Seasonal Fish Losses through Hauser Dam, Montana, 2007- 2008

Management of fish populations in Hauser Reservoir, Montana, is hindered by undesirable and unpredictable downstream fish entrainment through Hauser Dam. We quantified fish entrainment through the dam using hydroacoustics at turbine intakes from July 2007 to November 2008 and over the spillway from 21 May to 18 July 2008. Species composition was characterized using multiple netting gears. Total estimated entrainment was 145,470 ± 6,204. Annual entrainment from summer to autumn was higher in 2007 (n = 79,031 ± 4378) than in 2008 (n = 52,513 ± 3,966). Spillway entrainment was 19 percent of annual entrainment in 2008 and was correlated with spillway discharge; turbine entrainment was not. Turbine entrainment increased from summer to autumn in both years, probably in response to autumn turnover and releases of hatchery rainbow trout (Oncorhynchus mykiss). Spill entrainment in 2008 resulted in similar entrainment between summer and autumn, but autumn turbine entrainment increased in 2008. About 60 percent of entrained fish were smaller than 220 mm. We applied species composition by size to the hydroacoustic data to identify fish species entrained, but many fish (n = 55,529 ± 4,397) could not be reliably assigned to species because concurrent net catches did not include individuals of similar size. Total entrainment of identified fish was made up of mostly rainbow trout (Oncorhynchus mykiss; 33.3%) and walleye (Stizostedion vitreum; 30.2%). Identification of patterns in spatial and temporal fish losses affords fishery managers the ability to make more informed decisions about operation of this dam

Investigation into Bias and Variability in Estimates of Population Size and Biomass when Catches of Individuals are Large Relative to the Total Population

Biomass of fish populations has traditionally been estimated by multiplying the average weight of captured fish by the estimated number of fish, with its variance estimated as the product of two variances. We present a method for estimating fish biomass in small streams (< 5 m wetted width) that uses a finite population correction factor (FPC) to take advantage of the fact that a relatively high proportion of the total population is normally captured and can be weighed during removal estimates. For these captured fish, measurement error is related to scale accuracy and field conditions. For the portion of the population that is not captured, we used a randomly stopped sums estimator (RSS) to estimate the total weight and variance of this non-captured proportion of the population. We also evaluated FPC and RSS methods individually to determine which of the four methods--(1) combination of FPC and RSS (FPCRSS), (2) traditional (hereafter OLD), (3) FPC, or (4) RSS—performed best. We also incorporated biomass estimates for fish that were captured, but not weighed, using length-weight regression predictions (FPCRSSreg). Performance of these estimators was evaluated using both simulated and field data. We based performance on reduction in the coefficient of variation (CV) of the biomass estimate and coverage of 95-percent confidence intervals (proportion of trials for which the 95-percent estimated biomass confidence intervals included the true biomass). The FPCRSS method had the narrowest CVs and the OLD method had the widest CVs for both the field and simulated data. Because of the high variance for the OLD method, 95-percent CIs for this method included the true biomass for a higher proportion of trials (nearly 100%) than 95-percent CIs for the FPCRSS method, but the coverage of the FPCRSS method for two-pass removal estimates was 80 percent or better for capture probabilities of 0.5 or higher. Using simulated data, we found that removal estimators are biased and that these biases are more pronounced at lower capture probabilities and lower population sizes. This bias in removal population estimators causes a bias in biomass estimates and was partly responsible for poorer coverage of 95-percent CIs. Our attempts to correct for population estimate bias resulted in much wider confidence intervals for both population and biomass estimates. For 607 field biomass estimates where all captured fish were weighed, the median CV for the FPCRSS method (0.05) was significantly lower (Wilcoxon sign-ranked test: P < 0.001) than the OLD method (0.76). When a portion of captured fish was not weighed, but estimated using length-weight regression relationships, the FPCRSSreg method had significantly lower CVs (median = 0.06; Wilcoxon sign-ranked test: P < 0.001, n = 130) than the old method (median = 0.86)

Photographic analysis of natural and impounded salt marsh in the vicinity of Merritt Island, Florida

Qualitative analyses of available photographs and maps of Merritt Island, Florida provide a large-scale, historical perspective of ecological changes of the marshes in the vicinity. Sites that deserve closer scrutiny can be identified. Secondarily, such an analysis provides a geographical orientation essential for communication not only between newcomers and those familiar with the area, but also among those familiar with the area but who refer to sites by differing methods. Photographs and maps from various sources were examined. Below are listed what we consider to be the most useful subset of these for ecological and geographical assessment of salt marsh impoundments on Merritt Island, Florida. (Document has 25 pages.

