U.S. Department of the Interior

U.S. Geological Survey

USGS Open-File Report 2006–1074

Pool) and three observed lower than predicted catches (Pools 4 

and 8 and Open River). Much of the difference between predicted 

and observed total annual catch, for the entire program and 

among RTAs, was because the largest gizzard shad (Dorosoma 

cepedianum) and threadfin shad (D. petenense) catches on record 

occurred in 2002. 

During our evaluation in 2001, we also predicted that annual 

collections under the six-gear design should result in 9% 

reduction in the total number of species collected annually for 

the entire program (Table 2). As predicted, the fish component 

observed an overall 9% reduction relative to the historical 

average. However, differences between predicted and observed 

annual species counts varied among RTAs. Annual species counts 

in 2002 were below predictions for Pools 4, 8, and 26 and Open 

River, whereas in La Grange Pool we observed the same number 

as predicted, and in Pool 13 we observed one more species than 

predicted. It is difficult to place these deviations into context with 

only 1 year of post-design change data. We do expect annual 

species counts to vary over time because all of the predicted 

losses in annual species detection were associated with species 

Gear Efficiencies in the Fish Component of 

the Long Term Resource Monitoring Program: 

Predicted Versus Observed Catch

By Brian S. Ickes 

Environmental monitoring programs are frequently designed 

to track changes in key physical, chemical, and biological 

features of an ecosystem. As such, these programs provide 

critical information for detecting changes in system state, 

investigating mechanisms associated with observed changes, and 

making resource management decisions. Because monitoring 

programs require significant investments of time, money, and 

human resources, periodic evaluations of monitoring programs 

are necessary to determine if the sampling design adequately 

addresses program goals and objectives. Periodic evaluations also 

permit assessment of a program’s ability to provide adequate and 

useful information for changing management and science needs. 

In 2001, we evaluated the Long Term Resource Monitoring 

Program (LTRMP) sampling design for fish on the Upper 

Mississippi River System by analyzing data from stratified 

random samples collected during 1993–1999 in six Resource 

Trend Areas (RTA; Figure). Specifically, we investigated 

whether the sampling design could provide nearly the same 

amount of information it presently does with fewer sampling 

gears. Results and recommendations are in Ickes and Burkhardt 

(2002); available at http://www.umesc.usgs.gov/documents/

reports/2002/02t001.pdf. Our goals were to assess 

information provided by each gear used to monitor fishes in 

the LTRMP, engage program partners in a discussion on the 

relative value of each gear within the present sampling design, 

develop alternative sampling designs based on simulations 

of historical program data and expert opinion, and optimize 

the implementation of various alternative designs. Following 

our investigation and consultation with program partners, we 

eliminated 4 of the 10 gears used since program initiation in 

1989. 

Collections from 2002 provided the first opportunity to assess 

the accuracy of our predictions. We were unable to incorporate 

additional contemporary data because sampling was curtailed in 

the northern RTAs in 2003, and curtailed for the full program in 

2004. These reductions were budget driven and independent of 

studied and planned gear reductions implemented in 2002. Thus, 

data deriving from 2003 and 2004 have questionable value in a 

prediction validation context for assessing the quantitative effects 

of 2002 gear reductions. Based on simulations of program data 

from 1993 to 1999, our investigation in 2001 predicted that a 

six-gear design would retain 65% of historical annual catch, but 

with considerable variation among RTAs (Table 1). In 2002, total 

program catch was more than 2 times greater than predicted from 

historical data simulations. Three RTAs observed higher than 

predicted total annual catches (Pools 13 and 26 and La Grange 

Figure. The Upper Mississippi River System and locations of the six Resource 

Trend Areas monitored by the Long Term Resource Monitoring Program.
USGS Open-File Report 2006–1074

uncommon in the catch, making their detection uncertain for any 

given year. 

The value of changes to a monitoring network must be weighed 

against the costs of ceasing to collect particular types of data. 

Periodic evaluations of monitoring data force those responsible 

for implementing a program to critically assess the scientific 

and fiscal performance of the monitoring network. It also 

encourages users of program data to critically assess the value of 

the information provided in the context of their management and 

science needs. Such reflection is the foundation of an adaptive, 

partnership program. Details of the options considered by the 

partnerhship and subsequent analyses are in Ickes and Burkhardt 

(2002). The reductions in fish sampling gear implemented by the 

LTRMP in 2002 resulted in savings of time, effort, and money, 

with little apparent loss of information. Thus, the evaluation 

process used to assess these changes appears to have been 

successful in creating efficiencies within the Program while still 

achieving program goals. 

Ickes, B. S., and R. W. Burkhardt. 2002. Evaluation and proposed 

refinement of the sampling design for the Long Term Resource 

Monitoring Program’s fish component. U.S. Geological Survey, 

Upper Midwest Environmental Sciences Center, La Crosse, 

Wisconsin, October 2002. LTRMP 2002-T001. 17 pp. + 

Appendixes A–E. CD-ROM included. (NTIS #PB2003-500042)

This report is a product of 

the Long Term Resource 

Monitoring Program.

For more information contact

Brian S. Ickes

U.S. Geological Survey

Upper Midwest Environmental Sciences Center

2630 Fanta Reed Road

La Crosse, Wisconsin 54603

Telephone: 608-781-6298 

E-Mail: bickes@usgs.gov

http://www.umesc.usgs.gov

Mean Annual Total Catch

RTA 10-gear design Predicted 6-gear design Observed 6-gear design

Pool 4 68,857 46,857 (68%) 36,945 (54%)

Pool 8 54,000 26,143 (48%) 22,574 (42%)

Pool 13 46,571 17,714 (38%) 36,750 (79%)

Pool 26 25,429 18,286 (72%) 47,820 (188%)

Open River 17,571 17,143 (98%) 11,804 (67%)

La Grange Pool 83,286 67,000 (80%) 270,905 (325%)

Total 295,714 193,143 (65%) 426,798 (144%)

Table 1. For each Resource Trend Area (RTA) within the Long Term Resource Monitoring Program (LTRMP), the mean 

annual total catch of fish under 10-gear sampling design from 1993 to 1999, and the predicted and observed catch under 

the 6-gear sampling design implemented in 2002. Numbers in parentheses are the percentage of the total catch under 

the 10-gear sampling design that was predicted and observed in 2002 under the 6-gear sampling design

Table 2. For each Resource Trend Area (RTA) of the Long Term Resource Monitoring Program (LTRMP), the number of fish species collected each year and the 

seven-year annual mean under the 10-gear design, 1993 – 1999, and the predicted and observed number of species under the 6-gear design in 2002 along 

with the difference between the numbers predicted and observed (percent deviance from the 7-year mean in parentheses).

Year

Resource Trend Area

Pool 4 Pool 8 Pool 13 Pool 26 Open River La Grange Program Total

10-gear design

1993 73 78 65 62 66 64 111

1994 74 75 61 62 61 63 107

1995 59 72 61 70 72 68 108

1996 66 75 59 67 67 69 111

1997 71 76 67 66 67 66 113

1998 68 75 65 63 63 75 115

1999 73 72 69 67 71 65 114

Average (1993-1999) 69 75 64 65 67 67 111

6-gear design in 2002

Predicted 64 (-7%) 70 (-7%) 58 (-9%) 62 (-5%) 65 (-3%) 67 (-0%) 101 (-9%)

Observed 58 (-16%) 65 (-13%) 59 (-8%) 59 (-9%) 63 (-6%) 67 (-0%) 101 (-9%)

Difference -6 -5 +1 -3 -2 0 0