Flexible seaward migration of Dolly Varden Salvelinus malma in the Shiretoko Peninsula, Hokkaido, Japan
The migratory history of Dolly Varden Salvelinus malma was investigated in 30 streams in the Shiretoko Peninsula, Hokkaido, Japan, which is in the southern part of their distribution. Captured Dolly Varden were classified into two categories by their body coloration: silvery fish were thought to be an anadromous form, and non-silvery fish a fluvial form that remains in freshwater throughout its life. Forty-seven of 1,739 Dolly Varden collected in the spring and ten of 2,126 Dolly Varden collected in the autumn were silvery fish. Twenty silvery fish and 120 non-silvery fish were examined by analysis of otolith Sr:Ca ratio. Three silvery fish from autumn and 15 non-silvery fish had migrated to salt water or brackish water. The other specimens of silvery fish were regarded as smolt or pre-smolt before seaward migration. The present study suggests that Dolly Varden in the Shiretoko Peninsula have a flexible migratory history, where some of the non-silvery fish utilize marine environments while some individuals follow an anadromous life history.
Migratory timing of masu salmon and Dolly Varden smolts exiting the Uebetsu River near the Shiretoko World Heritage Site, Hokkaido, Japan, and potential angling effects
Numbers of masu salmon and Dolly Varden in streams in the Shiretoko Peninsula, location of the Shiretoko World Heritage Site in north eastern Hokkaido, appear to be declining. One concern is whether masu salmon smolts continue to migrate during July, after the existing May to June angling closure established to protect migrating smolts in eastern Hokkaido. Smolt timing and relative abundances were monitored in the Uebetsu River near the World Heritage Site from May to July during 2005–2007. Each year some masu salmon smolts emigrated during July, especially in 2005 when 82% of smolts captured were caught that month. In contrast, most anadromous Dolly Varden smolts emigrated prior to early June when stream temperatures <8°C. Mean fork lengths of smolts in both species decreased during the runs. The current fishing closure period (May to June) may be insufficient to protect masu salmon smolts in this unique area from angling.
Morphological characterization of Eustrongylides sp. larvae (Nematoda, Dioctophymatoidea) parasite of Rhinella marina (Amphibia: Bufonidae) from Eastern Amazonia.
Absctract Eustrongylides spp. nematodes have birds as final hosts and uses other vertebrates as intermediate/paratenic host (fish, amphibians and reptiles) and have zoonotic potential. In amphibians, the larvae may be located in the subcutaneous tissues, liver and mesentery, between the muscle fibres, especially in the lower limbs. Rhinella marina, which is widely observed in Brazil, has exhibited complex diversity in its helminth fauna, reflecting the unique habitat of the Amazon biome. For the first time, this study describes the morphological aspects of third-stage larvae of Eustrongylides sp. in Rhinella marina from Santa Cruz do Ararí, Marajó Archipelago, Eastern Amazonia, using light and scanning electron microscopy.