DEPREDATION OF CATFISH BY DOUBLE-CRESTED CORMORANTS AT AQUACULTURE FACILITIES IN OKLAHOMA

Oklahoma has about 324 ha of surface water in catfish (Ictalurus spp.) production. The state also supports a large number of migrating and wintering piscivorous birds, particularly double-crested cormorants (Phalacrocorax auritus). To address concerns of aquaculture facility operators regarding loss of fish to cormorants, we asked 11 operators to conduct regular counts of piscivorous birds at each facility. These data were used to determine factors affecting cormorant density at facilities and to estimate amount of catfish lost to cormorant depredation. Cormorant density (birds/ha/day) was positively correlated with surface area of water in production at facilities \u3c10 ha (r = 0.621, P = 0.004) and negatively correlated with percentage of forested shoreline at each facility (r = -0.518, P = 0.016). Distance to nearest major reservoir or river was not significantly correlated with cormorant densities. To estimate depredation, we assumed a daily intake of 0.4 kg of fish per cormorant and used the average number of birds counted at participating facilities. Cormorants consumed an estimated 7,196 + 8,729 kg ( x + SE) of catfish, valued at $13,672-$36,195 (depending on size offish consumed), or about 3-7% of Oklahoma catfish sales in 1993

DEPREDATION OF CATFISH BY DOUBLE-CRESTED CORMORANTS AT AQUACULTURE FACILITIES IN OKLAHOMA

Oklahoma has about 324 ha of surface water in catfish (Ictalurus spp.) production. The state also supports a large number of migrating and wintering piscivorous birds, particularly double-crested cormorants (Phalacrocorax auritus). To address concerns of aquaculture facility operators regarding loss of fish to cormorants, we asked 11 operators to conduct regular counts of piscivorous birds at each facility. These data were used to determine factors affecting cormorant density at facilities and to estimate amount of catfish lost to cormorant depredation. Cormorant density (birds/ha/day) was positively correlated with surface area of water in production at facilities \u3c10 ha (r = 0.621, P = 0.004) and negatively correlated with percentage of forested shoreline at each facility (r = -0.518, P = 0.016). Distance to nearest major reservoir or river was not significantly correlated with cormorant densities. To estimate depredation, we assumed a daily intake of 0.4 kg of fish per cormorant and used the average number of birds counted at participating facilities. Cormorants consumed an estimated 7,196 + 8,729 kg ( x + SE) of catfish, valued at $13,672-$36,195 (depending on size offish consumed), or about 3-7% of Oklahoma catfish sales in 1993

Nesting Habitat and Behavior of Spiny Softshell Turtles Apalone Spinifera Hartwegi in the Missouri River, MT

Little is known about the nesting behavior and habitat of the western spiny softshell (Apalone spinifera hartwegi) in Montana where they are at the northern extent of their range and are a state Species of Concern. Our objective was to document nesting behavior, habitat, and timing in a 97-kilometer reach of the Missouri River. We radio-tagged 47 female turtles and attempted to locate nesting areas using telemetry, visual surveys from jet boat and on foot, and by observation from shore-based blinds. We located 27 nests; 15 were on islands, 12 were aggregated, and 2 were depredated. Nesting occurred following the peak river stage from about July 7 to July 28. Twenty-three nests were in mixed gravel and 4 nests were in sand substrates. Distance from water’s edge to the nest ranged from 1.9 m to 27 m and height of nest above the water surface elevation ranged from 0.25 m to 1.9 m. Vegetation at nest sites was sparse, ranging from 0 to 15 percent vegetative cover. Emergence of hatchlings was documented for 17 nests and occurred from about September 1 to September 20. All 17 successful nests were in gravel substrate; we did not document any emergence from nests in sand. Lack of emergence from sand nests may be related to the cumulative thermal regime in the nest chamber during the period from peak discharge until the onset of freezing in autumn. In 2012, we will investigate the thermal environment in gravel and sand nesting substrates

Nesting Ecology of Spiny Softshell Turtles on the Missouri River in Montana: Zoogeographic and Management Implications

The nesting ecology of western spiny softshell turtles (Apolone spinifera hartwegi) in Montana, where they are at the northern extent of their range and a state Species of Concern, is poorly known. We used telemetry, visual surveys, observation from shore-based blinds, and remote cameras to document nesting behavior, habitat, and timing in a 97-km reach of the Missouri River. We located 25 nests in 2011 and 97 in 2012. Most nests were in mixed-gravel substrates; only 3 percent were in pure sand. Vegetative cover at nest sites was sparse. Mean distance of nests to the water’s edge was 13.7 m and mean height above the water surface elevation was 0.7 m. Proportion of nests found on island and mainland habitats were similar in 2011, but 90 percent of nests were on islands in 2012. Predation occurred on 46 nests; mainland nests incurred higher predation rates than island nests. Nesting followed annual peak river stage, and mostly occurred in the afternoon. Durations of nesting, incubation, and emergence periods were similar in both years, but nesting and emergence occurred about three weeks later in 2011 than in 2012. Only 36 percent of nests were successful in 2011, but 60 percent were successful in 2012. Flooding in 2011 probably decreased nesting effort and success by reducing habitat availability and delaying the onset of nesting, which thereby prematurely ended incubation. However, flood events maintain and create nesting habitats by clearing vegetation and depositing substrates. Premature termination of incubation suggests that the northern range of this species is probably limited by successful incubation

