chyths greiitJcr tliitii 700 800 111. (Jeiicrally, the nets and trawls can be
towed lroriaoiitdl,y i i i a stcible c:otitlitioii uhove 400-500 m, but below
thow clel)tJin, I)c~uune ot’ currwit ecluipmcnt, problems, they often
waador vc*rtic.nll,v over a rltiigc of 100-200 m. In addition, the number
of shrimps pvr t i & haul in off en smctll. I n many cases the lower
litnits of pelagic. shrimps am not, defined.
The vertkd distribution of’ shrimps, us well us that of other
rrustaceitii mrtc.roplankton in general, iR principally modified by food
supply, light pwwtxatioii and tanpcrature, although other physical
VtwiaLblCs such i Ls salinit~v, dissol ved oxygen and hydrostatic pressure
must8 also t)c? involved. I’rcsnmal)l,y, sotne of these variables interact,
ats part of ti complex of mvironnieuttd factors.
Generally, tho shrimps occur at dcpths where the food supply is
grtutest. ‘I‘hcir tlistribution is con(-entrated in the depths where more
food (copepods tLnd other mesoplankton) descending from upper layers
is available. Therefore they form comparatively thin layers in
shdlower depths in poorly productive areas, whereas they occur in a
much thicker layer in the productive areas. According to Vinogradov
( I ! W ) , in the subarctic: region of thc north-western Pacific where it is
highly protlucti ve, the shrimp biornuss gradually increased below
500 r n , rewhing its rntLximum in 1 000 3 0c)O m depths. Its proportion
in the totit1 pltmkt,gn biornns8 iiicrcwed with increasing depth. and
W M highcnt i t i tlic 2 000-4 000 m depth. The shrimps practically
dis~ppeni~etl below 6 000 i n , i~lthough isolated specimens of Hynumodorn
gluci(iZi.9 sotnc~tiinc~n ocwirred itt, greatc.r depths. The dominant species
varied tlistitic.tly with iricrc~idng deptJi. Only Swgesks sirnilis and
1ibrvtLc of’ littorid tlccupods wcre found above 200 m. In the 200-800 m
depth the c.oiic*eirt rittioii of Henthtwp~anama (as Gennadas) borealis was
ltwge, whereas in the 760 - 1 500 m irl!/rnrnodora frontulis was the most
ubiuidtiiit np(*iw. Then. N. ylarinlis plttyed the greateRt, role in
plankton in thc 2 000 4 000 in depth (Fig. 2). The ahrirnps were found
oiily nbovc I 000 i n iii the urcas betwccn 30”N and 10”N. In thiH poorly
produc.tivcb t r o p i c d r(*gioii t h i r gr(’iLt(’Ht coiicentration W ~ H
found in the
20& 500 rn tlqjths, tnhtit in, initnc4int,c!ly iuljucont to t h e ~irotlur:tivc*
zoti(’.
111 thc i)i’o(luc.tivc (v{utLtoritd rcgion, the role of H h r i m p was
cwpwislly prwt iri thc 1 000 2 000 tn a m 1 aomewhat smaller in thc
600 1 000 ni t l c p t t i . Below 2 000 m the proportion of shrimp tiomas8
in t h e t o t d plunktori went down to zero (Table 111). As shown in
Fig. 1, our suniplrs showed similar trends although the proportion of
nhi-imp in the total biomass at euch depth was usually greater than
t hitt of Viiiogrttclov due to the different sampling method. The shrimps
were ciistritwted t i l t to 1 ,500 m depth at W N .
4 w H -12
0
towed lroriaoiitdl,y i i i a stcible c:otitlitioii uhove 400-500 m, but below
thow clel)tJin, I)c~uune ot’ currwit ecluipmcnt, problems, they often
waador vc*rtic.nll,v over a rltiigc of 100-200 m. In addition, the number
of shrimps pvr t i & haul in off en smctll. I n many cases the lower
litnits of pelagic. shrimps am not, defined.
The vertkd distribution of’ shrimps, us well us that of other
rrustaceitii mrtc.roplankton in general, iR principally modified by food
supply, light pwwtxatioii and tanpcrature, although other physical
VtwiaLblCs such i Ls salinit~v, dissol ved oxygen and hydrostatic pressure
must8 also t)c? involved. I’rcsnmal)l,y, sotne of these variables interact,
ats part of ti complex of mvironnieuttd factors.
Generally, tho shrimps occur at dcpths where the food supply is
grtutest. ‘I‘hcir tlistribution is con(-entrated in the depths where more
food (copepods tLnd other mesoplankton) descending from upper layers
is available. Therefore they form comparatively thin layers in
shdlower depths in poorly productive areas, whereas they occur in a
much thicker layer in the productive areas. According to Vinogradov
( I ! W ) , in the subarctic: region of thc north-western Pacific where it is
highly protlucti ve, the shrimp biornuss gradually increased below
500 r n , rewhing its rntLximum in 1 000 3 0c)O m depths. Its proportion
in the totit1 pltmkt,gn biornns8 iiicrcwed with increasing depth. and
W M highcnt i t i tlic 2 000-4 000 m depth. The shrimps practically
dis~ppeni~etl below 6 000 i n , i~lthough isolated specimens of Hynumodorn
gluci(iZi.9 sotnc~tiinc~n ocwirred itt, greatc.r depths. The dominant species
varied tlistitic.tly with iricrc~idng deptJi. Only Swgesks sirnilis and
1ibrvtLc of’ littorid tlccupods wcre found above 200 m. In the 200-800 m
depth the c.oiic*eirt rittioii of Henthtwp~anama (as Gennadas) borealis was
ltwge, whereas in the 760 - 1 500 m irl!/rnrnodora frontulis was the most
ubiuidtiiit np(*iw. Then. N. ylarinlis plttyed the greateRt, role in
plankton in thc 2 000 4 000 in depth (Fig. 2). The ahrirnps were found
oiily nbovc I 000 i n iii the urcas betwccn 30”N and 10”N. In thiH poorly
produc.tivcb t r o p i c d r(*gioii t h i r gr(’iLt(’Ht coiicentration W ~ H
found in the
20& 500 rn tlqjths, tnhtit in, initnc4int,c!ly iuljucont to t h e ~irotlur:tivc*
zoti(’.
111 thc i)i’o(luc.tivc (v{utLtoritd rcgion, the role of H h r i m p was
cwpwislly prwt iri thc 1 000 2 000 tn a m 1 aomewhat smaller in thc
600 1 000 ni t l c p t t i . Below 2 000 m the proportion of shrimp tiomas8
in t h e t o t d plunktori went down to zero (Table 111). As shown in
Fig. 1, our suniplrs showed similar trends although the proportion of
nhi-imp in the total biomass at euch depth was usually greater than
t hitt of Viiiogrttclov due to the different sampling method. The shrimps
were ciistritwted t i l t to 1 ,500 m depth at W N .
4 w H -12
0