Evaluation and Proposed Refinement of the Sampling Design for the Long Term Resource Monitoring Program's Fish Component
Abstract : 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 causal mechanisms of the observed changes, and making resource management decisions. Because monitoring programs require significant investments of time, money, and human resources to implement and maintain, 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. We evaluated the Long Term Resource Monitoring Program's (LTRMP) fish sampling design by analyzing data from stratified random samples collected from 1993 to 1999 in six Trend Analysis Areas (TAAs). Specifically, we investigated whether the sampling design could provide similar information with fewer sampling gears. Our goals were to identify and quantify information provided by each gear used to monitor fish in the LTRMP, develop alternative sampling design scenarios based on our analyses and expert opinion, and engage program partners in a discussion on the relative value of each gear within the present sampling design. Community characterization (presence or absence), community structure (relative abundance within the full community), and detection of annual changes in single-species catch-per-unit-effort (Lubinski et al. 2001) are the primary information provided by the fish component. Our analyses considered differences in these measures among TAAs, gear types, sampling strata, seasonal sampling period, and fish size. Results were made available to program partners through a Web site for review and comment. Based on these analyses, program partners developed a suite of potential options for component refinement.
Reduced condition factor of two native fish species coincident with invasion of non‐native Asian carps in the Illinois River, U.S.A. Is this evidence for competition and reduced fitness?
Non-native, Asian carps bighead Hypophthalmichthys nobilis and silver Hypophthalmichthys molitrix have been present in the Illinois River since the early 1990s. The Long-Term Resource Monitoring Program (LTRMP) has been collecting bighead and silver carps in routine monitoring of the La Grange Reach, Illinois River, since 1995 and 1998, respectively. Despite variable recruitment, Asian carps abundance and biomass have increased since 2000, as evidenced by commercial landings, and Asian carps now dominate the fish community on La Grange Reach. Previous research suggests dietary overlap among bighead and silver carps and two native Illinois River fishes, gizzard shad Dorosoma cepedianum and bigmouth buffalo Ictiobus cyprinellus. Total length and mass data from c. 5000 fishes were used to test for changes in gizzard shad and bigmouth buffalo body condition after Asian carps establishment and investigate potential competitive interactions and changes in fitness. Analyses revealed significant declines in body condition of gizzard shad (� 7%) and bigmouth buffalo (� 5%) following the Asian carps invasion from 2000 to 2006. Segmented regression analyses showed no significant change in the rate of decline in gizzard shad condition after 2000, whereas the rate of decline in bigmouth buffalo condition increased significantly after 2000. Statistically significant differences in gizzard shad condition after Asian carps establishment (2000–2006) was observed, whereas condition of bigmouth buffalo was significantly lower in all years following Asian carps establishment as compared to 2000. Declines in gizzard shad and bigmouth buffalo condition were significantly correlated with increased commercial harvest of Asian carps and poorly correlated with other abiotic and biotic factors (e.g. temperature, chlorophyll a and discharge) that may influence fish body condition. These results may suggest that Asian carps are influencing native planktivore body condition, and future research should focus on determining whether food is limited in the Illinois River for native planktivores and other fish species.
Growth of Selected Fishes in Navigation Pool 8 of the Upper Mississippi River: A Test of the Flood-Pulse Concept.
Abstract : Size-specific growth of bluegill, black crappie, and freshwater drum was significantly different over four years in Navigation Pool 8 of the upper Mississippi River. Differences in growth were positively related to annual hydrographs for bluegill but less related to hydrographs for black crappie and freshwater drum. These results are consistent with predictions of the Flood Pulse Concept. Extensions of analysis of covariance (ANCOVA) models were used to account for differences in growth due to the size of fish and tested for annual differences in growth rates. Planned comparisons examined differences in growth among years with a large flood event, two years of normal hydrology, and a drought. Some sizes of bluegill and freshwater drum, but not black crappie, grew significantly faster during the flood year than during years of normal flow. Some sizes of bluegill and black crappie grew slower during the drought year when freshwater drum were not sampled. Growth curves for bluegill and black crappie indicate that the magnitude of the effects on growth rate was greater for the drought year than for the flood year. Differences in growth rate among years were most apparent for bluegill from 50 - 100 mm, black crappie greater than 200 mm, and drum longer than 100 mm. These data suggest that (1) patterns in growth for some riverine fishes are consistent with the Flood Pulse Concept, (2) droughts may be of greater consequence than floods to riverine communities, and (3) growth responses related to hydrology arc size- and species-specific.