-At high population densities, the amphibious and herbivorous mudskipperBoleophthalmus boddarti construct mud walls around their territories as a means of reducing aggression between neighbours. Because of the walls, territories contain pools of water and exposed mud slopes. Whilst the density of benthic diatom prey was highly variable, the highest was found on the exposed mud slopes and the lowest on the boundary walls. Fish grazed mainly on the mud slopes. There were no significant differences in diatom density between territorial and non-territorial areas or between grazed and non-grazed areas within territories. The variation of the diatom density, however, was reduced within territories. The mud walls are considered to play a secondary, indirect role in maintaining populations of diatoms within territories.

Effects of location, diel period, tidal condition and water clanty on the size and distribution of the shallow water fish assemblage of the non-estuarine Kuwait Bay, were investigated using a beach seine and a small research trawl during spring and summer 1989. Total numbers, biomass and numbers of species differed markedly between Doha, a sandy shore environment, and Kazmah, an extensive intertidal mud flat. When fish were present in large numbers there was a marked die1 effect at both locat~ons with many more fish captured during the mght. Tidal effects were influenced by turbidity and the age structure of the assemblage. In clear water during spring, very young Liza carinata from the seine catches formed shoals at the edge of the rising tide both day and night, while fish 2 mo older formed shoals only on daytime r~s i n g tides. At Kazmah during spnng, h~g h turbidity obscured any tidal effects in the seine catches. In shghtly deeper water, sampled by trawl during spring, Leioynathus decorus showed an asymmetrical hdal migration In summer, beach seine catches were much higher on the rising tide. Summer trawl catches did not show a consistent tidal effect

No abstract

The intertidal migrations of shallow water fishes in Kuwait Bay were studied during two 24 h periods using an otter trawl. Most species wereconcentrated at a location corresponding to Low Low Water mark. At the other tidal levels some fishes migrated with the tide to High High Water mark through a horizontal distance of up to 2 km. Any effect of day and night on the catch was masked by the effect of tidal condition.Leiognarhus decorus (de Vis) was typically concentrated at Low Water but a proportion of the population followed the rising tide toward the shore. There was a die1 effect whichmay have been due to fish moving to shallower water at night compared with the day. Length-frequency distribution changed slightly with tidal state so that larger fish were not captured at High Water during the day. Of the fishes captured at high tide, the largest individuals of L. decorus were captured at a depth of 2.0 m deep. Solea elongata Day did not migrate with tidal fluctuations and was captured in large numbers only at Low Water. Arius tenuispinis Day was captured in shoals at or around Low Water.