NAGAWASA Kazue

OSADA Makoto

English

紀要類（bulletin）Symposium mini reviewdepartmental bulletin pape

OSADA, Makoto

NAGAWASA, Kazue

Tohoku University Repository (TOUR) / 東北大学機関リポジトリ

Fisheries-based Evaluation of CarryingCapacity for Scallops in Ogatsu Bay著者 OSADA Makoto, NAGAWASA Kazuejournal orpublication titleJournal of Integrated Field Sciencevolume 16page range 19-20year 2019-03URL http://hdl.handle.net/10097/00125663 191.  IntroductionScallop farming is one of major aquaculture industries in the Sanriku coast of northern Japan. The earthquake and huge tsunami on March 11 in 2011 brought devastating losses in the scallop culture as well as oyster, sea squirt and marine algae etc. In the process of recovering and reconstructing the aquaculture farm lost by the natural disasters, evaluation of environmental carrying capacity in each farming site is an essential task to guarantee a sustainable production of filter feeders like a scallop in the future. The environmental carrying capacity of the cultured filter feeders is basically considered by food availability based on a primary production in aquaculture waters. We focused on a transition of scallop farming after the disaster in Ogatsu Bay where scallops are predominantly produced and recovering began first in the coast of Miyagi prefecture. We monitored productivity based on the number of facility and annual production in the bay, and growth state (e.g., size, weight and indices of adductor muscle and gonad) were compared to pre-quake state with annual food availability.2.  Transition of productivity and growth state of scallopThe growth state was calculated as a production amount per rope based on the statistical data on the number of facilities and annual production in the bay provided by fisherman cooperative and compared to pre-quake level. In parallel, the scallops farmed by ear-hanging method at two farming sites of Ogatsu Bay were also used for another estimation of growth state. Shell size, weight of softbody, gonad and adductor muscle, and indices of each organ was evaluated and compared to the pre-quake data and between cultured depths divided into two layers each year. The overproduction of scallop beyond environmental carrying capacity in Ogatsu Bay was expected by a decline of growth state under certain level of food availability based on a primary production.The number of facilities for scallop farming and the annual production of the farmed scallop in Ogatsu Bay recovered to about 66% and 76% in 2014, respectively, compared to the data in 2010 (before the earthquake disaster). This means the number scallop cultured under the facilities was increasing every year since 2012 just after tsunami disaster. The productivity of scallop, which was calculated as an amount of production per rope where scallops were ear-hanged, in 2014 showed at 23.7 kg per rope lower than 30.9 kg per rope shown in 2013, even though the annual productions in 2013 and 2014 were almost the same. Total amount of chlorophyll a (above 20 m depth) throughout a year did not differ between 2014 and 2013, suggesting the same fluctuation level of the primary production as past. In 2014, the low-growth scallops (i.e., shell size, soft body weight) cultured in deeper layer was observed at two different farming sites as previously found before the earthquake in 2010. The adductor muscle index (adductor muscle weight (g)/whole soft body weight without gonad (g) *100) was kept at about 38 in both layers higher than previous level before the earthquake.3. DiscussionA food availability during study period was stable and kept at the same level as pre-quake period. The decline of productivity was observed in 2014 during the process of an increasing number of scallops. In the same year the low growth of deeper layer group compared with shallow layer group, which was markedly different from previous year, but similar to low growth at deeper layer in pre-quake year of 2010. It was suggested that the decreasing productivity was resulted from low growth of scallop cultured in lower layer of ear-hanging rope and a food availability for good growth of scallop was not sufficient for the scallops farmed in deeper layer in Ogatsu ©2019 Field Science Center, Graduate School of Agricultural Science, Tohoku UniversityJournal of Integrated Field Science, 16, 19-20Symposium mini reviewFisheries-based Evaluation of Carrying Capacity for Scallops in Ogatsu BayMakoto OSADA and Kazue NAGAWASA Graduate School of Agricultural Science, Tohoku University, Sendai 980-8572, JapanKeywordsscallop, productivity, growth, food availabilityCorresponding Author Makoto OSADA, makoto.osada.a8@tohoku.ac.jpAbstractCarrying Capacity for Scallop Culture in Ogatsu BayM. Osada and K. Nagawasa20Bay in 2014. The state of scallop farming in 2014 was thought to reach first stage of overproduction showing low productivity with low growth at deeper layer, but still kept the same level of adductor muscle proportion as an indicator for second stage overproduction (Fig. 1).It may be a time that the producers need to re-consider and regulate the amount of production to accomplish a sustainable and efficient production of scallop as a filter feeder on the basis of environmental carrying capacity estimated in Ogatsu Bay.AcknowledgementsWe are grateful to the farmers of Fishery Cooperative in Ogatsu Bay for their support to collect cultured scallops and the staff of the Onagawa Field Science Center of Tohoku University for their assistance. This work was supported by the Tohoku Ecosystem-Associated Marine Sciences (TEAMS) from the Japanese Ministry of Education, Culture, Sports, Science and Technology. This work has been published in Nippon Suisan Gakkaishi, 82 (3), 321-329, 2016.ReferencesNagasawa, K., D. Takahashi, N. Itoh, K. Takahashi and M. Osada (2016) Growth of Japanese scallop Mizuhopecten yessoensis farmed by the ear-hanging method between different water layers and estimation of the productivity for farmed scallops in Ogatsu Bay (northeastern Japan) following the 2011 great east Japan earthquake. Nippon Suisan Gakkaishi, 82 (3): 321-329 (in Japanese).Osada, M., K. Nagasawa and A. Sekizawa (2018) Approaches to the restoration of bivalve aquaculture after tsunami disaster, Nippon Suisan Gakkaishi, 84 (6): 1070-1073.Fig. 1.  Present state of productivity and growth characteristic of scallop farming in relation to food availability and scallop density in Ogatsu Bay.

