Fisheries authorities have seized boats and nets as part of stepped-up enforcement of a salmon-fishing ban on the Fraser River.

The measures are being taken to enforce a ban that applies to all salmon species and to all fishing sectors, including commercial, sport and aboriginal fisheries, says Nicole Gallant, acting area chief for the Lower Fraser with the federal Department of Fisheries and Oceans.

"We [continued] to increase our enforcement presence this past weekend to monitor any illegal fishing that's taking place during this closure," Ms. Gallant said.

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Fisheries officials announced the ban earlier this month as a result of low numbers of sockeye salmon returning to the Fraser River to spawn as well as higher-than-normal water temperatures, which can affect fish as they swim upstream.

Sockeye is prized for its colour and flavour.

"We have had [closures] before but this is an unusual circumstances where we have both the low numbers of fish returning and the hot water temperatures which basically closed the river – and increased the enforcement patrols," Ms. Gallant said.

Over the past 10 days, fisheries officials have seized nine boats and 60 nets and opened nearly 30 investigations into alleged poaching incidents. The stepped-up patrols, involving about 30 employees, are expected to continue while the ban remains in effect.

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The closing applies to the stretch of water between the mouth of the Fraser in the Lower Mainland to just north of Yale, Ms. Gallant said.

Members of the public who think they see illegal fishing activity on the Fraser should call DFO's Observe, Record and Report line, Ms. Gallant said. Some fisheries, including the catch-and-release sturgeon fishery, are still allowed.