Fishermen have different perceptions than management authorities of long-term trends in resource outcome. This complicates co-management between individual resource users and these authorities. In this study the capacity to perceive trends is formalised with the statistical power to detect a true trend. This power is larger where trends are steep, the variance around trends is small, the number of years in the series is large, and when a greater risk to wrongfully conclude for a trend is accepted (Type I error). In order to predict which trends and patterns are visible and for whom, variability in daily, monthly and annual catches is assessed and compared for different types of fish and fisheries. This study shows that inter-annual variability and the persistence therein are responsible for a 'governance dilemma' that is found in the choice between costly draconic measures with a large impact and thus public proof of their legitimacy rather than more feasible but less effective measures. Authorities have an 'administrative gain' over individual fishermen in the perception of time trends, because they use spatially aggregated data that contain less variability. Recommendations are given on how to overcome this difference in the capacity for trend perception by enlarging the 'evaluative capacity' of both fishermen and authorities, especially where the two cooperate in co-managing a fishery. These problems in trend perception exist as well in agriculture. For instance, variability of annual crop yield in rainfed agriculture is high, and downwards trends due to soil degradation therefore hard to perceive for the individual farmer. Finally, the example from 17th and 18th century whaling illustrates how cognitive limitations because of ignorance of graphical and statistical tools, together with extremely high inter-annual variability, also constrain the perception of time trends in resource outcome.
|Award date||12 Dec 2001|
|Place of Publication||Enschede|
|Publication status||Published - 12 Dec 2001|