci" age respectively;
%IS arid %IA = perceritrige of fish claSsificil as having "correct" sex and "correct" age
respectively. Age/sex 2 -9 years of age. where m== malt:s and f == femaIes. sum m+f ,
fOf given age. SUM = sum of an ages (2-9).
.
=
",
"
,
-
...• ,. ...
. OTOLITH"
>'" • ,....- . ,v·~~·~ ".'; ',,".-,-, .,'.".'
......
,,_,~.
,~"
~',
AGE/SEX CS IS %JS" CA IA %JA CS
0 5 0
2m
5 0
0 3
4 1 20 5 0
2f
0 3
Sum2 ....
9 110 10
0 6
3m
5 0
0 5 0
0 8
3f
2 3 60 4 1 20 11
7 3 " 30 ...9 .. 1 " 10 .19
Sum3
4 0
4m
0 4 0
0 11
4f
3 2 40 5 0
0 8
o ,19
~
Sum4
7 2 22.2 .9
0.4 1 20 10
sm
5 0
5f
4 1 ·20 4 1 20 '9
Sum5.,.
9 1 ." 10 . 8 21··20 .19
4 1 20 4 1 20 8
6m
6f
3 2 40 2 3 60 10
Sum6···.·
7 3 .. 30 . ·.6 4 .. 40 .18
7m
2 0
0 1 1 SO 2
7f
2 2 50 1 3 75 4
Sum7....· .4 .2 33.3 2 ,4 66.7 .6
8m
1 1 50 2 0
0 2
2 1 33.3 2 1 33.3 3
8f
Sum8,
·3 .2 40 <.4 .1 .,20 ,"5
0 2
9m
3 0
0 3 0
0 3 0
0 3
9f
3 0
SUm9 ..
·0 .,6 0 "" 0 ·5
6
SUM . ", 52 14 21.2 54 12 18.2 97
o .,.,.
o
~>!-'"
o .....
..'
...
. ' .. ... ,..•......".,
BODY"...,..,..•.".. ,.."....
.,........
!",
~
IS %JS . ' CA IA %JA
0
0 3 0
0
0
0
0 3 0
0 60 . 0
1 11;1 ,9 0
0
0
0 10 1 9.1
1
519 I. 1 ., ,5
3 21A 8 6 42.9
0 .. 0 8 0
0
;3 13.6 .16 6 27.3
1 9,1 7 4 36A
0
0 7 2 22.2
,,1 .•,,, 5 14 6 30
1 11,1 7 2 22.2
1 9,1 8 3 27.3
.2 ,. 10 .15 5 ... 25
0
0
0 2 0
0
0 2 2 50
O,~,O .. 4 .2 33.3
0
0
0 2 0
1
33.3
0
2
0
0
0 .·. . 4 ..1 ,20
'0 1 1 50
0
0
0
0 3 0
0 -.. 0 ~4 ··1 .. 20
7 ' 6.7 82 22 21.2
o · ...
•
GutVik et a1.: Growth tiM age discrimination in~itchfloU1ider
,
17
,
FIGURE LEGENDS
a
Figure .1. Weight aS funetion of length in otoliths of maie and femaIe witeh flounder from ~Wangen,
. riorthem Norway. A and B; wet weighlS of right arid left otolithS reSpCctively; Cand 0, dry weighlS oe
right and feft otoliths respectively; E and F, ash weighlS of right arid left otoliths re~tively.
Figure 2. Lengihs and weightS of otoliths aS a fUnction oe fish age !Ud from otoliths iri male arid female
witeh flounder from Malangen, riorthem Norway. A arid B; leniths of right and left otoliths
. respectively; C and 0, wet weightS of right and left otoliths respeetively; E and F, drY weighlS of right
and left otoliths ~tivelY; G and H, ash weighiS of light and left otolithsreSpectively.
Figw-e. 3•. A) Totäl length, . B) eaudal length, arid C). head length as a funetion of fish age .ud from
, ,: otoliths in mate arid female witeh flounder from MaIängen,rlorthem Norway.
Figure4. Variation in the contribution ofbOdy cOmponents (dorSal aridventralfl1lelS, "skeleton". gonad,
liver, stomaeh with contenlS) to total bOdy weight (Sunl of all eomponenlS total body) as funetion oe
age i'ead frÖrit otoliths in witeh flounder rrOm Malangen. nOlthem Norway. A and B. weighlS fer males
and feritates respectively; C arid D. pelCenLages foe males arid feritates resPectively.. . ..
.
Figure 5. Vanation in the weight ofbOdy comJ>onentS (dorsal and ventral mletS, "skeleton". gonad.liver.
stcimach with ·conr.enlS)
funetion of age in .male and femate witeh flounder froin, MaIaitgeri.
northem Norway~ A. doCsaJ. fiUet; B. ventral fiUet; C, liver; D. gonad; E. slomach weight with
eontenlS; F. " s k e l e t o n " . .
.
