No.91 (March,2017)
No.91 (March,2017)
A-541 Mitsuru TORAO and Takashi YANAGIMOTO
Mitochondrial DNA analysis of population structure in
odd-year pink salmon（Oncorhynchus gorbuscha）from the Nemuro
Strait, Hokkaido, Japan
In this study, we evaluated the genetic structure of the odd-year brood line of pink salmon Oncorhynchus gorbuscha populations sampled from the eight rivers in the Nemuro Strait, eastern Hokkaido, in 2015. Pink salmon sampled from the Sashirui, Rausu, Shunkari-kotan, Kunbetsu, Ichani, Shibetsu, Touhoro, and Nishibetsu rivers were examined using the three mitochondrial DNA（mtDNA）regions（COI, ND 5, and D-Loop）. We observed no significant genetic differences in the three mtDNA regions among the pink salmon populations from the eight rivers. However, genetic differences were observed between the odd- and even-year lineages of the pink salmon populations that returned in 2014. Moreover, when comparing COI and ND5 regions with the previously reported data of the Rusha River facing the Okhotsk Sea in 2008 and 2009, significant differences were observed only between different lineage groups. These results suggest that the genetic structure of the pink salmon populations in the Nemuro Strait region have similarities within the even- or odd-year lineages. Moreover, the two-year life cycle of pink salmon has resulted in the odd- and even-year lineages being genetically isolated in eastern Hokkaido. In addition, the haplotype and nucleotide diversities indicated greater differentiation within the even-year than within the odd-year lineage in the Nemuro Strait population.
In this study, we evaluated the genetic structure of the odd-year brood line of pink salmon Oncorhynchus gorbuscha populations sampled from the eight rivers in the Nemuro Strait, eastern Hokkaido, in 2015. Pink salmon sampled from the Sashirui, Rausu, Shunkari-kotan, Kunbetsu, Ichani, Shibetsu, Touhoro, and Nishibetsu rivers were examined using the three mitochondrial DNA（mtDNA）regions（COI, ND 5, and D-Loop）. We observed no significant genetic differences in the three mtDNA regions among the pink salmon populations from the eight rivers. However, genetic differences were observed between the odd- and even-year lineages of the pink salmon populations that returned in 2014. Moreover, when comparing COI and ND5 regions with the previously reported data of the Rusha River facing the Okhotsk Sea in 2008 and 2009, significant differences were observed only between different lineage groups. These results suggest that the genetic structure of the pink salmon populations in the Nemuro Strait region have similarities within the even- or odd-year lineages. Moreover, the two-year life cycle of pink salmon has resulted in the odd- and even-year lineages being genetically isolated in eastern Hokkaido. In addition, the haplotype and nucleotide diversities indicated greater differentiation within the even-year than within the odd-year lineage in the Nemuro Strait population.
A-542 Yasuyuki MIYAKOSHI,Hirofumi HAYANO,Hajime OMORI,Makoto FUJIWARA, Katsumi TAKEUCHI and Mitsuhiro NAGATA
Overwinter survival and smolt run of masu salmon
stocked in upper old-growth and lower clear-cut reaches of a river in northern
Hokkaido
In this study, we compared the overwinter survivals of the juvenile masu salmonan>（Oncorhynchus masou）stocked in the upper old-growth and lower clear-cut reaches of the Masuhoro River in northern Hokkaido, Japan. Two size groups of the hatchery- reared masu salmon（mean weights were 13.9 g for the large-sized group and 9.3 g for the small-sized group）were stocked in the Masuhoro River in October 1998. In the spring of 1999, the numbers of the downward-migrating smolts and resident-type parr were surveyed for each group, and their overwinter survivals were estimated. The overwinter survivals of the large-sized groups（19.2% in the upper and 14.1% in the lower reaches）were higher than those of the small-sized groups（9.4% in the upper and 10.2% in the lower reaches）in both reaches of the river. The average survival rate of the fish stocked in the upper reach（14.3％）was slightly higher than that of the fish stocked in the lower reach（12.2％）. The mean smolt size of the fish stocked in the lower reach （13.0 cm） was larger than that in the upper reach（12.5 cm）. These results indicate that the instream habitat conditions, such as the abundance of instream cover, affected the overwinter survival of the juvenile masu salmon, and the canopy conditions affected the growth of smolts in spring.
In this study, we compared the overwinter survivals of the juvenile masu salmonan>（Oncorhynchus masou）stocked in the upper old-growth and lower clear-cut reaches of the Masuhoro River in northern Hokkaido, Japan. Two size groups of the hatchery- reared masu salmon（mean weights were 13.9 g for the large-sized group and 9.3 g for the small-sized group）were stocked in the Masuhoro River in October 1998. In the spring of 1999, the numbers of the downward-migrating smolts and resident-type parr were surveyed for each group, and their overwinter survivals were estimated. The overwinter survivals of the large-sized groups（19.2% in the upper and 14.1% in the lower reaches）were higher than those of the small-sized groups（9.4% in the upper and 10.2% in the lower reaches）in both reaches of the river. The average survival rate of the fish stocked in the upper reach（14.3％）was slightly higher than that of the fish stocked in the lower reach（12.2％）. The mean smolt size of the fish stocked in the lower reach （13.0 cm） was larger than that in the upper reach（12.5 cm）. These results indicate that the instream habitat conditions, such as the abundance of instream cover, affected the overwinter survival of the juvenile masu salmon, and the canopy conditions affected the growth of smolts in spring.
A-543 Hidetsugu YOSHIDA and Makoto KANAMORI
Effectiveness of using Alexandrium tamarense density
for predicting the occurrence of paralytic shellfish poisoning in scallops in
Funka Bay, Hokkaido, Japan（Note）