depth anomaly ?

looking at ocean topographical map of Mendocino County. Lines showing depths are all consistent in size on the map except the one south of fish Island. looks to be about 1 mile long in the tenth of a mile wide. I'm thinking it's a deep Trench. anyone with fishing knowledge fishing area that can confirm ? or is it just a glitch on my map.

should have mentioned its Anchor Bay. this is a map that I'm looking at

Fish Rock! Check out posts with Anchor Bay in them, there is info on the board, and at least a couple of folks that know that area really well.