Fiiure 6. Oiscriminänt funetion 3naIysis involving'otoiith chMacreristies Oengths. arid wet, dry. arid aSh
weighiS of right and left otoliths) in witeh floundCr from Malangen. northem NorWay. A and B. plot oe
the flISt two diScriminant axes (OFI arid OF2) showing 95% corifidence ellipses fer centroids (rßates
and fernales combined) b3sed on "read" age (age read, frOm otoliths) and "preweted" age (age
designaied from discriniinant fmietion analysis) respectively; C an~ D. plot of the fllSt discriminant
axis (OFl) agiUnst "read" arid "preweted" age respeetively (sexes separated)
,
,
.
Figu.re 7. Oiscriminant funetion arialysis ,of age (2-9 YM-Old) ändsexinvolving bÜdy length (tOtal
length~ starid3rd length, and head length)and bodY oompcinentS (dorSaI arid ventral mletS, "skeleton".
gonad, liver,' stomach with contenlS) in witeh flourider froin Malangen, northem NorWay. A arid B.
plot of the fliSt two discrimmant aies (OFI arid Of2) showing individual 95% confidenee ellipses for
centroidS of maIes(lower) and females (upper) from 3 tO 6 years-old (ellipses fer otherages omitted
due tri excessive intermixil1 g) bäSed on "read" age(age read from otoliths) and "pfedieted":lge (age
designated frOm discriminant functiOli 8ßaIysis) respectively; C and D. plot of the flISt diseriminant
axis (DFl) agamst "read" arid "preIDeted" age reSpectively (sexes distinet). E and F, plot of the second
discriminant
(OF2) agamst "read" and "predicrCd" age fesPectively. with Cleveland smoother
trend inserted separately the tWo sexes. .
. , '
Figw.e 8. The percentage "incorrect" clas8ification of sex arid age m witeh flounder, from Malarigen
(noriheni Norway) usmg otolith- and bOdy-base<i diSCriffiinant funetion aßalYsis (OFA). A) %
"ineorreCt"
usmg otolith-baSed OFA,. B) % "incorrect" sex. uSing body-baSed OFA; C), %
~incomcl- agcusirig otolith-b3Sed OFA, D) % "incorrect" age uSmg bÖdy-blised DFA.A orion
"correcl- agc and Sex denoied byage read crOiri the otolith and sei deieiniined rrOm anatomical
examination oe the gon3ds respeetively. Otolith-baSe<i OFA mvolves: the lengths. arid wet-. cirY-, and
ash weights of right and left otoliths; body-baied OFA involves: toi.aI lengih, standard length, and head
length, and weights of dorSal and ventral fllletS. "skeleton". gOrlad, arid livet. Agelsex 2 -9 years oe
. age. whcre m = males and f= females. == m+f for given age, S = sum orall ages (2-9).
'.'
Fiiure 9. Plots oe "predieted- age (age designated from discriminant fmiedon analysis) against "read" age
(age read from otoliths) in the case of A) otolith (lengths. and wet, drY. and ash weighlS of right and
left otoliths) baSed discriminarii function arialysis~ andB) bOdy length (totallength~ stand3rd length,
arid head length) and bodY compcinerit (dorsal and ventr3I fillets, "skCleton", gonad. liver, stornaeh
With conterits). baSed. disenrninant fUnetion aitalysu. inWiteh flounder frorit Malarigen. noithem
Norway. Nö:s by the dat3. pointS denote the nwnber of obSeiVations.
=
e
,.'.:.>
as a
wS
•
sex
s
a
,---------------------------
-
-
--
--
I
80
..
~
!
Riaht Otolith
A
Left Otolith
Q
B
Q
Q
D
Q
70
60
.... SO
.c::l
.!f
0
~
....0
~
40
30
20
10
80
c
.e
70
~
Q
Q
Q
60
!
....
.c::l SO
.!f
0
~
40
...
30
>Q
20
10
80
E
60
~
40
9
9
"
.ca SO
.!f
0
<•
9
70
-..a
-....
.ca
P
Q
•
30
20
10
3.2
3.9
4.6
S.3
6.0
6.7
7.4
3.2
3.9
Otolith IODlth (mm)
4.6
S.3
6.0
6.7
7.4
C~vd..d~. ,c/9:2
Rilht Otolith
7.4
Left Otol ith
~-~
0
A
0
--.§a 6.7
....CIO
.c:l
-..
l:l
u
.c:l
~
6.0
5.3
4.6
0
0
3.9
3.2
80
0
D
E
0
P
G
0
H
C
0
70
~
CIO
60
.c:l
50
0
~
40
0
30
-..
a
.!f
..
~
20
10
80
70
~ 60
-.a.
.c:l
.!f
0
50
~
40
...
30
>.
Q
20
10
80
Q
70
~ 60
-..
EI
.c:l
.!f
SO
0
40
-<•
30
~
.c:l
20
10
1
2
3
4
5
6
7
8
9
1
2
R.OI" 1'0 (YOln>
3
4
S
6
7
8
9
40
-e
-....
3S
Co)
..cl
30·
ee
c:
--.... 2S
0
~
~
20
•
1S
35
-a
-....
Co)
30
..cl
ee
c:
«)
-...
