A low cost 1-cm accuracy electronic fish measurement board

Measurements of fish lengths are a basic requirement of most fisheries monitoring programmes globally, however traditional methods for collection of this data entails inherent inefficiencies and errors. Electronic devices for measuring fish and shellfish have been developed commercially, but for many organisations the cost of these devices is prohibitive. Low cost “build your own” devices have also been described, but construction of these requires considerable knowledge of electronics. Here, a design is presented for a USB electronic fish measuring board that can be assembled at low cost from “off the shelf” materials. This board was assembled using a set of skills that would be available in most research organisations. The design uses noncontact sensors activated by placing a magnet on the measurement board, which is easy to waterproof. The device is connected to a tablet computer, where a VB.NET programme records and validates the data. A running total of the estimated weight of the sample is provided, based on length-weight relationships. Length frequencies collected by both a conventional measuring board and this electronic board from the same commercial catches for 6 fish species showed no significant differences. The design described here allows the construction of a low cost unit which simultaneously improves both efficiency and accuracy of fish length data collection with minimal electronic construction skills.