'I-IIE UIOI,O(:Y 01' P K I L A ~ ~ I C '
S I I I ~ L M P S IN ' C ~ I E OCEAN
25 1
oc.cbttt-s i ~ t 110011 ;111(1 t ~ ~ i ( l ~ t ~ g l t t
~.c~sl~c-c.t ivclly 'l'hcl ibrnl~lit rldt. of' vertical
111ig1-t~tioti I - ; L I I ~ ~ ( ~ ~
f' vo11t lcbss ~ I I ~ I I I
I00 t t t it1 11108t~ neriti(* sl)c%ci(w to 600
700 111 ctv IIIIII*I* 111 ~('~1'l'il.l h j ) ( V ' i l ' ~ 01' (~'PILV(&S itt~d S C ~ ~ ~ I L .
How' -
cbVelp, tit(. 111i~jol'it~y Of' 1l1c~nopl~~ilgi(~ it]ll)t';ll'N to I'illlgC t)~t\\~eCll 100 ~ l l d .
400 111.
f l
Lhc- tlit~r~~i\l rrlig~-iet~ion is c*onsid(brt.ci to bc inhrrent, and the endogctc~is r t 1 1 i s t i t I i i . l%rldjakov (1970) stated that the
t t i t ~ n ~ i ~ l
vc.rt,ic.i~l tttigrl~tio~l is t l l ~ r(*st~lt~ of a11 alt(*rnatioxl of phases of
higlt ittlri low :l(*tiviLy of' 111)~ilrd r~~ot~ioti. 'l1he rnaximurn velocity of
clown\vitrtl t~ligri~t,iot~ of iL ~ ) o p ~ ~ l t ~ t i o ~ ~
of rVcr!/ia ~ T I P I J ~ M ,
obsc1rved hy net
~ibll1l)iiltg~ i ~ l i ( 1 I)s il(~ho-so~~ncic>r, was ~bbout fi.2 tn/h it1 tho ~ o c a l
sti~gc..
I5 rn/h in csa~-l,y pod-lurviil stages and 108 rn/h in aclults, whereas the
41 vcxra~gc sinking velocity of freshly killed individuals under similar
t~~~vironn~c.nt,i\l oonditionq was about 6.6 m/h, 16 m/h and 120 m/h
r't~sl)~ctivc~ly (O~nori, unpublished). Thc velocity of the descentling
~ ~ q ) t ~ l a t , i o ~ ~
r i ~ n t ~ o t
be deemed the velocit,y of' actual downward movenlc111t of i ~ t i
inciividual ,shrimp, 1,ecaust: the ~llrirnp swims intermittently
1111, t1101t down, hut t,hi> ntat ~novernent is t l o w ~ l ~ i ~ r ~ t .
However, a simple
c*otlt pi~risor~ of t l ~ t b sinkil~g v(~loc~it,y of thr freshly killed individuitls of
AS. 11rrrr~s with the. tit~sc.c~t11 vc.loc*ity ofthe ])opulat+ion appears to support,
Itl~dji~ko\.'s cbo~lsitlerrttio~~. a t k ' i ~ ~ t
i l l ~ , I I ( ~
CBRO of' f.?pipc>lagic. and upper
n~c~sopt~litgit. sllrir1)ps hi~ving to x1)('~ifi(' floating ,rde~i(*(~s. that the
I K I ~ I I I ~ ; L ~ ~ ~ I \
is i~ttribt~t~c.tl to piissivc~ sit~ltil~g duritlg the f)hitsta of low
loc.orr~otol.~~ irc.tivit,y. At tht> sittltt* ti~n(>, it. is ~ L I ) I ) A I * ~ I ~ ~
that the migrants
I~c~vc, t,hc ('i~l)it('itr~ t,o 21 (vrtain P X ~ ~ * I I ~
t , ~ 1'01itr01 their locornotory
ac'tivit,,y so tBlli~t tjll(>y (lati agg~'c~gi~t(~ t,o optimurn c~nvironmental conditions. 'l'lli~ is evide~lt from a vitri(%t~l of sourcrs including echoso~~ntlir~g fiw ti)(. dctc*ction of tltc! uoni(8 s(-t~tf(*ring laycr~ wllc.n* in many
(*ILNLW t ht x sl)(~bd of tllr (It~~(~erldi11g ~)ol)l~litt io11 is ~imilar t,o that of the
irst~elltling l~op~llntion.
I'revio~~s work i ~ ~ l d
O I I ~ ( l i ~ t i ~
sttgg(-st tJhi~tg, principally, various
spwicbs in t I)(* I I I ) ~ ( T 1 OOO-I~I ~tritttitrl h4v (liiy III~IY IJC grouped ci(bcording
to thchir ~ ( \ ~ ' t i ( ' i ~ l
~nigritt~iol~ into fivt. ~ I ' O I I ~ H (Fig. ri). rlth(hsta g~~oups
~III-ludc o11ly atlolt~sc.c~r~ts i ~ ~ i d
aclults.
( 1 ) h1:litl ptrt of' populi~tio11 in Itp1)er 1.50 III Iilyc~r botli night and clay.
Nr1.itic1 i~tld c\~~il~elagic. ,s~)et*irs inc.luding all rtlembers of the genera
.-I r.c>tr.s. I ' e i ~ o s i ~ ~ i d
1,r~~Zfor.
(2) $ul.fi~c.c~ - - 100 nl (night) to 150-300 111 ((lay).
ITppt'r rncsopelagic sl)ccies : 8or!jcslcn nrcbtic.us, S. si~nilis, S ~ r g i a
ltrce~ts. I'rcxiplmir~rt sivndo ( 13 ixso).
