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Part of Lake surveys

North American Standard Index Netting

This lake survey method employs standardized nets to assess Northern Pike, Walleye and other fish populations during the summer months.

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Lake surveys

Overview

The Alberta government is in the process of calibrating North American Standard Index Netting (NASIN) to monitor Walleye and Northern Pike populations. 

NASIN typically occurs in the summer months of June, July and August when water temperatures are above 18°C. Sampling during the warm summer weeks avoids collecting fish that spawn in the spring or fall which could bias catch rates. 

Standardized multi-mesh gill nets are set at random locations between 2 and 15 metres deep, set for 17-19 hours (i.e., a net-night), and then reset in new random locations the next day.

Sampling effort is proportional to lake size, so larger lakes can require more effort. This standardized method is used in other locations was recently calibrated in Alberta.

  • Why NASIN nets are used

    The NASIN method has been proposed by the American Fisheries Society as a standard for sampling angler harvested freshwater species in North America. Many agencies have begun conversion to this standard (Bonar et al. 2017) to enable comparisons of fish populations.

    Another advantage of this method is that it serves as an additional standardized assessment tool to Fall Index Netting (FIN). Each method is performed at different times of the year, which allows for a greater sampling window: 

    • NASIN (June-August)
    • FIN (September-October) 

    This translates into increased opportunity to conduct lake assessments and allows for a quick response to angling issues and potential increase angling opportunities in Alberta.

    The nets are designed as a community index standard, meaning they that may can  be calibrated to other species.

  • Comparing NASIN with FIN

    The North American Standard Index Netting (NASIN) method will not replace Fall Index Netting (FIN) but will serve as an additional standardized assessment tool and allow fisheries biologists increased opportunity to conduct fish population assessments.

    NASIN and FIN answer the same questions about the abundance, structure and health of a fish population.
     

  • Catch per Unit Effort (CUE)

    Catch per Unit Effort (CUE) refers to the catch of fish by a specified method. The method is standardized by a unit of effort, so it provides a sound basis for comparison amongst fish populations.

    For NASIN survey, the unit of effort is a net-night, which represents one standardized gill net, set on average for an 18-hour period.

    Typically, the NASIN catch rate is reported as the average for the survey at a lake. So, a NASIN CUE of 10 northern pike per net-night means that an average of 10 fish were captured per net per 18-hour set (or 10 northern pike/net-night).

    Number of fish killed during a NASIN assessment

    The NASIN method is very effective at assessing the status of walleye and northern pike.

    Every effort is made to limit fish mortality by understanding how many fish are required to make an accurate assessment and planning the survey accordingly, however NASIN assessments do kill fish.

    The number of nets set each day is limited so the catch can be closely monitored, and once sufficient data is collected the survey is concluded.  Typically, a small proportion of the lake's fish population (usually less than 1 -3%) are killed sampling.

    After sampling, if fish are appropriate for human consumption, Alberta biologists are required to provide the fish to local Indigenous peoples or to persons on approved subsistence lists.

Data collected through NASIN

During a NASIN survey, biologists collect data on Walleye and Northern Pike populations including the number and species of fish caught. Standard index nets are primarily used to monitor Walleye and Northern Pike populations, but information is also collected from other species, including: 

  • Burbot
  • Lake Whitefish
  • Minnow
  • Sucker 
  • Yellow Perch

The information collected from each fish includes:

  • age
  • gender
  • length
  • maturity
  • weight

Catch rates of fish species (for example: total Walleye captured per net-night) are calibrated to the abundance of those species. A common method is to calibrate catch rates to other indexes of abundance for example catch rates from creel surveys or population estimates conducted using various mark and recapture methods. 

At this time, the focus of NASIN is to develop calibrations for Walleye and Northern Pike and with time, expanded to other species.

Using the survey data

Catch rates

Catch rates (i.e., number of fish captured per net-night) of Walleye and Northern Pike are a measure of the population's abundance, with higher catch rates meaning there are more fish in the lake.

The abundance of adult fish is compared to the standardized thresholds for 5 broad categories of risk to the long-term sustainability of the fish population, with higher densities of fish having lower risk.

Fish age and size distribution

The sizes and age of fish can tell biologists about the health of the population. For example, too few fish living to old age can signal overharvest, while poor recruitment can be indicative of poor spawning habitat. 

Fish Sustainability Index and Fisheries Management Objectives

Biologists use fish age and size distribution information, as well as a variety of data on water quality, access, development, and habitat threats as part of Alberta's Fish Sustainability Index (FSI).

These assessments as well as the Fisheries Management Objectives are used to determine the most appropriate sport fishing regulations for a lake. This landscape-level assessment allows for consistent comparisons of fish sustainability and status over time.

For more information on fish conservation and management in Alberta see:

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]

Previous Summer Profundal Index Netting