Differences in conservation candidate tidal rivers by cross‐taxon analysis in the Japanese temperate zone

Abstract

1. For effective biodiversity conservation, verifying the correspondence of conservation sites among taxa and identifying the environmental characteristics of these sites are essential; however, only a few such studies have been performed in estuaries. The aim of the present study was to verify the surrogacy of estuarine gobies and crabs, to identify tidal rivers of high conservation priority, and to describe their environmental characteristics. 2. Distribution data for gobies and crabs were collected from 158 tidal rivers in the Kyushu region, Japan. Three conservation scenarios were analysed based on the distribution data of gobies alone, of crabs alone, and of both taxa, in order to assess the correspondence of the conservation candidates (i.e. tidal rivers) between taxa. 3. The degree of correspondence was poor for the candidates selected on the basis of the distribution data of gobies or crabs separately. More efficient candidates were selected based on the data for both taxa. The environmental characteristics of tidal rivers with high irreplaceability for conservation differed between the taxa. Tidal rivers forming and maintaining large tidal flats covered with fine sediment might have high irreplaceability for goby conservation, whereas rivers with saltmarshes connected to supratidal and intertidal zones might have high irreplaceability for crab conservation. 4. Tidal rivers with a high priority for conservation were identified by overlapping the candidates for three scenarios. These tidal rivers are not necessarily large, but have steep basins with river mouths that are less exposed to ocean waves. Moreover, the percentage of artificial areas in these rivers was low, suggesting that these rivers have not been exposed to excessive anthropogenic disturbance that leads to loss of estuarine habitat. 5. These results show that gobies and crabs are not surrogates for one another.

Sediment temperature characteristics and their relation to distribution patterns of two sentinel crab species in intertidal flats in western Japan

“…1 ). These sites represent the geographical distributional ranges where M. japonicus and M. banzai are sympatrically distributed 21 , and the presence of M. japonicus and/or M. banzai has been found in previous surveys 2 , 28 , 29 . In Japan, these two species inhabit sandy and muddy intertidal flats in the lower intertidal zone and are active on the tidal flat surface during daytime low tides in the non-winter months 16 , 22 .…”

“…The management of estuarine ecosystems is an urgent global issue. Estuaries are transitional zones between terrestrial and marine areas, where various intertidal habitats such as tidal flats, salt marshes, coral reefs, and mangrove forests are formed 1 , 2 . These intertidal habitats provide several ecosystem services; nevertheless, they are threatened by degradation and loss due to anthropogenic pressures 3 , 4 .…”