ittijust its t l t y t 11 cllst rihr~t ion to sornc ol)t.irnt~rrl s~rhrnilri~lo light rc.girnc.
iuld tnigri~t(hs i t 1 rc.sponi:cb t,o vitrit~t~io~~s, tliurl~itl or short t'cnn, ill light
irltcr~sit,y. 'l1I~is l ) e ~ I ~ i ~ v i o ~ ~ l ~
;tgrchcn wc4I wit11 the tnovenicbnt of the sonic.
s(.i~t,t,t.t+ir~g li~yc~r*s 1.c.c.ordct1011 thc ~ ~ c - l ~ o - s o ~ ~ r ~ t l ~ ' ~ '
with ~ ~ C ( I I I C I I C , V
200 K H z
( I . I . Si\~nl)l(.~ r ( ~ v ( ~ i ~ l d
t h ~ t
t,ho tlist~.il)utions of t,hrcc groups of'
i~trinii~lx wcrtb of'lcrl str't~tifit~(1 i l l or i11'011lld ~citttoring layers ; from
uppt>r to Iowc~~., Ittrphnusia silteilis Sam, S~rgia Irtcms and rr~yctoyhid
fishcs (Otnori 01 r ~ l . , 1!)73). AltJhorlgh Pig. 1 0 shows no evidence of a
" tr~idrtigl~t sil~ltirrg " 11or of a " (li~w11 rise ", there werch on other
oc~rusions iil)l):~~'c~rtt indic:i~tior~n thitt the scatterers tended to move
s o l l ~ c ~ ~ ~ ~ i b t
cI0wlI wiLrd iLf'f('l' stlll~(~t illld ;Lgttill & T ) ~ ) P O B C ~
f hf sllrfa~e just
prior to s t ~ t l r i ~ e
( tiuzit8iL, 1961).
[n the W L L ~ ~ C ~ I ' S
off soutll~rn Citlifortlitt t)uthyscapli divers confirmeti
t list CCI~O('S oft,ett came frorn the depth of 400-500 rn where they saw
so lrli~ny ~Se~geste~ sirnili~ that they cotlld not cou~lt them (Dietz,
1062).
this iLn>iL ~S'ergestes was aor~sisten tly associated with the lower
t~otnponr~lt of t t l c b scattering laycrrs (Barharn, 1963 ; Clarke, 1966).
According to Snlith ( 1 !)54), 1 3 in tlividuals or more of tt palaemorlid
shrimp, Yalnernonetrs vu,lgaris (Say), must be concentrated in 1 cubic
yi~rd (17 i11ds.lrr13) in ordtbr to be recorded as tt sollie scattering layer.
A s tho i ~ ~ . c i ~ s
of itconstic cross-section of R~rgestes sinzilis and Sergin
11cc.~ns iLrc i\l)o111 1-8 t i r i i t b , ~ greater t11i~n that of F"~laemo?~~tcs vulgaris
( ~ i t l v ~ ~ l ~ i t ( ~ ( l
ILS tht\ (Iorst~I iLrCit of t h ~
specivs), the popnlittion tle~isity of
itt I(~:Ls~ 9 illtls./rn3 is ncc:chss:lr.,y for tho sl)(!(-ic:s to co~istit~ute i L scattering
li~yor. I 11 fi~ct,, it, is suggcst,td t h i ~ t I~otll species form scvc:ral small
conll)~~('t swiirrns i l l tJ1ct xtxii; t l l v i~('tt11~1 l)op~~lt~tiotl cier~sit~ within a
swiinu i~xc~tv~cls 20 irl
ITsrri~lI~ tlu. sl~l'irl~l)~ livillg i ~ t . ) ~ ) ~ l s
500 700 111 dcptl-I by day arc.
t ritrlspt~l.t~l~t 01- scbrni t,l~iulspitt~~~it wit 11 scant t cr.ctl rcd c.hrornatol)hores.
At i~l)ol~t, 500 700 111 i \ s~l(lde*l~ fi~l~nitl c~l~allgc' occurs, the upper rnesop(tlt~gic. sl)tv~ios 1)(bi11g rcb1)larcd by those Ilaving u typically uniforrn
scal.let,-l-c~cl ~)igtticwti~tiot~. 'I'l~e pigrnc~r~tut~ion is not distinct ill younger
stirgegex, ir~rt t Ilt. 1)odj. grr~~lt1i~1I.v tarns lrtl in r~tlrrlt~ with increitsing tlcpth
of httbitrbt,, i ~ s
ol)scr\-ccl in A'!j,vt~~llrc.9pis debilis.
13u1~I~cr1t~oi1tl ( 1 !14'i, 1 !)40) i~n(l Yidtlwy~i ( l!j57) hnvc shown that in
thr gtSc.l1rls S(jr.!/r~stss s. 1. tilt' l)t-eseri(c 01- ahscwce of sl)ec.ializc1d Inminest.cXllt n~odific.i~tions of' I 1 1 t h gi~stn~l~epatir gIitn(l (the orgitns of Pesta),
togt.tl~c.r wit11 \ri~t'ii~tiol~s i l l 1)ocly c.olour-itt,iotr. provide i~ nilt,uritl basis
for t ht* r(\cog~~itioll of' twu S I I ~ ~ C I ~ O I ' I L .
