I don’t know which country is being talked about here but if I had to guess why fishing is proscribed, I’d hyphothesize that fishing had alwasy been classified by the state as being a “sport” (allowing fishing bodies to apply for grants, licences, etc.). Then, when Covid-19 mitigation measures were being drafted, all sporting activities were proscribed (possibly because many sports involve risk of transmission between participants and/or spectators. This is what happened in my country (Ireland) with hunting clubs. Despite being an activity that is pursued by individuals or very small groups, they were caught under a similarly wide umbrella.

I don’t envy legislators the task of having to drill down into every aspect of human behaviour and make ongoing risk assessments for it. For Level 5 restrictions in Ireland, a huge amount of effort went into determining what goods should be considered as “essential” so that shops selling them could stay open. Needless to say, they didn’t get it right and there are inconisistencies. However, legislators have to react quickly to changing circumstances while maintaining the requirement that their work be legally sound. Under such circumstances, I don’t expect the new (and temporary) rules to be perfect in every way. The best we can hope for is that they get the big picture right.

Recreational fishing was closed state-wide in Washington State for about a month as part of the initial lock-down. Granted it wasn't closed that long but the damage to 'follow the science' credibility was done. There were protests and public ridicule which probably led to the quick turn-around.