?SRCIIISlyn FISHERIES RESEARCH BOARD OF CANADA
Translation Series No. 2413
Growth of yellowfin sole Limanda aspera (P.) in West Kamchatka coastal waters
by V.I. Tikhonov
Original title: Rost zheltoperoi kambaly zapadnogo poberezh'ya Kamchatki
From: Izvestiya Tikhookeanskogo Nauchno-ISsledovaterskogo Instituta Rybnogo Khozyaistva i Okeanografii (TINRO) (Proceedings of the Pacific Scientific Research • Institute of Marine Fisheries and Oceanography) 73 : 127-140, 1970
Translated by the Translation Bureau( WDP.). Foreign Languages Division Department of the Secretary of State of Canada
Department of the Environment Fisheries Research Board of Canada Biological Station, St. John's, Nfld. Biological Station, Namaimo, B.C.
1973
24 pages typescript .- 1 )1
DEPARTMENTOUHÉSECRETARYOF, STATE SECRÉTARIAT D'ÉTAT -- - TR,KNSLATION BUREAU BUREAU DES TRADUCTIONS
MULTIL:INdUAL SERVICES DIVISION DES SERVICES CANADA DIVISION MULTILINGUES
TRANSLATED FROM - TRADUCTION DE INTO - EN Russian English
AUTHOR - AUTEUR V. I. Tikhonov
TITLE IN ENGLISH - TITRE ANGLAIS
The growth of the yellowfin sole off the western coast of Kamchatka
TITLE IN FOREIGN LANGUAGE (TRANSLITERATE FOREIGN CHARACTERS) TITRE EN LANGUE ÉTRANGÉRE (TRANSCRIRE EN CARACTLRES ROMAINS) Rost zheltoperoi kambaly zapadnogo poberezh t ya Kamchatki
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Izvestiya Tikhookeanskogo nauchno-issledovaterskogo instituta rybnogo khozyaistva i okeanografii
REFERENCE IN ENGLISH - RÉFÉRENCE EN ANGLAIS
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Izvestiya Tikhookeanskogo nauchno-issledovatel l skogo instituta rybnogo khozyaistva i okeanografii (Journal of the Pacific Scientific Research Institute of Fisheries and Oceanography),.Vol. 73, 1970, pp 127-140 (USSR)
UDC 597.587.9
The Growth of the Yellowfin Sole off the
Western Coast of Kamchatka
By V. 1. Tikhonov
In recent years there have been changes in the abundance and /127*
biological characteristics of the population of the yellowfin sole Limanda
aspera Pallas off the western coast of Kamchatka. Thus the average length
of the yellowfin sole began to increase after 1963. At the same time its
catch per hour of trawling increased, and the decline in total catch stopped,
and in the following years the total catch rose (Table 1).
* Numbers in the right-hand margin indicate the corresponding pages in the
original. UNEDITED TRAN:UATION For information only TRADUCTION NON REVISEE Information su/mont
SOS-200-10-31 Table 1
Population ChanF,es amonl Yellowfin Sole and its
Commercial nnloitation off the Western Coast of Kamchatka
•
1 0 ' . --.- .-"-- 1930 .• t•-., • •..:.:.. : .'.. ,., :1 it9n2 i .1):;3 . 1.... '. i 19:7;5 I 1 i • •• .• - I i i
2. • cM 23,5 27 Z3.0 2 3.1 23. 6,2 3. ,•. •. 1,5 0.9 0.0 0,7 0.8 4. - 111C. II, .174,5 -112.0 233,0 233.0 270,0 265,0
Key:
L. Biological and commercial parameters;
2. average length, in cm;
3. average catch per hour of trawling, in centners**;
4. total flounder catch, in thousands of centners.
If we consider that the yellowfin sole represents more than 40% of the commercial flounder stock, the reason for the increase in the catch of the latter should be sought primarily in the changes that have taken place in the population of this species. Data on the growth and size composition of the yellowfin sole for 1961 - 1966 were therefore analyzed, together with data for an earlier period.
We assess the growth of the fish in a population from a certain number of specimens constituting a biological sample. Errors are inevitable when the sample is taken. They arise from the selectivity of the fishing gear used, the change in the death rate with age, the distribution of the
** Translator's note. One centner equals 100 kilograms. 3.
errors fish in relation to their size, etc. These / affect the results of
the subsequent processing of the samples.
Ricker (1958) gives a brief analysis of the main methodà of studying
growth with their inherent shortcomings.
