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ICES CM 1991/K:2
POPULATI'oN PARAMETERS AND LlFE HISTORIES OF
THE DEEP-WATER PRAWN PANDALUS BOREALis
FROM DIFFERENT REGIONS.
E.M. NIlssen & C.C.E. Hopklns
Dept. of Aquatic Biology, The Norwegian College of Fishery Research,
University of Troms0, N·9001 Troms0, Norway
ABSTRACT
Based on our own data encompassing northerly populations of Pandalus
borealis stretching from Scandinavia to about 800 North, and data from the
literature spanning the entire geographical distribution of P. borealis, we
provide a summary of the major suites of Iife historles found In this specles.
Trends in growth rate, size/age at sex change and maturity, individual and
population fecundity, mortality rates (including fishing and natural
components) are examined with respect to one another and according to the
biological and physical characteristics of the various geographical locatians. It
is shown that although significant latitudinal trends are clearly present, ttie
effects of specific environmental conditions (e.g. "warm" or "cold" current
systems. at a given latitude, seasonal production cycles, and more recent
trends towards Increased fishing effort on previously unexploited stocks at
high latitude) are important factors modifying "latitudinal Iife cycle strategies"
for this species.
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INTRODUCTION
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Pandalus borealis, eommonly known as the deep-water prawn or pink shrimp, is an important
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speeies both eeonomieally and eeologieally in boreal seas (PaIsson, 1983; Shumway et a1.,
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1985: Mehl, 1989). Its geographieal distribution ranges from southern, warmer areas to
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northern. eoide'j· areas, with temperatures and latitudes rknging from -1
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The last few decades have seen much progress in the anatysis of life history parameters, and
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adaptation of these to authoehthonous and a1loethonous influenees, both of in terms of
biological and physical environment8J contexts (c1arke,l
High. Thls knoWl9dge has primariiy
.tieerl accumulate<:s and analysed on an inter-taxa or int~r-species level. The advantages of l!te
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history parameter analyses are many, and include a better understanding of how animals
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respond to perturbations as weil as enabling one to manage species in a harvesting context by
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using additional parameters than those traditionally applied within resouree management.
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There iso however, a lack of analyses and discussions
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plastieity to biotie or abiotic faetors.
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a single speeies' responses and
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P. borealis with its large range of environment and life hi~tory should be an ideal species to use
paper describes arid attempts' to
in developing aspects of life-history analysis. Ttie pre~ent
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quanti#y same of the life history relatect variation aeross' its geographle8t range, with emphasis
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on temperature and latitudinal effeets, including production and produetivity. The life history
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situations whieh are Iikely to lead to population eollapse through adverse climatlc and fisheries
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perturbations are highlighted.
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MATERIALS AND METHODS
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Where applieable and available, parameters of size-at~age, growth rate. mortatity rates. size
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and age at maturity with number of repeated spawning events (e.g. semelparity or degree of
iteroparityj, generation time and life span, number of cohorts/year elasses comprising the
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stock, fecundity, time (e.g. month) of spawning and egg hatching (with intervening ovigerous
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period), environmental eonditions (e.g. water temperature, primary production cyele), have
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been extraeted direetly from the literature. Sources of these data are aeknowledged in the text.
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Several of the methods and teehniques applied by various authors for extraeting the above
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named dynamic population parameters are describect by Frechette & Parsans (1983).
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Otherwise, where considered neeessary. we have applied ELEFAN (Gayanillo et a1., 1988),
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MULTIFAN (Fournier et a1., 1991), and the NONUN program of SYSTAT (Wilklnson. 1988;
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deSCribed by HOPkinS & Nilssen, 1990) to separate
respective cohorts. and extrcict gro~h
length-frequ~ncy
distributions into their
~nd mortality parameters.
Same earlier works (e.g. Hjort Be Ruud, 1938; Rasmussen, H;lS3) present totallength (TL) data
rether than the presently accepted carapace length (CL) units. TL can be converted to
ci (see
Butler, 1964; Haynes & Wigley. 1969; Rasmussen, 1953).
The classical von Bertaiantty growth function (von BertaJanffy, 1938) is frequently appliect to
descrlbe groWth when seasonaJ oscillations are not apparent:
1)
where
Lee = asymptotic length, 4 = length at age t
(year), K
=
growth constant and
ta =
origin of the gro'Nth curve: Its commonest seasonally oscilhiting modification is:
2)
4 =L
" [l_exp-K(t-to) +CK/2 pi)*sin(2 pi(t-ts>-sin2 pi(t-1o»]
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where where Lee = asymptotic length,
origin of the grOwlh curve, C
4 = lengtti at age t (year), K = growth constcint arid ~
=
=constant expressing the amplitude of growth asciIIation, ts =
sterting point of oscillation with respect to t=O. However, several other forms may be found in
the literature (Ursin, 1963a, b; Pitcher and MacDonald, 1973; Lockwood, 1974; Cloern and
Nichals, 1978 ).
•
Although the von Bertalanffy growth functlon (VBGF; von Bertalanffy,
Ü~38) is the most
commonly applied growth model used for Pandalus borealis, it Is not necEissarilY fully
applicable to describe the discontinuous groWth <I.e. moulting) of prawns. Ttie parameters
derived through VBGF fitting should thus be considerect to be estlmates only (te.
approxlmate). Consequently. camparisans of the parameters on an inter-stock basis need to
be conducted with cautlon. Furthermore, as K and
lco
are not Independent (I.e. palrWise as
arie increases the other decreases), it follows that estimations and camparisans of the
parameters In the VBGF are problematical (Bayley. 1977). However, arecent promising
solution is that of the GroWth Performance (GP) index (Moreau et BI.• 1986):
MortBlitY can be calculated In several different ways. Where data is staooardised per unit (e.g.
numbers per sampling unit), mortality may simply be expressed by comparing numbers at the
start and end of a specific time period. Others usa the catch 6urve technique, either plotting
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riumbers ägainst prEldieted (see Ricker, 1975) or relative age (so called length-converted
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method; Jones, 1984).
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PANDALUS LlFE HISTORY PHENOMENA
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GROWTH
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Growth is the change of size (traditionally expressed as length units, but also "mass"/energy
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units) related to a time/age scale. Traditionally data for P. borealls is simply plotted or
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tabulated as size-at-age. However, size-at-age data alone provides no information about
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growth rates. Growth rate expresses the change of slze per unit time. Discussions of how
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growth rates, either with or without adherence to the VBGF model, may be statistically
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compared and tested are presented in Nilsen et aI. (in press).
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Growth in CL of Pandalus may or may not exhibit seasonal oscillations. A lack of demonstrable
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the case in most stock assessment work) of sampling, .or it may be real. However, hardly any
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literature is available documenting growth of P. borealis where seasonal growth models have
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been applied (but see Hopklns & Nilssen, 1990). Seasonal oscillatlons basically have two
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components, 1) aperiod of positive growth, frequently lasting from spring to autumn, and 2) a
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period of "stagnation" occurring during the winter period. Delineation between th~ posi~ive
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growth and stagnation periods is marked by a so-called "winter point" rNP, the turning point in
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time when growth accelerates after seasonal stagnation). Stagnation in .CL does not
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necessarily imply that negative CL-growth rdegrowth") occurs.
