11111nI)(~rs in ordi~iary p l a ~ ~ l < t o ~ ~
lict,s 1)ccanse of their i~bility to avoid
jl(at,s. 'rlicy (VLYI
(#;tpt111'(~1 with li~rge nets or t(raw1s. The recent
i n ~ l ) r o v t ~ r ~ ~ ( ~ ~ i t s
in st~n~l)linj: g ~ a r
itlit1 technique, as seen in the Tucker
~ t c - t ('l'~i(:Iii.~*, I !Hi1 ; Ili~vies ;~ntl IJarh~~rn, 1969), Isaacs-Kidd midwater
trawl (I K1\.l'll) ( LHIL~LCY ib~ld Kidci, 1953 ; Aron, 1959), OltI-net (Omori.
19(;5). Bongo-net (Mc(1owi~n and Brown, 1966) and RRIT8 (Clarke,
19(iC)), hiwc ti~cilitat4ltl tho study of pelagic shrimps. However such
large ~ ~ c t s
and trawls are mostly towed in depths shallower thav
1 000 ~ n ,
n11d qt~antitat~ivr collect,ion is difficult because shrimps are
g o i ~ e r i ~ l l ~
pi~tc~hily dist,ributetl both vcrt,ically and horizontally. The
ttvi~ilablc t1;~tit enablo 11s to describe orily cl~aracteristic features of the
species oomposit,ioii and vertical dist~~*ibutio~i in the 0-1 000 m water
roli~rnr~ an(\ the life lii~t~ory of predominant species.
Silicth 1!,63 thc staff of' the plankton laboratory of the Ocean
Itesearc*h I nxtjitute has conducted an extensive plankton survey
using t,he OKI-net and ZKMT. The survey covers a wide area in the
north-western Pacific Ocean in depths ranging from the surface to
about 1 500 rn. During the course of this investigation, attention has
been paid to the analysis of the life of pelagic shrimps as well as other
midwater animals, and we have obtained much information on their
biology although some results have not been published as yet.
Such circunist~nces prompttad me to summarize our present knowlectgc of thcb biology i~ntl c.cology of pelagic shrimps, and review all
nvi~~ili~ble prt.vio~is litc~rirt~urc wit 11 our data. [ hope this study will be
1rsef111 in fitturcl invcstigatiotis 01' the shrirnps in the ocean.
IT. (:EN ERAL FISAT~IRIES OF Y EI,A(XIC SHRIMPS
Tlic 11u111bc~r of' sl)rc.ics of' tlcc.apocl crnstaceans which pans their
p e r ~ n t k ~ i ~ i t
life ill thc prlagicb phiis(. is rr~lativctly small cornparcd with
the richiiesx o f the benthic. fbrnix. Systomatically, a11 reprt*sentative
genera belo~ig to the Ni~t,ant i i ~
h1ac:rura. The number of pelagic species
is less than 210 out of i~ total of about 1 940 species in this supttrscction,
and most of these are i~~clrideci in the subfamilies Aristeinae and
Sergestinao of the section Penaeidea or the families Pasiphaeidae,
Oplophoridae tuid Pandalidae of the section Caridea. Table I show8
major genera and representative species of pelagic shrimps. For some
species, such as Sympasiphaea imperialis Terao and Eupasiphae gibsi
Wood-Mason, which are rarely found in deep water, i t is uncertain
whether thcy have a true pelagic mode of life. Several benthic shrimps
arv known t,o be distributed in midwater at night, although they live
on or in tht. bottom ~ediment~s by day. I t is probable that the species
in such geiiera iia Ariatapus, Aristeon3orpha and Benthcscymus of the
lict,s 1)ccanse of their i~bility to avoid
jl(at,s. 'rlicy (VLYI
(#;tpt111'(~1 with li~rge nets or t(raw1s. The recent
i n ~ l ) r o v t ~ r ~ ~ ( ~ ~ i t s
in st~n~l)linj: g ~ a r
itlit1 technique, as seen in the Tucker
~ t c - t ('l'~i(:Iii.~*, I !Hi1 ; Ili~vies ;~ntl IJarh~~rn, 1969), Isaacs-Kidd midwater
trawl (I K1\.l'll) ( LHIL~LCY ib~ld Kidci, 1953 ; Aron, 1959), OltI-net (Omori.
19(;5). Bongo-net (Mc(1owi~n and Brown, 1966) and RRIT8 (Clarke,
19(iC)), hiwc ti~cilitat4ltl tho study of pelagic shrimps. However such
large ~ ~ c t s
and trawls are mostly towed in depths shallower thav
1 000 ~ n ,
n11d qt~antitat~ivr collect,ion is difficult because shrimps are
g o i ~ e r i ~ l l ~
pi~tc~hily dist,ributetl both vcrt,ically and horizontally. The
ttvi~ilablc t1;~tit enablo 11s to describe orily cl~aracteristic features of the
species oomposit,ioii and vertical dist~~*ibutio~i in the 0-1 000 m water
roli~rnr~ an(\ the life lii~t~ory of predominant species.
Silicth 1!,63 thc staff of' the plankton laboratory of the Ocean
Itesearc*h I nxtjitute has conducted an extensive plankton survey
using t,he OKI-net and ZKMT. The survey covers a wide area in the
north-western Pacific Ocean in depths ranging from the surface to
about 1 500 rn. During the course of this investigation, attention has
been paid to the analysis of the life of pelagic shrimps as well as other
midwater animals, and we have obtained much information on their
biology although some results have not been published as yet.
Such circunist~nces prompttad me to summarize our present knowlectgc of thcb biology i~ntl c.cology of pelagic shrimps, and review all
nvi~~ili~ble prt.vio~is litc~rirt~urc wit 11 our data. [ hope this study will be
1rsef111 in fitturcl invcstigatiotis 01' the shrirnps in the ocean.
IT. (:EN ERAL FISAT~IRIES OF Y EI,A(XIC SHRIMPS
Tlic 11u111bc~r of' sl)rc.ics of' tlcc.apocl crnstaceans which pans their
p e r ~ n t k ~ i ~ i t
life ill thc prlagicb phiis(. is rr~lativctly small cornparcd with
the richiiesx o f the benthic. fbrnix. Systomatically, a11 reprt*sentative
genera belo~ig to the Ni~t,ant i i ~
h1ac:rura. The number of pelagic species
is less than 210 out of i~ total of about 1 940 species in this supttrscction,
and most of these are i~~clrideci in the subfamilies Aristeinae and
Sergestinao of the section Penaeidea or the families Pasiphaeidae,
Oplophoridae tuid Pandalidae of the section Caridea. Table I show8
major genera and representative species of pelagic shrimps. For some
species, such as Sympasiphaea imperialis Terao and Eupasiphae gibsi
Wood-Mason, which are rarely found in deep water, i t is uncertain
whether thcy have a true pelagic mode of life. Several benthic shrimps
arv known t,o be distributed in midwater at night, although they live
on or in tht. bottom ~ediment~s by day. I t is probable that the species
in such geiiera iia Ariatapus, Aristeon3orpha and Benthcscymus of the