Gale Bravener

Laboratory Estimates of Salmonine Egg Predation by Round Gobies (Neogobius melanostomus), Sculpins (Cottus cognatus and C. bairdi), and Crayfish (Orconectes propinquus)

ABSTRACT The continued lack of natural reproduction by lake trout (Salvelinus namaycush) in the Great Lakes has prompted development of models focused on the potential negative effects of interstitial predators. To aid in parameterization of such models we investigated the effect of temperature (1–2°C, 4–5°C, 7–8°C, and 10–11°C), predator group size, interspecific competition, egg density (60–6000 eggs m−2), and an alternate food source on egg consumption by slimy (Cottus cognatus) and mottled (Cottus bairdii) sculpins, round gobies (Neogobius melanostomus), and the native crayfish (Orconectes propinquus) in the laboratory. Egg consumption by the sculpins and round goby all increased over the range of temperatures investigated (ca 0.5 eggs·day−1 at 1–2°C to 1.5 eggs·day−1 at 10–11°C). Predator group size affected consumption; fewer eggs were eaten per individual slimy sculpin and round goby at densities of 5 or 10 per tank than 1 individual per tank. There was no effect of interspecific competition on egg consumption by slimy sculpins or round gobies at a density of 10 individuals per tank for various species combinations (10:0, 9:1, 5:5, 1:9, 0:10). A type II functional response to egg density was observed for sculpins, gobies, and crayfish although at extreme densities per capita consumption by crayfish and gobies declined. The presence of zebra mussels (Dreissena polymorpha) did not affect the number of rainbow trout (Oncorhynchus mykiss) eggs eaten by round gobies whose mussel consumption averaged 75% BW·day−1. Of the four species examined, round gobies appeared to be the most effective egg predator while crayfish were the least.

Evaluating harvest-based control of invasive fish with telemetry: performance of sea lamprey traps in the Great Lakes

Physical removal (e.g., harvest via traps or nets) of mature individuals may be a cost-effective or socially acceptable alternative to chemical control strategies for invasive species, but requires knowledge of the spatial distribution of a population over time. We used acoustic telemetry to determine the current and possible future role of traps to control and assess invasive sea lampreys, Petromyzon marinus, in the St. Marys River, the connecting channel between Lake Superior and Lake Huron. Exploitation rates (i.e., fractions of an adult sea lamprey population removed by traps) at two upstream locations were compared among three years and two points of entry to the system. Telemetry receivers throughout the drainage allowed trap performance (exploitation rate) to be partitioned into two components: proportion of migrating sea lampreys that visited trap sites (availability) and proportion of available sea lampreys that were caught by traps (local trap efficiency). Estimated exploitation rates were well below those needed to provide population control in the absence of lampricides and were limited by availability and local trap efficiency. Local trap efficiency estimates for acoustic-tagged sea lampreys were lower than analogous estimates regularly obtained using traditional mark-recapture methods, suggesting that abundance had been previously underestimated. Results suggested major changes would be required to substantially increase catch, including improvements to existing traps, installation of new traps, or other modifications to attract and retain more sea lampreys. This case study also shows how bias associated with telemetry tags can be estimated and incorporated in models to improve inferences about parameters that are directly relevant to fishery management.

A portable trap with electric lead catches up to 75% of an invasive fish species

A novel system combining a trap and pulsed direct current electricity was able to catch up to 75% of tagged invasive sea lamprey Petromyzon marinus in free-flowing streams. Non-target mortality was rare and impacts to non-target migration were minimal; likely because pulsed direct current only needed to be activated at night (7 hours of each day). The system was completely portable and the annual cost of the trapping system was low (

Evaluation of a Sterile-Male Release Technique: A Case Study of Invasive Sea Lamprey Control in a Tributary of the Laurentian Great Lakes

4,800 U.S. dollars). Use of the technology is poised to substantially advance integrated control of sea lamprey, which threaten a fishery valued at 7 billion U.S. dollars annually, and help restore sea lamprey populations in Europe where they are native, but imperiled. The system may be broadly applicable to controlling invasive fishes and restoring valued fishes worldwide, thus having far reaching effects on ecosystems and societies.

Factors Influencing Capture of Invasive Sea Lamprey in Traps Baited With a Synthesized Sex Pheromone Component

AbstractInvasive species can have detrimental impacts on native species and ecosystem services for humans. A technique that involves sterilization and release of males into wild populations of the same species can be useful in the control of invasive or pest species. A sterile-male release technique (SMRT) was used on a novel vertebrate system, the invasive Sea Lamprey Petromyzon marinus in the Great Lakes, in an attempt to control population size. Sea Lamprey populations in the Great Lakes have been suppressed since the 1950s by (1) pesticide applications to kill larvae in streams and (2) barriers to block upstream spawning migrations. Here, we present a literature review and meta-analysis of the SMRT by using a case study from the St. Marys River, where the SMRT was applied as an experimental method of Sea Lamprey control from 1991 to 2011. Observations obtained from the St. Marys River during and after SMRT application were used to evaluate whether the SMRT was effective at suppressing reproduction. Ma...