Most often, the average length of the fish of each age group in
the sample is determined, and a growth curve is constructed from the data
• derived. Here we are concerned with fish of different year-classes, each
of which differs in certain characteristics related to the abundance of the
year-class and the conditions under which it developed. Moreover, owing to the
selectivity of the fishing gear the younger age groups in the samples are /128
represented by rapidly growing specimens, while deolder age groups are represented
by slow-growing specimens. Therefore the growth rate determined from such a
curve will be lower than the average growth rate of fish in the population.
A curve plotted from the data of reverse calculations is free of
errors introduced by the - selectivity of the fishing gear, but the length of
younger age groups found this way proves to be too low, since old, slow-
growing fish have been used for calculation.
In order to describe the growth of yellowfin sole during the period
under consideration we considered it best to average the data from direct
measurements for a number of years, later clarifying them by calculations.
In the process, the differences in the growth of individual year-classes
were smoothed out.
When we determined the average length of the age groups we used not
only fish with a full number of years, but also certain specimens with
the following year's increment. From their scales we calculated •the length
corresponding to the last annual ring. The calculations were based on the
formula of the direct proportionality between the length of the body and the 4.
size of the scale. It may easily be shown that in this case the use of this formula caused no significant error.
The length of a fish may be calculated from the radius of the annual ring on its scales using the formula of direct proportionality
1 orfrom the formula that allows for the length of the fish at thé moment that the scale is established 1 r
; 1 R 1 where L is the length of the fish;
1 is the calculated length;
, r is the radius of the annual ring;
Ris the radius of the scale;
a is the length of the fish at the moment that the scale
is established.
SubtraCtion of the first formula from the second gives the difference a (1---4 Where the average value a is constant, this expression will be smaller in proportion as the difference R - r is smaller, i.e., the smaller the increment along the edge of the scale. When the increments are small, the error introduced by using the formula of direct proportionality, is small.
Table 2 gives the average sizes of the age groups of yellowfin sole obtained from direct observations.
5.
Table 2
The Growth of the Yellowfin Sole from
Direct Observations (in cm)
I 0 ; 0 :1 p a r r 1.1 ( '• à ! ------5 0 10 i 2 :.i -1 7 . _ _ 8. 9 _ _ ------3. 8.3 P.M0 15,6 10.9 22,5 25.5 27.8 ;29,0 32,3 26.1 28 6 30.8 33.1 4. r..8 13,1 16.1 19,0 :L7
!! 8,5 I n.2 15,9 19,0 2::,."; 25,8 28,3 30,3 32,8 ...•■■■■•••••■••••••••■•••••......
Key:
1. Sex;
2. age;
3. males;
4. females;
5. males and females
/129 The data in Table 2 clearly show the characteristic features of
flounder growth. To begin with,their growth rate is slow. A comparison of the
growth of fish in different populations of this species shows that the yellow-
fin sole grows more slowly off the western coast of Kamchatka than in other
regions of the Far East (Fig. 1). N. S. Fadeev (1963) explained the peculiarities
in the growth rate of the fish of separate populations by the different duration
of their vegetational period. This explanation is confirmed for the flounder
of Peter the Great Bay and Sakhalin Bay by observed differences in the growth
rate.
The duration of the vegetational period doubtless influences growth,
but in the region that we examined the presence of still other factors no less
important than the fattening season must be assumed. Thus in Olyutorskii Gulf, 6.
where the vegetational period is no longer than it is off the western coast of Kamchatka, the growth rate of flounder is much higher (see Fig. 1).
Given the generally slow growth rate of the flounder off the western
coast of Kamchatka, the difference in annual increments between the juveniles
and the older age groups is small: the total increment during the first
four years only slightly exceeds the overall increment of the subsequent
four years, whereas among flounder in Peter the Great Bay the increment
in the first period is twice as great as that in the second.
P. A. Moiseev (1953) believes that the rapid growth of juvenile
yellowfin sole is a species adaptation ensuring quick escape from the
influence of predators and primarily sculpins. According to our information,
sculpin abundance in this region is no less than in Peter the Great Bay
(as much as 16 to 20% of the trawl catch), but no accelerated growth of
juvenile flounder has beèn observed here. The difference in the growth rates
of males and females is also slight and reaches 1 to 2 cm only in the older
age groups. The maximum size of flounder evidently does not exceed 47 cm.
