Everybody knows this one. If you want a big fish, throw a big bait. It is in the magazines, it is on the rocks at two in the morning, and it is why half the plugs in a surf bag are longer than anything a striper is likely to see that week.
It also has a lot of stomach data against it.
The dataset that ought to settle it
Between 1997 and 2000, Massachusetts biologists opened 3,006 striped bass stomachs from the North Shore, Cape Cod Bay and Nantucket Sound, June through September. The fish ran from about 11 inches to a shade over 45. Just over half the stomachs — 1,720 — had anything in them at all.
Then they did what nobody does at the tackle shop: for every stomach with measurable prey, they plotted the average size of that prey against the length of the fish it came out of.
For Atlantic menhaden — the archetypal big bait, the thing you snag and live-line precisely because you want a big fish — the answer was:
prey length = 51.0 + 0.03 × bass length, r² = 0.02, across 241 stomachs.
That r² is the share of the variation in prey size explained by the size of the predator. Two percent. Run it across the fish anyone actually catches:
| Bass | Menhaden it ate | Sand lance | All fish prey |
|---|---|---|---|
| 16 in | 2.5 in | 3.1 in | 2.3 in |
| 28 in | 2.8 in | 4.2 in | 3.7 in |
| 35 in | 3.1 in | 4.9 in | 4.7 in |
| 43 in | 3.3 in | 5.6 in | 5.6 in |
Add twenty-seven inches of striped bass and the bunker gets about eight tenths of an inch longer.
Being fair to the statistics: that slope is not zero, and the authors report it as significantly different from zero. It is simply near-empty — in their words, the regressions "accounted for very little of the variability" between prey size and bass length. Across the whole sample the average fish prey was 2.6 inches and the average crab just over an inch. Counting all fish prey together, size did rise with the bass, from about 2.3 inches for the smallest bass to 5.6 for the largest (Nelson et al. 2003) — the menhaden line is the one that stayed nearly flat.
It is not that they cannot
The obvious objection is that this is a mouth problem: small bass are limited, big bass are not, so of course the average barely moves.
It is not that either. Prey fish in those stomachs ranged from half an inch to twenty inches. Big bass do eat big things. It is just not what they mostly do.
The telling detail is at the other end. For sand lance, menhaden and rock crab, the smallest average prey size rose only slightly across the whole span of bass examined. Big fish add larger prey to the top of the range. They do not raise the floor.
Green crab is the exception that proves the instrument works. There, both the minimum and the maximum climbed almost linearly with bass length, and the authors read it as bass actively selecting the largest crabs they can swallow — constrained by the mouth rather than by the chase. So when a striped bass does size-select, this dataset sees it plainly. The flat menhaden line is not a measurement failure. It is a result.
A 2009 study makes the same point from the other side. It put juvenile striped bass and juvenile bluefish together, found their gape allometry similar, and states flatly that gape "did not determine maximum prey sizes eaten." Bluefish still took larger prey relative to their own length, and on identical prey were simply the more efficient predator. A striped bass eats smaller prey than a bluefish of the same size because it is a striped bass, not because it cannot open wider.
Why a big fish would pick a small meal
The Massachusetts authors argue prey selection here is largely passive — mediated by how often an attack on a given size of prey actually succeeds, rather than by the fish deciding what it fancies. Smaller prey get eaten more because smaller prey are easier to catch.
That part has been measured in juvenile bluefish, which eat the same forage in the same estuaries (Scharf et al. 1998). Fed two kinds of prey, as prey length relative to predator length rose from 0.20 to 0.65, their capture success declined linearly, and handling time increased exponentially.
That is the economics of a big bait from the fish's side. A longer prey item is less likely to be caught at all, and costs disproportionately more to get down when it is.
A second bay, the same answer
In the Chesapeake, a separate team worked through 2,703 striped bass from 1998 to 2001. For their largest class — fish over 700 mm, call it 28 inches and up — bay anchovy made up 16 to 29 percent of the diet by weight in spring and summer. The authors called it a greater reliance by larger striped bass on small pelagic prey.
Bay anchovy. One of the smallest baitfish on the coast, in the biggest fish in the sample. Different estuary, different decade, different team, same direction.
What does move prey size
Something sets the size of the average meal. It just is not the fish.
The place does, and not subtly. Sand lance was 1.3 percent of diet by weight on the North Shore and 15.8 percent in Cape Cod Bay. Lobster was 11.7 percent on the North Shore and 0.5 percent in Cape Cod Bay. Same species, same summer, an hour's drive apart.
The Massachusetts authors put it plainly: piscivory in striped bass is not fixed. It depends on prey abundance and availability, on body size, and on foraging habitat. Body size is on that list — nobody says it does nothing. It is the weakest of the three, and the only one anglers act on.
September is when this turns over. The menhaden those bass ate in August and September were 30–145 mm fish, which the authors tie directly to young-of-the-year menhaden moving seaward out of the estuaries. Prey size climbs in autumn because of what becomes available, not because the bass grew.
Two caveats. These fish were caught mostly on rod and reel, with some gillnet and long-line, and 77–90 percent came in between 6am and noon — so the dataset cannot speak to when bass feed, and it is largely a sample of fish willing to eat what someone was offering. And prey identity moves faster than prey size: a 2012–2016 resample of Salem Sound found Atlantic mackerel at nearly 43 percent of diet by weight, a more than tenfold jump, with menhaden well behind. Do not read the 1990s species list as current.
What to do with it
A big plug is not wrong. It is just not more right because you want a big fish. That is the link the data cuts. This is not an argument for downsizing either — it is an argument that the fish you are hoping for is the wrong reason to pick a lure.
The small end never closes. Large bass add bigger prey without giving up the small stuff. When the water is full of two-inch bait, a thirty-eight-inch fish is not holding out for something better.
Match the month and the water, not your ambition. Prey size is a property of the place and the season. In September on this coast that genuinely points bigger — because of what is swimming there, which is a reason you can check.
How StripedLines uses this
StripedLines is built for striped bass. The app's size advice follows which prey the water and the month support — a property of the bait, never of the fish you are hoping for.