Two large commercial lobster pots were taken from Castletown beach between 9pm on Saturday 9am on Sunday.
The pots were left out overnight along with two orange buoys and a set of tags identifying the owner.
The orange buoys display a three-digit number which can be traced back to the owner.
Police are urging fishermen to remain vigilant to ensure that these items are not sold on locally.
The pots are described as being around 3ft in length and 2ft in width, made from metal and would be hard for a person to lift alone.
Officers would like to speak to anyone who may have seen any suspicious behaviour in the area. If you can help, call police headquarters on 631212.
The fishing community is urged to check property to ensure it is clearly marked as this will help to discourage further incidents of a similar nature.