25
'0
~
'0
c:
.... 20
~
t:n
•
15
6.0
-a
S.S
S.O
"g
.ca
.... 4.5
ee
= 4.0
0
'0
~
0
==
3.5
3.0
2.S
1
2
3
4
S
6
Read ale (yean)
7
8
9
500
•
400
.....
~
...
300
...ilu
200
.1:1
....utIO
Male
A
Female
B
~ Skeleton
El Stomach+Contenti
lSl Oonad
(2) Liver
• Ventral rillet
o Dorsal fillet
~
100
0
100
D
C
80
-...
c:II
60
u
u
u
l:loe
40
20
0
2
3
4
5
6
7
8
9
2
3
Read ale (years)
4
5
6
7
8
9
------
-
•
~ ~t::-t'.
Rcf. S" .19-".==
"
120
120
A
-....
.-:....
-.-•C
100
Q
20
~
cf
Q
Q
,Q
80
01
--.,....
tlÖ
Q
.c
B
100
80
0
4)
~.
...
--
60
4)
0
60
-...e
40
~
20
Cool
Cool
40
d'
\1
Q
Q
0
0
4.5
3
C
\1
D
e
3.6
-....
~
--;.:;....
Q
2.7
,Q
.!l
2
;
;
...0
'U
1.8
>
~
•
Q
Q
0
1
0.9
0.0
0
6
200
-S...
E
F
5
-S..
,Q
.st
;
..•Q
4)
4
,Q
;
3
...=
•
g
Q
0
cf
Co)
+ 2
..c:a
..
rn
rn
•
1
0
100
0
Co)
Q
Q
.!f
Q
•a
150
1
2
3
4
5
6
7
8
9
50
0
1
2
3
Read age (yeara)
4
S
6
7
8
9
,
A
....
..
....='
..
2.5
B
2
3
CI
CI
CI
CI
•
-....!
..
2
.. 6
1.2
3
4
.9
u
2
6
2
...
33Jd
32
-0.1
0"4
5
22 ;
54
5Q
2
3J7
2
2
-1.4
2
2
u
.!I
2
Q -2.7
2
2
7
-4.0
-9.0
-5.6
-2.2
1.2
7
4.6
8.0
-9.0
-5.6
Diacriminant function 1
-2.2
1.2
4.6
8.0
Diacriminant function I
8.0
..
..
4.6
..•
1.2
CI
.S
u
CI
....='
CI
oS -2.2
!...
u
-=
Q
-5.6
~
-9.0
1
2
Q
3
4
ROld
S
6
1'0 (YOln>
7
8
9
1
2
3
.
Predicted
S
6
1'0
(yoan)
7
8
9
70
A
60
><
u
CIIt
....Co) 50
u 40
'"'""'
0
30
c
20
~
10
0
OTOLITH DFA
(,)
-
2m 2f • 23m 3f • 3 4m 4f
70
60
><
0
CIIt
....Co) 50
40
0
""
0"'" 30
Co)
c
20
~
10
0
4 Sm sr • 5 6m 6r • 6 7m 7! • 1 Sm
I
B
sr • 8 9m
9f • 9 S
BODY OFA
-
2m 2f • 23m 3f • 34m 4f
70
u 60
llO
~
....Co) 50
40
0
...0"'" 30
Co)
c=
20
~
10
0
0
llO
aI
....
Co)
...
""0
0
-Co)
g
4 Sm Sf
I
S 6m 6f • 67m 7f • 1 Im Sf • 8 9m 9f • 9 S
r-
C
f-
OTOLITH DFA
I-
I-
ff-
~
f-
I
I
I
I
LI,
,
I
2m 2r • 23m 3f • 3 4m 4f
70
60
50
40
30
20
10
0
I
I
'-
'-
4 Sm SC
I
'-
'-
'-
I
I
I
I
I
S 6m 6f 161m 1f • 1 Im If • I 9m 9f • 9 S
r-
D
BOOY OFA
f-
:.
f-
If-
,
I-
~.
~
z
:l<
«
.'
~i~
I-
I
I
I
I
h~LL
2m 2f • 23m 3f • 34m 4f
I:·
I
'""
~
j
~
,.
;{
~
~
~
4 Sm SC
I
~
LL
I
~,
l;
I
I
S 6m 6f 161m 1f • 1 Im Ir • I 9m 9f • 9 S
AGB/SEX
J
~~ ~.:d. r/c; 7' ~-6
,
10
QIlI
1-4
aI
-
A
· 1
8
·2
4)
>-
4)
co
6
aI
..
.
"0
4)
u
· 8
9.
.4
"0
4)
1-4
·2
·2
·6
· 1
· 1
· 1
·6
-
· 4
·2
9.
~
~
· 1
10.
2
1.
0
10
-•
1-4
aI
B
•4
8
4)
-
>-
4)
CO
6
aI
..
"0
4)
.9
19.
"0
4)
1-4
~
6.
2
0
0
2
•4
· 3
•4
• 1
• 15
•1
1.
•4
3.
• 14 • 1
15.
4
•1
•3
•1
•1
3.
1.
4
6
Road alO (yoao)
8
10