Why does the mudskipper Boleophthalmus pectinirostris form territories in farming ponds?

The mudskipper Boleophthalnus pectinirostris maintained territories in farming ponds during the cold season between November and February. There were two types of territory, one was surrounded by mud-walls, and the other was without mud-walls. Both types of territory were entirely covered by shallow water. The area of walled territories was significantly bigger than that of non-walled ones. The nearest neighbour distance of walled territories was significantly shorter than that of non-walled territories. In January, fish surface activity occurred between 1200 and 1500 hours at which time the territorial water temperature reached a maximum, being significantly higher than that of the air, mud surface or deep burrow. The territorial sediments exhibited a significantly greater benthic microalgal biomass (chlorophyll-a and total chlorophyll-a) as compared to the non-territorial sediments. The present study indicates that B. pectinirostris forms a territory during the cold season to keep a pool of water that encourages diatom growth and enables the fish to engage in surface activity.