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Fish Sampling
The objective of the National Lake Fish Tissue Study is to estimate the national distribution of the mean levels of 268 persistent, bioaccumulative, and toxic (PBT) chemicals in fish tissue from lakes and reservoirs of the contiguous United States.
- Sampling Design
- Lake Definition
- Target Species
- Composite Samples
- Quality Assurance Program
- Sampling Schedule
- Documents
Sampling Design
EPA worked with partner agencies in states, tribes, and the federal government to collect fish for the National Lake Fish Tissue Study at 500 lakes and reservoirs in the contiguous United States (lower 48 states) over a period of four years (2000-2003). These lakes were randomly selected in 1999 from River Reach File 3 (RF3), which provided the best available GIS coverage for lakes and reservoirs at that time. RF3 contained over 270,000 lakes that could be potentially selected for the fish study. The Great Lakes and the Great Salt Lake were excluded from this set of lakes before initiating the lake selection process. The lake selection process was based on an unequal probability survey design.
The lakes are divided into six size categories with varying inclusion probabilities to decrease the extent to which small lakes dominate the sample. These size categories (based on surface area) are as follows: 1-5 hectares, >5-10 hectares, >10-50 hectares, >50-500 hectares, >500-5000 hectares, and >5000 hectares. The sampling design incorporates spatial constraints to achieve better geographic representation.
Lake Definition
For this study, a lake is defined as a permanent body of water with a permanent fish population that has a surface area of at least 1 hectare (about 2.5 acres), a depth of at least one meter, and at least 1000 square meters of open, unvegetated water.
Target Species
Target fish species are identified to limit the number of species included in the study. Target species are selected in accordance with EPA's Guidance for Assessing Chemical Contaminant Data for Use in Fish Advisories, Volume 1: Fish Sampling and Analysis (Third Edition, November 2000), with preferences cited in EPA's Field Sampling Plan for the National Study of Chemical Residues in Lake Fish Tissue (September 2002, Revision).
Fish Composite Samples
Sampling consisted of collecting two fish composites per site (one composite of predators and another of bottom dwellers). Each composite contains 5 adult fish of the same species and of similar size (so that the smallest individual within the composite is no less than 75% of the total length of the largest individual).
Sample analysis requires 560 grams of tissue for analysis of fillets for predator composites and whole bodies for bottom-dweller composites.
Replicate samples were collected from about 10% of the lakes to estimate sampling variability.
Quality Assurance (QA) Program
A Quality Assurance Project Plan (QAPP) was developed and approved by EPA to support fish sampling activities for this study. The Quality Assurance Project Plan for Sample Collection Activities for a National Study of Chemical Residues in Lake Fish Tissue (May 2000) establishes data quality goals for all sample collection and handling activities, and describes the Quality Assurance/Quality Control(QA/QC) techniques employed by field teams to support those goals. EPA ensured consistency in fish collection, handling and shipping through:
- orientation and training for study participants
- participation of experienced fisheries biologists
- preparation and distribution of a detailed field sampling plan
- implementation of detailed Standard Operating Procedures for all sample collection and handling activities
- distribution of identical field sampling materials to all sampling teams
- daily tracking and coordination of sample shipments through a centralized source
- preparation (filleting and homogenization) of fish tissue samples in a controlled (laboratory) environment
Sampling Schedule
EPA and its partners initiated the first full field sampling season for the National Lake Fish Tissue Study in 2000, and continued to collect fish for the study through 2003. Fish samples collected during 2000, 2001, 2002 and 2003 are designated as first, second, third and fourth year samples, respectively. Most fish composites were collected during the summer and fall of each sampling year. It took an additional year to complete analysis of the fish tissue samples.
Documents
Quality Assurance Project Plan (QAPP) for Sample Collection Activities for a National Study of Chemical Residues in Lake Fish Tissue (PDF) (114 pp., 611K, About PDF). The Quality Assurance Project Plan (QAPP) describes the quality assurance/quality control (QA/QC) requirements for collecting, handling, and shipping fish for the National Lake Fish Tissue Study. It was approved by the Office of Science and Technology's (OST's) Quality Assurance Officer in May 2000.
Field Sampling Plan for the National Study of Chemical Residues in Lake Fish Tissue (PDF) (40 pp., 814 K, About PDF). The field sampling plan is a field manual presented in a question-and-answer format that specifies all essential fish collection, handling, and shipping information for state, tribal, and federal sampling teams collecting fish for the National Lake Fish Tissue Study. It includes a project description, detailed standard operating procedures (SOPs) for fish collection, and instructions for completing field forms and labels and for shipping fish samples.