Nesting Ecology of Spiny Softshell Turtles on the Missouri River in Montana: Zoogeographic and Management Implications

The nesting ecology of western spiny softshell turtles (Apolone spinifera hartwegi) in Montana, where they are at the northern extent of their range and a state Species of Concern, is poorly known. We used telemetry, visual surveys, observation from shore-based blinds, and remote cameras to document nesting behavior, habitat, and timing in a 97-km reach of the Missouri River. We located 25 nests in 2011 and 97 in 2012. Most nests were in mixed-gravel substrates; only 3 percent were in pure sand. Vegetative cover at nest sites was sparse. Mean distance of nests to the water’s edge was 13.7 m and mean height above the water surface elevation was 0.7 m. Proportion of nests found on island and mainland habitats were similar in 2011, but 90 percent of nests were on islands in 2012. Predation occurred on 46 nests; mainland nests incurred higher predation rates than island nests. Nesting followed annual peak river stage, and mostly occurred in the afternoon. Durations of nesting, incubation, and emergence periods were similar in both years, but nesting and emergence occurred about three weeks later in 2011 than in 2012. Only 36 percent of nests were successful in 2011, but 60 percent were successful in 2012. Flooding in 2011 probably decreased nesting effort and success by reducing habitat availability and delaying the onset of nesting, which thereby prematurely ended incubation. However, flood events maintain and create nesting habitats by clearing vegetation and depositing substrates. Premature termination of incubation suggests that the northern range of this species is probably limited by successful incubation

Performance of Westslope Cutthroat Trout Released into the Upper Cherry Creek Drainage Using Remote Stream Incubators

A major effort to conserve westslope cutthroat (Oncorhynchus clarkii lewisi; WCT) is underway throughout Montana. One of the larger WCT conservation projects is onging in the Cherry Creek drainage of the Madison River. About 105 km of stream and a mountain lake are being treated with piscicides to remove nonnative trout, and WCT are being introduced into the drainage using remote stream incubators (RSIs). We are evaluating the relative success of different wild and hatchery stocks of WCT released into Cherry Creek. Here, we report on survival, abundance, growth, condition, and dispersal of WCT in the upper Cherry Creek drainage during the first three years of releases. Two streams of similar size, upper Cherry Creek and Cherry Lake Creek, meet to form main Cherry Creek. Cherry Lake Creek is colder than upper Cherry Creek (average August temperature about 3?C colder).Known numbers of WCT embryos were placed into RSIs at two sites in upper Cherry Creek during 2006 and 2007, one site in Cherry Lake Creek during 2006 and 2007, one site in Pika Creek (a tributary to Cherry Lake Creek) during 2008, and in an un-named spring-fed tributary to main Cherry Creek just below the mouth of Cherry Lake Creek during 2008. Fry that hatched in each RSI were captured and counted prior to release. Population abundances were estimated by single and multiple-pass electrofishing in 100-m sample sections located systematically throughout the upper reaches of the drainage. Estimated survivals from egg to fry, fry to age- 1, age-1 to age-2, and age-2 to age-3 ranged from 13 to 80 percent, 7 to 80 percent, 21 to 100 percent, and 100 percent, respectively. Survivals in the colder stream, Cherry Lake Creek, were lower than in the warmer stream. Over 3500 WCT occupied the upper Cherry Creek drainage by 2009. Fish dispersed short distances upstream and long distances downstream, but downstream dispersal appeared relatively discrete, with WCT filling available habitat near RSIs before occupying reaches further downstream. Early growth of WCT was much slower in colder streams, but by age-3 little difference existed among streams. Conversely, condition factors of WCT were slightly lower in upper Cherry Creek (averaging 0.88 to 0.95) than in Cherry Lake Creek (0.92 to 1.11). The introduction of WCT in upper Cherry Creek has been successful to date; however, natural reproduction by introduced WCT has not yet occurred, but is expected to occur next year

Thermal Adaptation of Westslope Cutthroat Trout

Populations of westslope cutthroat trout (Oncorhynchus clarkii lewisi), a State species of special concern, have declined throughout their native range. Genetic introgressions, mainly from rainbow trout (O. mykiss), but also from Yellowstone cutthroat trout (O. c. bouvieri), and habitat loss are believed to be the leading causes of this decline. Populations that remain are often small and isolated, thereby increasing their risk of inbreeding depression and extinction. Translocation projects may offer a solution by infusing new genetic material into populations and potentially increasing their probability of persistence. However, local adaptations must be considered when selecting a donor population. We investigated thermal adaptations of four wild populations of westslope cutthroat trout from the Missouri River drainage and one hatchery population from the Washoe Park Trout Hatchery, Anaconda, Montana. Two wild populations were deemed to be from warm streams and two from cold streams. Fish were spawned streamside and at the hatchery. The resulting embryos were placed in experimental systems at 8, 10, and 14 °C. Survival was monitored throughout incubation. Post-embryonic growth was measured 90 days after hatching. Relationships between population performance and natal stream thermal characteristics were examined for adaptive differences