2008 RESEARCH HIGHLIGHTS

JANUARY

Research Need: Is there competition between fish and fowl in wetlands?

Research Highlight: Waterfowl managers are concerned when walleye are extensively raised in wetlands because of the potential fish-fowl competition for forage. In this study walleye greatly reduced the fathead minnow population. Decreasing the fathead minnows released predation pressure on zooplankton, an important lower trophic level that would foster macroinvertebrate production. However, walleye consumed primarily macroinvertebrates once fathead minnow populations became suppressed. Nevertheless, consumption estimates of invertebrates by walleye were substantially less than those for fathead minnow. Stocking age-0 walleye was an effective biomanipulation tool that substantially reduced fathead minnow densities and improved zooplankton densities. Assistant Unit Leader Dr. Steven R. Chipps was part of a research team that published these findings (figure by Escher).

FEBRUARY

Fish bioenergetics models have flourished in recent years (see figure). As with any model, the accuracy of bioenergetics models can be hampered by uncertainty in model parameters. Chipps’ review showed that field and laboratory tests of bioenergetics models often result in poor agreement between model predictions and independent data. Nonetheless, bioenergetics modeling continues to be used to make important management decisions. Recent tests of model predictions have shown that parameter uncertainty is influenced by factors such as feeding rate, physiological adaptations, and prey composition and abundance. Working with Illinois Natural History Survey scientist Dave Wahl, Chipps proposed reducing the uncertainty in modeling applications by using a framework that highlights the importance of (1) model evaluation, (2) hypothesis-based parameter testing, and (3) improved communication between model developers and model users. Adherence to this framework will help reduce uncertainty in modeling applications and simultaneously contribute to a broader knowledge of fish physiology and feeding ecology. (Chipps, S. R. and D. H. Wahl. 2008. Bioenergetics modeling in the 21^st century: reviewing new insights and revising old constraints. Transactions of the American Fisheries Society 137:298-313.)

MARCH

Stocking pallid sturgeon is part of the recovery effort as is long-term monitoring. Both practices are addressed in a recent M.S. thesis by Unit Graduate Research Assistant (GRA) Bryan Spindler, who says “understanding the distribution and habitat requirements of juvenile pallid sturgeon could benefit how stocking and monitoring is done.” He developed a habitat assessment tool for juvenile pallid sturgeon that integrated information from known capture locations with physical habitat and macroinvertebrate abundance data. He compared habitat between capture (n=25) and non-capture (n=49) locations downstream of Fort Randall Dam (Figure). Four variables successfully discriminated capture from non-capture locations: 1) water depth > 2 m, 2) proportion of sand substrate, 3) dipteran abundance, and 4) ephemeropteran abundance. Spindler predicted pallid sturgeon occurrence in eight 3.2 km river segments. He was correct for 88% of the capture areas and 100% for non-capture areas. The percent of area classified as potential capture locations in eight river segments ranged from 22 to 64%, indicating the patchiness of good habitat for juvenile pallid sturgeon. Patches have a special combination of biotic and abiotic characteristics that influence juvenile pallid sturgeon occurrence. Chipps supervised the study.

APRIL

Accuracy of bioenergetics models varies with feeding rate of fishes and may be associated with error in measuring fish metabolism. Metabolic rate of fishes is a key parameter in energy budget formulations and can strongly influence accuracy of model predictions. GRA Steven Ranney tested the hypothesis that metabolic rate of age-1 largemouth bass [mean (SE) = 105.9g (1.77); n = 24] varies with feeding history. Different feeding regimes were applied to two size classes of fish – i.e., maintenance rations of fathead minnows for larger fish and ad libitum rations for smaller fish – over a nine week period such that body mass was similar prior to metabolic measurements. (Figure shows how weight of ad libitum fish caught up with maintenance fish.) Fish that were fed maintenance rations had metabolic rates (i.e., oxygen consumption) that were only 63% of those fed ad libitum (0.00230 vs. 0.00368 g O₂/g/d). The percent difference between predicted versus observed food consumption for fish fed ad libitum was moderate (11%) indicating that the bioenergetics model provided a reasonable fit to observed values. However, metabolism was overestimated for fish fed maintenance rations. These findings highlight the importance of feeding history in parameterizing fish metabolism. Incorporating feeding history into sub-models for metabolism in bioenergetics models will improve their predicative accuracy and allow fisheries biologists to make better decisions regarding fish populations. Chipps was faculty advisor. Ranney is now heading to Montana State University to pursue a Ph.D. degree in the Montana Coop Unit.

MAY

No highlight to report in May.

JUNE

No highlight to report in June.

