<Table> Rock Island <Tr> <Td_colspan="2"> Rock Island, as seen from the eastern side of the island </Td> </Tr> <Tr> <Td_colspan="2"> Rock Island Location of Rock Island off the coast of Trinidad </Td> </Tr> <Tr> <Th_colspan="2"> Geography </Th> </Tr> <Tr> <Th> Total islands </Th> <Td> </Td> </Tr> <Tr> <Th_colspan="2"> Administration </Th> </Tr> <Tr> <Td_colspan="2"> Trinidad and Tobago </Td> </Tr> <Tr> <Th_colspan="2"> Demographics </Th> </Tr> <Tr> <Th> Population </Th> <Td> Uninhabited (2015) </Td> </Tr> <Tr> <Th_colspan="2"> Additional information </Th> </Tr> <Tr> <Td_colspan="2"> Member of the Five islands group of islands </Td> </Tr> </Table> <Tr> <Td_colspan="2"> Rock Island, as seen from the eastern side of the island </Td> </Tr>

What is the main use of rocky islands off the coast