Jeffrey J. Rach

Toxicity of Candidate Molluscicides to Zebra Mussels (Dreissena polymorpha) and Selected Nontarget Organisms

Many compounds have been marketed for control of zebra mussels (Dreissena polymorpha), but most compounds lack comparable toxicity data and have not been tested on nontarget organisms. We tested the toxicity of 18 chemicals to two sizes of zebra mussels, two nontarget fish (rainbow trout, Oncorhynchus mykiss and channel catfish, Ictalurus punctatus), and a unionid mussel (threehorn wartyback, Obliquaria reflexa) under standard conditions. Organisms were exposed to the chemicals for 48 h in “soft” reference water (pH 7.7, alkalinity 6 × 10−4 m/L (30 mg/L) as CaCO3, and total hardness 40 mg/L as CaCOj) at 17° C. Zebra mussels and unionid mussels were held in untreated reference water for another 48 h after exposure to measure delayed mortality. The LC50 values and 95% confidence intervals were compared among test organisms. Potassium chloride, Bayluscide (a registered molluscicide), and Clamtrol CT-1 (a poly quaternary ammonium compound) were the most selective chemicals tested against zebra mussels. They were two to three times more toxic to zebra mussels than to the nontarget species. Most of the remaining chemicals lacked the desired toxicity or were more toxic to fish than to zebra mussels.

Behavioral responses to disturbance in freshwater mussels with implications for conservation and management

Knowledge about the ability of freshwater unionid mussels to recover from physical disturbance is important to their conservation and management. Threatened species may be disturbed by relocation to refugia as a conservation measure, and some species are disturbed by size- and species-selective harvesting of shells for use in the production of cultured pearls. The activity of freshwater unionid mussels generally decreases with water temperature, but intra- and interspecific differences in the frequency and distribution of recovery behaviors following disturbances at specific water temperatures have not been previously quantified. We observed righting, moving, and burrowing behavior of 4 mussel species, Amblema plicata plicata, Potamilus alatus, Fusconaia flava, and Lampsilis cardium, at 3 water temperatures (7, 14, and 21°C). The temporal frequency (intensity) and times-to-1st-event of behaviors were analyzed using proportional hazards models. Righting events and consecutive movements occurred at different intensities among temperatures and species. For righting, intensity increased by 8%/°C within the range of 7-21°C. Subsequent movements increased in intensity by 10%/°C. Amblema plicata was the slowest to respond, and had an intensity of turning upright only 27% of that for P. alatus. The intensities of movements for A. plicata and F. flava were 16% of those for P. alatus. Lampsilis cardium righted themselves most quickly, and had an intensity of righting 124% of that for P. alatus. The distribution of the 3 behaviors among treatment groups at 1 wk was analyzed with a proportional odds model. The distribution of righting, moving, and burrowing 1 wk after disturbance was described entirely by high-order interactions in our proportional odds model. Therefore, that model revealed little interpretable pattern in the endpoint data and it was less sensitive than our analysis of time-to-event data for measuring the effects of disturbance. We attributed the difference in sensitivity between the 2 models to the greater information content of time-until-event data. For similar studies of occurrences of key events, times to events should be recorded and interpreted whenever feasible and consistent with study objectives. Our results suggest that water temperature has an important effect on the outcome of mussel conservation projects and commercial harvesting activities. Our modeling approach, applied to other species, could help guide decisions about which species can safely be disturbed and the optimal seasonal timing of those disturbances.

Effects of Handling and Aerial Exposure on the Survival of Unionid Mussels

Abstract We conducted a relocation study of unionid mussels in Navigation Pool 7 of the upper Mississippi River (river mile 713.2) to evaluate survival after handling and aerial exposure. Two separate studies were conducted to compare seasonal differences in mussel survival; the first was initiated in June and the second in October. Amblema plicata plicata (subfamily Ambleminae) and Obliquaria reflexa (subfamily Lampsilinae) were studied. Mussels were marked, held out of water for either 0, 1, 4, or 8 h, and then placed into a 3 × 3 m grid (divided into nine 1-m2 units). The mussels were re-examined after four-five months to measure mortality in the control and treatment groups. Mussels of both species had >90% survival after aerial exposure up to 4 h in both studies. However, survival (number recaptured live/number recaptured live and dead) of mussels showed a decreasing trend with duration of exposure in the first study, but not in the second study. The overall recovery of marked mussels (number recaptu...

Crayfish Control with Traps and Largemouth Bass

Abstract We attempted to control a population of papershell crayfish (Orconectes immunis) in an 11-hectare fish-rearing impoundment in Jackson County, Wisconsin, by using traps and by stocking largemouth bass (Micropterus salmoides). Crayfish were harvested with traps during the summer of 1985, and the pond was stocked with 386 largemouth bass (mean weight, 1.1 kg) in spring 1986. The pond was drained in the fall of 1985 and 1986, and crayfish burrow counts were made to estimate the population. In 1985, we trapped more than 18,000 crayfish, of which 72% were adult males. Trapping had minor effect on the young-of-the-year crayfish. In 1986, the crayfish population was reduced by 98%, predation by largemouth bass being the probable major cause of the reduction.

