Predator–prey systems of drifting seaweed communities offthe Tohoku coast, northern Japan, as determined by feeding habitanalysis of phytal animals     

MINORU  SANO  MICHIO  OMORI  KAZUYA  TANIGUCHI 《Fisheries Science》2003,69(2):260-268

ABSTRACT:   We collected phytal animals (fauna associated with drifting seaweeds)off the Tohoku coast in northern Japan in May and June 1994 to examine their feeding habits. Phytal animals were assignedto the following three feeding habit groups: (i) carnivores preyingon crustaceans: a gammarid ( Stenothoe sp.) and a decapodmegalops; (ii) omnivores feeding on crustaceans and pinnate diatoms:a cirripede ( Lepas anserifera ), three gammarids ( Calliopius sp., Jassaslatteryi and J. marmorata ), an isopod ( Idotea metallica ),a decapod crustacean ( Planes cyaneus ), a decapod megalopsand two caprellids ( Caprella penantis and Caprella mutica );and (iii) herbivores grazing on pinnate diatoms, fucoids and seaweedsother than fucoids: three gammarids ( Allorchestes angusta , Amphithoelacertosa and Perampithoe lindbergi ), an isopod ( Cymodocejaponica ) and a polychaete ( Platynereis bicanaliculata ).Pinnate diatoms in the gut contents were composed mainly of Licmophora spp., Navicula spp., Nitzschia spp.and Cocconeis spp. and seaweeds other than fucoids (i.e. Ectocarpussiliculosus and Sphacelaria furcigera ). The latter twoalgae seemed to be epiphytes on drifting seaweeds. These resultssuggest that phytal animals play an important role in drifting seaweed communitiesthrough trophic linkage with two primary producers (i.e. driftingseaweeds and the epiphytes growing on them).  相似文献   

Effects of juvenile size at release and early marine growth on adult return rates for Hokkaido chum salmon (Oncorhynchus keta) in relation to sea surface temperature     

TOSHIHIKO SAITO  TOSHIKI KAGA  KAZUYA NAGASAWA 《Fisheries Oceanography》2011,20(4):278-293

Using path analyses, we investigated relationships between size at release from hatcheries, the early marine growth of juveniles, and adult return rates for chum salmon from five river stocks of Hokkaido, Japan, in relation to sea surface temperature during ocean residence. Marine growth was estimated using scales collected from 11 760 adults of age 0.3 (1980–2004). The growth and survival of each stock appeared to have a different suite of regulatory processes. Interannual variability in return rates was mainly regulated by size at release in two stocks from the Sea of Okhotsk. A similar relationship was found in one stock from the Sea of Japan, but growth during coastal residency also affected their return rates. In two stocks from the Pacific coast of Hokkaido, variability in return rates was not related to size at release or to the coastal growth of juveniles, but with offshore growth in the Sea of Okhotsk, the nursery area for juveniles after leaving Japanese coastal waters. Whereas coastal growth tended to be negatively correlated with size at release in some stocks, offshore growth was positively associated with the August–November sea surface temperature in all stocks. This study confirmed that mortality of juvenile salmon occurred in two phases, during the coastal residency and the late period of the growing season, but the relative importance of both phases varied by stock and region, which probably regulated year‐class strength of Hokkaido chum salmon.  相似文献