This paper not to bo ci ted 1d thout prior ro1'oronco to tho author
Intornational Council 1:01" tho
Exploration of the Soa
C.N. 1967/G:J
Ocmorsal Fish (Southcrn) Committcc
Notos on tho aga and growth of Pagollus cantabricus (Asso)
trodontus (Oolar.) of' northorn Spnin.
= P.
con
by
F. Ramos and O. Ccndrcro
Laboratorio Ocoanogrnf'ico
Santandor, Spain
•
Ouring tho months of: Nareh nnd April the Spanish Instituto of: Ocen
YJgraphy carriod out trawl 'solcctivi ty cxperienecs :Cor halte of:f: the northern
eoast of: Spain. A pre1iminary rcport of' these experieneos has beon submited
to the Liaison Committoo. In tho twonty-one exporimontnl hau1s a largo quan
ti ty of: Page11us eantabrieus (Asso) 1ms eaught in tho by-ca teh. Sineo i t i6
a very important speeios ~or Spnnish f'ishorios nnel there are :Cew 01" no dntn
about its biology, it' 1ms thought n good chanco to gather some in:Co'rmation
abo\.t it, f:or the cateh eovored a quito ,ddo rango 01' 5iz05, 15 to /17 eenti
metors.
Thc t,~enty-ono hauls took a toto1 towin~ timo of' 52 hours 3'1 minutos, and aro shown in tho diagrnmmo of' !'iguro 1. Tho eatch or P. eontrodon
tus was 520 Kg, whieh givo a' yiold of' 9,9 lq; pOl" hour.
Length eomposition of: tho eatclles is i1lustrnted in :f'igurc 2 and
is givon in total numbors and in porcontages.
Age and.
grO'\~th
•
Agas were determinod by tho monns of: otolith rendings. Tho otoliths
all tho speeionms enught 1'1'01"0 tnl{on mnldng a trnnsvorso, vortieal cut on
top of' tho haad, slightly bohind tho oyes. In most easos the otolith beeomes weIl eonspieuous nf:tor doing thnt and i t is vory easy to take out. Soma
seal es wero also taken f:rom aneh f:ish in ordor to eheel{ tho otolith ronding
01" to help to determino the age if: the reading was dif'f'ieult. Allotoliths
were rend by trans:>areney, immerscd in 702 aleohol nnd with the help of' a
very 1000~-pO'\'7ered lens. This is gonornlly a vory good mothod, f'or. annual
rings are perf:oetly elear in the otolith, as i t ean be seen in the pietures
of figuraJ. Otoliths woro weIl readable practieally in every ease, and
readinf's ean bo' thought as highly reliablo. Only a fo,~ spocimons r.ad di!'f'.!.
cult otoliths beeauso of: eheel~ rings f'or whieh the holp of sealo r~ading
was required. The number of' diseardod otoliths was vory low.
~
Ago f:requerieies of: tho sampIe aro givon in f'igUro J. Mean lengths
at ages have been f:ound to bo as f:ollows.
,
.
-2-
Age
2
3
Length 18,1 20,98
5
6
7
8
28,08 30,13 31,58 34,65 36,77
9
10
11
12
38,75
41,2
41,95
44,5
}lean lcngth at age 2 is probably 10wer than 18,1 ~entimeters,
f'or some of' the smallest f'ish o:f' this age group either escapotho trawl
or have not been recruted yct. This could partly explain thc big di:f':f'orence betwcen lengths o:f' ages 3 and 4: (7,1 centimeters) while it is
only 2,88 centimeters between ages 2 and 3, when P. cantabricus =(centro
dontus>" had to have a presumably :f'aster growth.
For the estimation o:f' growth parameters, an estimate of: L~ has '(
been found f'rom "the plot It/lt+l' which gave the equation (:figure 4)
l~+l = 6,569 + 0,878046 l
•
t
and a value 01 Lc:...= 53,86 contimeters, and also e- K =0,878046, there:fore K = 0,12776. This indicates a practically continuous growth, that
is to say a great 10ngevity.
The observation of' gonads gavethe :following results:
Males ••••••••••••••••••••••••• 244 (27,0 %)
•
Females ••••••••••••••••••••••• 205 (22,8 %)
Bisexual •• ~ ••••••••••••••••••• 261 °(28,8 %)
Undetermined •••••••••••••••••• 195 (21,4
%)
Resume
L'etude de l'age et de la croissanee de la dorade (Pagellus ean
tabricus = centrodontus) (Asso»
de la eote du nord de ~'Espagne en
partant des leetures des otolithes est decrite dans eette eommunication.
On a trouve la suivante expression pour l'equation de eroissance ode von
Bertalanffy:
[
]
.
_0,1277 (t+l,018)
l.
= 53,36 l-e
t
Le caleule de l'age limite a donne
A O,95
= 22,4 ans."
-3-
On a fait des ob$ervations sur le sexe et la maturite sexuelle.
27,0 pour cent des echantillons etaient mäles, 22,8 pour cent femelles,
28,8 pour cent bisexuelles et 21,4 pour cent non determines. Ceux-ci
etaien~ toujours individus de moins de 4 ans d'age. Les premiers signes
de maturite sexuelle sont trouves chez les poissons de longueur totale
d'environ 24 centimetres.
Lesend oC Cigures
Fig. 1. Map showing the experimental hauls oC the selectivity experiences.
Fig. 2. Length distribution oC catches oC P. centrodontus. Upper graph,
in total numbers; lower graph, in percentages.
Fig. 3. Otoliths oC P. centrodontus. Left: specimen oC 19 centimeters,
age 2 years old; center: 4 years old, male, size 27 centimeters;
right: 5 years old female, size 30 centimeters.
"ig.
•
4. Plot It/lt+l
Cor estimation of L~
•
•
... 40'
.IFig •. 1.A. Map showing partially ·the experimental hauls of. the.selectivity
experiences.
-~-------------------:----------==~--------==----•••••
__._ •.•• .:'-:;-_.....
......__...
--..-=:-r=- _._..
.... ':.,
~~.-:-..
----....----_.--"--,~----=
~_
~-=~ ...;:~-.::....
~
5'
FIG.18
" 2d
Fig. 1.B. }mp showiug partially theexperimental hauls 01 the select1vity
experiencese
•
40&
';-
-
•
•
•
•
•••
Fig.
le.
Nap sho\dng partially the experimental hauLs. 01'
the selectivity experiences.
•
•
F~g. 2.A. Length d~stribution of catches of P. can
tabricus, in total numberso
.
~
·Figo 2.B. Length distribution of catches of Po can
tabricus in percentageso
r - - - - - - - - - - - - - - - - - - -- - - - -- - -- --
•
_._--
---.~-_.___..Il'_~
_
,
I
Otoliths
•
o~
P. cantabricus: Lert: specimen
19 cm, aga 2+; center: 4 years old male, si
Zß 27 cm; right: 5 years oIe female, size-
"
JO cm.
~~
c_
,J/
/'
/.,/
I
I
.,'./
I
(/
:r
!
...
,/
.,".
•
/
"
,
" .,
,"
"
//
'"
,/
/
,
,,
I
., / '"
/
'"
/ /
/
1>//
"
.
'Fig. 4. Plot It/l~+1
•
•
.
•
.
" ... t.
for estimation of L~