Mass measurements indicate that fish of this length represent no more than
hundredths of a percent of a population. Moiseeev (1953) indicates that the
maximum length of yellowfin sole off the western coast of Kamchatka reaches
48 cm. Moiseev's data apply to the early 1930's, that is, to the time when
the population had not yet been commercially exploited. The maximum size fish
are, of course, always females. The length of males, according to our
observations, does not exceed 43 cm.
The determination of the ages of fish older than 9 or 10 years from . inexact, their scales is / since it is difficult to distinguish between the annual .
and supplementary rings along the edges of the scales. The same difficulties
arise when working with otoliths (Fadeev, 1963). Researchers studying the 7.
yellowfin sole from different regions believe that its maximum life span is 15 years. Given the average length of females of age 9 4.* as about
33 cm, and their maximum length as 47 cm, the increment of the last five years is 14 cm, which is possible with an average annual increment of no less than 2.8 cm, i.e., the same as in fish of middle age. Direct verification of this assumption is difficult, but some data can be derived indirectly on the basis of weight increase.
Many species of flounder grow nearly isometrically; in this type of growth the ratio of the linear dimensions to the increase in the length of the fish does not change, and the weight is proportional to the cube of
the length. Some deviations from this relation are caused by change in the
specific gravity of the - fish owing to different degrees of fatness, water
and fat content of the tissues, etc. In the yellowfin sole off the western
coast of Kamchatka weight is proportional to length in an almost cubic
relationship. The weight-length ratio is expressed by the following formulas
(P is weight in grams, and L is absolute length in cm):
males P 0,0101( (Igr' —1,9)32+3,058SM-) ( 1 ) fem les—. P.---•G,0fri952 (2) males ac--y.lm_:! c:J77',! L 2,0681 H3,12201e.). reLizàles]
* Translator's note. The figure "9+" is a rendition of the original Russian desyatigodovik, literally "ten-year-old", i.e., a fish in its tenth year of life. Similarly elsewhere the literal expression "the weight of six- to ten-year-olds" has been translated as"the weight of fish age 5+ to 9 -FP, and so on. Again elsewhere in the Russian original, where fish ages have been given in numerals rather than words, these same numerals have been reproduced in the translation. 8.
Fig. 1 - The growth of yellowfin sole in different regions: 1 - Peter the Great Bay (loiseev, 1953); 2 - southWestern Sakhalin (Fadeev, 1963); 3 - OlyutOrskii Gulf; 4 - western coa'st of Kamchatka. . In order to calculate the growth of the older age groups, the ratio /131 between the weight of the fish and their age must still be expressed. The leveling of the weight of fish age 54-to 94- in accordance with the formula for a parabola expresses weight as a function of age (P is weight in grams, and
T is age):
ror Liales , ' ( 1.1 ror . • 'I'. 'f : c ,
The weight of the older age groups of yellowfin sole, and the length that corresponds to this weight, both of which have been *-termined using the above formulas, agree fairly well with the results of direct observations. The maximum size of the male recorded during the analyses was 43 cm, and the [maximum] weight, 1,160 grams. According to formula (4), the weights of males age 15 and
16 years are 1,073 and 1,231 grains respectively; hence they reach their maximum weight between the ages of 15 and 16 years. The maximum weight of females that we recorded, was 1,500 g. The weight of a female age 14+, as calculated from
Formula (5), was 1,515 g. It is to be noted that some females weighing 1,500 g
ranged in length from 42 to 45 cm; their weight would therefore be more than
1,500 g when they achieved their maximum size. It may hence be assumed that
females, too, reach their maximum weight at the age of between 15 and 16 years.
The following should be noted with regard to the maximum age of
the yellowfin sole. Although it is assumed to be 15 years, we found no published
information to the effect that the age and corresponding length of the oldest
fish had been reliably determined. The age, therefore, at which, by calculation,
the nctual maximum weight is achieved, i.e. from 15 to 16 years, may be assumed
to be the maximum. The size corresponding to the calculated weight of fish
age 144- may be determined from formulas (1) and (2): in males it is 43.9 cm,
and among females, 47.4 cm. These values are close to observable maximum sizes. 10.
This conformity points to the possible use of the above formulas for reverse calculation. They may be used to determine the weights of the older age groups from 11 to 15 years and, from the weight, the corresponding length. The results of these calculations will be considered below.