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Length-at-age data for P. borealls are described :for the North Sea (Allen, 1959,. off
coast;
Northumbe~and
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Anon., 19n, 1988), Gulf of :Maine, USA (Haynes & Wigley, 1969;
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Rinaldo, 1981; Apollonio et aI., 1986; Mclnnes, 1986; Terceiro & Idoine, 1990; Fournier et aI.,
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1991), Newfoundland and Labrador. Canada (Parsons. 1988; Parsons et aI., 1989), British
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Columbia, Canada (Butler, 1964), Gutf of Alaska, USA (Fox, 1972), West Greenland (Horsted &
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Smidt, 1956), Iceland (Anon., 1977; Skulad6ttir& J6nsson 1980; Skutad6ttir, 1981), fjords of
and
southern
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northern Norway, arid Spitsbergen (Hjort & Ä'uud, 1938; Rasmussen, 1953,
1007a, b; Thomassen. 1976, 1977; Hopkiris & Nitssen,
Ses (Fontaine, 1975: Teigsmark, 1983).
1900; Nilssen, in press), and the Barents
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CL growth has been showen to be positively effected by water temperature (reviewed by
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Shumway et al., 1985 and Apollonio et al., 1986). Accordingly, the fastest growth rates and
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shortest life spans are seen in southern and warmer areas
(e.g. North Sea and Gulf of Maine),
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while the slowest groWth rates and longest life spans are seen In northem and
cold~r areas
(e.g. Spiisbergen, Jan Mayen, Greenlarid, northElm Iceland). However, several authors have
shown appreclable variability bEltWeen year-classes at giVEln locations (e.g. Skulad6ttir, 1981;
Hopklns
&.
Nilsseri, 1990), influencing variations in temperature, population delnsity aod
recruitment that occurs at any particular locality.
Examinatiori of growth datä wittl regard to longevity and temperature (Fig. lA) show a positive
relationship betWeen groWth performance (GP) and temperature, and
anegative relationship
between GP and longevity. This is in accordancEl with expectation arid with the sc8Jar
I~erature
ior aquatic organisms in general (PoweIl, H~79; Hoenig; 1983; ROff, 1991).
The relationship between
Lee
and
K across
the geographical range of
P.
boreal/s, using
published values al1d those recalculated from the literature (Fig. 18) show orlly a weak positive
trend, but w~h a wlde confidence limit. The basic positive relationship is of course in agreement
With sc8Jing expectations and the V8GF literature (Raff, 1991). However, examlnation of tha
relationship for specific data sets at given areas obviously indicate
has to be borne in mind that
Lee
aclearer relationship, bUt it
and K are not independent of each other in the VBGF
formulation (see Materi8Js & Methods, and 8ayiey, 1977; Hopkins & Nilssen, 1990).
are not independent and their distributions in the present data
Loo arid K
are slgnificantly skewed wtth
regard to normal~ (se Fig. 18, and Moreau et aI., 1986). The normaJ distribUtion of the GP
index is gocid, reflecting supporting the contention that it is a better measure of groWth than
either Loo or
i< (Moreau et a1., 19S6).
In considering ihe reasons underlying the observed relationship between growth and
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temperature. it is important to note thai growth is also effeeted by foöel and energetic
constralnts. TtiEi history of temperature physiology shows that attempts to expiain higher order
processes such as respiration or groWth as single processes respol1ding simply to temperature
have lad to more confusion than understanding (Clarke, 1987; 1991). The slowing of groWth
rates appears to
be an unavoidable conseQuence of the effeet oi a lowereet temperature on
physlology, äittlough the precise mechanisms involved appear to be complex. wtiere grO'Nth
rates in boreat or polar organisms are slow we cannot coriclude that this is necessarily due to
direet limitation by temperature, for we cannot dismiss the possibility that growth rates are sloVt
tor same other reason (Clarke, 1991). The evidence suggests strongly thai the slow growtli
rates of many high latitude organisms are probably, at least in part, due to
ci seasonäl supply of
fOod. Gro'Nth is Iim~ect bY resouree availability, not iemperature. Thus the apparent correlations
between temperature and grO'Nth in
P.
borealis may 8Jso refleet differences in the timing,
. duration and quality of the organic proeJuetion eyde (e.g. Phytoplankton).
6
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SURVIVALlMORTALITY
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Few studies have estimated monaJity rates in P. borealis (Table 1). The data in terms of annuaJ
rates of instantarieous total monBlity (Z) range from 0:5 to aboui 2, with a mean of 1.2 (95%
confidence limit
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=0.3). Amongst the highest
are those determined from semi-enclosed fjordic
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populations with high fishing intensity as weil as predation by cod (Thomassen, 1977; Hopkins
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& Nilssen, 1990). Sy far the lowest, especiaJly considering a short longevity and high
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temperature, are those from the Gulf of Maine. Few of these data have been obtained by
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following a panicular year-class over time; most are gross estimates as they use combined
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data from several year-classes. Hopkins & Nilssen (1990) appear to be the only authors who
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calculatect Z for specitic year-classes during their lives.
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Examination of monaJity data with regard to longevity and water temperature (Fig. 1C) shows
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a negative relationship between Z and longevity, while a weak positive relationship between Z
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and temperature is apparent. The relationship between longevity (which is influenced by
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monaJity rate) and temperature shows that lite span increases with decreasing temperature.
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There is a positive relationship between growth performance (GP) and Z. These findings agree
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weil with previous postulates for P. borealls (Hopkins et aI., in press) and the scaJing lit:rature
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(Adams, 1980; Charnov, 1991a; b; c).
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SIZE AND AGE AT MATURITY, SPAWNING/HATCHING
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Several factors are knowii to inflUE3nce sex change and thus the age and size at maturity in
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borealis. The age of sex change is related to individual body size, and accordingly there. is
m~turity (RasrrlUssen, 1953; Fox, 1972).
much geographie variation in age at sex change and
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Temperature has been shown to be imponant in effecting the age at sex change/maturity, with
, age at maturlty generally being inversely related to 'temperature (ApO/lonio et aI., 1986;
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Rasmusseii, 1953; 1969). As temperature, arid thus growth rate, influence the age at sex
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change, variations in the environment can give rise to marked variability in the timingl age of
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sexual maturity between cohons at given localities (Rasmussen, 1953, 1969; Hopkins &
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Nilssen, 1990). Despite the impression that size and age at maturity are influencecl by
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latitudinat/temPElrCiture gradients, fishing intensity is clearly a modifying 'actor. Cherno" (1981),
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analysing the data of Jensen (1965), proposed that the age of sex change should be most
senSitive to the adult mortality rate and not to groWth
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with higher adult monaJity
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selecting tor a shorter time spant äs males. There is
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abä~ic correJation balwaen the intensity of
the tishery and changes in size at sex change (as the fishery primarily targets tor the larger
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females. However, in the inajority of field dat3 it iso practicaJly impossible to separate the groWth
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rate effect trom the monality rate effect (see other section~ of the present paper).
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Low temperatures appear to adversely
eggs (Rasmussen, 1953;
~'ffebt ;he mafur~tion' ~f females
and/or investmEmt in
A~ollonio et a1., 1986; Berenboim, 1982). In low temperature areas
populations may lack ovigerous females and have a markect preponderance of juveniles.
Berenbolrri (1982) considered that the bottom -; °C isotherm in May in the Barents Sea forms
the boundary betWeen the reproductive part of the area and the "sÜnils" zone. In the coldest
part of the range of P. borealis in the 8arents S~a (s.g. the eastern area towards Novaya
zembiya),
ä relatively
large number of "deacr eggs are tound on the pleopOds of berriect
females. In this same area, spawning of individual femaies occurs every alternate year
(8erenboim, 1982; Teigsmark, 1983); this may be associatect wlth the energetic demands of
a1locating enough energy towards egg production after the previous year's matunation
and
spawning have depleted body reserves.
