The best guess project: Testing the accuracy of Hawaii recreational fishermen's estimates of fish weight

In Hawaii, non-commercial fisheries data are collected by sampling catch dockside as fishermen return from a fishing trip. Review of recent data suggested that it was difficult for surveyors to weigh or measure larger yellowfin tuna (ahi); weights were obtained from only 15 percent of the larger ahi. In some cases, fish were simply too large to be weighed or measured; in others, fishermen did not want them handled. Measuring only the smaller ahi creates a bias in estimation of average weight that is difficult to quantify.

One possible solution is obtaining weight estimates from fishermen. To test this method, NOAA Fisheries teamed up with a popular Hawaii recreational fishing tournament to conduct the Best Guess Project in June 2007 and 2008. Oahu’s Ahi Fever Tournament is the largest small boat tournament in the state, with over 800 participants annually. The tournament draws both experienced and novice fishermen and ahi is the primary catch.

In total, over 50 percent of the estimates were within 10 lbs of the actual weight. The most accurate estimates were within the 100-150 lb range. This paper describes the methods used, results of our analyses, and incorporates data collected at 2008 tournaments throughout the state.