We shall now attempt to clarify data on the growth of the younger age groups. The sizes of these groups as given in Table 2 were obtained from direct measurements and hence must be slightly above average, since in trawling the largest specimens are selected from among the fish comprising the left ascending portion of the catch curve. The attempt to apply reverse calculations based on a formula for direct proportionality has demonstrated the influence of the Rosa Lee* phenomenon on the result. It is generally known that one of the reasons for this phenomenon can be the fact that no allowance is made for the
length attained by the fish by the time at which the scales are established.
The effect of this factor can be avoided if the formula used for the calculation
does not include the above value. This formula was substantiated by Graham
(1956), who came to the following conclusion. The initial equation is
where L is the length of the fish;
A is the length attained by the time the scales are established;
R is the size of the scale;
K is the coefficient of proportionality between the increment
of the fish and that of the scale.
* Translator's note. "Rosa Lee" is a direct rendition of the original Russian
Roza Li. 11.
The same equation for the length of the age group t will appear as
where r is the size of the annual ring on the scale, corresponding /132
[i.e., the ring] to the age t.
these two equations with regard to 1 permits the The solution of t derivation of a formula for 1 that :oes not contain A: t
1 — --- In order to use this formula it is necessary to know the coefficient expressing the ratio between the increment in the length of the fish and the increment in the scale; in addition, this ratio should be nearly linear.
Investigation of the ratio of the length of the body to that of the scales is usually done according to a special set of methods. Since scale sizes differ on different parts of the body, for purposes of measurement scales are taken from the same point on the bodies of fish. The location of this point is determined by counting the horizontal and vertical rows of scales. We attempted to use the usual scale samples collected under field conditions for determining the age of yellowfin sole. The scale sample was taken from the middle of the right side of the sole's body, between the lateral line and the dorsal fin.
Of the entire sample no more than 10 to 12 scales differing slightly in size, entered the scale preparation. The average arithmetical value of the sizes of all the scales in the preparation was taken as the scale size of a given specimen.
The average scale size could be different for another specimen of the same length.
When a sufficiently large number of fish of each size was analyzed. howevf.r, all of the random deviations evened out, and an average scale size was derived for fish of a given length. Thus we determined the size of the forward radius of the scale for a group of fish that included more than 2,000 specimens. 12.
Fig. 2 shows the ratio of the increments in the body and scales of the,yellowfin sole. This function is not rectilinear. The curvature of the line, however, is so slight that without much error it can be considered as consisting of rectilinear sections characterizing juvenile and mature fis!.
The corresponding lines were traced on a graph. The following equations were derived: for malecs 7:i10,1 ' for fauales—,--::. y -• —13.06 150,1x, for juveni1es-:,...:1
The break dividing the graph line into almost rectilinear sections occurs at a fish length of about 14 cm and a scale radius of 0.95 mm. The length of fish whose annual rings are larger than 0.95 mm, can be determined directly from the graph. This ring size is usually observed at the age of
4 and older. The length of a specimen age 3+ derived in this way serves as a reference value for calculating the length of younger age groups from the formula
The above yellowfin sole body-scale size ratios are average. When the growth of individual fish is calculated from their scales the appropriate correction must be introduced (Chugunova, 1959). Thus the average length of males with a scale radius of 1.5 mm, is 21.6 cm. If a fish with this scale radius is 23 cm long, the lengths calculated from the graph must be multiplied by 1.06 (23:21.6 = 1.06).
If we combine the data from direct observations and those from calculations , we can describe the change in the length and weight of the yellowfin sole during its entire life cycle (Table 3). The increase in length
and weight with age takes place gradually, without large fluctuations in
the value of the increment. L.S. Berdichevskii (1961) demonstrated that in many commercial species the maximum weight increment occurs after the first spawning. /133
The commercial exploitation of these fish at this age is not only of practical advantage, but also promotes a more complete assimilation of the food resources - of a body of water.
383 - 360 340
320 2/1/ 300 - e 280 260 1 240 220 - 2 00 - /80 - '760 - 120 - 00 - 30 60 40 20 R 1 23
Fig. 2 - The ratio of the increments in the body and in the forward radius of the-scale of the yellowfin sole: . L - absolute length; R - scale radius; 1 - males; 2 - females; 3 - juveniles; 4 - males and females (1932). 14. to
There is no such maximum increment in the yellowfin sole, owing possibly to the lengthiness of the maturing period. Fig. 3 shows the curves of the increments of length and weight in relation to the growth for the preceding year.
