As someone who is a top identifier in salmoniformes, for a while I’ve always been interested in these large rainbow trout observations (oftentimes in high numbers as well) that always struck me as being held in ponds like fish you would have as pets and take care of, or as individuals that are being held outside in ponds to be harvested for restaurant use, since they’re always in towns or villages. However, after finally researching on these guys in a few Google searches, this doesn’t seem to be the case. From what I’ve found, it appears that these fish are in fact maintained, but it looks like it’s for the purpose of promoting a standard of cleanliness and prevention of pollution within the culture of the country, as well as being provided for tourism, and does appear to be a type of stewardship. Under these definitions, would these trout be considered captive on iNaturalist? Does anyone have any personal experience, either by visiting one of these canals, working with them, or some other experience that can elaborate further on what they know about these trout? Are these guys actively surviving on their own or are they being fed by people? My main concern with these trout is that, while yes, they may actually be wild and considered as such, but Japan also has some properly wild/introduced/invasive populations of rainbow trout outside of their canal systems, which can and do pose a problem to native cherry salmon populations via competition for resources, and I think some sort of distinction between these two is necessary, but I don’t fully know how these rainbow trout in the canal systems (which probably make up somewhere around 90% of all rainbow trout observations in Japan) should be marked on the site.
I think it comes down to whether the fish can/do leave the canals or not. If the canals are just large linear impoundments, and people put the fish there, but they don’t/can’t leave it’s fair to call them captive. If the fish are moving around large aquatic systems, though, even if they were introduced there, wild is probably better. If feeding is supplementary (like tourists throwing them stuff), I still don’t think that would make them captive. If they can’t survive without continued human feeding/vet care, then captive is probably better.
For observations further south thank Hokkaido (where the species seems to be more straightforwardly established), just eyeballing some of the relevant canal observations on a map, I think a lot of these canals do join up to larger bodies of water. I think I’d leave them as wild, and:
handle this distinction via a project or observation field.
I agree, the primary question is whether they are able to leave the canals, not whethere they are being fed. If the can’t leave, they are no different to horses in a paddock. A human put them or their ancestors into an artificially constructed impoundment area with the intention that they would survive and grow by eating the food naturally available there. Even if they breed within the impoundment - just as horses do - and they survive solely on naturally avilable food with no supplementation -just as horses do - they aren’t wild because the only reason they are there is because a human intended them to be there.
Only if the fish are free to leave the canal system and enter natural waterways, should they possibly be considered wild, Doesn’t mean they definitely would be wild, but without that criterion being met, they definitely aren’t wild. Once again, this would be analgous to feral horses in the US or Australia. Many horses are clearly captive, many are clearly wild. Some are edge cases that could techically leave beacuse there are no fences and some even occasionally mingle with wild herds, but mostly choose to remain where they were placed. The edge cases don’t invalide the fact that the horses that are put behind fences and walls are captive because they are only there because a human put them (or their ancestors) there. It doens’t matter if a human hasn’t fed them for 10 generations, they are still just a captive domestic herd.
Worth noting that just because they join up with other bodies of water, doesn’t mean the fish are free to move. I don’t know much about fish, but if the conditions in the contiguous water bodies make it difficult for the fish to move (eg high salinity, low oxygen), they might still be contained. Again, analagous to horse in paddock that is fenced on three sides, with the open side being steep hills or an expense with no water. The horses could technically leave, but they almost never will, and remain captive.
So, are fish stocked by people into closed systems always captive then? That doesn’t quite make sense to me.
I think there’s always going to be some question when it comes to the size of the system. I think pretty much everyone would agree that koi in a koi pond are captive. That’s a pretty small pond.
A stocked fishing pond with a non-native species where fish are fed and restocked annually? I’d call that captive too.
A large lake which was stocked with a non-native game species which, while closed, allows fish to move to different habitats and the fish aren’t fed/otherwise cared for/restocked. I’d say wild from there on “up”.
Systems are always “closed” at some level, so there will always be some judgment call.
But in this case, if the canals are closed, the fish are non-native and intentionally stocked, and the fish are continuously cared for, I think captive is most reasonable - it basically sounds like aquaculture. If the canals are open though, I think that would be key and would go with wild, since even though the fish would be stocked and cared for, they can leave.