Stock assessment by larval surveys of the winter population of Todarodes pacificus Steenstrup (Cephalopoda: Ommastrephidae), with a review of early works
This is a study of larval abundance and distributional pattern of the winter population of the Japanese common squid, Todarodes pacificus Steenstrup, based on plankton net collections made by the R/V Soyo-Maru during January to March (1959–1976) in the seas extending from the south of Kyushu to the...
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1983
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ftoceanrep:oai:oceanrep.geomar.de:34398 2023-05-15T16:02:09+02:00 Stock assessment by larval surveys of the winter population of Todarodes pacificus Steenstrup (Cephalopoda: Ommastrephidae), with a review of early works Okutani, Takashi Watanabe, Taisuke 1983 text https://oceanrep.geomar.de/id/eprint/34398/ https://oceanrep.geomar.de/id/eprint/34398/7/1265.pdf en eng Taylor & Francis https://oceanrep.geomar.de/id/eprint/34398/7/1265.pdf Okutani, T. and Watanabe, T. (1983) Stock assessment by larval surveys of the winter population of Todarodes pacificus Steenstrup (Cephalopoda: Ommastrephidae), with a review of early works. Biological Oceanography, 2 (2-3-4). pp. 401-431. info:eu-repo/semantics/restrictedAccess Article PeerReviewed 1983 ftoceanrep 2023-04-07T15:28:28Z This is a study of larval abundance and distributional pattern of the winter population of the Japanese common squid, Todarodes pacificus Steenstrup, based on plankton net collections made by the R/V Soyo-Maru during January to March (1959–1976) in the seas extending from the south of Kyushu to the Pacific coast of central and eastern Honshu. The larval abundance index (LI) was compared with CPUE (catch per boat day), an index of recruitment of adult stock size. The main spawning ground of this population is located to the southwest of Kyushu. The larvae (rhynchoteuthion) grow while they are advected by the Kuroshio Current to the northeast. Hence early larvae are more abundant in the west, while advanced larvae are more abundant in the east. Mortality seems to be highest for stages up to several millimeters DML than for later stages. The stock size of the Pacific winter population has fluctuated greatly. It declined since the peak 1960 year class to very low levels. The decrease of the stock size took place in three phases. 1960–1963: While the stock size (CPUE) of the 1960 year class was large, the larval population (LI) produced by this year class was very low, resulting in a decrease of recruitment (CPUE) in following years. 1964–1969: The larval abundance for the 1964 year class was second highest (next to 1960) but the recruitment was remarkably low, probably because of unfavorable conditions for survival during the period between larval and advanced stages. This failure caused a further decrease of larval abundance for the 1965 and subsequent year classes. 1970–1976: The larval abundance remains at a very low level and CPUE has declined since 1970. Because of the short life-span (one year) of this squid, abrupt decreases of larval abundance and/or recruitment have a serious effect on stock size. The future recovery of the stock will depend on biotic and physical conditions that are favorable for the survival of early stages south of Kyushu. A significant positive correlation between catch per effort of ... Article in Journal/Newspaper DML OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) Pacific |
institution |
Open Polar |
collection |
OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) |
op_collection_id |
ftoceanrep |
language |
English |
description |
This is a study of larval abundance and distributional pattern of the winter population of the Japanese common squid, Todarodes pacificus Steenstrup, based on plankton net collections made by the R/V Soyo-Maru during January to March (1959–1976) in the seas extending from the south of Kyushu to the Pacific coast of central and eastern Honshu. The larval abundance index (LI) was compared with CPUE (catch per boat day), an index of recruitment of adult stock size. The main spawning ground of this population is located to the southwest of Kyushu. The larvae (rhynchoteuthion) grow while they are advected by the Kuroshio Current to the northeast. Hence early larvae are more abundant in the west, while advanced larvae are more abundant in the east. Mortality seems to be highest for stages up to several millimeters DML than for later stages. The stock size of the Pacific winter population has fluctuated greatly. It declined since the peak 1960 year class to very low levels. The decrease of the stock size took place in three phases. 1960–1963: While the stock size (CPUE) of the 1960 year class was large, the larval population (LI) produced by this year class was very low, resulting in a decrease of recruitment (CPUE) in following years. 1964–1969: The larval abundance for the 1964 year class was second highest (next to 1960) but the recruitment was remarkably low, probably because of unfavorable conditions for survival during the period between larval and advanced stages. This failure caused a further decrease of larval abundance for the 1965 and subsequent year classes. 1970–1976: The larval abundance remains at a very low level and CPUE has declined since 1970. Because of the short life-span (one year) of this squid, abrupt decreases of larval abundance and/or recruitment have a serious effect on stock size. The future recovery of the stock will depend on biotic and physical conditions that are favorable for the survival of early stages south of Kyushu. A significant positive correlation between catch per effort of ... |
format |
Article in Journal/Newspaper |
author |
Okutani, Takashi Watanabe, Taisuke |
spellingShingle |
Okutani, Takashi Watanabe, Taisuke Stock assessment by larval surveys of the winter population of Todarodes pacificus Steenstrup (Cephalopoda: Ommastrephidae), with a review of early works |
author_facet |
Okutani, Takashi Watanabe, Taisuke |
author_sort |
Okutani, Takashi |
title |
Stock assessment by larval surveys of the winter population of Todarodes pacificus Steenstrup (Cephalopoda: Ommastrephidae), with a review of early works |
title_short |
Stock assessment by larval surveys of the winter population of Todarodes pacificus Steenstrup (Cephalopoda: Ommastrephidae), with a review of early works |
title_full |
Stock assessment by larval surveys of the winter population of Todarodes pacificus Steenstrup (Cephalopoda: Ommastrephidae), with a review of early works |
title_fullStr |
Stock assessment by larval surveys of the winter population of Todarodes pacificus Steenstrup (Cephalopoda: Ommastrephidae), with a review of early works |
title_full_unstemmed |
Stock assessment by larval surveys of the winter population of Todarodes pacificus Steenstrup (Cephalopoda: Ommastrephidae), with a review of early works |
title_sort |
stock assessment by larval surveys of the winter population of todarodes pacificus steenstrup (cephalopoda: ommastrephidae), with a review of early works |
publisher |
Taylor & Francis |
publishDate |
1983 |
url |
https://oceanrep.geomar.de/id/eprint/34398/ https://oceanrep.geomar.de/id/eprint/34398/7/1265.pdf |
geographic |
Pacific |
geographic_facet |
Pacific |
genre |
DML |
genre_facet |
DML |
op_relation |
https://oceanrep.geomar.de/id/eprint/34398/7/1265.pdf Okutani, T. and Watanabe, T. (1983) Stock assessment by larval surveys of the winter population of Todarodes pacificus Steenstrup (Cephalopoda: Ommastrephidae), with a review of early works. Biological Oceanography, 2 (2-3-4). pp. 401-431. |
op_rights |
info:eu-repo/semantics/restrictedAccess |
_version_ |
1766397746164531200 |