'I1I1(b
n~~bgcnus I Y P ~ ! ~ P S ~ P . S
S. S.
iuld tnigri~t(hs i t 1 rc.sponi:cb t,o vitrit~t~io~~s, tliurl~itl or short t'cnn, ill light
irltcr~sit,y. 'l1I~is l ) e ~ I ~ i ~ v i o ~ ~ l ~
;tgrchcn wc4I wit11 the tnovenicbnt of the sonic.
s(.i~t,t,t.t+ir~g li~yc~r*s 1.c.c.ordct1011 thc ~ ~ c - l ~ o - s o ~ ~ r ~ t l ~ ' ~ '
with ~ ~ C ( I I I C I I C , V
200 K H z
( I . I . Si\~nl)l(.~ r ( ~ v ( ~ i ~ l d
t h ~ t
t,ho tlist~.il)utions of t,hrcc groups of'
i~trinii~lx wcrtb of'lcrl str't~tifit~(1 i l l or i11'011lld ~citttoring layers ; from
uppt>r to Iowc~~., Ittrphnusia silteilis Sam, S~rgia Irtcms and rr~yctoyhid
fishcs (Otnori 01 r ~ l . , 1!)73). AltJhorlgh Pig. 1 0 shows no evidence of a
" tr~idrtigl~t sil~ltirrg " 11or of a " (li~w11 rise ", there werch on other
oc~rusions iil)l):~~'c~rtt indic:i~tior~n thitt the scatterers tended to move
s o l l ~ c ~ ~ ~ ~ i b t
cI0wlI wiLrd iLf'f('l' stlll~(~t illld ;Lgttill & T ) ~ ) P O B C ~
f hf sllrfa~e just
prior to s t ~ t l r i ~ e
( tiuzit8iL, 1961).
[n the W L L ~ ~ C ~ I ' S
off soutll~rn Citlifortlitt t)uthyscapli divers confirmeti
t list CCI~O('S oft,ett came frorn the depth of 400-500 rn where they saw
so lrli~ny ~Se~geste~ sirnili~ that they cotlld not cou~lt them (Dietz,
1062).
this iLn>iL ~S'ergestes was aor~sisten tly associated with the lower
t~otnponr~lt of t t l c b scattering laycrrs (Barharn, 1963 ; Clarke, 1966).
According to Snlith ( 1 !)54), 1 3 in tlividuals or more of tt palaemorlid
shrimp, Yalnernonetrs vu,lgaris (Say), must be concentrated in 1 cubic
yi~rd (17 i11ds.lrr13) in ordtbr to be recorded as tt sollie scattering layer.
A s tho i ~ ~ . c i ~ s
of itconstic cross-section of R~rgestes sinzilis and Sergin
11cc.~ns iLrc i\l)o111 1-8 t i r i i t b , ~ greater t11i~n that of F"~laemo?~~tcs vulgaris
( ~ i t l v ~ ~ l ~ i t ( ~ ( l
ILS tht\ (Iorst~I iLrCit of t h ~
specivs), the popnlittion tle~isity of
itt I(~:Ls~ 9 illtls./rn3 is ncc:chss:lr.,y for tho sl)(!(-ic:s to co~istit~ute i L scattering
li~yor. I 11 fi~ct,, it, is suggcst,td t h i ~ t I~otll species form scvc:ral small
conll)~~('t swiirrns i l l tJ1ct xtxii; t l l v i~('tt11~1 l)op~~lt~tiotl cier~sit~ within a
swiinu i~xc~tv~cls 20 irl
ITsrri~lI~ tlu. sl~l'irl~l)~ livillg i ~ t . ) ~ ) ~ l s
500 700 111 dcptl-I by day arc.
t ritrlspt~l.t~l~t 01- scbrni t,l~iulspitt~~~it wit 11 scant t cr.ctl rcd c.hrornatol)hores.
At i~l)ol~t, 500 700 111 i \ s~l(lde*l~ fi~l~nitl c~l~allgc' occurs, the upper rnesop(tlt~gic. sl)tv~ios 1)(bi11g rcb1)larcd by those Ilaving u typically uniforrn
scal.let,-l-c~cl ~)igtticwti~tiot~. 'I'l~e pigrnc~r~tut~ion is not distinct ill younger
stirgegex, ir~rt t Ilt. 1)odj. grr~~lt1i~1I.v tarns lrtl in r~tlrrlt~ with increitsing tlcpth
of httbitrbt,, i ~ s
ol)scr\-ccl in A'!j,vt~~llrc.9pis debilis.
13u1~I~cr1t~oi1tl ( 1 !14'i, 1 !)40) i~n(l Yidtlwy~i ( l!j57) hnvc shown that in
thr gtSc.l1rls S(jr.!/r~stss s. 1. tilt' l)t-eseri(c 01- ahscwce of sl)ec.ializc1d Inminest.cXllt n~odific.i~tions of' I 1 1 t h gi~stn~l~epatir gIitn(l (the orgitns of Pesta),
togt.tl~c.r wit11 \ri~t'ii~tiol~s i l l 1)ocly c.olour-itt,iotr. provide i~ nilt,uritl basis
for t ht* r(\cog~~itioll of' twu S I I ~ ~ C I ~ O I ' I L .
'I1I1(b
n~~bgcnus I Y P ~ ! ~ P S ~ P . S
S. S.