The increment drops constantly after the first year of life. The insignificant increase in increment at the age of 10 to 12 years is evidently explained by the peculiarities of the feeding of large fish. If we do ncit consider the younger age groups, which have no commercial significance, the sharpestdrop in linear and weight increment occurs in the eighth year of life. It is hence advisable to /135 catch fish no younger than 7 years of age; moreover the commercial length should, at least, be no lower than the average size of fish age 6+, i.e., about 26 cm.
The interests of reproduction also dictate the conservation of fish younger than 7 years of age, s±nce on the whole they are immature and do not take part in spawning.
o/
-
b- B —
,
-
20 -•--••••
J 2 3 / 6 7 a .(,) 10 11 12 13 14 13 cru —Age
Fig. 3 - Change in the relative increment of the yellowfin sole (in %): A -length; B - weight; 1 - males; 2 - females. 15.
in • f-i
•
•er "1".■ • z 1 - ... • •■•■ - 1r,
c, cz•
t-- -••• t- • . ■ ■ •••• .•%;.
CI zz, — • r;:) ••■
C')
I •:* t 1..-; he
•—I C0 C ff t •••■ c.) C'à ; . o •••". cs) le - - c•-.• ”.
So el c )
c.; co cz o t co 5 cc fin Cl C1
f f•-• 0 010
llow ••••4 CI • ■C.7 CI o CI CI CI t Ye
as Im4 10 of 10 e' 1 ri *-1 9.4 c-t Co ht
rn c • co) i
te 1■1 s We d We C0 CI trZ •••■• te3 h an
t 0
t•-■1 r-I
a") C•-".' c0 • e:
t-
-1"
•.. ms; les.
••-• ma gra fe 0 • : • ei z•• in d in
= • • • 6 • • cs CO s; C.- CO h, •D an t les; ht, a)
ice • • cU ig d les >4 a) ma tl) cs0 In leng fe we ct1 ma f'• • •
7. 5. 8. 4. 1. C•41 • One of the factors determining.fish growth is population abundance.
Representattves of the family Pleuronectidae usually serve as the classic example of species with only slight fluctuations in abundance. If among species with a broad foraging area and à marked capacity for renewal strong year-classes can exceed poor year-classes by many tens of times, the eight-fold increase in the abundance of one of the year-classes of P. platessa in the Baltic Sea, recorded
•y-Hempel, is viewed—as a rare case -the only:one in .20 years (emskaya, 1961).
Since, however, each population is adapted to its own amplitude of fluctuation of abundance (NikolTskii, 1965), even slight changes in abundance cannot fail to affect. the habitat of flounder.
•An analysis of the size composition of yellowfin sole has established that the year-classes of 1961 to 1966, as represented in the population, differed
-in-abundance. Fig. 4 showscurves. of -the,relative changes in. the. size composition, plotted using Siind's method. The deviations in the abundance of the size groups are expressed in percentages of the average level for 1961 - 1966. Two maximums of relative abundance were recorded for yellowfin sole in 1961: a strong maximum for fish up to 20 cm long and a weak maximum for fish longer than 32 cm, whereas the number of fish from 20 to 32 cm long was much below average. Since the yellowfin sole is the main commercial species of flounder off the western coast of Kamdhatka, the low abundance of commercial-size fish affected the total founder catch. From 1961 to 1963 it dropped in this region from 454,500 to 233,000 centners.
The yellowfin sole is fully exploited commercially beginning at the length of 26 cm. The "wave" of high-abundance year-classes (to judge from sizes it was represented /137 mainly by the year-classes of 1955 to 1957) passed this limit in 1964, and there wasrio further drop in the catch: in 1964 the catch was 233,000 centners, as in the preceding year.' In 1965, when large numbers of the fish of the abundant year-classes were commercially exploited, the flounder catch off the western coast of Kamchatka rose to 270,000 centners. In 1966 the catch dropped again to 265,600 centners, since the absolute abundance of large fish'was small and its relative 17.
increase no longer, affected the increase in the biomass.
: %
■ -f-. - \ 99.51 \ -
(1. s - 9 I /P--\ Ji7 % r-
z \„/ r [ 1 • 0; ' ' .92. f gy 1:,,,? (X / ....,.....: -.-77-- - - ,------p V9b.
°/.
... ;P r•re jet „.„-,..-1 \ - / - z . \ P r C .ç g • cP e ",? . t - 700111,'1, 91- ,
Lgo
o
Fig. 4 - Relative changes in th size composition of yellowfin sole (in %). 18.
