water at thc post-larval stage arid move seaward again when they
have matured sexudly (Idyll imd Sission, 19(i6 ; Kurata, 1971). Larvae
of oceanic pelagic xhrinips, 11s nieatio~ieci previously, live nearer the
sttrfwc tliiin (lo thc adiilts, ttrd thc watcr layers occupied by different
stages may be moving iit different rates und even in different directions.
In order to aiiswer the questions about how far a larva can travel and
whiit proportion of larvat. are lost through being carried into unsuitable
onvironincnts, many more 81 udics art’ neccled on the behaviour of
larvae at, various stages of tbvt4opmcwt kind on the movement of
wnkw iniLnsw rit vctrious plwes arid tirncs. I am of the opinion that
t?vm for spwies which show tt very wide geographicd distribution,
reproduction iiricl replocwnrnt of it popiilation generally take place in
tt restricted itrcti.
Seasonal off’sliore-inshore movement which might be related to
reproduction was observed in Sergestes similis off the Oregon coast.
The largest inshore catches were made during winter, the largest
offshorr catches were during summer (Pearcy and Forss, 1969).
VLIT. FOOD RELAWONSHIPS
A. Il’ood and feeding
(Yrcnerdly, dl~capod crustticcans tire prcdators or omnivores, and
c’nn utilizc ViLrioiIs k i d s of food. They may scavenge decomposing
d c d ninteriiil in ritldition to taking living prey. G u t contents of pelagic
shrimps Lire uwinlly wcll-macernt,rd cmtl mostly unidentifiable. This
arnorphous nitLteriti1 appcarrt to consist primarily of crustacean fragrnents and matted aggregations of fil)rous and granular debrin. Somc:
may httve originated from dig(vitrd phytoplankton. At any rate, this
is not, ciitircly thc result of digestive prowsse8, but also a r i m from the
decomposed nature of the material at the tinw of its ingention. The
recognizablc remains siiggcst that smtLII crustaceans, caluiioid copepods
and euphausiids romprise the bulk of tlw diet, but frustulefl of dirttomn,
k’orsminiferit, hooks of t:haotognaths aiitl fish scales are freqiiently
present. There in also some indication of cimnibulism.
We cannot ignore the fact that shrimps feed on organisms after
they are in the net (Cham, 1940). This suggest8 that the cxamiriation
of gut contents in the past) might httve Ird to some misunderstanding
of their normal diet when the shrimps were collected in plankton nets.
According to Jiidkiiis and Fleminger (1972) thc diversity of calanoid
species froin the guts of Sergeetes sitnil& wax much greater in net,
samples tlitlri in fish-caught specimens : 42 species were identified in
the net samples, but only 7 were found in the fish samples. They
have matured sexudly (Idyll imd Sission, 19(i6 ; Kurata, 1971). Larvae
of oceanic pelagic xhrinips, 11s nieatio~ieci previously, live nearer the
sttrfwc tliiin (lo thc adiilts, ttrd thc watcr layers occupied by different
stages may be moving iit different rates und even in different directions.
In order to aiiswer the questions about how far a larva can travel and
whiit proportion of larvat. are lost through being carried into unsuitable
onvironincnts, many more 81 udics art’ neccled on the behaviour of
larvae at, various stages of tbvt4opmcwt kind on the movement of
wnkw iniLnsw rit vctrious plwes arid tirncs. I am of the opinion that
t?vm for spwies which show tt very wide geographicd distribution,
reproduction iiricl replocwnrnt of it popiilation generally take place in
tt restricted itrcti.
Seasonal off’sliore-inshore movement which might be related to
reproduction was observed in Sergestes similis off the Oregon coast.
The largest inshore catches were made during winter, the largest
offshorr catches were during summer (Pearcy and Forss, 1969).
VLIT. FOOD RELAWONSHIPS
A. Il’ood and feeding
(Yrcnerdly, dl~capod crustticcans tire prcdators or omnivores, and
c’nn utilizc ViLrioiIs k i d s of food. They may scavenge decomposing
d c d ninteriiil in ritldition to taking living prey. G u t contents of pelagic
shrimps Lire uwinlly wcll-macernt,rd cmtl mostly unidentifiable. This
arnorphous nitLteriti1 appcarrt to consist primarily of crustacean fragrnents and matted aggregations of fil)rous and granular debrin. Somc:
may httve originated from dig(vitrd phytoplankton. At any rate, this
is not, ciitircly thc result of digestive prowsse8, but also a r i m from the
decomposed nature of the material at the tinw of its ingention. The
recognizablc remains siiggcst that smtLII crustaceans, caluiioid copepods
and euphausiids romprise the bulk of tlw diet, but frustulefl of dirttomn,
k’orsminiferit, hooks of t:haotognaths aiitl fish scales are freqiiently
present. There in also some indication of cimnibulism.
We cannot ignore the fact that shrimps feed on organisms after
they are in the net (Cham, 1940). This suggest8 that the cxamiriation
of gut contents in the past) might httve Ird to some misunderstanding
of their normal diet when the shrimps were collected in plankton nets.
According to Jiidkiiis and Fleminger (1972) thc diversity of calanoid
species froin the guts of Sergeetes sitnil& wax much greater in net,
samples tlitlri in fish-caught specimens : 42 species were identified in
the net samples, but only 7 were found in the fish samples. They