Comparison of Three Baits for Trapping Crayfish

Abstract In late summers of 1985 and 1986, the efficacies of two commercially manufactured crayfish baits (one each in block and pelleted form) and dead fish as attractants for trapping the mud crayfish Orconectes immunis were assessed in a small Wisconsin lake (area, 5.7 hectares; maximum depth, 6 m). Five sites on the lake were sampled continuously for a 30-d period each year, and each site was fished with three traps. Total harvest of crayfish was 3,949 in 1985 and 2,226 in 1986. Traps with pelleted bait (Crawfish Bait Jumbo) caught more than the others by a 3-to-1 margin in 1985 and by a 2-to-1 margin in 1986. The commercially prepared baits were easier to handle, lacked a putrid odor, required less labor and no refrigeration, and were more readily available than fish carcasses.

Development of an Antimycin-Impregnated Bait for Controlling Common Carp

Abstract The common carp Cyprinus carpio is a major problem for fisheries and wildlife managers because its feeding behavior causes degradation of valuable fish and waterfowl habitat. This study was designed to evaluate the effectiveness of an antimycin-impregnated bait for control of common carp. The toxic bait contained fish meal, a binder, antimycin, and water. The ingredients were mixed together and made into pellets. This bait was force-fed to common carp or administered in a pond environment, where fish voluntarily fed on the bait. The lowest lethal dose in the force-feeding study was 0.346 mg antimycin/kg of fish and doses that exceeded 0.811 mg antimycin/kg were toxic to all fish. On three occasions, adult common carp held in 0.004-ha concrete ponds were offered 10 g of toxic bait containing 5.0, 7.5, and 10 mg antimycin/g of bait and the mean mortalities 96 h later were 21, 35, and 51%, respectively. Three tests were conducted in 0.04-ha earthen ponds each containing 100 adult common carp; these ...

A Sampling Method for Conducting Relocation Studies with Freshwater Mussels

ABSTRACT Low recovery of transplanted mussels often prevents accurate estimates of survival. We developed a method that provided a high recovery of transplanted mussels and allowed for a reliable assessment of mortality. A 3 × 3 m polyvinyl chloride (PVC) pipe grid was secured to the sediment with iron reinforcing bars. The grid was divided into nine 1-m2 segments and each treatment segment, was stocked with 100 marked mussels. The recovery of mussels after six months exceeded 80% in all but one treatment group.

Chemical Control of Fish and Fish Eggs in the Garrison Diversion Unit, North Dakota

Abstract The Garrison Diversion Unit involves the proposed transfer of Missouri River water to a large part of eastern North Dakota for agricultural and industrial uses. Some of the water would flow into Canada through the Red River of the North. Canadian officials are concerned that some nonindigenous species might be introduced to their waters; namely, gizzard shad (Dorosoma cepedianum), rainbow smelt (Osmerus mordax), common carp (Cyprinus carpio), and Utah chub (Gila atraria). We investigated toxicants that might be used to augment other barriers that have been proposed. Chemicals tested against fish eggs and larvae were rotenone, potassium permanganate, chlorine, acrolein, cyanide, fluoride, ammonia, and nitrite. Eggs were generally more resistant than larvae. Only three of the toxicants demonstrated potential to control both eggs and larvae of the species of concern. Rotenone was the most toxic, followed by chlorine and potassium permanganate. Effective exposures required 6-24 hours at concentration...

Winter Harvest of Bluegills in 1976-1977 from Lake Onalaska, Wisconsin

Abstract A winter creel census of bluegills (Lepomis macrochirus) conducted on Pool 7 (Lake Onalaska, Wisconsin) on the Upper Mississippi River in 1976-1977 used a half-day sampling schedule and car counts to estimate angler numbers. The calculated harvest was based on these counts plus data from interviews with 3,429 anglers. The total estimated harvest for the 17-week fishery (22 November-18 March) was 233,061 bluegills taken by 25,402 anglers during 96,519 hours of fishing (2.41 fish per hour). Of the bluegills harvested, 52% were taken during the first 5 weeks of the fishing season. Average length and weight of bluegills harvested was 178 mm and 136 g, respectively; total estimated weight of the catch was 31,696 kg.

Aspects of the Life History of the Calico Crayfish with Special Reference to Egg Hatching Success

Abstract Life history data were collected on adult (≥25 mm carapace length) female calico crayfish (Orconectes immunis) in conjunction with an egg-hatching study during 1986–1988. Eggs stripped from 10 females in October 1986 and 10 females in September 1987 were pooled each year and hatching success was monitored for samples of 100 eggs placed in each of eight diluter aquaria at 12°C. In fall 1987, berried calico crayfish were cultured at 12, 25, and 30°C and hatching was monitored. Data on length, weight, and number of eggs produced were collected for 28 females in September 1987 and 36 females in April 1988. An additional 456 female crayfish were checked for the presence of eggs. Hatching success was 86% in 1986 and 89% in 1987. The eggs on berried females held at 12°C started to hatch within 33 d. At 25°C, hatching started within 10 d. At 30°C, no hatching occurred, the eggs became orange (indicating death), and most of the eggs later developed fungal infections. The average number of eggs carried was...