Burrowing Activities of Goby Fish in the Recent Intertidal Mud Flats along the Navinal Coast, Kachchh, Western India

Behavioural activities of the goby fish-Periophthalmodon septemradiatus were observed in the intertidal zone around Navinal coast in the Gulf of Kachchh, western India. Intertidal zone is broad, and comprise of creeks, which are muddy and vegetated by mangrove on eastern side and ridge runnel systems on western side of the study area which are hospitable for the goby fish. Different types of biogenic activities are observed such as crawling, pellet making, grazing and burrowing. The crawling activity is part of movement of the goby fish from one burrow to another burrow and pellet making activity is part of burrow modification. The grazing activity is feeding on the surface mud after receding of tide and exposure of the tidal flat by left and right movement of the front part of the body. The most conspicuous activity is burrowing, they construct unlined, vertical to incline ‘I’, ‘J’ and ‘Y’ shaped branched, circular to oval burrows with varying diameter and depth. In the muddy sediments goby fish produced circular to oval rimmed muddy lumps as surfacial expression around the burrows and further produced funnel shape depression and downward extended cylindrical holes, while in the runnels burrows are usually small and simple. The trail is consisting of fin marking on either side of the tail marks (grooves) which are radiate around the burrows. Occasionally burrows are interconnected in more than one burrow system which is nested within single funnel structure on the surface. The burrow systems of the goby fish in the intertidal sediments serves for protection and dwelling purpose and most importantly these burrows are irrigated by water which supply the oxygen and keep body surface wet. The overall dimensions of the burrow decrease towards the lower intertidal zone. In all, behavioural structure produced by the goby fish marks the combined activity of dwelling, feeding and grazing. The complex behavioural mechanisms have helped the goby fish to survive and flourish in the harsh intertidal environments along the Navinal Coast, in the Gulf of Kachchh.