Hi Chip,
I fish Pt Defiance quite a bit, from what I have heard and read over the years is that the dogfish come in to spawn this time of year. They are usually pretty thick at the Pt. in July. They will start to thin out at the end of the month and in to August but as long as you are fishing herring, whether it is mooched or trolled you will be into the pesky dogfish. I mostly troll and use hooches which cuts way down on the dogfish, but they will still hit those also. Anyway you look at it, you just have to deal with em'!!!
Good luck and tight lines, Jeff