S I I I ~ L M P S IN ' C ~ I E OCEAN
25 1
oc.cbttt-s i ~ t 110011 ;111(1 t ~ ~ i ( l ~ t ~ g l t t
~.c~sl~c-c.t ivclly 'l'hcl ibrnl~lit rldt. of' vertical
111ig1-t~tioti I - ; L I I ~ ~ ( ~ ~
f' vo11t lcbss ~ I I ~ I I I
I00 t t t it1 11108t~ neriti(* sl)c%ci(w to 600
700 111 ctv IIIIII*I* 111 ~('~1'l'il.l h j ) ( V ' i l ' ~ 01' (~'PILV(&S itt~d S C ~ ~ ~ I L .
How' -
cbVelp, tit(. 111i~jol'it~y Of' 1l1c~nopl~~ilgi(~ it]ll)t';ll'N to I'illlgC t)~t\\~eCll 100 ~ l l d .
400 111.
f l
Lhc- tlit~r~~i\l rrlig~-iet~ion is c*onsid(brt.ci to bc inhrrent, and the endogctc~is r t 1 1 i s t i t I i i . l%rldjakov (1970) stated that the
t t i t ~ n ~ i ~ l
vc.rt,ic.i~l tttigrl~tio~l is t l l ~ r(*st~lt~ of a11 alt(*rnatioxl of phases of
higlt ittlri low :l(*tiviLy of' 111)~ilrd r~~ot~ioti. 'l1he rnaximurn velocity of
clown\vitrtl t~ligri~t,iot~ of iL ~ ) o p ~ ~ l t ~ t i o ~ ~
of rVcr!/ia ~ T I P I J ~ M ,
obsc1rved hy net
~ibll1l)iiltg~ i ~ l i ( 1 I)s il(~ho-so~~ncic>r, was ~bbout fi.2 tn/h it1 tho ~ o c a l
sti~gc..
I5 rn/h in csa~-l,y pod-lurviil stages and 108 rn/h in aclults, whereas the
41 vcxra~gc sinking velocity of freshly killed individuals under similar
t~~~vironn~c.nt,i\l oonditionq was about 6.6 m/h, 16 m/h and 120 m/h
r't~sl)~ctivc~ly (O~nori, unpublished). Thc velocity of the descentling
~ ~ q ) t ~ l a t , i o ~ ~
r i ~ n t ~ o t
be deemed the velocit,y of' actual downward movenlc111t of i ~ t i
inciividual ,shrimp, 1,ecaust: the ~llrirnp swims intermittently
1111, t1101t down, hut t,hi> ntat ~novernent is t l o w ~ l ~ i ~ r ~ t .
However, a simple
c*otlt pi~risor~ of t l ~ t b sinkil~g v(~loc~it,y of thr freshly killed individuitls of
AS. 11rrrr~s with the. tit~sc.c~t11 vc.loc*ity ofthe ])opulat+ion appears to support,
Itl~dji~ko\.'s cbo~lsitlerrttio~~. a t k ' i ~ ~ t
i l l ~ , I I ( ~
CBRO of' f.?pipc>lagic. and upper
n~c~sopt~litgit. sllrir1)ps hi~ving to x1)('~ifi(' floating ,rde~i(*(~s. that the
I K I ~ I I I ~ ; L ~ ~ ~ I \
is i~ttribt~t~c.tl to piissivc~ sit~ltil~g duritlg the f)hitsta of low
loc.orr~otol.~~ irc.tivit,y. At tht> sittltt* ti~n(>, it. is ~ L I ) I ) A I * ~ I ~ ~
that the migrants
I~c~vc, t,hc ('i~l)it('itr~ t,o 21 (vrtain P X ~ ~ * I I ~
t , ~ 1'01itr01 their locornotory
ac'tivit,,y so tBlli~t tjll(>y (lati agg~'c~gi~t(~ t,o optimurn c~nvironmental conditions. 'l'lli~ is evide~lt from a vitri(%t~l of sourcrs including echoso~~ntlir~g fiw ti)(. dctc*ction of tltc! uoni(8 s(-t~tf(*ring laycr~ wllc.n* in many
(*ILNLW t ht x sl)(~bd of tllr (It~~(~erldi11g ~)ol)l~litt io11 is ~imilar t,o that of the
irst~elltling l~op~llntion.
I'revio~~s work i ~ ~ l d
O I I ~ ( l i ~ t i ~
sttgg(-st tJhi~tg, principally, various
spwicbs in t I)(* I I I ) ~ ( T 1 OOO-I~I ~tritttitrl h4v (liiy III~IY IJC grouped ci(bcording
to thchir ~ ( \ ~ ' t i ( ' i ~ l
~nigritt~iol~ into fivt. ~ I ' O I I ~ H (Fig. ri). rlth(hsta g~~oups
~III-ludc o11ly atlolt~sc.c~r~ts i ~ ~ i d
aclults.
( 1 ) h1:litl ptrt of' populi~tio11 in Itp1)er 1.50 III Iilyc~r botli night and clay.
Nr1.itic1 i~tld c\~~il~elagic. ,s~)et*irs inc.luding all rtlembers of the genera
.-I r.c>tr.s. I ' e i ~ o s i ~ ~ i d
1,r~~Zfor.
(2) $ul.fi~c.c~ - - 100 nl (night) to 150-300 111 ((lay).
ITppt'r rncsopelagic sl)ccies : 8or!jcslcn nrcbtic.us, S. si~nilis, S ~ r g i a
ltrce~ts. I'rcxiplmir~rt sivndo ( 13 ixso).