The ovigerous period (months from spawning to egg hatching) in
P. borea1Js varies from 5 to
11 months (Fig. 2), and lasts ionger in the northern and colder parts of the species'
geographical range than in the southern and warmer parts. As females do not moult during the
ovigerous periOd growth of females in the northernmost areas stagnates
arid
separation of
year-classes of ferriales is very difficult. Egg hatching appears to be related to the peak of the
phytoplankton spring bloom, as the early pelagic larvae
tead on phytoplankton. lha duratlon of
tha pelagic stage appears to be shorter irl tlle soUthern 8reaS than In the northem areas, 9.g. 23 months in the
0510 fjord. North Sea compared with Spitsbergen arid Labrador (Rasmussen,
1953; Parsons et a1., 1987).
.
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FECUNDITY AND REPRODUCTIVE EFFORT
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As applied in the majority of studies on P.
borealls fecundity is usäd to simply describe the
number of eggs attached to aberried female. An extension of thls is to express this relatect to
femaJe b6dy size (either CL or weight). Reproductlve output (RO)' describes weight-specific
gonad production (e.g. weight of eggs produced/weight of matemal femaJe). RO is not a true
. energetlc measure, while reproductive effort (RE, that fraction of ttle total energy flux divertEKi
to repr6ductioll) is (Clarke, 1987). It is also important to note that most authors descrlbe
discrete individuell anlrTial output (fecundity,
Ra or RE), while life-time outpUt may be ci more
relevant parameter as it reflects Iife tabia considerations. A turther dimension is to eonsider
population output, for semelparous or iteroparous regimes. Discussions of these points are
provldect by Clarke
(1987) alld Clarke et aJ. (in press).
Fecundity in P. borealis earl varY seasonally, annually and betWeen areas mai<lng c1ear cut
conclusions dlfficult (Parsons & Tucker, 1986). The fecundlty of the species has been studied in
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southern Norway (Rasmussen, 1953), northern Norway cThomassen, HJ77; Nilssen, 1984), the
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North Sea (Allen, 1959), Iceland (Skulad6ttir et a1.; 1978), West Greenland (Horsted & Smidt,
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1956), the Barents Sea (Teigsmark, 1983; Berenboim, 1982), and the Gulf of Maine (Haynes &
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Wigley, ,1969), and trom several regions of the Canadian northwest Atlantic (Parsons & Tucker,
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1986). Individual fecundity generally increases with increasing body size. Egg number per
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female generally increases as a tunction of CL according to apower curve with an exponent of
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about 3 (range ca. 2.0 to 3.5). Egg numbers per female vary with geographical area and range
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from about 600 to 4,900 depending on the size of the female (Shumway et a1., 1985) (Fig. 3)..
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As slower body growth is associated with delayed age at maturity,
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this' is generally
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associated with increased size at maturity, this results in northern populations exhibiting higher
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~armer
fecundities per female than those further south and in
.,.
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waters (literature cited above).
Furthermore, as the mean bodY size of 'northern/cold
, wäter spawners is aJso generaily
spawn~rs,
eleväteti comparect with southern/warm water
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due to the spawning population
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exhibiting a greater degree of iteroparity (Le. several year-classes comprising the spawning
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stock), this also contributes to higher mean tecunditles per female prawn in the
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n~rthernmostlco~~er. regions. ~owever, few stud,ies Lhave . qUantif~ed a ,re~i~e of early
maturation (and semelparity) but with fewer eggs per fe!'1a1e, and possibly (but see section on
mortality rates) higher numbers of survivors at this time (EI.g. tha North Saa,
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see Ailfin 1959),
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compared at the other extreme with a regime of later maturation, and with greater eggs per
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female, but with possibly fewer survivors at this increased age, partly compensated by
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iteroparity. This will only be answered when simulations incorporating life and fertility tables are
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carried out, using "ground truth" data.
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Although it is clear that temperature effects growth rates in P. borealis in a positive manner,
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and thus elevates the size of first time spawners with resultant increases in fecundity per
fec~nditY. It shouici be borne in mind that
female, it is not the only way in which it can effect
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temperature may effect fecundity for a given length of female at a specific location. Apollonio et
.
.
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äi. (1986) demoristrat~ an inverse relationship between fecundity (eggs per femaJe) for
fem8Jes of
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afixed 25 mm CL änd bottom temperature. Support for this relationship is provlded
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by a laboratory study conducted over two reproductive cycles at temperatures ranging from 2I.
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9°C (Nunes, 1984). Interestingly this appears to be in accordance with predictions regarding
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elevated reproductive outputl effort for P. borealis based
, on energetic arguments for greater
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aJlocations of energy towards reproduction with increasing latitude, and thus lower ambient
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temperatures (see Clarke 1987; Clarke et aJ., in press).
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BetweEm Kosterfjord in Sweden and Krosstjord in Spitsbergen egg volume and organic content
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of eggs of P. borealis increased with latitude (Clarke et a1., in press). Reproductive investment
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9
variect from
s~e to site, but was not correlatect with either iatitude or egg size. The data
iridicated that egg size and reproductive investment vary from location to loeation, and are
uncorrelated. Egg size is relatecJ to feecting and other conditions awaiting the larvae, whereas
reprOctuctive im;estment is dietated by feeding conditions for the adult. The different scBJes
over which these two parameters vary (from season to season in RO, and over evolutionary
time for. egg
Siz~) mean that any general relationship between reproductive investment arid egg
size will be vary difficult to demonstrate.
':,'-;
FISHERIES AND CLiMATE:
IMPORTANT STRUCTURING INFLUENCES
,
.' '.,'"
,
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in a historic31 perspective
, (
P.
~'>
borealis fisheries developE!d first in temperate waters (e.g. the
Nortri Sea, southern ScancJinavia) and then later became established in increaslngly northern
waters (e.g. Greenland, northern Norway, the Sarel1ts Seal. Secause of this, few detaiis exist
regarding the population parameters of unfished stock in the more southern areas, while a
number of stUdies from northern regions provide details of virgin or Iightly eXPtoitEld stocks.
Descriptions of various aspects of P. borealls fisheries and the targetB<i stocks have bean
providect by Jensen (1965; the Skagerrak), Smidt (1965, 1967, 1969, 1981; Grssnlarld waters),
Hopkins & Nilssen (1990: a riorth Norwegian fjord), Nilssen (in press: a Sp~sbergen fjord),
Rasmussen (1942, 1951; 1953, 1967a, 1967b; Norway and Spitsbergen), Hjort & Ruud (1938;
soUthern regions of No~ay), and il1 Frady (1981; numerous details for northeastern and
riorthwestern North America). Details regluding geaf and ~perations are reviewect by Shumway
et aJ. (1985).
•
An illustration of same of the pertinent mechanisms arid scenarios is weil iIIustratect from
SpitsbergEln waters (Nilssen, in press: Nilssen & Hopkins, unpubl.: Figs. 4 & 5). In Isfjord there
was a signiflcant change in mean CL of females between 1981 arid 1991 which was inversely
. rehited to the laOdings (Fig. 4), te. an increase in fishing mortBJity
arid proportionateiy rechiced the prevalence
(F> rectuced the stock size
0; larger sized fem2Jes. Lalldings then decreased,
and tha stock recovered with a concomitant increase in female CL due to a combination of
batter growth rates and rElduced mortality (Fig. 4). This is particular1y evident in changes in the
proportion of femaJes larger than 25 mm CL in the size-frequency distributions (see Fig. 5). The
findings here are similar to those described by Jensen (1965).