Zemskaya (1961), when she analyzed the growth of P. flesus of the
Baltic Sea, concluded that in a heavily thinned population of. this species
fluctuations in year-class abundance have no effect on food supply and'that • here
is henCe no link between year-class abundance and fish growth.
, 1 .•• • 1 + 0,7
i ,.,.„,• r.. ,:, 1 )- , - I .i.o.,,e li é 4. '3s
n 1 1 + ee 2
•i ‘ \ 1- -..D0,2 ' f
gyemow-oe.e...* Y955 î9G 957 91:15 î959 -
Fig. 5 - Strength of year-classes and growth of the yellowfin sole: 1 - index of year-class strength; 2 - deviations from the average increment.
The recorded differences in the strength of yellowfin sole year-
classes are sufficiently large to affect the nature of their growth. The total percentage of specimens age 5+ and 6+ of this year-class in samples can be used
as an index of year-class abundance. Analysis has shown that this feature can be
used to single out, as relatively strong, the year-classes of 1955-1957, i.e.,
the same as from Sând's curves. Deviations in the average length of the age
groups from the average level for 1961-1966 have been used to describe the growth
of each year-class.
19.
Data on juvenile growth were derived using reverse calculations,
and later the average deviation in the growth of the fish of each year-class for
the first six years of its life was determined. The deviations in growth and
the relative strength of individual year-classes are compared in Fig. 5. The
inverse relation between the growth of a year-class and its abundance is clearly
evident. The,main,reason.for this is ,to be found in the de. terration of the
food supply for the abundant year-classes. The same thing is indicated by an /138,
analysis of the growth of the older age groups. From 1961 to 1963 and from
1964 to 1966 the habitats of the older age groups were different. Up to 1963
the abundance of the strong year-classes virtually did not affect these habitats.
After 1963 the abundance of the older age groups increased, and their growth
slowed. Fig. 6 clearly shows the shift to the left of the variation curves of the
length of fish age 7+ to 9+ in the second period. Habitat conditions were more
favorable for the younger groups in the second period, and the variation curve
of length shifted to the right (Fig. 6 shows only the growth of fish age4+).
z 20
15 I. , ‘■
5 5
• 22 24 26 2Ô 30 J2 34 35 CM 74 25 28 .30 32 34 38 4cm
•:. ... /‘ . 20 i ‘ f 1
13 . /‘ 1/4 1 \ I s' lf. C II \ 5 ! / \u—
,71.2 ,_7.1 •75 ,. 18 49 212 cei 1t7,5 15.5 1Z5 f9,5 215 23.5 255 . cm
Fig. 6 - Size composition of age groups of the yellowfin sole i A - 7+; B - 8+; C - 9+; D - 4+. 1 - 1961-1963; 2 - 1964-1965. 20.
The recorded changes in growth were relatively brief, since they were determined by the occurrence of several seasons that were favorable for the reproduction or survival of individ-ial year-classes of yellowfin sole. At the same time, a comparison of our data with those of previous investigators suggests the occurrence of changes that have encompassed lengthy periods. Growth indices of the yellowfin sole off the western coast of Kamchatka in different years are compared in Table 4.
Table 4
Changes in the Growth Rate of the Yellowfin Sole
(in cm)
2. Fio3pacT 1, r 0 ;1 hi 7 8 9 10
3 • itri :+frctsvir.t, 25.3 29.7 noA n1.1 4. IP ■ t:!(..11'n 27.0 2'.).8 :un o 19.; ILtnwect;1 30M at.e; 33.5 g 1031--19G maim: ;laiimbul . 28.3 0.3 32,ü
Key:
1. Years;
2. age;
3. according to Moiseev;
4. (Polutov, Ershikova);
5. (Odeberg, Pashkeev);
6. (our data). The first line of Table 4 shows the growth of fish in a population /139 completely untouched by commercial operations (4oiseev used Krivobok i s data for
1931), and the second and third apply to the period when commercial fishing developed intensively. Our data describe a population considerably thinned by commercial fishing operations. As may be seen from Table 4, the size of the fish of different age groups, which was comparatively large in the natural population, remained practically unchanged until the beginning of heavy commercial fishing (the flounder catch in this region increased sharply in 1952), then followed a drop in size, most clearly evident in a thinned population.
