NSW DPI Fisheries officers began surveillance after noticing unattended handlines in Goobang Creek, off the Lachlan River last month.

They had been conducting routine patrols of the creek and the river when the lines caught their eye on weekend of May 15 and 16.

Watching the lines resulted in officers speaking to two men in relation to the matter, and the seizure of a massive haul including more than six kilograms of Murray cod fillets.

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Eighteen sets and unattended hand lines were seized from the Goobang Creek, as well as another 30 handlines the pair had in their possession.

No setlines or unattended lines are permitted in inland waters.

Four mutilated Murray cod, nine opera house yabby nets and a gaff were also taken by Fisheries personnel.

Opera house nets were banned in NSW on April 30. Since then, only up to five lift nets - pyramid, hoop or combination of both - can be used to catch yabbies in inland waters and then only where it's legal to use such nets.