Closed seasons and size limits — how to find the numbers, which differ by prefecture

This app deliberately does not print a minimum size or a closed season for each species. That is not laziness. In Japan, take restrictions are set by each prefecture's fishery adjustment regulation — there are 47 sets of them, and they are revised. Printing one number as if it were national would hand you a rule that is wrong in the next prefecture along. What this app gives you instead is the fact that a rule exists, and the route to the version of it that applies where you are standing.

What the rules cover

• Minimum sizes: taking fish below a stated length is prohibited, with the species list varying by prefecture.
• Seasonal closures, often around spawning, during which taking a given species is prohibited outright.
• Gear and method restrictions: spears, diving apparatus, cast nets, fish-attracting lights.
• Area restrictions: protected waters and prohibited zones.
• Separately from all of this, species held under fishing rights — abalone, sea cucumber, spiny lobster and others — may not be taken by anyone but the rights holder. Doing so is poaching.

Finding the rule that applies

• 1. Search the prefecture name with gyogyo chosei kisoku (fishery adjustment regulation). The text sits on the prefecture's fisheries division site or on e-Gov, the national law database.
• 2. Look for the prefecture's guide for recreational anglers — usually a PDF, far easier to read than the regulation itself, and often with the species and sizes laid out as a table.
• 3. For rivers and lakes, read the managing cooperative's own angling rules as well. Prefectural rules and cooperative rules are separate things.
• 4. Confirm on site: tackle shops, charter boats, the cooperative office, the desk at a managed fishing park. Many ports post the current notice at the gate.
• 5. Screenshot it before you leave. Reception at the water is often poor.

How the length is measured

The same number means different fish depending on whether the rule uses total length or fork length (snout to the fork of the tail). The guide will define which one it uses, so read the definition along with the number. Keep a tape measure in the cool box; if it matters, measure rather than guess. Wet the tape, measure quickly, and do not lay the fish on dry ground.

When in doubt, put it back

Unclear rule, borderline size, more fish than you can eat — all three have the same answer. If you are releasing, release it alive. Wet your hands, keep it off hot dry concrete, and give the photo ten seconds, not two minutes. Unhook it with pliers; if the hook is swallowed deep, cutting the line short is generally considered to give the fish a better chance than digging the hook out. Put it into the water and watch it swim, rather than dropping it from height.

Every number in those regulations is a line somebody drew after studying that particular sea. Staying inside the line does not require memorising all 47 versions; it requires the habit of looking up the official page once before you go.