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Surveying lake fish populations
Lake surveys measure the structure (ages and lengths) and abundance (number) of fish populations. As different fish species have different behaviours, different methods are required to get an unbiased sample and assessment of the integrity of fish populations:
Fall Index Netting
During the fall when water temperatures are between 10°C and 15°C, Walleye, Northern Pike, and other species are more evenly distributed throughout the lake, which allows biologists to use a provincially standardized approach called Fall Index Netting (FIN).
North American Standard Index Netting
North American Standard Index Netting (NASIN) is another form of standardized index netting that can occur during the summer months, when water temperatures are above 18°C, to measure Northern Pike populations.
Summer Profundal Index Netting
Summer Profundal Index Netting (SPIN) is an adaptable methodology that can be used to assess Lake Trout populations in a wide range of lake sizes over a short period of time. The SPIN method adapts to the characteristics of Lake Trout ecology and minimizes mortality to assess these sensitive populations.
Data collected through lake surveys
All lake surveys collect the same information from fish populations. This information is used to determine the status of the fish populations and includes:
- number of each fish species caught
- biological data from each fish (age, gender, length, maturity, weight)
Using the survey data
Catch rates
Catch rates (number of fish captured per unit of effort) of Walleye, Northern Pike or Lake Trout are a measure of the population’s abundance, with higher catch rates indicating there are more fish in the lake.
Length, age and size distribution
Length and age of fish show us the structure of a population, and the distribution of sizes of fish can provide clues on what factors may be limiting the population.
For example, few large fish can indicate an overharvest issue and few small fish can indicate an issue with habitat and spawning success.
Fish Sustainability Index (FSI)
Lake survey data, as well as data on water quality, access, development, and habitat threats, are used to inform Alberta's Fish Sustainability Index (FSI).
The FSI gives each population a score from very low to very high risk to sustainability. The FSI brings consistency to individual fish stock assessments and provides a province-wide evaluation of the status and sustainability of Alberta fish species.
Resources
Contact
Connect with Environment and Protected Areas Outreach Services Team:
Hours: 8:30 am to 4:30 pm (open Monday to Friday, closed statutory holidays)
Email: [email protected]
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Lake surveys