MyCatch Benchmarking with DFO Survey Data

A major challenge faced by many citizen science projects is the uncertainty around sampling bias (Brick et al.). If the data is collected from a biased sample, the results will also be biased. Without a properly randomized sample, it can be difficult to know if the results accurately reflect reality or are skewed in some way. One strategy for addressing this uncertainty is by “benchmarking” results from citizen science projects against gold standard methodologies. There are a wide range of methods that are commonly used, such as randomized mail-in surveys, creel surveys and netting surveys. Where these gold standard methods are available for comparison, they provide a powerful tool to evaluate the potential bias in a citizen science project. This is the approach used by MyCatch to evaluate the bias from our sampling (Johnston et al.).

BACKGROUND

MyCatch was launched in May 2018 as a way for anglers to report their catch information for scientific research. It was released through an existing website, Angler’s Atlas, that had a strong base of approximately 100,000 registered members, as well as receiving roughly one million anglers on the website each year.

The initial goal was to determine if this angler reporting tool (combination of website and app) could produce reliable results on catch rates — a common metric generated from creel surveys. Data from across Canada was collected, with catch rates generated for over 4,000 thousand waterbodies coast to coast.

Thanks to the support of the Alberta Conservation Association, we were able to carry out detailed analyses on the data collected from anglers in the province of Alberta. A critical part of this analyses was comparing the anglers who participated in our survey with the population of anglers across the province, to see how representative our sample was compared to a properly randomized sampling project. Fortunately we were able to find a “gold standard” survey carried out by Fisheries and Oceans Canada (DFO).

Every five year, DFO conducts mail surveys of recreational fishing activities in Canada’s provinces and territories to assess the economic and social importance of these fisheries. This survey data follows a randomized sampling design and is seen as a representative sample of anglers and angling effort across the country, and is an excellent database to benchmark MyCatch data against.

RESULTS

In our first formal analysis, we used the Alberta DFO survey for 2015, and compared it with data collected by MyCatch in 2018. Overall, the distribution of angler residency was quite similar, with only a slight increase in urban residency through the app – potentially due to less awareness of the app in rural areas. The distribution in angling effort was also similar, with the majority of anglers fishing in the region they resided in. 

There were statistically significant differences in the relative composition of caught species between the app and mail survey, but the overall trend was consistent with walleye and northern pike being the most fished species. The app reported proportionally more northern pike and lake trout catches; potentially due to locational preferences and anglers choosing which catches to pursue and report.

The general similarities in data collected through the DFO mail-in survey and the MyCatch app suggest that while the app shouldn’t be used as a complete substitute, it may be of use as a supplementary monitoring tool in the years between mail-in surveys.

These results were published in the Canadian Journal of Fisheries and Aquatic Sciences in 2021, and you can access to the full paper here.

_{Header image from Angler’s Atlas member bdayton.}