'Charnov, in aseries of papers (Charnov et a1., 1978; Charnov, 1979.. 1981. 1989ä;b) has
examined via iheoretical and empiric2J considerations. severat aspects of the effects
6i fishing
mortality and exploitation on P. borealis. These inter aJia demonstrate that increasing fishing
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mortality (F, and probably also total mortality Z) will be reflected in a trend for decreasing age
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at sex change, with the thinning effect of fishing on population density providing increased
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individual growth rates. As fishing removes a disproportionate amount of larger Individuals, and
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thus females, it will result in even more skewed sex ratios than normal in favour of males.
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Although these conclusions are specifically directed at P. borealis they are basically no
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different than classical findings from basic evolutionary life-history theory, especially within the
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realm offish (Pianka, 1970; 1972; 1978; Stearns, 1976; Stearns & Crandall, 1984).
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~h~ngeS piay an
80th shorter and longer term temf?erature or climatic
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importärit role in the
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biology of P. borealls (see also earlier sections). As these environmental changes may effect
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growth, mortality, and recruitment of this specles, there is Iittle doubt that such variations may
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have repercussion on fisheries yields thrClugh either ävallcibility (animäJs actively move oUt of a
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previously fished areal and productivity (via dynamic population characteristics). The effects of
tempeniture changes are partlcula~y feit at the extre~es of the temperature ranges, be they
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high or low. Temperature changes may provide varylng results on 'different life-stages of P.
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L.
borealis (see earlier, and reviews by Shumway et a1., 1985 and Apollonlo et a1.; 1986;
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Berenboim & Lysy, 1987). In the southernmost par:ts of its range development of high
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temperatures are particularly problematical (e.g. Gulf of Maine, Fladen Ground in the North
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Sea, and the Skagerrak), while the reverse Is true In the northernmost part of its range (e.g.
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Greenland, the Barents Sea, Spitsbergen, Labrador), and negative effects on landings are weil
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documented (e.g. Rasmussen, 1953, 1967a; Horsted & Smidt, 1965: Apollonio et a1., 1986;
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Nilssen, in press).
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The natural conclusion regarding the combined effects of fisherles and climatlc change, is that
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a relatively acceptable fishing lntensity at one moment may quickly turn drastlc, when
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environmental changes occur rapldly. An appreclation of thls synergistic effeet is still not
appreciateCi slJfficiently in fisheries management. Glob1al climate 'change, at least In the longer
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term, will very probably result in expanded areas for P. borealis distribution at higher latitude
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and larger fisheries ylelds, whlle the southernmost and lower latitude areas will probably result
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in the opposite. The southernmost stocks of P. borealis have a tendency for a shallower
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distribution than the northernmost ones (Shumway et .a1., 1985), such that the negative effects
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of warming will be partlcularly prevalent on stocks and their fisheries in these regions.
I
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•
11
PRODUCTION AND PRoDucTi\iliv
Although tl1a biomass (standing stock, expressecJ as weight per unit ares. or volume, 8) of a
population is an important measure of abundance, It is ttie produCtion (P, the change of
biomass per unit time) and,productlvity (PIS, or turn-over rate of biomass) which determines
the potential for the populations mass groWth and remewi:ll. A prEldator or fishery haiVests,
sensu stricto, pr6duction and prOductivity (both are dynamie rate measures) rathar than
and various
biomass (a staile measure). Further detaiis regardirig definitions
measuring prOduction and prOductivity are found in several classicaJ tiilndbooks
,~
.~'
methOds of
(B.g.
Crisp,
,'''',
,
1971: Winberg, 1971).
•
Allen (1971), ~orking on ttie assumption of
population
pis is equivalent to the
ci stable
age struCture, asserted that the annuaJ
annual instantaneous rate of totaJ mortality (Z), providing
that mo~a1itY is exponentlaI and that individual g~oWth ean be desc~bed by the V8GF. ThiJs,
giVen these provisions, in'eJireet estimates of Piä for
P.
borealis can be extractect from tl1e
literature describing mortaJity.
Few direct, bona tide
calculati~ns of Por P18 tiave been carried out for P, borealis. Hopkins
(198n and Hopkins et aJ. (in press) have earriect oUt catculations of
ä, P, and PIS for whole
cohorts (also with regard t,o age-group) and the whole population of P. borealis from Balsfjord,
northern NOrWay, and examined model simulations within observed variations of groWth
(expressect as K in the V8GF> and mortallty (Z) observed over a decade. Ouring the study
period
Kand i
were empirici:llly positively assoclatect in 8a1sfjord P; bore8Jis, in agreement
with the generBlIY acceptect philosophy that, on an annual basis, faster groWth rates are
•
assoclated with higher mörtailtY rates and vice versa (see 8evelton & Holt, 1959; Charnov,
1979; Teigsmark, 1983; Ebert, 1985). Maar. biomass and produetion of
about
ci
col1ört varied by
2.5 times, due to the' influemce of changes in groWth rate and mortaJity. Age-relatect P18,
decreasing with aga of prawn was verj sensitive to changes in groWth and mortatity
combinations. Coholt and pöpuiation P18 vaiues rangect from abolit 1.5 to 2.2, in agreement
with predictions basect on the "scalar" literature for aquatlc invertebrates of similar bOdy size
and longevity generation time
(see Waters, 1969;' Zaika, 1970; Allen, ; 971: R~bertson.
1979;
8anse & Mosher, 1980; 8rey, 1990).
.The interplay betWeen growth rate (K) arid mortallty
(Z)
is this confirmSd
as being a major
gover~ing factor in the IJroduction and prOductivity of P. borealis Ü"lopkins et
study of population
P, ~, arid PIS and mean individual weight
in press).
A
cW>, oi .marine macrobenthic
inverteb,rates showect a hlghly significant dependence of P on
depended only on Wend riot on
aJ.,
ä
arld
W,
whereas P
18
B(8rey, 1990). Hopkins et a1. (in press), using amOdelllng
12
I
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,
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and statistics approach (baseel on field-data inputs), demonstrateel highly significant positive
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relationships between Z, P/B, and K. on the one hand and P and Bon the other. for Balsfjord
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P. borealis. The novelty of the results for P. boreal/s. besides emphasising the basic agreement
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with Brey's (1990) inter-species and inter-taxa comparisons. is that they also draw attention to
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the natural intra-specific variability of P/B within limits set by both Z and K (Hopkins et a1.• in
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press).
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.
These findings regarding the prOduction and prOductivity of P. boreails (Hopkins et at.:· in
."
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press) emphasise that a10ng an increasing latitudinal gradient (or indeed one of decreasing
~! total
temperatlJre) individual growth rates and annual rates
maturity and thus generation time will increase and
,
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pis wili
,.
decrea~e.
mortality will
(see also
accordlngly decrease
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Beverton and Holt. 1957; Peters. 1983; Calder, 1984; Schmidt-Nielsen. 1984). This is
summarlsed in Fig.
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In terms of exploitation hazards. the low turn-over rate (P/B) of cold water/high latitucle P.
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borealls stocks. coupled with larger size/age at maturity emphaslzes that overfishing will be
pariicula~y pr~v8JEmt
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when fishing effort and mesh size effects combine to reduce the
, •.
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ovigerous female stock towards the minimum physiological maturation size (I.e. size of sex
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change). Periodie (but at present not temporally pr~ictable) frigid events In these ar~as
underscores the requirement for prudent management strategieS with buffering capabilities.
I
I
Alterations of
!
a population's
reproductlVe characteristic
, throuQh differeniiät exploitation or
& Carscadden. Ui78).
environmentllt change may reduce population fltn'ess (Leggett
•
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Increasing exploitation of a P. borealls population has been shown to change growth rates.
F;"
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size and age at maturity. and relative size and/or age distributions. A1though the mechanism is
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primarily steered through mortality. it should be envisaged as part of the realm of density
lha potentiai differe~ce of n~tu~at mortality rates betWeen pop~iaiions
may iead to variSd responses to speCific exploitation rates. Management of P. borealis flsheries
dependent regulation.
