Recreational fisheries are classic examples of coupled natural-human systems with a human system (recreational fishers) and a natural system (fish populations) dynamically coupled, often over large spatial scales. The spatial extent and complexity of these systems makes them particularly hard to study and manage. Of particular importance in these systems is catch, the critical link between the natural and human systems that represents the number of fish caught by fishers. In order to better understand how the human system operates, it is critical to understand how fishers react to changing fish abundances which they often assume are proportional to catch. We used a whole-lake manipulation of fish abundance to assess whether changes in abundance resulted in proportional changes in catch and compared these results to an un-manipulated reference system. Abundance manipulations were conducted using electrofishing and angling methods. Fish were collected weekly and transferred from our treatment basin to a holding basin. Paired with weekly abundance manipulations were estimates of fisher catch on both the treatment and reference systems using a controlled group of fishers. A generalized linear model was fit to the resulting data to assess the nature of the relationship between fish abundance and catch.
Results/Conclusions
The best fitting model to our data took the form of a power curve. This shape of the relationship between fish abundance and fisher catch is of ecological importance because it demonstrates that fisher catch can remain relatively constant over a wide range of fish abundances, a phenomenon known as hyperstability. Fish abundance may be declining in a system but a non-proportional decline in catch will allow fishers to maintain relatively constant catch on a declining abundance of fish. Hyperstable catch encourages fishers to continue fishing in the system, unknowingly driving the fish population further towards collapse. Because of the controlled nature of our whole-lake experiment we are able to rule out mechanisms previously identified as drivers of hyperstability (i.e. sorting of fisher skill) and instead hypothesize that hyperstability can result simply from non-random site choice by fish and fishers. This common fisher behavior will need to be taken into account by managers in order for sustainable use of the fishery to occur.