Research in the Baltic and North Seas, carried out by several scientists, and studies by Soviet investigators in the seas of the Far East
(qoiseev, 1953), have shown that when the flounder population is thinned by commercial fishing, the growth rate of the remaining specimens increases. In our case the opposite occurred. This fact cannot be explained by a random selection of data from different years. An analysis of scale material has confirmed somewhat different growth patterns in the natural population and that growth itself has been more rapid. We studied scale material from the archives of the
Kamchatka Division of TINRO collected during expeditions on the trawlers Toporok the (1932) and Gaga (1941) off the western coast of Kamchatka. Despite / fact that that the scales were in a poor state of preservation and / the collections were representative mainly of large fish, the material confirmed that there had been a change in the nature of growth (Table 5). • 22.
Table 5
Radius of Annual Rings on the Scales of
Yellowfin Sole (in mm)
4.1gQ b lb 3 b b .1 • •• YeQrs• .- . • ______- _ to_ ).213 , 7"; ').11 1 1.10 1.11 1.70 1 ,97 2. 20 2.10 2.1.10 0.; .1 0.09 1.:i; 1,52 1.7ti 1.90 2.11 2.35
In all age groups among fish in the natural population the radius
of annual rings was 8 to 12% more than in the thinned populion. The ratio
of the growth of fish to that of scales, which was established only for large fish
(see Fig. 2) also indicates that in the natural population the length increment per
unit of scale increment was greater: the inclination of the regression line
was 240, whereas in 1961-1966 it was only 150. The recorded characteristics
of scale growth confirm the conclusion made from a comparison of data for
different years.
Thus among the yellowfin sole off the western coast of Kamchatka
there occur changes in the growth rate that are related to population abundance.
The appearance of several abundant year-classes brought about a deceleration in the
growth of juveniles and, after a corresponding period, a deceleration in the
growth of older fish. This deceleration took place despite that fact that
during the six-year period of observations the population abundance declined,
this decrease being recorded not only for the yellowfin sole, but also for
other flounder species. The natural consequence of this phenomenon should have
been an increase in the amount of food for the remaining fish sufficient, if
not for an increase in the growth rate, then at least to support it at the
previous level, when several abundant year-classes appeared. This did not
happen, and the concurrent ratios between individual flounder species are not
the cause of the above phenomenon, since the food supply deteriorated at the time 23.
of a general drop in the abundance of.flounder in this region. Within the population a better growth rate was observed when there was a greater abundance, at least until /140 the end of the 1950's. Evidently during this period there was a change in the habitat of the population resulting in a deterioration of the food supply. The reasons for this change are as yet unclear, but there can be no doubt as to its seriousness for commercial fishing off the western coast of Kamchatka. It is evident that the size of the commercial stock depends primarily upon recruitment and only to a slight degree upon an increase in the growth rate of the population as a result of thinning of the latter.
Cnnclusions
1. The'yellowfin sole grows more slowly off the western coast of
Kamchatka than in other regions of the Far East; its relative increment drops • evenly, and there is an accelerated drop in increment in the eighth year of life when the fish is over 26 cm long.
2. The flounder growth rate slowed when the abundant year-classes of
1955-1957 appeared in the population.
3. The growth rate in a commercially exploited population is lower than in a natural population, and the drop in -the growth rate coincides in time approximately with the beginning of active commercial fishing.
4. The ratio of the growth of flounder to the growth of their scales is curvilinear, but can be expressed without significant error by rectilinear sections having a different inclination for large fish and juveniles. •
24. Bibliography
1. Berdichevskii, L.S. Biological fundamentals of rational fisheries
management. Trudy of a conference on fish
abundance dynamics. Moscow, Publishing House
of the Academy of Sciences of the USSR, 1961.
2. Zemskaya, K.A. The growth of fish in a population with an
insignificant amplitude of fluctuations in
abundance. Problems of Ichthyology, Vol. 1,
No. 4 (21), 1961.
. 3. Moseev, P.A. Cod and flounder of the Far Eastern seas.
Izvestiya TINRO (rINRO Journal), Vol. 40, 1953.
4. Nikol l skii, G.V. The theory of fish population dynamics.
Nauka (Science) Publishing House, 1965.
5. Fadeev, N.S. Commercial and biological description of the yellowfin sole of Southern Sakhalin Izvestiya.
TINRO (TINRO Journal), Vol. 49, 1963.
6. Chugunova, N.I. Manual for the study of fish age and growth. Moscow, Publishing House of the Academy of Sciences
of the USSR, 1959.
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