JULY

Former Assistant Unit Leader Kenneth F. Higgins is now a volunteer for the U. S. Fish and Wildlife Service. His assignment – revisit five historic duck research study sites in the Dakotas and southern Canada, where he helped conduct duck nesting and production studies in the 1960s, and document change. The sites were: Waubay area (South Dakota), Woodworth area (North Dakota), Minnedosa and Roseneath area (Manitoba), Redvers area (Saskatchewan), and Lousana area (Alberta). The Waubay area now has good wetland conditions and high waterfowl pair abundance, but the other areas were in fair to poor wetland condition and duck pair populations were well below average. For example, at two sites canvasback pairs and brood counts equaled all time lows. Higgins noticed other changes at the Canadian sites such as: giant Canada geese and ravens were common whereas none occurred before, fewer clumps of aspen and poplar trees, more oil wells, less dairy farming and more canola cropping, fewer farm sites, more cattail wetlands and less bullrush wetlands. Higgins found similar changes during an earlier study at Waubay. Higgins gave presentations in July to biologists at the Delta Marsh Station in Manitoba, the Prairie Pothole Joint Venture office in Crookston, Minnesota, and at the Central Flyway Technology Committee meeting in Overland Park, Kansas. Higgins just submitted four manuscripts from past students’ work to the South Dakota Academy of Science and works a day or two each week at South Dakota State University (SDSU), where he is an Emeritus Professor.

AUGUST

No highlight to report in August.

SEPTEMBER

Update on Rocky Mountain Sandhill Crane Research

This is the Unit’s largest project in scale and time – some recent analysis allows preliminary conclusions about crane behavior on the principal wintering grounds (Bosque del Apache National Wildlife Refuge and surrounding private lands). Preliminary results for the winter of 2005/2006 show post-migrant cranes (November observations) foraging primarily in alfalfa (6%) and small grain fields (9%) on private lands and in alfalfa (53%), corn (15%), and wetlands (4%) on public lands. By mid-winter, crane use of private lands decreased to <5%. Mid-winter crane use (January observations) of public lands increased 9%, with the highest use in alfalfa (55%) and corn (16%) fields and a 7% increase in crane use of wetland habitats. Pre-spring migrant cranes (February) were observed only in wetland habitats located on public lands. Eighty-seven percent of the cranes found in wetlands were foraging. The apparent switch from crop based foods to natural foods found in wetland habitats suggest a change in the seasonal life cycle of the cranes and their need for foods that will support not only migration but pair bonding and breeding. Ph.D. student Tandi Perkins and M.S. students Brett Beasley and Diana Iriarte are working on energetics models that will be used by refuge managers to ensure that the appropriate foods are made available to cranes as they carryout their seasonal cycle events throughout the winter.

OCTOBER

Escarpment in the Dakotas: A Unique Geology and Fish Assemblage

GRA Luc Borgstrom is studying North Dakota streams flowing from the Escarpment to the Red River. He pulled together the following summary of the unique streams for both states for a talk at a recent water conference. The Prairie Coteau Escarpment ecoregion is a distinctive ecosystem, rising 300 to 600 feet in elevation from the Minnesota and Red River valleys. In South Dakota the geological formation fosters deciduous forest growth in riparian areas and seven cool, perennial streams that have unique fish and wildlife habitat in the headwaters (1,572 mi²) of the Minnesota River. The escarpment ecoregion continues in North Dakota where its influences on water and wildlife are more obvious in northern tributaries to the Red River than in southern tributaries. The streams in North Dakota that flow through the escarpment provide clear water and habitat for nine species of conservation priority such as: blacknose shiner, finescale dace, hornyhead chub, largescale stoneroller, logperch, northern redbelly dace, pearl dace, pugnose shiner, and silver chub, as well as a trout fishery in Turtle River. In South Dakota 60 fish species, of which 56 were native and four were introduced, were documented during the last 150 years. At least 47 of these (45 native, two introduced) are currently present. Species of concern such as blacknose shiners, horneyhead chubs, carmine shiners, central mudminnow, western banded killifish, northern redbelly dace, golden redhorse, and blackside darter are present. Abundance of these fishes has been related to mean stream width, temperature, and riffle habitat.

NOVEMBER

It is easy to find common things, but finding rare ones is more difficult (Duh!). Detection probability is the probability that a species is collected if it is present at the sampling site at that time. Detection probabilities have been applied to terrestrial animals for many years, but aquatic applications have lagged – this situation may change because of recent publications by Ms. Cari-Ann Hayer, (M.S. Auburn University), a Research Associate with the Coop Unit (figure shows Hayer and SDSU students electrofishing a Black Hills stream). Hayer summarizes her most recent publication by writing “When sampling it is difficult to detect all the individuals in a particular sampling area. The assumption of 100% detection and equal probability of capture among and between species is usually violated.” Detection probabilities account for the differences among species and help to make better inferences about population size and structure leading to improved management decisions. Hayer used detection probabilities in Alabama to relate fish presence to habitat, season, and watershed, and in South Dakota for evaluating fish distribution models (North American Journal of Fisheries Management 28:1259). In our ongoing studies of North Dakota stream fishes detection probabilities will be part of the investigation of the habitat and seasonal use of blue suckers, which may be difficult to capture (especially some year classes). We can also make inferences about which sampling methods are more efficient.

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