Fisheries-based Evaluation of Carrying Capacity for Scallops in Ogatsu Bay

紀要類（bulletin）Oral Sessionsdepartmental bulletin pape

Fisheries-based Evaluation of CarryingCapacity for Scallops in Ogatsu Bay著者 OSADA Makoto, NAGAWASA Kazuejournal orpublication titleJournal of Integrated Field Sciencevolume 16page range 29-29year 2019-03URL http://hdl.handle.net/10097/00125671 29Oral Session1-7. Fisheries-based Evaluation of Carrying Capacity for Scallops in  Ogatsu BayMakoto OSADA and Kazue NAGAWASAGraduate School of Agricultural Science, Tohoku University, Sendai 980-8572, JapanScallop farming is one of major aquaculture industries in the Sanriku coast of northern Japan. The earthquake and tsunami on March 11 in 2011 brought devastating losses in the scallop culture as well as oyster, sea squirt and marine alga etc. In the process of recovering and reconstructing the aquaculture farm lost by the natural disasters, evaluation of environmental carrying capacity in each farming site is an essential task to guarantee a sustainable production of filter feeders like a scallop in the future. We focused on a transition of scallop farming after the disaster in Ogatsu Bay where scallops are predominantly produced and recovering began first in the coast of Miyagi prefecture. We investigated productivity based on the number of facility and annual production in the bay, and growth state compared to pre-quake state with annual food availability. The decrease in productivity of scallop resulting from a low growth of scallops in deeper layer was observed in Ogatsu Bay in 2014, suggesting that a food availability reducing with depth was not sufficient for the increasing scallops farmed in deeper layer in Ogatsu Bay in 2014. It may be a time that the farmers need to reconsider and regulate the amount of production to accomplish a sustainable and efficient production of scallop as a filter feeder on the basis of environmental carrying capacity estimated in Ogatsu Bay.Makoto OSADA (E-mail: makoto.osada.a8@tohoku.ac.jp)Professor, Laboratory of Aquacultural Biology. Bivalve mollusks is commercially important as an aquaculture organism in the world. The artificial seed production of bivalves based on reproductive control is required for improvement of productiveity in aquaculture. I focus on gonial cell multiplication, oocyte growth, and spawning (oocyte and sperm release) in bivalve mollusks, in which these processes are precisely regulated by endocrine systems. Some of endocrine regulatory molecules are shared among animals with some homology to vertebrates and others possess unique molecules to regulate reproduction.1.    Thitiphuree, T., K. Nagasawa and M. Osada (2019) Molecular identification of steroidogenesis-related genes in scallops and their potential roles in gametogenesis. The Journal of Steroid Biochemistry and Molecular Biology, 186: 22-33.2.    Osada, M. and T. Matsumoto (2017) “Endocrine control of gametogenesis and spawning in bivalves” in Physiology of Molluscs, Vol. 2(6), Apple Academic Press, pp. 179-219.

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Fisheries-based Evaluation of Carrying Capacity for Scallops in Ogatsu Bay

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