.,
,,,...
.
.".,
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at present is highly empiricaJ and there is a tendency to apply the successful exploitation
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parameters obtaineel in one population to the others (Savard & Parsons. 1990). Differences in
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life cycles, should increasingly be taken into account when developing ecologically acceptable
,
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management strategies.
;
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ACKNOWLEDGEMENTS
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, . . ,.,.
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'
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.".. .
.... ."'"
.
. . ' ...
This forms contributlons to the project "Prawn and flsh communities in the 8arents Sea"
(NorWegian Fisheries Research Couneil, No. 1101-500.069),
8a1sfjordl Projeet of
University of Troms0. aod to MARE NOR (Research Programme on NOrlh Norwegian Coastai
Ecology).
I
"
tila
!
I
the
•
13
REFERENCES
Adams.
1980. Life history patterns in marine fishes and ih~ir conse<:iuences for fisheries
, management. Fish. Bull. 78(1): 1-12.
Allen, JA 1959. On the biology of Pandalus borealls Kn~Yer. with referimce to population off
the Northumberland Coast. J. mar. bloi. Ass. U.K., 38: 189-200.
Allen, K.R. 1971. Relation betWeen production and biomass. J. Fish. Res. Bd Cant 28: 1573, 1581.
.
P.S.
a
Anon. 1977. Report of the working group on assesment of Pandall.is borealls stocks. ICES CM
1977/K:l0. 27 pp.
Anon. 1988. Report of the working group on the assessment of Pandalus stocks. ICEs
1988/Assess:14. 37 pp.
Apollonio, S., Stevenson, DK. and Dunton, E.E. 1986. Effects of temperatureon the biology of
the northerri shrimp, Pandalus borealis, in the Gulf of Maine. NOAA lech. Rep. NMFS
42.22 pp.
BansEl. K. & S. Mosher 1980. Adult bOdy mass and annual production biomass relatioriships of
field populations. Ecal. Momogr. 50: 355-379.
Bayley. P.B. 1977. A method for finding the limits of appiicatlon of the von Bertalanffy growth
model and statistical estimates of the päiameters. J. Fish. Res. Bd. Cant 34: 10791084.
Berenboim. B.I., end" Lysy, A.YtJ. 1987. Effects of oceanographic faetors on populational
shrimp (Panda/us borealls Kr0yer) in the Barents Sea arid Spitsbergen
structure
area.ln
effect
oceanographlc condltlons on distribUtion and population
dynamlcs
commercial flsh stocks In the Barents Sea~ pp. 243-250. Ed. by H.
Loeng. Proc. 3th Soviet-NorWegian Symp., Murmansk, 26-28 May 1986. Institute of
Marine Research. Bergen, NorwaY.
Berenboim. B.I. 1982. ReprOductiori of the shrimp Paridalus borealis in the Barents
Oceanology 22(1): 85-89.
BertaianftY, L. von 1938. A quantitative theory of organic groWth.
Blol.l0(2): 181-213.
Beverton, R.J.H. & S.J. Holt 1957. On the dynamics of exploited fish populations. Fish. Invest.
. Lorld. Sero 2, 19: 1-533.
Beverton, R.J.H. & S.J. Holt 1959. A review of the lifespäns arid mortattty rates of fish in nature
and their retation to growth and other physiological characteristics. In:" CISA
Foundation Colloquia
Aging. Vol. 5. The lifespan of animals. pp. 142-180. Ed. by
. G.E.M. Wolstenholme & C.M. O·Connor. J. & A. Churchill, Lendon.
Brey.
1990. Estimating productivttY of macrobenthic invertebrates from biomass and
iridividuat weighl Meeresforsch. 32: 329-343.
Butler, T.H. 1004. Growth, reprOduetion, and distribution of pandBJId shrimps in British
Columbia. J. Fish. Res. Bd. Cant 21(6): 1403-1452.
Caider, W.A. 1984. Slze, 'unc:t1on and Ilfe history. HaNard University Press, Cambridge Mass.
431 pp.
.
Charnov. E.L.; D. Gotshall &. J. Robinson 978. Sex ratio: adaptive response to popullition
fluctuätionin pandciJid shrimp. Sclence 200: 204-206..
Charnov. E.i... 1979. Natural selection and sex change in pandBJid shrimp: test of a Iife history
theory. Am. Nat.113: 715-734.
. Chernov, E.L. 1981. Sex reversal in Pandalus borealis: effect of a shrimp fishery? Mar. Biol.
Lett. 2: 53-57.
Charnov. E.L & B. Bergström 1987. Alternative Iife histories in sex changing shrimp: a
.
pheriotypelimited ESS.
Ecal.l:
Charnov, E.L 1989. Sex c::hange and population f1uctuations in pandaJid shrimp. Am. Nat.
134(5): 824-827.
'
Chlunov, E.L. 1989. Naturai selection on aga at maturity shrimp. Eval. Ecal. 3: 236-239.
cr..
•
oi
The
0'
0'
Sea..
Hum.
•
on
T.;
i
Eval.
107-111. .
in
'.
,.
Charnov. E.L 1990. Retative size at theorisei of maturity. (RSOM) is an interesting riumbflr ir
cnjstacean groWth (Decapoda. PandaJidae). Cruitaceana 59: 108~109.
Charnov. E:L.1991. Evolution of life hist6iy parameters in animSls wiih irideterminate growth.
particular1y fish. Evol. Ecol. 63-68.
Charnov. E.L .1991. Pure numbers. invariants
symnietry in the evolution of life histories.
Evol. Ecol. 5: 339-342.
I
.
Charnov, E.L 1991. Evolution of iite history variation among female mammaJs. prOc. Natl.
Acad. Sei. 88: 1134-1137.
".
.
Clarke. A. 1987. Temperature. latitude and reprOducilve effort). Mar. Ecol. prOg. Sero 38: 89-
!
5:
and
I
L, "
"..
..
" .,.,.,.,
>
" ,,99. . '..
Clarke, 1991. What is cold adaptation and how should we measure it. Amer. Zool. 31: 81-92.
Clarke. A.. C.C.E. Hopkins & E.M. Nilssen (in press)., Egg size arld reproductive output in the
,
deep-water prawn Pandalus boreslis. Functlonal
$: SSS-$$$.
'
Cloern. J.M.and F.H. Nichols 1978. A von BertaJanffy groWth mOdel with seasonatlY va;Ying .
coefficient. J. Fleh. Res. Bd. Carl. 35: 1479-1482.
Ecol.
i..~9:':~3~'1~~.e
Cole.
popuiatlon consequences ofllife hisiory
p~enomeni Quart.
Rev. Blol.
of
Crisp, D.J. 1971. Eriergy measurements. Pp. 197-279 In: MethOds tor the Study
Marine
BenthoslGBP Handbook No. 16. 8lackWell~ OXtord.
Ebert. T.A. 1985. Sensitivityof fitness to macroparameter changes: an anSlysls of surviVorship'
and individuaJ groWth in sea urchin lite histories. OecologJ8 65: 461-467.
Fontaine. 8. 1975. Age et croissance theriQues de Pandalus boreal/Sr Kreuer 1838 dans
IAtlantiQue du Nord.ICES CM 1975/K:24.
,
Foumier,D.A.. J.R. Sibert and M.. Terceiro, 1991. Amilysis of lengthfrequency sarnPtes with
relative abuildance data for the Gulf of Maine northem shrimp (Pandalus boreails) by
the MULTIFAN method. Ca". J. Fis". Äqualt: SeI. 48: 591-598.
