No fish weir, trap or wharf shall be extended, erected or maintained except in accordance with this chapter. No fish weir, trap or wharf shall be erected or maintained in tidewaters below low-water mark in front of the shore or flats of another without the owner's consent, under a penalty of $50 for each offense, to be recovered in a civil action by the owner of said shore or flats. This chapter applies to all herring weirs and traps, but does not apply to other weirs or traps, the materials of which are chiefly removed annually, provided such weirs or traps do not obstruct navigation nor interfere with the rights of others. This section shall not affect any wharves so erected or maintained on the 21st day of April, 1901.