Great start to a nice research project!
I took the liberty of dividing gape by length and found that your very small samples are quite constant within a species and definitely show a trend.
HSB avg gape/length=0.094
SMB avg gape/length=0.124
LMB avg gape/length=0.174
So, HSB may be roughly half the gape width per body length as LMB.
Furthermore, I ran across the paper below which has info from Ohio research.
You can add two points for HSB: 22/220mm and 32/335mm.
Those yield gape/length=0.100 and 0.096. (min for smaller class cited as 190mm elsewhere in paper) The published data are in line with Bill's data.
Transactions of the American Fisheries Society, Vol. 127, No. 1, 1998, pp. 84-94.
http://kb.osu.edu/dspace/bitstream/handl....pdf?sequence=1
we estimated the largest prey that predators could consume by comparing gizzard shad body depth to hybrid striped bass mouth width. Hybrid striped bass efficiently consumed prey that were at their morphological limits of consumption. For hybrid striped bass shorter than 250 mm, the largest potential prey size was 80 mm (body depth = 22 mm), whereas for hybrid striped bass of 310-360 mm, the largest potential prey size was 120 mm (body depth = 32 mm). Regressing capture efficiency against the proportion of the maximum gape for each prey, we found no relationship for either predator size (linear regression, F = 0.07, df = 1, 8; P = 0.80 for large hybrid striped bass; F = 0.30, df = 1, 12; P = 0.60 for small hybrid striped bass). Consequently, hybrid striped bass in the laboratory can consume prey whose limiting dimension equals their maximum gape without reducing capture efficiency.