.
Fox. W.W. 1972. Dynamlcs öf '. exploted Paridalid shrimps and an evaluation of
management models. Ph. D. Thesis. Univ. Washington. Seattle. 194 pp.
Frady. T. 1981. ProceecJings of. the Intfunätional PandSJid Shrimp Symposium. [Paper
presentect at KOdiak AKt Feb. 13-15. 1979) [Sea Grant Rept. 81-3) A1aska Sea Grant
Prog. Vniv. AK. Fairbanks. AK. Jun. 19~11. 519 pp.
Frechette, J. & D.G. Parsons 1983. Report of shrimp ageing woi1<shop held at Ste. Foy,
Quebec. in May and at Danmouth. Nova Scotia in November 1981. NAFO Sei. Coun.
Studie. 6: 79-100.
Gunderson, ~980. Usir'g ~.K selection theo,y to predict natural mortaJity. Can. J. Fish. Aquat.
•
9PP:
of
I
, " S~I. 37: 2266-2271.,.
....;
.
Gunderson. D. & P.H. Dygert 1988. Reproductive effort
as a predictor of natural mortality rate.
1
J. Conl. Explor. Mer. 44: 2 0 0 - 2 0 9 . j
.'
Hay;,es. E.B. and R.L Wigley 1969. Biology of the northern shrimp, Pandalus borealis, in the
.
Gulf of Maine. Trans. Ame... Fish. Soc. 98(1): 60-76.
.'
Hjort. J.• arid Ruud. J.T. 1938. Deep-sea prawri fisherj(~s and their problems. Hvair4d. Skr•• 17:
I
1-144.
.
I,..
..'.
" "
Hoenig, J.M. 1983. EmpiricaJ use of longevity data to estimate mortality rates. Fish. Bull. (U.S.)
I..
..... -_.. 1' • ..".
,
• >
•
<"
:_."
',.
• •< .
.
" ,
..'
"
, . : ,"
'
,
.
'
.' 82(1): 898-902.
'. .
. j . , , .'.'
.
". '
,
Hopkins, C.C.E. 1987. Scenario of groWth and mortaJity: a spreadsheet prochjction-model
,
PiJndalus borealis. ICES CM 1987/K:51, 24 PP:
Hopkins, C.C.E. & E.M.,Nilssen 1990. Population biology of the deep-water prawn(Pandalus
in BaJsfjord. northem NOrWay: I. Abundance. mortaJttY and growth. 19791983. J. Cons. Int. Explor Mer 47: 148-166.
:
in press: An age-group arid cohort productio;;
Hopkins. C.C.E.; E.M. Nilssen & N.
mOdel of the deep-water prawn Pandalus bor~alis, with modei anaJyses of changing
in
borealis)
Swanberg
i
l
,t
~
I
t
•
•
..
•
••••••• J..
•
15
dynamic populiition parameters. proceecUngs of ICES Symposium on Shellflsh Ufe
,HI.torh;'. and Shellfl.hery Model., Rapp. P.-v. Reun. Con•• Int. Explor. Mer.
Horsted, SA, and Smidt, E. 1956.' The deep saa prawn (Pandalus borealis KR) in Greenland
waters. Medd. Kommn. Oanm. HavUnders., 1(11): 1-118.
Horstect, SA, and Smidt, E. 1965. Intluence of cold water on fish and prawn stocks in West
Greenland. ICNAF Spec. Publ. 6: 199-207.
Jensen, A.J.C. 1965. Pandalus borealis in the Skagerak (h,ingth, groWth arid changes in the
stock and fishery yield). Rap. P.-v. Reun. Con•• lnt. Explor. Mer 156: 109-111.
Jones, R. 1984. Assessing the effects of changes in the explotation pattern using lenth
compositional data (with noies on VPA and cohort analysis). FAO FI..... Tech. Pap.
(256): 118 pp.
.
Johnson, L. 1981. The thermOdynamic origin of ecosystems. Cant J. Flih. Aquat. Scl. 3ä: 571590.
Leggett, W.C. & J. Carscadden 197i S J. Fist. Res. Bd Cant 36: 987-1011.
.
Lockwood, S.J. 1974. The use of the von Bertalanffy growth E!qUl1ltion to describe the seasonaJ
growlh of fish. J. Con•• Int. Explor. Mer 35(2): 175-179.
Mclnnes, D. 1986. Interstate fishery management plan for the northeln shrimp (Pandalus
borealis Kr0yer) fishery in the western Gulf of Maine. Atl. States Mar. Fllh. Comm•
Fllh. Manage. Rep. No. 9.
Mehl, S. 1989. The Northeast Arctic cOd stock's consuption of commerciaJly exploited prey
species in 1984-1986. Rapp. P.-v. Raun. Cons. int. Explor. Mer 188: 185-205.
Moreau, J., C. Bambino
D. Pauly 1986. Indices 0' overall growth performance of 100
tllapla (Clchlldae) populations. Pp. 201-206, In: Maclean, J.L, LB. Dizon and LV.
Hosillos (ects.) The First Asian Fisheries Forum. Asien Fisheries Society, Maniala,
.
'.
Philippines. . '
Nilsen, R., 0.1<. Gutvik, E.M. Nilssen & C.C.E. Hopkins in press. Population parameters of
themwitch Glyptocephalus cynoglossus (L) (Pisces: Pleuronectidae) from MaJangen,
northern Norway. Fish. Res. $$: $$$-$$$.
. .
..' ,
'
Nilssen, .E.M. 1964. A comparlson
population structure, survi';~1 iUld 'ecundlty In the
deep-water präwn Pandalus borealis (Kmyer) on tWO traWllbg grounds In Balsfjord,
northern Norway. Cand real. thesis, UniversityofTromse.,195 pp. (In Norwegian).
. Nilssen, E.M. in press. Demography, fecundity, groWth and mortality of the i:!eep-water prawn
PandaILis borealls from Isfjord, SpitSbergen ('TSON). . Proce8dlngs of
Symposium on Shellflsh Ü'e Hlstorles and Sheit.lshery MOdels, Rapp. P.-V. Reun.
Cons. Int. Explor. Mer.
Nunes, P. 1984. Reprextuetlve and larval blologyo' nor1hern shrimp Pandalus borealis
(Kroyer) In relatIonship to temperature. Ph. D. thesis, University of A1aska. Fairbanks.
195 pp.
Palsson, 0.1<. 1983. The feeding habits of demersal fish species in Icelandic waters. Rit
Flskldelld. 7(1): 1-60.
Parsons, D.G. 1988. The effects of changes in envil'onmentaJ temperature on groWth arid
reproduction of. the northern shrimp (Pandaius borealis) from CartWright Channel
(Division 2G). NÄFO SeR Ooe. 88/78. SeI'. No. N1526. 7 pp.
Parsons, D.G., utiy, G.R., ani:! Chaput, G.J.. 1986.. Aga and growth of the ,.' riorthern shrimp
Pandalus borealls off northeastern NeWtouridland and soUthern Labrador. Trans. Am.
Fish. Soc., 115: 872-881.
Parsons, D.G. & G.E. Tucke" 1986. Fecundity" of northern shrimp, Paridalus borea;is
(Crustacea, Decapoda) in areas of the northwest Atlantic. Fis.... Bull. 84(3): 549-558..
Parsons, D.G., V.L Mercer & P.J. Veitch H389. Comparison of the growth of northern shrimp
(Pandalus borealls) from tour regions of the northwest Atlantic.· J. Nörthw. Atl. Fish.
Sei. 9: 123-131.
and
0'
.c:es
.
:
~
j
,
,
_ . ~'
"
"
I
~-.
