The whole business of size limits can get confusing! There are quite a few species that have no legal minimum size; two more I think are flounder and poutings - so you could quite happily fill up a bucket with dabs, flounders & pouts of any size to feed to the cat/make fish-cakes/boil up as a stew or whatever.
However, angling clubs have usually adopted the size limits established by the old Northern Federation of Sea Anglers, which will give certain minimum sizes for things like dabs (20cm) or flounders (25cm). Some take an extra step and up certain species by a few centimetres to avoid unnecessarily large bags of small fish being weighed in - such as upping flounders, for example, to 27 or 28cm. Probably the most commonly confused is the size for bass (there have been several posts in the past on this one!) - the legal size being 36cm, the "recommended retention size" being 41cm.
This is why when fishing matches it's worth checking the rules - I've fished matches where flounders, for example, have been 25, 27, 28 or 30cm depending on the event. Then, of course, there are your catch, measure and release match sizes (usually a minimum of 20cm, or 18cm for SAMF events) which are purely to reward the angler for their effort, as all fish are returned, not retained.
So long as you familiarise yourself with the sizes that the ICFA & DEFRA publish, you won't go far wrong (at least as far as the law is concerned!)
Gary
