North Temperate Lakes LTER: Pelagic Prey - Sonar Data 2001 - current

Total pelagic fish abundance data were collected annually in mid-summer (following stratification) using hydroacoustic surveys along a set of transects in each of eight lakes (Allequash, Big Muskellunge, Crystal, Sparkling, Trout, Mendota, Monona, and Fish), from 1981-1999 (Lakes Monona and Fish from 1995). Hydroacoustic data were not collected in 2000, but collection resumed in 2001 on Crystal, Sparkling, and Trout and continues to the present (with the exception of Crystal in 2004). In 2005, Lake Mendota was included in the annual sampling rotation. This dataset includes data from lakes Crystal, Sparkling, Trout and Mendota from 2001 through present. Lake Mendota was not surveyed in 2020 due to COVID-19. Big Muskellunge lake was included back into the sampling rotation in 2020 and will now be surveyed annually.

These data represent 1) species-specific whole lake density estimates and average length (target strength (dB)); 2) depth-stratified (1m) species-specific density estimates and average length by 200m transects; and 3) individual depth-specific target length (not assigned to species).
Dataset names for the aforementioned are below.
1) North Temperate Lakes LTER: Pelagic Prey Whole Lake Density - Sonar Data
2) North Temperate Lakes LTER: Pelagic Prey Interval Density - Sonar Data
3) North Temperate Lakes LTER: Pelagic Prey Single Target - Sonar Data

Although rare, large targets representing predatory species were excluded from the density estimation for pelagic prey species (when n<3 were caught in vertical gillnets) using the proportion of large targets identified during single target analysis on each lake. Pelagic fish densities for lakes Sparkling, Crystal, Big Muskellunge, and Mendota are for the entire basin of each lake. The data shown for Trout Lake represent densities in the south basin only. Number of current sites: 5