16
,',' ,',
' .,.' ' , .',.,
Pauly, 0.1982. Studying single species dynamics in a tropical multispecies context. In: Theory
iild Management ofTropleal Fisherles, pp. 33-70. Ed. by O. Pauly & G.I. Murphy
. ICLARM, Manila, and ~SIR.0' Cronulla. 360 pp'.
Peters, R.H. 1983. The eeologlcal Implleatlons of body slze. Cambridge University Press,
Cambridge. 329 pp.
, \
Planka, E.R. 1970. On r- and K- selection. Am.
106: 581-588.
Pianka, E.R. 1972. rand K selection or b arid d selectiol1? Am. Nat. 106: 581-688.
Pianka, E.R. 197ft Evolutlonary Eeology. Harper & Row, New York. 397 pp.
Pitcher, T.J. and P.O.M. MacDonald 1973.Two mcx:Jels for seasonal groWth in fishas. J. Appl.
I.
0
'
"
'.:
'
Nat.
I... ,.
" ,
.,,.
Eeol. 10(2): 599,-606.,
Powell, O.G. 1,979. Estimation of mortality and growth parameters from the length-frequency in
the catch. Rapp. P.-v. Reun. Cons. Int. Explor. Mer 175: 167-169.
.
Rasmussen, B. 1942. 9m dypvannsreken ved Spitsbergel1. FlskOlr. Skr. Sero HavUnders.;
7(4): 1-43. (In N o
rw
e g i a n )" .. :I
.
•
.
• '.",
,
.,
, Rasmussen, B. 1951. Problems in the fishery for deep sea prawns. Rapp. P.-Y. Reun. Clns.
, ' c
,'"
Perm.lnt. Expl~r. ~er 128: 79-81 ..
Rasmussen, B. 1953. On the geographlcal variation In growth and sexual development of the
deep sea prawn (PanCfalus bo;ealls Kr.). FllkDlr. Skr. Sero HavUnders., 10(3): 1-160.
Rasmussen, B. 1969.Variations in protandric hermaphroditlsm of Pandalus borealis. FAO Fllh.
Rep.57(3):1101-1106.
"
" , ..'
Rasmussen, B. 1967a Temperaturforhold og rekefiske I Skagerrak 1962-1966. Fiskets Gang,
47: 842-847. (In Norwegian)
I ,
,',
Rasmussen, B. 1967b. The fishery for deep sea prawn int Norway. Mar. 13101. Ais. Indla Proe.
"
Symp. on Crustaeea, Part IV: 1437-1441.
l
,
Ricker, W.E. 1975. compiJtation
interpretation of blologicaJ
statistics of fish populations.
i
"I.".
0'
i
'..
"
..
'.
' c
,
<
,
,
',.'
o.
,',
•
'
",
afld
o.
'
.
Bull. F18h. Res~.~d Can., No. 191',382 pp. .
Rinaldo, R.G. 1981. PopUlation allelsment of the northern shrimp, Pandalus borealis,
..
(Kreyer) In tlle Gulf of Maine, 1965-1975. Ph.O.;Thesis, Unlv. Maine, Orono, 210 p.
Robertson, A.I. 1979. The relationshIp betWeen anmial productlon:blomass ratios and Ilfespan
.
for marine macrobenthos. Oecologla 38: 193-202.
Roff, DA 1984. Reproductlve strategies in flatfish: a first synthesis. Can. J. Fish. Aquat. Sei.
39: 1686-1698. ,
Roff, DA 1991. The evolution of life-history variation in fishes, with particular reference to
flatfishes. Neth. Z. Sea Res. 27(3/4): 197-207.
Savard, L & D.G. Parsons 1990. Geographie variations In the lite history of Pandalus boreaiis
from>,.'.' the northwest Atlantic. ICES Symposium on Shellflsh Ufe Historie. aiid
Shellfllhery Models, 1990. Paper. No. 27.4 pp. ~
,
'
Schmidt-Nielsen, K" ,
1984..
Scallng: why 18 aillmal lize I10lmpOrtSnt? Cambridge University
.
Press, Cambridge. 241 pp. "
,i.
Shumway, S.E., H.C. Perkins, O.F. SChick
A.P. Stickney 1985. Synopsis of biological data
on the pink shrimp, Pandalus borealis Kreyer, 1~38. NOAA Tech. Report NMFS30, 57
pp.
I
Smidt, E.l965. Oeep-sea prawns andthe prawn fishery in Greenland waters. Rapp. P.-v.
Reun.Clns. Perm.lnt. Explor. Mer 156: 100-104.
Smidt, E. 1967. Oeep sea prawn (Pandalus tJorealls) Kr.) in Greenland waters: Biology al1d
fishery. Mar. Bial. Alloe. Indla, Proc. SympOsium
Crustac:ea, Part. IV: 1448,
I
1453.
,
.
,.',
-.
,-.,-',
. ".' 1.
,-.'
'
."
,,'
" . ,\
Smidt, E. 1969. Pandalus in Greenland waters: its fishery and biology. FAO Fish. Rep. 57(3):
893·901.
:
Smidt, E. 19fH. Environmerital conditions and shrimp stocks at Greenlaoo: Pp. 391-392 In: T.
Frady (Ed.) Proc. International Pandalid Shrimp Symposium, Kodiak, Alaska. Feb. 1315, 1979. UniV. Alaska, Sea Grant Rep. 81-83.
0
\."
•
!
..
•
"C,
"
"
.
!
I
,,,,.-
' . , '
j
anet
on
I,
j.
j
I
I
I
1
II
I
I
I
'
•
_.. ..
-
•
17
Skulad6ttir, U. 1981. The deviation method. A simple method for detecting year-classes of a
population of Pandalus. borealis from length distributions. Pp.. 283-306, In: T. Frady
(Ed.) Proce9dings of the International Pandaiid- Shrimp Symposium, Kocliäk, Alaska,
13-15 Feb. 1979. Univ. Alaska, Sea Grant Rap. 81-3.
.
Skulad6ttir, U. &
J6nsson 1980.· Reekja~ vid Island. [Siology of Pandalus borealis in
.
Icelandic waters) . .4:glr 73(2): 86-95, 117.
Skulad6ttir, U., E. J6nsson and I. Hallgrfmsson .1978. Testing for heterogeneity of Paridalus
borealis populations at leerand. ICES CM 1978/K:27, 41 pp.
Squires, H.J.1968a. Relation of temperature to growth and self-propagation of Pandalus
borealis in NeWtoundland. FAO Fist.. Rep. 57(2): 243-250.
Squires, H.J. 1968b. Some aspects of adapt~l.tion in decapOd Crustacea in the north-west
Atlantic. FiSh. Res. Bd Can. Stud. 1260: 215-223
Stearns, S.C. 1976. Life-historY täctics: a review of the ideas. Q. Rev. Biol. 51 cl): 347.
.
Stearns, S.C. & R.E. Crandall 1984. Plasiicity for age and size at sexual maturitY: life-history
response to i.mavoidable stress. Pp. 13-29 In: G.W. Potts & R.J. Wootton (I~ds.), Fish
reproductlon: strategles and taetlel. Academlc Press, LOrldon.
Teigsmark, G. 1983. Populations of the deep-sea shrimp (Pandaius borealis Kr0yer) in the
8arents sea. FlskDlr. Skr. Sero HavUnders., 17: 377-430.
Terceiro, M. and J.S. Idoine 1990. A practlcal assessment of the performance of Shepherd's
length .composition analysis (SRLCA): application to Gutf .of Maine northern Shrimp
(Pandalus borealis) survey data. Fish. Bull., U.S. 88: 761·773.
