[b:trovx6c8]North Otago Area: Unfortunately the Shag and Waianakarua Rivers are suffering from a toxic algal bloom and people are advised not to let children or dogs swim in these waters. The cause of the bloom is unknown but it seems to occur during prolonged low flow periods.[/b:trovx6c8]
This is an extract from an Otago fishing report in January and it doesn’t mention that fish caught in these rivers are unsuitable for eating.
Best to be sure, but I’m sure fish and game would have mentioned it if fish caught in waters with this algae were contaminated.