The Merriam-Webster definition of "pinch" is to squeeze between your thumb and finger often in a painful way. In the manner I'm using the word, the pinch is tidal water squeezing through a "finger" of land and an opposing "thumb" like peninsula. It happens on large scales in bays as well as in smaller waters like tidal creeks. Wherever it happens, tidal flow accelerates, creating an ideal feeding opportunity for predatory fish such as striped bass.
Last week while trolling hard jerkbaits for stripers, I followed my usual routine of marking each catch location with a waypoint on my chart. The first fish came not far from the back of the tidal Maryland creek I launched in. The big red "X" waypoint on the chart was next to another I had marked last spring. Continuing toward the larger tidal river, my trolling path passed under a bridge. Another larger fish slammed the rod backwards in it's holder and started pulling drag.
After releasing a healthy 24-inch striped bass, I leaned forward to the monitor and zoomed out. The two waypoints behind me were between two narrow strips of land pointing toward one another. The waypoint for the one I just caught was under a bridge - another place the tidal flow is bottlenecked. Further into the tidal river on the chart, a series of waypoints dotted along a much wider expanse of water pinched between two opposing points. I zoomed back in and then zoomed along a rip rap shoreline to bigger water.
Out there, birds worked vast acres of baitfish with the occasional tail flip and corresponding surge of gulls to that spot. Catching fish under the gulls was easy, but bigger ones hit along the rip rap leading out to the narrowest part of that tidal river. I set up on a current seam formed by the outgoing tide, casting 7 inch soft plastic jerkbaits on 1 ounce heads, popping them violently off the bottom. That elicited another pop on the drop.
I also caught them in areas away from the seam. The seam might have been a productive micro feature, but the mile and a half wide macro feature of a lot of water being pinched by two points of land was more important. It answered why the fish were there - increased flow and multiple ambush points. It took zooming out and looking at multiple years of waypoints to see it.
Not all productive pinches are easily identified on a two dimensional map between two opposing points that bottleneck current. Out in the middle of a larger bay, far from any constrictive land mass I had dropped several waypoints over many seasons. I knew the structure that those fish were associated with, and it wasn't a pinch between two land masses.
It was however still a pinch. The main river channel turned, exposing a steep shallowing ledge between 48 and 6 feet of water in a short distance. Much of the water raced parallel to this transitional depth contour. Some of it slid uphill and over that shallow flat. The fish were almost always caught in the 10 to 18 foot depth range along the ledge. At dusk, the stripers could be caught shallower - even up on top of the 6 foot beginning of the drop off.
Even though it was in the middle of a wide expanse of water, the water was still being pinched. It was bottlenecking between the flat surface and a ledge that tapered up shallow quickly. The "pinch" in this case was on a different plane - one that is perpendicular to and thus not visible on the two dimensions which a traditional map offers. But bathymetric maps or charts that have depth contours are able to show us those ledges that pinch current. Find one that coincides with the land mass that pinches too, and you'll have the kind of current bottle neck that will hold fish on any tide. You just may have to zoom out far enough to recognize it!