Ttiomassen. T. 1976. Growth. reCruitmE!nt and mortality of Pandalus borealis (Kr0yer), in
8a1sfjorden. northern Noiway. ICES CM 1976/K:31. 16 pp.
Thomassen. T. 1977. Comparison of growth. fecundity and mortality betWeen!Wo populations
of Pandalus borealis in northern Norway.ICES CM 1977/K:38. 16 pp.
Ursin,
1oo3a. On the incorporation of temperature in the von Bertäianffy growth equation.
Mectd. Danm. Fllk. HavUnders. 4(1): 1-16..
Urs!n. E. 1963ti On the seasonal variation of groWth rate arid. groWtti parameters in Noiway
poUt (Gadus esmarkJ) in the Skagerrak. M8dd. Danm. Fllk. HavUnders. 4(2): 17-29.
Waters. T.F. 1969. The turnover ratio in prOduction ecology of freshwater invertebrates. Am.
Nat. 103: 173-185.
Wilkinson, L 1988. SYSTAT: The system for statisticS. Systat Inc., Evanston IL 822 pp.
Winberg. G.G. (Ed.) 1971. Methods for nie eltimatJon of prOduetlon of aquatle animali.
Academic Press, London. 175 pp. ' . .
. .
.
Zaika, V.E. 1970: Relationship .between productivity of marine molluscs and thair Iife span.
Oeeanology 10: 547-552.
E.
a
•
E.
_.~
.
18
Table 1. Pertinent Iife-history parameters of Pandalus borealis from various studies and
geographical regions. '-00 and Kare the asymptotic length and growth constant
respeetively of the von 8ertalanffy growth ,function (V8GF); GP is the growth
performance index; Z, F. and M, are the instantaneous annual rates of total mortality,
fishing mortalty, and natural mortality respectively; AGFS is the age at first spawning;
AG
provides an estimate of max. Iife span; MS and MH are months of spawning
max
and hatching respectively. OV is the ovigerous period i.n months. oe is average
ambient temperature. Further details on the derivation of these variables/parameters
are given in Materials and Methods.
Arell
Author
Barents Sea
Teigsmark (198
Fontalne (1975)
25.6
26.7
27.4
31.4
Northern Norway. Balsfjord
Thomassen (1977)
28.4
Hopklns & NIlssen (1990) 28.00
26.75
Thls study (1979/1980)
28.40
K
GP
z
0.374
0.283
0.235
0.192
2.39
2.31
2.25
2.28
0.818
0.757
0.533
-.---
F:
0.40 2.51 -.-0.35 2.44 1.90
0.41 2.47 2.12
0.341 2.44 2.07
M
lsfjord. Spltsbergen
Nflssen (1990)
Alaska
Fox (1972)
27.45
3.5
4.5
5.5
3.5
-,--
3.5
3.5
3.5
3.5
5
4
2.5
5
5
-.--
-.--
25.90 0.361 2.38
22.99 0.415 2.34
25.62 0.283 2.27 -.--
Ber1"9 Sea
Ivanov (1969)
31.28 0.355 2.54
Western Gulf of Alaska
lvanov (1969)
36.97 0.236 2.51
North Sea. Skaqerrak
Anon. (1977. 1988)
North Sea. Fladen
Anon. (1977, 1988)
Br. Columbla. Vancouver
8utler (1964)
U.K •• Northumberland
Allen (1959)
4.5
4.5
10
oe
Aug
May 9
Aug
May 10
Ju/Au Ma/Ju 11
2
1
0
2
7
Au/Se
Au/Se
Au/Se
Au/Se
4
4
Ma/Ap
Ma/Ap
Ma/Ap
Ma/Ap
Se/Oe Ma/Ap
2
2
2
2
8
8
8
8
•
7.5 5
5
5
5
5
5
Aug
Mar
8
4
5
9
9
5
9
5
5
5
12
10
o
o
o
o
1. 5
4
6
-.--
5
5
9
7
-.--
2.5
2.5
2.5
7
7
7
-.--
-.--
2.5
2.5
2.5
2.5
7
8
OV
MH
MS
8
0.505 2.58
35.26 0.165 2.31 1.05
33.61 0.204 2.36 1.00
AGE max
-.--.--.--.--
Gulf of P1alne
32.00 0.46 2.67 1.50
-.-Haynes & Wigley (1969)
1.47 1.22 0.25
Clark & Anthony (1981)
29.00 0.180 2.18 0.90 -.-- -.-Rfnaldo (1981)
35.2 0.36 2.65 0.54
-.-Mclnnes (1986)
-.--.---.Apollonf et al. (1986)
-.-Tercefro & Idofne (1990) 33.0 0.32 2.54 0.45
31.0 0.39 2.57 0.72
Fournfer et al., (1991)
29.2 0.45 2.58 0.72
Labrador
-.-37.71 0.17 2.39 -.-Parson et al. (1986)
-,-31.43 0.168 2.22
Parson et a1. (1988)
-.-32.00 0.167 2.23
leeland. Arnarfjordur
-.-31.0 0.16 2.19
Anon. (1977)
28.0 0.129 2.01
Skuladottfr (1981)
-.-28.0 0.142 2.05 -.--.-28.0 0.271 2.33 -.-Southern Norway. Oslofjord
Rasmussen (1953)
AGFS
-.--,--
Aug
May 10
Au/Se Ap/Ma· 9
1
1
Ma/Ap
2.5/3.5 7
2.5
7
0.7
1. 5
4
6
27.20 0.410 2.48 1.95 0.7
1
1. 5
4
6
28.76 0.474 2.56
-.--
1. 5
4
-.---
-.--
1.5
3
34.50 0.240 2.46
1.5
0.6
No
Ma/Ap 5.5 8
Oe/Oe Ma/Ap
5
8
19
Figure legend••
Fig. 1A, B, C. Various relationships between K, Leo, longivety, total mortality
(Z), growth performance (GP, moreau et al. 1986) and ambient
temperature ('C) of Pandalus borealis.
Fig. 2. Comparison of ovigerous periods (including spawning and hatching
periods) of Pandalus borealis from different parts of the world.
Temperatures are approximately the mean annual bottom temperatures
(from Haynes and Wigley, 1969)
•
Fig. 3. Various relationships between carapace length and number of eggs per
female from different areas.
Fig. 4. Relationship between mature female carapace length (CL, mm) and
biomass and landings (relative to 1983) of Pandalus borealis from
Istjord (Spitsbergen), between 1981 and 1991.
Fig. 5. Carapace length trequency distributions of female Pandalus borealis
trom Istjord (Spitsbergen), 1981-1991, indicatlng effect of fishing
exploitation.
Fig. 6. Variability in carapace length (CL, mm), survival (numbers of individuals
standardised to a startlng constant), relative to age (years), and data on
'-00' K, Z, and age at first spawning (AGFS) of Pandalus borealis from
different areas classified on a continuum of "warm" to "cold"
environments. HG = high growth rate. SG = slow growth rate.
~
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TEMPERATU RE ( C)
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36
•
34
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32
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30
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28
26
24
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0.5
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0.6
K
12
10
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Z
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U
4
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25.5 27.0 28.5 30.0 31.5 33.0 34.5 36.0
10
LOO
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6
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4
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2
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11
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Growth performance index
113
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18
20
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24
26
28
CARAPACE LENGTH (mm)
30
32
3
e
e
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L/
20
15
VIII.l981
VIII.l988
N-109
N-790
10
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V111.1 990
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18
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20
22
24
26
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CARAPACE LENGTH (mm)
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10
20
22
l
24
26
28
CARAPACE LENGTH (mm)
30
30
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1000
32
i
,
I
I
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800
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AGE (years)
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10
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