and diiy zoopliiiikton. lint the seusonid cyrle was not significant
betwecvi I5"N and 3"N. 0 1 1 the other hibnd, in the western South Indian
Orrrtn nlotig I 10°K t,lic cwrstawt~ii ii~icroti~kt~on, tigain including large
niimbtw of riiphtm4itix, ili(;rviLsth(l in May -Anpist, iii the waters
twtwcon !)"S and I S":lO'S, with tlw niiiiiniii owwring betweeti t)txembcr
ltiitl I ( ' e b r ~ i ~ y
(I,c~gand, i WN). Our (liit~it in Sagami Hay anti idjaoeiit
waitmd indicatnc that tho shrinip h m a s s is more stable throughout
the y~atr tJim other zoopltinkton. The variation is not statistically
dixtinguishthle t ~ s
a seasonal cy:yc.lo. 'l'hix stability might be due to these
animids having (bither gencmlly 1ong:c~ lifk cycles or slower responses
to environmcntid changes drie to thcir higher trophic level.
Awordiiig to Aietiwa (ISM), tho ))roportion of pelagic shrimps in
the totlad zooplttiikton and microtic~kton biomass in the upper 1 000-m
strittnrn off thr Pticific coast of Juprin was comparatively stable, being
3 to J3'%,. r i i Sagami S a y the shrimps comprise 12% of the total
biomass (Aizawa arid Marumo, 1967).
Th3 rok of shrimps in thc pliinkt,on community is not great in
sub-polar regions and it increases with increasing species diversity
in sribtropiral and tropical regions. In samples with the ORI-100 net,
180 ~ r n
in diimetcr Itrid 1.0 mm in mesh openings, the proportion of the
shrimp biomaw to the zooplankton and inicroiiekton in the upper
I 000-m stxatum at night st 44"N, :%7":IO'N, 30"N, SOON, l0"N and 0"
i h i g 150"E in the western l'iloifi(* in 1)tvember wits 32%, 6-3%,,
I I -6%, (0 500-111 stratum), 1 6 * 7 ~ 1 3
8.7% (0-500-m stratum) and
L5-2%,, rc:dpec.tivelv. These tltitu sugg(viC that shrimps generally
comprise about, lOo(, of the totid hioiniiss at, 0-1 000 m in temperate
and tropicttl regions (Fig. I). A t ci>(*ll sampling station the shrimps,
euphuusiids and fish cqonstituted t he main part of the micronekton and
tlioqe tlnirnds together made up 24 to 72';4, with an average of . 5 6 : / 0
of the whole biomltss. k:uphau~iids were usuully abundant in the
shdlow layera, whereas shrimps arid fish formed the greatest portion
of tltic> bioiniiss in the doep layers. A t it rough estimate the shrimps
form 1 Ti- 25g; o f t he microrirkton arid itre comparable to the euphausiids
(3s- 500;,) ~ t i d the fish (20-450(,).
1 v. \ I #HTI('AL ~)IS'I'RIB~JTION A N D JtELATED ~'RORLEMS
A . &?wral wrtical distribution
Peliigi(: xliritnps iiro clistributrd ut various depths ranging from the
wrfaer to iit Iwst 1 OOO-fi 000 m. Up to now, t,hfir vertic:al distribution
has mostly hceri xtudicd with nets or trtbwls without dosing mechani~mrr.
Sampling h-y the oi)cning-closing net has wsrcdy becn oond uc:krl in the
betwecvi I5"N and 3"N. 0 1 1 the other hibnd, in the western South Indian
Orrrtn nlotig I 10°K t,lic cwrstawt~ii ii~icroti~kt~on, tigain including large
niimbtw of riiphtm4itix, ili(;rviLsth(l in May -Anpist, iii the waters
twtwcon !)"S and I S":lO'S, with tlw niiiiiniii owwring betweeti t)txembcr
ltiitl I ( ' e b r ~ i ~ y
(I,c~gand, i WN). Our (liit~it in Sagami Hay anti idjaoeiit
waitmd indicatnc that tho shrinip h m a s s is more stable throughout
the y~atr tJim other zoopltinkton. The variation is not statistically
dixtinguishthle t ~ s
a seasonal cy:yc.lo. 'l'hix stability might be due to these
animids having (bither gencmlly 1ong:c~ lifk cycles or slower responses
to environmcntid changes drie to thcir higher trophic level.
Awordiiig to Aietiwa (ISM), tho ))roportion of pelagic shrimps in
the totlad zooplttiikton and microtic~kton biomass in the upper 1 000-m
strittnrn off thr Pticific coast of Juprin was comparatively stable, being
3 to J3'%,. r i i Sagami S a y the shrimps comprise 12% of the total
biomass (Aizawa arid Marumo, 1967).
Th3 rok of shrimps in thc pliinkt,on community is not great in
sub-polar regions and it increases with increasing species diversity
in sribtropiral and tropical regions. In samples with the ORI-100 net,
180 ~ r n
in diimetcr Itrid 1.0 mm in mesh openings, the proportion of the
shrimp biomaw to the zooplankton and inicroiiekton in the upper
I 000-m stxatum at night st 44"N, :%7":IO'N, 30"N, SOON, l0"N and 0"
i h i g 150"E in the western l'iloifi(* in 1)tvember wits 32%, 6-3%,,
I I -6%, (0 500-111 stratum), 1 6 * 7 ~ 1 3
8.7% (0-500-m stratum) and
L5-2%,, rc:dpec.tivelv. These tltitu sugg(viC that shrimps generally
comprise about, lOo(, of the totid hioiniiss at, 0-1 000 m in temperate
and tropicttl regions (Fig. I). A t ci>(*ll sampling station the shrimps,
euphuusiids and fish cqonstituted t he main part of the micronekton and
tlioqe tlnirnds together made up 24 to 72';4, with an average of . 5 6 : / 0
of the whole biomltss. k:uphau~iids were usuully abundant in the
shdlow layera, whereas shrimps arid fish formed the greatest portion
of tltic> bioiniiss in the doep layers. A t it rough estimate the shrimps
form 1 Ti- 25g; o f t he microrirkton arid itre comparable to the euphausiids
(3s- 500;,) ~ t i d the fish (20-450(,).
1 v. \ I #HTI('AL ~)IS'I'RIB~JTION A N D JtELATED ~'RORLEMS
A . &?wral wrtical distribution
Peliigi(: xliritnps iiro clistributrd ut various depths ranging from the
wrfaer to iit Iwst 1 OOO-fi 000 m. Up to now, t,hfir vertic:al distribution
has mostly hceri xtudicd with nets or trtbwls without dosing mechani~mrr.
Sampling h-y the oi)cning-closing net has wsrcdy becn oond uc:krl in the