Sensitivity of fish density estimates to standard analytical procedures applied to Great Lakes hydroacoustic data

Patrick M. Kocovsky; Lars G. Rudstam; Daniel L. Yule; David M. Warner; Ted Schaner; Bernie Pientka; John W. Deller; Holly A. Waterfield; Larry D. Witzel; Patrick J. Sullivan

doi:10.1016/j.jglr.2013.09.002

USGS · 70048318

Sensitivity of fish density estimates to standard analytical procedures applied to Great Lakes hydroacoustic data

Patrick M. Kocovsky·Lars G. Rudstam·Daniel L. Yule·David M. Warner·Ted Schaner·Bernie Pientka·John W. Deller·Holly A. Waterfield·Larry D. Witzel·Patrick J. Sullivan

View original source ↗Export metadata ↓

Abstract

Standardized methods of data collection and analysis ensure quality and facilitate comparisons among systems. We evaluated the importance of three recommendations from the Standard Operating Procedure for hydroacoustics in the Laurentian Great Lakes (GLSOP) on density estimates of target species: noise subtraction; setting volume backscattering strength (S v ) thresholds from user-defined minimum target strength (TS) of interest (TS-based S v threshold); and calculations of an index for multiple targets (N v index) to identify and remove biased TS values. Eliminating noise had the predictable effect of decreasing density estimates in most lakes. Using the TS-based Sv threshold decreased fish densities in the middle and lower layers in the deepest lakes with abundant invertebrates (e.g., Mysis diluviana). Correcting for biased in situ TS increased measured density up to 86% in the shallower lakes, which had the highest fish densities. The current recommendations by the GLSOP significantly influence acoustic density estimates, but the degree of importance is lake dependent. Applying GLSOP recommendations, whether in the Laurentian Great Lakes or elsewhere, will improve our ability to compare results among lakes. We recommend further development of standards, including minimum TS and analytical cell size, for reducing the effect of biased in situ TS on density estimates.

Explore related subjects

Journal of Great Lakes Research Article

Source-reported bounding extent: 41.38° to 48.85° latitude; -92.11° to -76.3° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Patrick M. Kocovsky, Lars G. Rudstam, Daniel L. Yule, David M. Warner, Ted Schaner, Bernie Pientka, John W. Deller, Holly A. Waterfield, Larry D. Witzel, Patrick J. Sullivan. 2013. Sensitivity of fish density estimates to standard analytical procedures applied to Great Lakes hydroacoustic data. https://doi.org/10.1016/j.jglr.2013.09.002

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Groundwater nutrient contributions to surface water in the upper Maumee River basin

Harmful algal blooms triggered by nutrient loading have negatively affected Lake Erie water quality for decades, but the role groundwater plays in transporting nutrients to tributary streams is unclear. Here, we apply a multi-scale approach to investigate groundwater nitrogen (N) and phosphorus (P) dynamics at the field scale, along a groundwater flow path, and at the Maumee River basin scale. Unsaturated zone monitoring indicates that macropore flow is the primary mechanism for N and P leaching with nitrate and orthophosphate (OP) concentrations from macropore samplers more than double those from soil-matrix samplers. Shallow (< 4.5 m) groundwater nitrate concentrations indicate the timing of saturated-zone nitrate fluxes is crop dependent with more nitrate mobilized during the maize growing season whereas concentrations below soybeans can remain elevated (> 3 mg/L) through winter months. A three-end-member hydrograph analysis for the upper Maumee River basin indicates that tile drains transport most subsurface N and P with greater than 15,000 kg per day of nitrate transported between January and May. Orthophosphate concentrations in tile drainage at an edge-of-field site correlate well with concentrations in a nearby tributary of the Maumee River. While runoff is the dominant source of OP loading, tile drainage and groundwater discharge contributed an estimated 36% of OP load during a 2018–2022 analysis period with most subsurface loading occurring between January and March. These findings highlight how best management practices (such as cover crops and tile drainage control structures) can be used to help limit leaching and tile effluent during the nongrowing season.

Indiana↗

USGS2026

Application of novel encounter and predation models to the natural behavior of slimy sculpin Cottus cognatus

Sculpins play a critical mid-trophic role in lacustrine food webs, converting production by benthic and migrating pelagic invertebrates into biomass available to higher trophic levels. Although sculpin diets and habitat choices are relatively well described, much less is known about their in situ behavior which governs trophic interactions and, in part, prey behavior. We measured the natural behavior of slimy sculpin Cottus cognatus in Lake Champlain using video data originally collected to quantify Mysis diluviana abundance in benthic habitat. After characterizing slimy sculpin movement behaviors according to body size, we incorporated these data into encounter and predation rate models at the individual and population levels, the latter based on bottom trawl data from Lake Champlain. Saltatory movement varied with body length in terms of distance traveled, duration traveled, and duration at rest, but strike distances at prey did not vary across individual sculpins. Slimy sculpin predation rate increased with depth and was limited by pursuit time rather than prey availability, and their populations exerted predation rates on Mysis up to 5 predation events/m 2 /day. Assessment of benthic predation risks affords the opportunity to test hypotheses about the role of predation risk in Mysis diel vertical migration (DVM), and DVM more broadly. Furthermore, the methods we describe here can easily be employed for other benthic fishes such as the invasive round goby Neogobius melanostomus .

New York, Vermont↗

USGS2026

Thermal habitat use of lake trout in Lake Erie

Understanding the thermal habitat use of fish populations is vital for effective rehabilitation or management, particularly in the face of climate change, given limited thermal tolerances of some species. In Lake Erie, lake trout ( Salvelinus namaycush ) rehabilitation efforts by means of stocking have been ongoing for four decades. However, high water temperatures and lengthening periods of stratification may be hindering reestablishment efforts by contributing to unfavorable conditions for spawning and natural recruitment. We used acoustic telemetry to quantify weekly temperature occupancy of adult lake trout in Lake Erie and evaluated whether temperature occupancy differed relative to fish total length and sex. We found that lake trout occupied water temperatures similar to temperatures occupied by other Great Lakes lake trout populations during summer stratification. During fall, lake trout in Lake Erie occupied warmer temperatures than Lake Huron populations but similar temperatures to Lake Ontario populations. Occupied temperatures decreased with increasing body size during a 7-week period of mid- to late-summer stratification, but not during early summer or fall. Male and female lake trout did not differ in weekly temperature occupancy during any season. These findings reveal similarities with successfully reproducing populations, which suggest that adult temperature occupancy is unlikely to be a major impediment to natural recruitment in Lake Erie.

Lake Erie↗